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Die industrielle Computertomographie (CT) ist ein gut bekanntes Verfahren zur zerstörungsfreien Prüfung von Werkstücken. In den letzten Jahren wird die CT aber zunehmend auch für dimensioneile Messungen von Werkstücken eingesetzt. Der wesentliche Vorteil der CT liegt in der Kompletterfassung mit hoher Messpunktdichte, die auch für andere Messverfahren unzugängliche, innere Geometrien einschließt. An kleinen Bauteilen können Strukturen bis herunter zu wenigen Mikrometern gemessen werden, wodurch sich das Verfahren gut für die Messung von Mikroteilen eignet. Nachteilig ist, dass viele Einflussgrößen das Messergebnis beeinflussen, was die Rückführung der Messergebnisse, die Bestimmung der Messunsicherheit und die Definition von Spezifikationen für CT-Anlagen erschwert.
Der Beitrag stellt nach einer Einführung in das Verfahren Anwendungsbeispiele der CT an Mikroteilen vor. Darüber hinaus geht der Beitrag auf Prüfkörper und -verfahren zur Einmessung und Überprüfung von CT-Anlagen ein und berichtet über aktuelle Normungsaktivitäten. Abschließend werden Möglichkeiten zur weiteren Steigerung der Auflösung aufgezeigt, um zukünftig möglicherweise auch Nanogeometrien messen zu können.
For differentiating the applicability of various numerical welding Simulation methods as well as unifying the prerequisites and the Steps to be taken in Simulation, normative codes are required for the user. Since any standard-like documents are currently still lacking in this field, DIN German Institute for Standardization has set up the Standards Committee NA 092-00-29-AA "Welding Simulation" dealing with the preparation of respective documents. This committee was initiated in partnership with the joint committee FA 12 "Weld Simulation on Application" of the Research Association of DVS German Welding Society.
The objective of this Standardization work in the field of numerical welding Simulation is to prepare a DIN SPEC with a view to standardizing the approaches to the Simulation of various welding phenomena and processes over the long run. In a draft version of DIN SPEC 32534 that has already been prepared by the above mentioned Committee, the structure of the primary document was stated. The primary document specifies the application fields and the key terms of welding Simulation. In addition, the generally valid Simulation structure has been established which is intended to serve as a recommendation for customers and suppliers in formulating and handling a Service order as well as for persons who Start doing welding Simulation for the first time.
This article focuses on the presentation of the new DIN SPEC 32534-1 explaining the major Simulation Steps. It additionally addresses the Classification of the secondary documents depending on the welding process and on the desired Simulation result. Finally, it gives an overview of the other subject areas dealt with in the Standards Committee NA 092-00-29-AA "Welding Simulation" as well as of the international activities in this field.
Das CargoLifter Ballonkransystem nutzt die Prinzipien der Leichter-als-Luft-Technologie für das Heben von Gütern. Der mit leichtem Gas gefüllte Ballon drängt in der schwereren Luft nach oben und kann somit Lasten anheben. Im Gegensatz zu erdgebundenen Kränen ist für den Luftkran die Beschaffenheit des Bodens sekundär. Der Ballonkran wird an drei Winden verankert und über die im Kranknotenpunkt zusammengeführten Seile präzise gesteuert. Beim Heben und Versetzen verbleibt die Last unter dem Ballon, der stets 100% seiner Hubkraft auch bis zu 200m Höhe und selbst weiterem Versatz behält. Reichweite bedeutet beim CargoLifter Ballonkransystem statt mehr Ausleger mehr Seil.
Heavy gases in large quantities are used worldwide in various industries. Past incidents, such as the liquefied gas disaster in Viareggio (2009) have shown that these materials are difficult to handle in a safe manner. According to the German Hazardous Incident Ordinance (StörfallVO 2000 - 12. BIMSchV), plant operators with extended responsibilities must produce a report in which they verify that , in the event of an unintentional gas release, the surrounding area will not be aversely affected. Essential elements of this report are calculations of both the released mass flow and the gas dispersion. Using models such as the VDI guideline 3783 (state of the art in Germany) plant operators are able to predict the characteristics of likely gas dispersions. The presented experimental investigations were carried out at the BAM better understand heavy gas dispersion with high gas concentrations in the air (≥ 1 Vol.-%), as well as concentrations with approximately neutral density characteristics (≤ 3000ppm) in order to test the accuracy of the VDI guideline. The starting point for experimental trials was the heavy gas releases resulting from pipeline, vessel or standard gas bottle leaks, with mass flows of between 20 and 100 g s-1. Investigations on the gas-phase release process focused on the unsteady mass flow associated with releases from standard gas bottles. The experimental results will be used as comparative parameters for future simulations. The goal of these simulations is to develop a model with which calculation of the unsteady mass flow, based on the material characteristics for any gas, is possible.
Resistance to stress cracking by wetting solution is one of the selected properties together with the corresponding test method FNCT and tolerances for a comparison of polyethylene grades of one design type in the procedural rule on suitability proof for alternative plastic resins used for packagings and intermediate bulk Containers (IBCs) for the transport of dangerous goods.
The environmental stress crack resistance determined by Full Notch Creep Test (FNCT) represents the impacts from the stacking tests at 40 °C performed with Standard liquid wetting solution (without pre-storage) and with normal butyl acetate saturated wetting solution (pre-storage with normal butyl acetate). Environmental stress crack resistance determined with FNCT for the polyethylene grades was related to the times to failure of different jerrican samples made of these grades in stacking tests with 5 % wetting solution and a n-butyl acetate saturated wetting solution (pre-storage with n-butyl acetate) at 40 °C. The FNCT is suitable for comparison of polyethylene grades in relation to environmental stress crack resistance independent of their use as drum, IBC or jerrican material. The stiffness of polyethylene grades should be taken into account to the comparison as jerricans are not only chemically but also mechanically stressed.
Basierend auf Fallversuchen mit Transportbehältern für radioaktive Stoffe sowie auf einem Versuchsprogramm mit Holzproben wurden die Energieabsorptionsmechanismen identifiziert und ein Modell für das Verhalten von Fichtenholz bei axialer Belastung entwickelt. Das Modell zieht für die Kompression von Holz die seitliche Dehnungsbehinderung – im kontinuumsmechanischen Zusammenhang wäre das die Mehrachsigkeit des Spannungszustandes im Kontinuum – in Betracht. Die Energie, die vom Holz absorbiert werden kann, ist umso größer, je größer die seitliche Dehnungsbehinderung ist.
Für die Modellierung mit Finite Elemente Methoden wurden verschiedene Modellierungsstrategien untersucht, keine der vorgeschlagenen Modellierungsstrategien war in der Lage, dass Verhalten von Holz bei Druckbeanspruchung und großen Deformationen inkl. der Entfestigung zu modellieren. Bei Verwendung einer entfestigenden Fließkurve zeigt das Modell ausgeprägte Netzabhängigkeiten und numerischen Instabilitäten.
Für die Modellierung der Entfestigung mit Hilfe einer von der Mehrachsigkeit des Spannungszustandes gesteuerten Fließflächenevolution ist kein geeignetes Materialmodell vorhanden.
Anhand der Simulation eines Fallversuchs mit einem Behälterkörper und stoßdämpfenden Bauteilen im Maßstab 1:2 wurde gezeigt, dass zwar eine vollständige Modellierung des Stoßdämpferverhaltens inkl. Entfestigung nicht möglich war, aber das Stoßdämpferverhalten mit einer nicht-entfestigenden Fließkurve sinnvoll modelliert werden konnte. Eine Verifikation des Modellierungsansatzes am real zu modellierenden Bauteil ist zwingend erforderlich. Wenn signifikante Änderungen zwischen Verifikations- und Simulationsobjekt auftreten, ist die Zuverlässigkeit der Rechenergebnis als gering zu bewerten. Nur wenn die auftretenden Kompressionsmechanismen durch eine Analyse des Stoßdämpferholzes bestimmt werden können, ist eine zuverlässige Ermittlung von Stoßdämpferkräften- und verformungen möglich.
Influence of the main laser welding parameters on process stability and resulting weld quality were investigated. Effects of weld edge preparation on the weld appearance and quality were considered. The obtained welded joints were subjected to radiographic tests for detection of internal imperfections. Metallurgical characterisation of the samples regarding the resulting phase composition and hardness was conducted. Tensile and potentiodynamic tests were performed to evaluate the mechanical and corrosion properties. The results provide an insight into the advantages and limitations of the laser welding process for joining high-manganese alloyed stainless steels. Conditions for the production of defect-free and corrosion-resistant welds having good mechanical properties could be determined.
The present contribution highlights recent trends in investigating hydrogen diffusion and cracking in steel welds. For such studies, supermartensitic stainless steels (SMSS) have exemplarily been selected. These materials have been used for offshore and marine constructions for about two decades now. They present a versatility of improved properties such as high strength to thickness ratio, good weldability and good corrosion resistance. However, as shown by respective failure cases, SMSS welds might become prone to hydrogen assisted cracking and the degradation phenomena are more easily to investigate due to the nearly homogeneous martensitic microstructure than in other materials. Generally, it has to be distinguished between cracking that occurs during or shortly after fabrication welding, or during subsequent operation of SMSS components. In order to achieve crack avoidance during fabrication and service, conclusive test sequences have to be applied, ranging from field tests at real components and full scale tests investigating the materials behavior under real service conditions to basic and small scale tests, such as tensile and corrosion tests, oriented more towards a materials ranking. Considerable testing of SMSS welds has been carried out and the present paper particularly summarizes spotlights on 1:1 scale component testing of welded tubulars, slow strain rate testing and basic tests oriented to elucidate the hydrogen behavior and degradation in SMSS weld microstructures. Also, permeation tests, hydrogen dependent degradation of mechanical properties and thermal desorption spectroscopy are adressed. As a specific item, first results of lately conducted investigations for tracking hydrogen movement in such weld microstructures by using high energy synchrotron radiation are elucidated.
Charakterisierung der Wandler für Luftultraschallprüfung aus zellulärem Polypropylen-Ferroelektret
(2011)
In den letzten Jahren stieg die Anfrage für zerstörungsfreie Prüfung (ZIP) mit Luftultraschall deutlich. Die klassische ZfP mit Ultraschall nutzt Flüssigkeiten als Koppelmittel zwischen dem Wandler und dem Prüfkörper. Für die Prüfung von Gegenständen mit empfindlicher Oberfläche, die das Koppelmittel beschädigen oder verunreinigen kann, ist deswegen Luftultraschall besser geeignet. Eine mögliche Anwendung ist beispielsweise der Nachweis von Delaminationen in glas- und kohlefaserverstärkten Verbundwerkstoffen sowie Sandwichbauteilen, die in der Luftfahrt- und der Automobilindustrie eingesetzt werden.
The failure of laminates usually is initiated by the failure of the plies with the maximum transverse stresses. The failure of those plies generally reduces the load carrying capability of the laminate, even though they carry only a small part of the external load. The analysis of failure under off-axis stresses accordingly is essential for the prediction of the strength of laminates. This is taken into account in the "mechanisms based failure criteria" e.g. by Puck. Most of these inter fiber failure criteria are not based on the micromechanics of the failure process but on prescribed stress interaction functions. The failure of plies under transverse loading obviously is governed by the bond strength between fiber and matrix fiber. The interfacial debonding was studied e.g. by Paris et al. and Corea et al.. The bond strength between fiber and matrix usually is measured by using micromechanical tests e.g. pull-out, push-out or fragmentation tests. Stress analyses as well as fracture mechanical analyses show that the interfacial failure over a large range is dominated by shear stresses (Kim and Mai, Pisanova et al, Marotzke and Qiao). The stress distribution arising in those experiments however differs from the stresses acting in a lamina under transverse loading. In transverse failure of a lamina, radial stresses as well as shear stresses are dominating the failure process of the interface. In addition longitudinal shear stresses are present. Experimental work concerning off-axis loading of single fibers was done e.g. by Tandon and Kim and by Ogihara and Koyanagi. They studied the influence of the fiber alignment by using a specimen in form of a cruciform with skew wings.
Wear tests are often used in engine development in order to characterize the functional profile of surfaces interacting with lubricants. This paper proposes a new test procedure to determine Stribeck-type curves for the tribosystem piston ring/cylinder liner involving test pieces prepared from engine components. The Variation of the friction coefficient with sliding speed depends on the structure and Constitution of the base oil, the viscosity index, the surface topography of the liner and ring, and the friction modifiers used. Novel organic friction modifiers of low molecular mass not only reduce the friction coefficients under mixed / boundary lubrication, but also in the fluid film regime. In addition, the influence of surface roughness on the wettability of surfaces can be significant for both static and dynamic wetting. For this reason, the interaction of the lubricant with the surfaces was also investigated to enable a correlation between the surface properties of the liquid and solid phases and the tribological behavior.
Die Nutzung des Wertstoffpotentials von Abfällen und Reststoffen ist ein Grundpfeiler im Schutz von natürlichen Ressourcen. Dabei ist der Aufbau und Erhalt von Stoffkreisläufen im Baubereich - aufgrund der großen Menge an Baurestmassen - von besonderer Ressourcenrelevanz. Während in Zukunft im Sinne der Nachhaltigkeit schon bei der Errichtung von Gebäuden auch auf Möglichkeiten zur Stoffstromtrennung beim Rückbau geachtet werden sollte, sind die heute rückzubauenden Bauwerke nicht unter diesem Gesichtspunkt errichtet worden.
Der Fachbeirat beschloss im vergangenen Jahr Zulassungsrichtlinien für Kunststoffdichtungsbahnen, Schutzschichten, Kunststoff-Dränelemente und Geotextilien zum Filtern und Trennen und eine Richtlinie über Anforderungen an Verlegefachbetriebe, die von seinen Arbeitsgruppen vorbereitet worden waren, und nunmehr die Grundlage für die Zulassungstätigkeit bilden. In diesem Beitrag wird im Anschluss an die Ausführungen auf der letzten Fachtagung kurz über wesentliche Anforderungen und Zulassungsvoraussetzungen berichtet. Noch nicht verabschiedet sind die Richtlinien für Dichtungskontrollsysteme und Bewehrungsgitter aus Kunststoff. Auf den Diskussionsstand bei den Anforderungen an die Bewehrungsgitter wird etwas ausführlicher eingegangen, da sich neben den materialtechnischen auch bemessungstechnische Probleme ergeben.
The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of semiconductors and dielectrics by linearly polarized high-intensity Ti:sapphire fs-laser pulses (τ ~100 fs, λ ~800 nm) is studied experimentally and theoretically. In the experiments, two different types of LIPSS exhibiting very different spatial periods are observed (socalled LSFL low spatial frequency LIPSS, and HSFL - high spatial frequency LIPSS), both having a different dependence on the incident laser fluence and pulse number per spot. The experimental results are analyzed by means of a new theoretical approach, which combines the generally accepted LIPSS theory of J. E. Sipe and co-workers [Phys. Rev. B 27, 1141-1154 (1983)] with a Drude model, in order to account for transient changes of the optical properties of the irradiated materials. The joint Sipe-Drude model is capable of explaining numerous aspects of fs-LIPSS formation, i.e., the orientation of the LIPSS, their fluence dependence as well as their spatial periods. The latter aspect is specifically demonstrated for silicon crystals, which show experimental LSFL periods Λ somewhat smaller than λ. This behaviour is caused by the excitation of surface plasmon polaritons, SPP, (once the initially semiconducting material turns to a metallic state upon formation of a dense free-electron-plasma in the material) and the subsequent interference between its electrical fields with that of the incident laser beam, resulting in a spatially modulated energy deposition at the surface.
Upon multi-pulse irradiation, a feedback mechanism, caused by the redshift of the resonance in a grating-assisted SPP excitation, is further reducing the LSFL spatial periods. The SPP-based mechanism of LSFL successfully explains the remarkably large range of LSFL periods between ~0.6 λ and λ.
Nondestructive testing (NDT) methods are applicable in many ways for defect detection as well as optimization of packaging production processes. The visual inspection method is the technique which is mostly used, although neither the customer nor a skilled inspector may be aware of this.
Techniques like ultrasound for wall thickness measurement, the application of x-ray techniques or the use of dye penetrant techniques for crack detection are rather well known to the NDT family. However, acoustic emission techniques can also be helpful for the characterization of packaging materials. In this paper the employment of x-ray computer tomography (CT) for measurement of wall thickness in plastic jerrycans, especially on the edges, and its possible optimization of production processes will be discussed.
A comparison of the CT and ultrasonic examinations of wall thickness and the reliability of this measured data are also important points for the discussion, especially if some safety factors can be derived from the results.
The leakage test is also good for jerrycans, IBCs or other kinds of drums for the transportation and storage of dangerous goods. The disadvantage of this kind of test is that a lack of quality, e.g. wall thickness deterioration, cannot be detected if the wall thickness withstands the internal pressure. Therefore, especially for Quality assurance, the other, previously mentioned techniques are better for a statistical assessment of a batch. This paper is focused on the comparison of different NDT results with special emphasis on the large range of material mechanical properties.
Fires on waste dumps, surface landfills, Underground stowing or storage facilities of Recycling factories may have multiple harmful effects on individuals on site and on environment.
Possibly several tens of thousands of tons flare up plunging vast areas in smoke and releasing large amounts of flue gases. Experience shows that fire fighting takes days or even weeks and moreover, as long as hidden glowing nests exist fires may break out repeatedly weeks or months later. In the light of this, fire prevention is much easier to manage than extinction. It is of internst to identify the geometrical and physical conditions under which the mid-term or long-term storage of recycling materials can be performed avoiding self-ignition. Our Guideline presents a novel method developed at BAM which combines experimental tests on lab-scale with numerical simulations in Order to obtain permissible geometries of deposits and storage times at which self-ignition can be certainly avoided (Berger 2010).
Use of higher-alloyed metallic materials and duplex steels for transport tanks of dangerous goods
(2011)
Compatibility evaluations of selected metallic materials under the influence of dangerous goods are published in the BAM-List - Requirements for Tanks for the Transport of Dangerous Goods” as basis for substance-related prototype approvals for tank Containers designed for the carriage of dangerous goods.
There is a request of the tank manufacturing industry and transportation Companies to incorporate additional materials into the BAM-List, especially corrosionresistant materials because of the large number of corrosive dangerous goods.
One solution to solve corrosion Problems is to line the tank with a polymeric material, an alternative solution is the application of high-alloyed stainless steels and nickel-based alloys as there are alloy 926 (1.4529), alloy 31 (1.4562) and alloy 59 (2.4605).
But there is an interest to use cost-efficient steels with high strength values and concomitant adequate corrosion resistance such as duplex Steel 1.4362 too. This Steel grade was originally developed as a substitute for the austenitic grades 1.4404 and 1.4571. Due to the lower content of the alloy elements nickel and molybdenum this duplex steel is a cost-efficient alternative to molybdenum containing austenite.
Due to the limited number of corrosion test results with welded test samples of these high-alloyed materials and the duplex steel under the influence of corrosive dangerous goods a comprehensive test Programme was performed with these materials in Cooperation with ThyssenKrupp VDM and Deutsche Edelstahlwerke GmbH.
It can be concluded from the test results that the "superaustenitic steels” 1.4529 and 1.4562 as well as the nickel-based alloy 2.4605 are a really good alternative as tank materials for the transport of dangerous goods in comparison to the lining of the tanks. Due to the reduced alloying content, in particular Nickel (3.7 %) and Molybdenum (0.15 %), a lower resistance of the duplex steel 1.4362 compared to the austenitic CrNiMo-steels was observed in acidic media. The duplex Steel is an alternative to the austenitic steels, especially in alkaline media. The test results are included in the current 10th edition of the BAM-List and therefore available for the costumer.
Correlation of aldehyde emissions and fatty acids content in pine wood and oriented strand boards
(2011)
Indoor air quality is important for human health and comfort. To ensure good indoor air quality contamination by volatile organic compounds (VOC) should be minimised. The aim of the project is the reduction of unsaturated aldehydes which can emit from oriented Strand boards (OSB): These aldehydes have an impact on the health based evaluation of emissions from products for indoor use according to the AgBB (Ausschuss zur gesundheitlichen Bewertung von Bauprodukten, Committee for Health Evaluation of Building Products) scheine (AgBB 2010). The model OSB were produced in a pilot plant using well known raw materials (Pinus sylvestris at different trunk heights) under using various processing parameters (Wilke et al. 2011).
OSB emit predominantly monoterpenes and aldehydes. Aldehydes are oxidation products of fatty acids in wood. The conditions which affect the oxidation process are the fatty acid concentration and composition, the oxygen content, the sample surface and the presence of compounds which indicate, inhibit or stop the oxidation respectively. The oxidation rate rises with an increasing number of double bounds in the fatty acid, e.g. the oxidation rate between oleic, linoleic and linolenic acid correspond to 1:12:24. One of the most important products of fatty acid oxidation is hexanal. It is generated during the oxidation of linoleic acid. This study shows a direct correlation between aldehyde emission and oxidation, hexanal can be used as an indicator for oxidation.
With the implementation of glass casting in France in the second half of the 17th century, larger mirrors could be produced. So-called tin-mercury mirrors were made by coating glass with tin amalgam. Today, many historical mirrors are partly damaged, the image quality is compromised, and the material integrity of the mirror is threatened. The transformation from tin into an oxide starts at the surface of the amalgam and proceeds down to the glass surface. The mercury dissolves as a liquid or gaseous phase. The amalgam layer is destroyed, so that conservation is necessary. Conservators must follow strict safety precautions while handling amalgam mirrors because of possible mercury emissions and corrosion of the amalgam, during which elemental mercury accumulates near the mirror frame in droplets and is emitted into the air.
In a research project, the quantity of the mercury emissions from historical mirrors was examined and a technique to decrease these emissions was developed.
Indoor air pollutants influence the health and comfort of building occupants and consequently the energy consumption of the building. The pollutants are emitted by various sources.
Among these sources, building products are of particular importance. To control the emission of pollutants from building materials, a few different voluntary labelling Systems have been introduced in Europe. In Germany also mandatory “Principles for the health assessment of construction products used in interiors” have been applied for the technical approval of floor coverings since 2004. This procedure is based on the assessment scheine of the Committee for Health-related
Evaluation of Building Products (AgBBScheme). The sensory-limit settings for building-material label Blue Angel offer consumer to differ not only low-emission but also low-odour Building materials from another building materials.
Product emissions chamber testing involves a complex protocol with several sources of measurement uncertainty (ASTM, 2010; ISO, 2006). Despite the potential for significant variability in measurement results within and among laboratories, there is no Standard method available to assess the accuracy of emissions chamber test results. Recently, Germany’s Federal Institute for Materials Research and Testing (BAM) started a program to evaluate the performance of laboratories testing for the AgBB (German Committee for Health-related Evaluation of Building Products) labelling scheme (Wilke et al., 2009). Test method validation was conducted through interlaboratory studies (ILS) with over 30 participants. Simultaneously, the National Institute of Standards and Technology (NIST) and Virginia Tech (VT) started a program to develop a series of reference materials that mimic real building products, can be tested in typical emissions chambers, and have independently known emission rates (Cox et al., 2010). BAM, NIST and VT subsequently joined forces to conduct a series of inter-laboratory studies using the prototype reference material. A pilot ILS was conducted with BAM and NIST followed by an expanded ILS with several participating countries. Results from these interlaboratory studies have the potential to define an internationally-accepted Standard approach to validate results from product emissions tests.
Fusion welding is widely used in the automotive industry to join metal structures. It is well-known that distortions and residual stresses occur during and after the welding process. Many procedures exist to decrease these negative heat effects of welding, but are often coupled with highly cost intensive experiments. The implementation of a welding Simulation tool to reduce this very expensive experimental procedures is therefore of high interest. Despite the fact that the automotive industry is a key sector for Simulation procedures, welding Simulation Software is nevertheless not yet widely implemented. This is mainly due to the complexity of the Simulation tools requiring expert users and the resulting high time to Solution.
In this study, a new fast thermo-mechanical Simulation of a complex and large laser beam welded automotive sheet metal assembly with several non linear welds is simulated. Assumptions and simplifications of the complex physical welding phenomenon, which are made to keep the computational cost and the complexity of the Simulation in an industrial frame, are discussed. The calibration time of the phenomenological heat source model has been optimized with a very fast analytical thermal model and the resulting simulated temperature fields match perfectly with the measured ones. Additionally, the user experience and the time-to-solution are kept within a reasonable time frame for arr industrial environment. All Simulation results are validated with experimental results.
The application of fluorescent materials improves the visibility for of warning symbols. BAM has used a measurement device to characterize fluorescent materials, which is based on the two-monochromator method. The result of this measurement method is an illuminant independent characteristic of the fluorescent material, called the Donaldson matrix, In view of its age and speed, the measurement device had to be re-designed and re-built. The new measurement facility is explained in greater detail in the paper. First measurement results and a comparison to the older device are also described.
In comparison with traditional measuring Systems (pressure cells, piezometers and inclinometers which produce only point measurements) fibre optic sensors are well suited for spatiallydistributed monitoring purposes. The very tiny optical fibres of a diameter of less then 1 mm can operate as sensors in strong electromagnetic fields, under “harsh” explosive and Chemical environments and under ionizing radiation.
This article studies the three dimensional transient weld pool dynamics and the influence of joint preparation angle on welding of low carbon structural steel plates using the ForceArc® process. ForceArc is a new gas metal arc welding technology which allows adequate fusion and penetration with a smaller V groove angle. This enhances welding efficiency significantly because of reduction of layers and low material consumption.
The deformation of the weld bead is calculated with an accurate coupling of the heat transfer with fluid flow through continuity, momentum and the energy equations combined with the effect of droplet impingement, gravity, electromagnetic force, buoyancy, drag forces and surface tension force (Marangoni effect). Four different angles of V groove are employed with the same welding parameters and their influence on the weld pool behavior and weld bead geometry is calculated and analyzed, to allow subsequent calculations of residual stress and distortion of the workpiece.
Such a simulation is an effective way to study welding processes because the influence of all the welding parameters can be analyzed separately with respect to thermal cycle, weld bead formation, and the microstructure of the weld. Good agreement is shown between the predicted and experimentally determined weld bead dimensions. It was found that with a larger groove angle, the penetration depth increases. Furthermore, a higher wire feeding rate is needed to fill the larger groove. The model presented can be used for further analyses of GMAW processes as well as input data for the numerical calculation of welding induced residual stresses and distortions using Computational Weld Mechanics CWM.
Despite the numerous possibilities to influence the properties of repair mortars by modifications of the mixture proportioning, it is almost impossible to change an individual property without influencing other mortar properties. When optimising a mixture, it has to be decided for each individual case, which of the mortar properties needs to be treated with the highest priority. Most properties can be altered by several different measures, which may vary in effectiveness, side effects and cost efficiency. As the prevention of shrinkage induced constraining cracks is crucial for the durability and Service life of a concrete repair task, in the presented paper special attention is paid to the influences on the mortar’s shrinkage behaviour. On the basis of parameter studies it is shown, how it may be beneficial in certain cases to accept the worsening of some general properties if by this measure another property, which is essential for the individual application task, can be enhanced significantly. In general a tailor-made approach for the mixture proportioning seems beneficial but due to the complexity of the constituents’ interactions in repair mortars, it bears a high risk of unexpected malfunctions.
This paper presents volume heat sources and the corresponding functional analytical Solutions for the transient temperature field. The considered energy distributions are normal, exponential and parabolic. The method follows the common approach in Computational Welding Mechanics (CWM) to account for the physics of the welding process and the resulting temperature field by phenomenological models for heat conduction. Therefore, the used heat source models are apparent heat sources that incorporate the real heat input as well as the fluid flow in the weld pool and the latent heat connected with phase transformations. The heat source models provide welding characteristics like thermal cycle and Fusion line in the cross section within short computational time. Consequently, inverse techniques on basis of optimisation algorithms enable the adaptation of the models to the experimental data efficiently. Furthermore, the direct evaluation of the energy distribution for the experimental fusion line in the cross section is demonstrated which enhances the numerical optimisation by reducing the number of unknown model Parameters and providing a reasonable initial guess within the model parameter space. The proposed temperature field models are validated with real laser beam welding experiments.
In the present work, the titanium alloy Ti-6.8Mo-4.5Fe-1.5Al (Timetal LCB) was investigated with respect to the microstructural evolution during strain controlled fatigue loading. The alloy was developed to reduce the generally high material costs of β-alloys by substituting expensive beta stabilizers by using a standard Fe-Mo master alloy. One possible application seen in the automotive industry is the substitution os suspension structural parts currently made of steel, suc as suspension springs. These components require a high strength and fatigue resistance.
Prevention of the explosion of acetylene cylinders involved in fire: experiments and simulations
(2011)
In order to assess the effectiveness of water cooling of acetylene cylinders involved in fire, a total of 13 bonfire tests with 8.9-, 10
and 50-l-cylinders were performed. During the experiments the pressure
in the cylinder and the temperature at different locations within the porous material and on the Shell surface as well as the flame temperature were measured. Overall 8 burst tests were performed, in order to determine the times to explosion for the cylinders. Cylinders failed not later than 15 minutes from the ignition of the bonfire, often with generation of a fireball. During the other 5 tests, the fire was extinguished before the expected burst and the cylinder was cooled with water. In 2 of the 5 extinction experiments, the explosion of the cylinder could be prevented. Noticeably, in one case the on-set of the decomposition of acetylene had already been observed, before the cooling was started. In spite of that, the cooling was still effective. The interpretation of the current results and of the data from previous tests with 40-l-cylinder suggests that single acetylene cylinders involved in fire might be saved by cooling, if their pressure does not exceed a value of about 45 bara. The recorded values of pressure and temperature were used to develop and validate a mathematical model for the prediction of the heat transfer in acetylene cylinders during the exposure to fire and the afterward cooling. The predictions agreed well with the experimental results.
The inhalation of 222Rn (radon) is one of the most important reasons for lung cancer, after smoking. Usually, the geological subsoil and the building ground are the dominant sources for enhanced indoor radon levels. Additionally, building materials can increase indoor radon concentrations when these materials contain higher contents of 226Ra (radium), especially in combination with low air exchange rates. For a realistic estimation of indoor radon
concentrations, it is helpful to carry out measurements of radon exhalation rates from relevant materials using emission test chambers. In Germany, it is aspired to limit the total indoor radon concentration to 100 Bq/m3, whereby building materials should contribute at most 20 Bq/m3. Within a project financed by the German Institute for Construction Technology (DIBt), a practical oriented measurement procedure of the radon exhalation of building materials in accordance to ISO 16000-9 was developed to have a means for the assessment of these materials with respect to their indoor use. Test chambers with different volumes were used. The tested materials were mainly used for wall constructions (e.g., bricks, light-weight concrete) and have known specific radium activities and radon exhalation rates.
In 1882, the East-West suburban train viaduct was built through Berlin as part of the public traffic solution in the late 19th Century. Today, the only left over iron arch bridge is a pair of two arches Crossing the Spree river in the middle of Berlin. Before dismantling the former parallel two original pairs of iron arches and rebuilding new arches for the high-speed railway line through Berlin in 1997, BAM was involved in an extensive test program of the heritage iron arch structure. Especially the estimation of accumulated damage in critical details and the verification of the old material properties at early stage was important information to the bridge owners. The testing program included two strain and displacement measurement campaigns, non-destructive testing, materials testing and microscale metallographic analysis of critical details. The measured strain cycles were significant lower in number and size than expected. Most of the cycles were compression stress cycles only. The work was planned in Cooperation with the Berlin consultancy Professor Hilbers that was responsible for the design and calculation of the reconstruction measures. Additionally, after calculation of the possible reuse of the old arches, we compared measured data from strain measurements with the results from calculation.
The measured data and the calculated data show a good qualitative correlation.
Beside such well approved residues like fly ash, blast fumace slag, silica fume and crushed concrete orbrick, other materials, like waste incineration bottom ash, steel slag, biomass ash, industrial sludge or mixed demolition waste, bear the potential to be used in high-grade mineral building materials. However, sophisticated Processing technologies and progressive applications ofthe waste products are needed. The material efficiency has to be improved by further R&D activities. This paper Shows the activities ofthe working group “Saving Resources by Material Recycling” and presents research about the use of residues from industry, incineration processes and deconstruction for the production of high-grade mineral building materials.
For the design of gas explosion venting systems for confinements only little guidance is given when considering the constructional boundary conditions or process conditions. For this reason conservative assumptions are prevalent in practice and in many cases the protective Systems become significantly oversized. Such safety margins in venting areas can lead to a critical acceleration of the pressure rise. Finally, a gas explosion at turbulent conditions caused by oversizing of the venting area rather leads to an under-sized system and supports the deflagration to detonation transition (DDT). The present investigation was focused especially on the influence of certain obstacles as well as the effect of the initial pressures on the explosion venting behavior of methane-air-mixtures and of hydrogen-air-mixtures.
Ultrashort pulses lasers are tools of choice for functionalizing the bulk of transparent materials. In particular, direct photoinscription of simple photonic functions have been demonstrated. Those elementary functions rely on the local refractive index change induced when focusing an ultrashort pulse in the volume of a transparent material. The range of possibilities offered by direct photoinscription is still under investigation. To help understanding, optimizing and assessing the full potential of this method, we developed a time-resolved phase contrast microscopy setup. The imaginary part (absorption) and the real part of the laser-induced complex refractive index can be visualized in the irradiated region. The setup is based on a commercially available phase contrast microscope extended into a pump-probe scheme. The originality of our approach is that the illumination is performed by using a pulsed laser source (i.e. a probe beam). Speckle-related issues are solved by employing adequate sets of diffusers. This laser-microscopy technique has a spatial resolution of 650 nm, and the impulse response is about 300 fs. The laser-induced refractive index changes can be tracked up to milliseconds after the energy deposition. The excitation beam (the pump) is focused with a microscope objective (numerical aperture of 0.45) into the bulk of an a-SiO2 sample. The pump beam can be temporally shaped with a SLM-based pulse shaping unit. This additional degree of flexibility allows for observing different interaction regimes. For instance, bulk material processing with femtosecond and picosecond duration pulses will be studied.
The notched impact strength at -30 °C is one of the selected properties, together with the corresponding test method and tolerances, for a comparison of polyethylene grades of one design type in the procedural rule on suitability proof for alternative plastic resins used for packagings and intermediate bulk containers (IBCs) for the transport of dangerous goods.
The marginal drop heights determined with the drop test at -18 °C after pre-storage of the test samples with 55 % nitric acid at 40 °C only partly related to the notched impact strength at -30 °C. The Charpy method is only suitable for classifying the grade in relation to toughness behavior and using this classification for comparison with other grades. Notched impact strength can provide a qualitative indication if the test samples fail under shock forces.
Conditioning the design types with 55 % nitric acid for 21 days at 40 °C causes an increase in the marginal drop heights of the design types in drop tests at -18 °C when compared with design types without pre-storage. Post-crosslinking of the grades increases stiffness because of the acidic influence.
Für die Vorhersage der Containment Sicherheit beim Bersten von Laufrädern in Abgasturboladern müssen zum einen komplexe Verformungs- und Schädigungsvorgänge bei dynamischer Belastung einschließlich ihrer Temperaturabhängigkeit mit geeigneten Versuchen erfasst und gemessen werden, zum anderen müssen diese temperatur- und dehnratenabhängigen Kennwerte in weiterentwickelten Materialmodellen für das Verformungs- und Schädigungsverhalten abgebildet werden.
Im Rahmen dieses Vorhabens wurden drei Gusswerkstoffe untersucht. Für den Gusswerkstoff mit Kugelgrafit EN-GJS-400 wurden die weitestgehenden experimentellen Untersuchungen zur Charakterisierung des Materialverhaltens unter ein- und mehrachsigem Zug sowie unter Druck- und Scherbeanspruchung für ein breites Spektrum von Beanspruchungsgeschwindigkeiten und Temperaturen durchgeführt. Die Untersuchungen an den beiden weiteren Werkstoffen erfolgten mit auf der Basis der gewonnen Erkenntnisse optimiertem Aufwand. Der Schwerpunkt der Arbeiten lag dabei im Bereich hoher Beanspruchungsgeschwindigkeiten und höherer Temperaturen sowie deren Kombination.
Für die numerische Modellierung der Containment Sicherheit von ATLs wurde ein vorhandenes Materialmodell weiterentwickelt, so dass es in der Lage ist, das Verformungs- und Versagensverhalten von Gusswerkstoffen, wie z.B. den Zug-Druck-Unterschied, in Abhängigkeit von Spannungsmehrachsigkeit, Temperatur und Dehnrate auch für große plastische Deformationen zu beschreiben. Die Modellparameter wurden durch numerische Simulation von Experimenten an Proben bestimmt. Das Modell wurde in ein kommerzielles Finite-Elemente-Programm mit expliziter Integration implementiert und ist in der jetzigen Version auf FE-Modelle mit Volumenelementen beschränkt.
Das Materialmodell wurde im Rahmen dieses Vorhabens zunächst zur numerischen Simulation von Experimenten an gekerbten Proben unter Biegebelastung angewendet. In einem zweiten Schritt erfolgte die Verifikation des Bauteilverhaltens durch numerische Simulation der hochdynamischen Beschussversuche. Da in diesem Vorhaben das Materialverhalten jedoch nur für das Containment und nicht auch für den Rotor des ATLs untersucht wurde, hat man für das Projektil und das Bauteil den gleichen Werkstoff verwendet. Die Belastung in diesen Beschussversuchen ist vergleichbar mit dem Aufprall eines Rotorfragments auf das Containment des Abgasturboladers. Abschließend wurde die numerische Simulation eines Containment Tests an einem Abgasturbolader durchgeführt.
Die Nachrechnung dieser Experimente ist somit als ein Nachweis der Prognosefähigkeit des Materialmodells anzusehen. Numerische Stabilität der Userroutine konnte erreicht und eine gute Übereinstimmung mit den experimentellen Ergebnissen erzielt werden.
Für Polypropylen unterschiedlicher Stabilisierung wurden in künstlichen Bestrahlungstests sowohl die spektrale Empfindlichkeit als auch die Temperaturabhängigkeit der Rissbildung quantitativ ermittelt. Dafür wurde die Dauer bis zur Rissbildung sowohl bei spektraler Bestrahlung als auch bei Bestrahlung in einem UV-Leuchtstofflampengerät bei verschiedenen Temperaturen bestimmt.
Die Temperaturabhängigkeit konnte als Arrhenius-Abhängigkeit beschrieben werden; das Wirkungsspektrum wurde an eine Stufenfunktion angepasst. Anschließend wurde auch noch der Einfluss des Stabilisatorgehalts als Potenzfit parametrisiert. Die Einzelabhängigkeiten wurden zu einer Gesamtfunktion der Wirkungen in Abhängigkeit der Dosis zusammengesetzt, die es ermöglicht die Wirkungen unterschiedlicher Dosiskombinationen abzuschätzen.
Zur Validierung der Dosis-Wirkungsfunktionen wurden Freibewitterungsergebnisse aus Phoenix/Arizona herangezogen. Mit der Dosis, die sich aus den Wetterdaten dieser Freibewitterung ergibt, wurden anhand der Dosis-Wirkungs-Funktionen die jeweiligen Lebensdauern errechnet und mit dem experimentell bestimmten Versagen in der Freibewitterung verglichen.
Die Arbeiten erfolgten im Rahmen des ViPQuali-Projektes mit dem Ziel der Bestimmung der Materialkenngrößen.
The Konrad repository for not heat generating radioactive wastes was licensed first in 2002. But due to legal actions this license has not been finally confirmed before 2007. Subsequently, the Federal Office for Radiation Protection (BfS) began scheduling backfitting of the former iron ore mine into a repository. The licensed repository volume is 303,000 m3 based on estimations of expected waste volumes to be disposed off although the mine itself would offer a much larger volume. Once the repository is ready for Operation, waste packages can be disposed, but this is not expected before the end of this decade. Nevertheless, there is already today a great interest in qualified and certified waste conditioning and packaging for disposal requiring Containers, tested, evaluated and certified by BAM and BfS.
Key points of the Konrad license concern comprehensive requirements for waste products and Containers. Details are described in BfS reports, which constitute the basic documents for the license. Following the final license confirmation a revision of these documents has been requested in order to include considerations of water poisoning substances. This work is currently done by BfS in Cooperation with the NLWKN of Lower Saxony and the Institute for Safety Technology (ISTec). Concerning the specification for Containers themselves no or only minor changes are expected.
Concrete containing lightweight aggregates has been known since ancient times. To reduce weight, natural aggregates of volcanic origin, such as crushed lava or pumice, were used in construction purposes, for example for the Pyramids during the Mayan period in Mexico or for monumental structures in the Roman Empire. The most famous examples of this first application of lightweight aggregate concrete (LWAC) in Europe are certainly the Colosseum and the Pantheon. The Roman constructors used natural as well as artificial aggregates, such as pumice, crushed lava and crushed brick, to realise lightweight concrete applications in parts of these buildings. Still today, pumice is used in Germany, Italy, Japan and Iceland as aggregate for structural lightweight concrete.
Self-ignition behavior of mixtures of methane and oxygen was investigated in a temperature range from 600 to 800°C. Variations of mixture composition, inert gas content, temperature and filling rate of the ignition autoclave were carried out in order to establish process boundaries for high temperature partial oxidation processes. The tests show that considerably high methane contents are needed to avoid an ignition. Heating-up tests show that ignition is possible at surprisingly low temperatures. This can be attributed to pre-ignition reactions that produce more instable intermediates.
In contrast to other simulation fields like forming simulation, welding simulation is still not widely used in industrial environments. A high user expertise, a high time-to-solution and the result accuracy are the most important problems that hinder its extensively application. Different modeling approaches influence these aspects and an analysis of their implementation is of interest especially for the automotive industry as a key user for production Simulation.
Concrete is by far the most common building material in the world. Due to its good durability it is widely used in building envelopes. One major part of the embodied energy in concrete comes from the production of Portland cement that consumes around 3,500 MJ energy per each ton of cement. Globally 2.6 billion tons of Portland cement is produced and the consumption is increasing. Since concrete will be used as main building material also in future construction, it is reasonable to develop concrete building components with lower embodied energy.Using the example of an ultra-high performance concrete (UHPC) façade element, it is demonstrated how the embodied energy can be reduced by application of hydrothermal curing.
The influence of paper type and state of degradation on laser cleaning of artificially soiled paper
(2011)
Lasers can be a supplemental tool for restorers to overcome some of the limitations of traditional dry cleaning techniques for works of art on paper. The laser working range has to be optimized allowing for safe removal of contamination and limitation of damage to the substrate. This paper addresses the influence of paper type and state of degradation on laser working range. Three types of new paper (pure cellulose, bleached pulp paper, rag paper) were degraded and characterized with respect their degree of polymerization. Laser-induced damage thresholds of new and degraded paper were determined using SEM and viscometry. Additionally, artificially soiled model samples were made using two kinds of soiling, namely pulverized charcoal and soot-blackened standard test dust. Cleaning thresholds of soiled paper samples were evaluated. A working range for all combinations of paper and soiling between 0.05 J/cm2 and 0.5 J/cm2 was found for the application of 8-ns laser pulses at 532 nm wavelength.
Unter dem Motto „Innovation und Qualitätssicherung in der (Bio)Analytik“ werden in der Arbeitsgruppe Fluoreszenzspektroskopie der BAM, Bundesanstalt für Materialforschung und -prüfung, funktionelle Chromophor-Systeme, einfache Signalverstärkungs- und Multiplexingstrategien sowie innovative Validierungs- und rückführbare Standardisierungskonzepte für verschiedene fluorometrische Messgrößen und Methoden entwickelt. Im Mittelpunkt stehen dabei molekulare Fluorophore, Nanokristalle mit größenabhängigen optischen Eigenschaften (sogenannte Quantenpunkte, QDs) und fluoreszierende Partikel variabler Größe sowie Sonden und Sensormoleküle für neutrale und ionische Analyte und für die Charakterisierung von funktionellen Gruppen. Dabei erfolgen auch methodische Entwicklungen für die Fluoreszenzspektroskopie, die Fluoreszenzmikroskopie, die Milcrofluorometrie, die Sensorik und die Mikroarraytechnologie. Ziele sind u. a. das Design und die Untersuchung von multiplexfähigen selektiven und sensitiven Sonden für die Biomarkeranalytik, die Entwicklung von Methoden zur Charakterisierung der signalrelevanten Eigenschaften dieser Chromophor-Systeme und zur Charakterisierung von funktionellen Gruppen an Oberflächen und ihre Validierung sowie die Entwicklung und Bereitstellung von formatadaptierbaren, flexibel ersetzbaren
Standards für die fluoreszenzbasierte Multiparameteranalytik.
Das Endlager Konrad wurde bereits im Jahr 2002 als Endlager für nicht Wärme entwickelnde radioaktive Abfälle genehmigt. Jedoch wurde diese Genehmigung anschließend beklagt und konnte erst 2007 in letzter Instanz bestätigt werden. Nachfolgend hat das Bundesamt für Strahlenschutz (BfS) mit der Planung und Realisierung zum Umbau des ehemaligen Eisenerzbergwerkes zum Endlager begonnen. Das genehmigte Endlagervolumen beträgt 303.000 m3 und basiert auf Abschätzungen für die zu erwartende Abfallmenge. Das Bergwerk selbst böte ein deutlich größeres Volumen. Mit der Einlagerung von Behältern kann allerdings erst nach Fertigstellung des Endlagers und nach derzeitigem Stand voraussichtlich nicht vor Ende dieses Jahrzehnts gerechnet werden. Gleichwohl besteht bereits heute ein hohes Interesse an der endlagergerechten Konditionierung und Verpackung der für Konrad vorgesehenen radioaktiven Abfälle, wofür nicht zuletzt von der BAM bauartgeprüfte und vom BfS zugelassene Behälter erforderlich sind.
Kernpunkte der Endlagergenehmigung sind umfassende Anforderungen an Abfallprodukte und Behälter. Einzelheiten sind in den vom BfS der Genehmigung zu Grunde liegenden Berichten und Endlageranforderungen definiert. Diese enthalten vor allem Anforderungen an die Abfallprodukte und an die zu deren Verpackung erforderlichen Behälter. Mit der Genehmigungserteilung wurde auch eine Überarbeitung dieser Endlageranforderungen und hinsichtlich der Berücksichtigung Wasser gefährdender Stoffe gefordert. Diese Arbeiten werden derzeit vom BfS in Zusammenarbeit mit dem Niedersächsischen Landesbetrieb für Wasserwirtschaft, Küsten- und Naturschutz (NLWKN) und dem Institut für Sicherheitstechnik (ISTec) vorgenommen. Hinsichtlich der Anforderungen an die Endlagerbehälter wird allerdings davon ausgegangen, dass die für die Behälterbauartprüfung wesentlichen abfallprodukt- und behälterspezifischen Anforderungen davon nicht oder nur unwesentlich berührt sein werden.
Vibrationsprüfungen an sicherheitskritischen Ventilen: Zwei Beispiele aus Forschung und Anwendung
(2011)
Ventile für gasförmige Medien müssen neben dem Druck oft auch Vibrationsbelastungen durch ihren Einsatz ertragen.
Die dadurch entstehenden Massenkräfte können die Funktion des Ventils beeinflussen, indem z. B. die Anpresskraft im Ventilsitz dadurch verändert oder die Betätigungseinrichtung verstellt wird. Die schwellenden oder wechselnden Beanspruchungen können auch zu Ermüdungsschäden und damit zu dauerhaftem Funktionsverlust führen.
Bei der Vibrationsprüfung für ein pneumatisch ausgelöstes Schnellöffnungsventil eines CO2-Feuerlöschsystems wurde die relevante EN 12094-4 angewendet. Diese setzt Mindestanforderungen in Hinblick auf die Schwingfestigkeit durch eine Gleitsinusprüfung.
Im Gegensatz dazu steht die im Rahmen eines Forschungsvorhabens durchgeführte Vibrationsprüfung an einem Sicherheitsventil für Tanklastwagen, bei der ein umfangreicheres Prüfprogramm erstellt wurde, um vibrationsabhängiges Ansprechen des Ventils zu untersuchen.
The strength of laminates distinctly depends on the transverse strength of the laminas. The transverse failure is dominated by the adhesion between fiber and matrix. Usual strength criteria however do not take into account the adhesive strength explicitly. The determination of the interface strength is performed on the micromechanical scale using single fiber specimens. The fibers are loaded under off-axis loading while the debonding is monitored under a microscope. The stresses acting in the Interface are calculated by finite element analyses. It is found that for off-axial angles up to 35° interfacial debonding is the dominant failure mode while fiber breakage takes place at lower angles. The occurrence of fiber breakage and debonding under off-axis loading shows that the restriction to two potential failure planes - perpendicular or parallel to the fibers - as applied in common failure criteria has to be put in question.
Ingress of moisture and harmful ions (e.g. Chloride, sulfate) into cementitious materials is one of the major factors in defining their durability. Modifications of building materials by targeted deposition of surface functional agents that make the surface hydro- and/or oleophobic aim to minimize moisture and ion ingress, and thus extend Service life of the cement based structures. Water repellent and easy-to-clean coatings for inorganic Substrates have gained strong attention during the last few years and various formulations based on silicones or alkylpolysiloxanes have been developed. Cementitious building materials are highly complex Systems with many components and changing properties in the course of a building’s Service life. The interactions between the Chemical agents and the cement based materials depend on many factors. The Chemical properties of the material Substrate appear to be the most important but in the context of their influence on the functionality of silanes and/or siloxanes these characteristics have not been well understood yet. The aim of this study was to evaluate the effect of different blended cements on water repellent agents’ performance. Two organosilicon compounds
were applied on fresh blended cements containing limestone (L), fly ash (F), slag (S) and trass (T), and investigated in terms of their functionality.
The surface properties of functionalized blended cements were studied based on wettability, i.e. contact angle measurements, before and after exposure to artificial and natural weathering. The first results indicate that slag and trass more distinctly affect the water repellent Surface performance after aging.
DGZfP - Merkblatt elektrochemische Potentialmessungen zur Detektion von Bewehrungsstahlkorrosion
(2011)
Im DGZfP- Fachausschuss für zerstörungsfreie Prüfling im Bauwesen - Unterausschuss Korrosionsnachweis bei Stahlbeton haben sich die Universitäten München, Aachen, Stuttgart und Braunschweig sowie die BAM Berlin an der Überarbeitung des Merkblatts B 3: „Elektrochemische Potentialmessungen zur Detektion von Bewehrungsstahlkorrosion“ beteiligt. Das Merkblatt wurde komplett überarbeitet und bietet jetzt umfangreichere Hinweise zur Durchführung der Messungen und deren Auswertung. Wesentlich stärker als zuvor geht das Merkblatt auf mögliche Einflüsse und Fehlerquellen sowie die für eine Interpretation der Daten notwendigen begleitenden Bauwerksuntersuchungen ein. Die nachfolgenden Ausführungen greifen einige wesentliche Aspekte in enger Anlehnung an die Ausführungen des Merkblatts B3 auf. Das vollständige Merkblatt ist über die DGZfP e.V. online zu beziehen.
The goal of this study was to find a correlation between cleaning efficacy of substrates protected with anti-graffiti systems (AGS) and their porosity, surface roughness, and composition as well as usability of the Technical Testing Guideline for Anti-Graffiti Systems (TP-AGS, issued by BASt) for natural stone and brick/clinker masonry. The results showed that the cleaning efficacy mainly depends on the porosity of the substrate and the type of AGS. Also, higher surface roughness contributed to a lower cleaning efficacy. The results showed also that concrete panels and cement joints in masonry represented the worst case. The color change of all substrate materials compared to concrete was mostly within acceptable limits. Gloss changes were significant for a number of substrates. In particular, several of the wax-treated low-porosity substrates exceeded the threshold value of 10. The limit of water vapor permeability of the AGS prescribed in the TP-AGS might be too high for natural stone substrates. In general, the TP-AGS is useful for the determination of the efficiency factor of anti-graffiti agents on various substrates.
Die Bundesanstalt für Materialforschung und -prüfung (BAM) führt im Rahmen einer Verwaltungsvereinbarung mit dem Bundesamt für Strahlenschutz (BfS) Bauartprüfungen für Behältertypen durch, die für die Endlagerung von nicht wärmeentwickelnden radioaktiven Abfällen in das Endlager Konrad vorgesehen sind.
Zur Erlangung einer Eignungsbestätigung einer Behälterbauart für das Endlager Konrad müssen die Antragssteller die Einhaltung der vom BfS festgelegten behälterspezifischen Anforderungen nachweisen. Zentrale Bestandteile der Bauartprüfung sind die Sicherheitsnachweise zur Behälterauslegung gegen mechanische Betriebs- und Störfallbelastungen sowie gegen thermische Störfallszenarien. Die Prüfanforderungen umfassen hierbei Stapeldruckprüfung, Hebeprüfung, Fallprüfung, thermische Prüfung (Brand), ggf. einschließlich Dichtheitsprüfung zum Nachweis der Einhaltung von Dichtheitsanforderungen.
Neben der Nachweisführung mittels sogenannter Baumusterprüfungen oder Obertragbarkeitsbetrachtungen können die Nachweise alternativ mittels numerischer Sicherheitsnachweise erbracht werden, sofern deren hinreichende Verifikation nachgewiesen wird, Dies kann u. a. durch den Vergleich mit hinreichend gesicherten experimentellen Ergebnissen geschehen, Die hier vorgestellten Untersuchungen sind Teil des internen Forschungsprojektes ConDrop der BAM, das zum Ziel hat, erweiterte Prüfmethoden zur Fallprüfung an Stahlblechcontainern für das Endlager Konrad mittels numerischer Beanspruchungsanalyse zu entwickeln. Dazu soll ein Finite-Elemente-(FE)-Modell entwickelt und mit experimentellen Daten, die in Fallversuchen ermittelt werden, verifiziert werden.
Although identified on the basis of so-called instationaiy creep-tests the constifrvtive model of Eurocode 3 (EN 1993-1-2, 2010) - hereinafter refened to as EC3 - represents a non-linear rateindependent relationship between stress and meclianical strain. I.e. the experimentally observed phenomenou of creep at constant stress but linear time varying temperature is described only through the temperature dependence of the material parameters characterizing the EC3 constitutive model. As a consequence some important phenomena cannot properly be described: E.g. creep or relaxation at constant temperature, creep or relaxation at non-monotonic temperature rates or sensitivity of the instationary creep process on the temperatme rate.
The concept and technical details of the implementation of the developed integrated monitoring system within the IMO-WIND project are presented. The tasks of the components of the system and its requirements are described. Selected results from the continuous monitoring during operation of the plant M5000_2 regarding the task design verification and dynamic structural analysis are given.
Main topics of the research project BEGLARES are the restoration of "dalle de verre" concrete Windows and the development of repair techniques and mortars. This project is executed in Cooperation between Glasmalerei Peters GmbH, the University of York and the BAM Federal Institute for Materials Research and Testing. It is funded by the Federal Ministry of Economics and Technology. The main mechanism of damages, the development of repair mortar and special test specimens are presented.
Paper is one of the most important materials representing and witnessing human culture particularly as a carrier medium for text and image. As soiling hampers the reception of information, paper cleaning techniques are needed. Traditional mechanical and chemical cleaning methods are used by conservator-restorers. In some cases, a classical cleaning procedure of paper objects yields unsatisfactory results or a conventional treatment is even impossible. Especially, fragile paper objects cause problems due to mechanical instabilities. Laser cleaning as a non-contact method might be a way to overcome some of the limitations of classical cleaning techniques. Laser parameters have to be chosen to achieve removal of the soiling without influencing the artwork. Any immediate as well as long-term effects causing an irreversible change of the artwork have to be avoided. At present, most laser applications are found in stone and metal conservation, while laser treatment of complex organic materials like paper is still not fully developed for application in conservators' workshops. This contribution describes recent work of pulsed laser cleaning of soiled model samples. Pure cellulose, rag paper and wood-pulp paper were mechanically soiled with pulverized charcoal in a standardized procedure to make model samples representing essential characteristics of contaminated real-world artworks. Afterwards, model samples were cleaned using short and ultrashort laser pulses in the nanosecond and femtosecond time domain, respectively. An extensive analysis of the model samples after laser treatment using an optical microscope and a multi-spectral imaging system allows a comparison of the cleaning results obtained with both laser sources.
The 9 meter drop onto an unyielding target is one of the important mechanical tests within the safety assessment of transport casks for radioactive material. In general, the cask is equipped with impact limiters to reduce the dynamic load on the cask body by absorbing a major part of the kinetic energy. The impact limiters are often made of wood or aluminium. In this study an elastic-plastic material model with volume change was used to describe the stress-strain behaviour of wood found in crush tests. For aluminium, an elastic-incremental plastic material model with Cowper-Symonds parameters for strain rate depending material hardening was used to model the adiabatic stress-strain relations measured at specimens at constant ambient temperature. Hereafter simulations with a sophisticated finite element model were carried out and compared with different drop tests. Four drop tests of a half-scale cask model equipped with wood and aluminium impact limiters with different drop positions were selected to investigate the impact limiter behaviour during a 9 meter drop test. All drop tests were simulated with the same FE mesh but under different boundary and initial conditions.
This paper describes a structural reliability analysis utilizing monitoring data in the ultimate limit state with consideration of the uncertainties of the monitoring procedure. For this purpose the uncertainties of the monitoring data are modeled utilizing a new framework for the determination of measurement uncertainties. The approach is based on a process equation and Statistical models of observations for the derivation of a posterior measurement uncertainty by Bayesian updating. This facilitates the quantification of a measurement uncertainty using all available data of the measurement process. For the reliability analysis in the ultimate limit state, monitoring data can be utilized as a loading model Information and as proof loading, i.e. resistance model Information. Both approaches are discussed with generic examples and it is shown that the modeling of monitoring data in a reliability analysis can result in a reduction of uncertainties and as a consequence in the reduction of the probability of failure. Furthermore, the proof loading concept is developed further to account for the uncertain characteristic of proof loading due to the measurement uncertainties which is consistent with the framework for the determination of measurement uncertainties. These approaches and findings can be utilized for the assessment of structures for life cycle extension and the design of monitoring Systems.
To ensure a high operational reliability of offshore wind turbines (OWEC) with economically acceptable repair and maintenance efforts, comprehensive diagnosis and supervision concepts are required. Automatic monitoring Systems will be an essential part of such concepts. Because of the fact, that during Operation there will be static and dynamic interaction between the components ‘structure’, ‘machinery’ and ‘blades’ it is necessary to develop the monitoring techniques in an overall concept. These monitoring Systems are supposed to be applied for the design and testing as well as for the Operation and maintenance phases. The knowledge of the dynamic behavior of wind turbines is important both for the design and for a safe Operation. The available monitoring data from a period of three years, allow first conclusions on the long-term Operation of such Systems in terms of quality requirements to the instrumentation to the structure and the rotor blades
Standardized test methods by which the efficacies of conventional Chemical wood preservatives against insects determine their toxic effects against larvae of wood boring beetles or their feeding prevention by termites. Although alternative control strategies to the application of biocides exist, such as interference with insect behavior during mating or when searching for suitable breeding and feeding sites, their acceptance, too, depends on efficacy evaluation. This is why new test set ups are needed which take behavior modifying control strategies into account. This paper will demonstrate how new laboratory tests must be designed or how existing Standards can be altered to reliably interpret insect behavior including its successful manipulation in a standardized format.
The geological storage of carbon dioxide (Carbon Capture and Storage, CCS) in depleted gas reservoirs or in saline aquifers is a widely discussed issue. Carbon dioxide may induce corrosion on the piping steels during compression, transportation and injection. Therefore,
selection of appropriate piping steels is a key factor in order to increase the safety and reliability of the CCS technology, and to keep the processes cost-effective.
The here described subproject of the COORAL project (German acronym for “C02 purity for capture and storage”) deals with the levels of impurities in the C02 stream that will be acceptable when using specific steels. Material exposure to carbon dioxide (C02) containing
specific amounts of water vapor, oxygen (02) sulfur dioxide (S02), nitrogen dioxide (N02), carbon monoxide (CO) can be a challenge to steels. Within this subproject 13 different Steels are tested for suitability as materials used for compression, transportation and injection Units within the CCS chain.
Fibre-optic sensors for early damage detection in plastic insulations of high-voltage facilities
(2011)
Fibre-optic sensors (FOS) have great potential as online damage detectors when integrated in HV accessories. Among their well-known use as temperature and strain sensors, there are some more opportunities of use, e. g. they can intimately be embedded in polymeric insulations of HV cable terminations and joints to detect and monitor partial discharges right at the location of their origin. Two FOS types for early PD detection were investigated: an embeddable fibre-optic acoustic sensor to measure acoustlc waves in polymeric insulations generated by PDs, and a fluorescent optical fibre to detect first optical effects during ionization processes in the insulation material. The paper descrlbes these methods, related monitoring Problems and shows first test results.
Fiber optic sensors are increasingly used because of their outstanding performance or if special requirements avoid the application of conventional electrical sensors. The scientific background for optical fiber sensors is well developed; however, the characteristic of sensors applied in rather harsh environment are almost always different from characteristics determined in laboratory or before its installation. In order to achieve long-term stable function and reliable measurement data after application and under harsh environmental conditions, guidelines for characterization and specification of sensor components are needed as well as methodologies for testing the sensor performance must be developed. Performance tests carried out revealed that there are still some restrictions with respect to long-term reliable use: first, some sensor products available on the market are not very often appropriately characterized, described and validated; second, application procedures are not always defined due to a lack of understanding the micromechanical issues in the interface zone between sensor and measuring object. Application procedures and profound knowledge of materials behaviour are necessary to get results from the sensor that can be reliably used. The paper describes first guidelines to prove the quality of fiber optic strain sensors, a testing facility developed for unbiased tests and certification of surface-applied sensors as well as result from comparison of commercially available strain sensors.
Residual stresses arising during welding, especially in high energy beam welding, can reach levels up to the material specific yield strength causing service life mitigating consequences through stress relaxation or stress corrosion cracking. A number of processes were developed like stress relief annealing or the low-stress-no-distortion-technique to reduce these stresses.
But such methods are only applicable for wider welds and simple component geometries or they are cost-intensive. The method presented in this paper uses the welding beam after welding in a defocused mode for heating the material regions in a certain distance from the weld on both sides. With this process it is possible to decrease the stresses in small welds with high stress gradients without any contact surfaces or additional equipment. Dependent on the component geometry and on the laser power it is possible to use different parameters for this process. The adjustable process parameters are the radius and the power of the defocused beam and the transversal and longitudinal distances between the welding and the defocused beam. In this work the mechanism and the influence of the process parameters are investigated by FEM-simulation and a number of experiments on the ferritic steel S355J2+N with 5 mm thickness. The best experimental result presented in this paper shows a stress reduction of about 73 %.
Die ZfP versucht mit Hilfe von Messdaten, die sie aus z. B. einer Impuls-Echo-Messung gewinnt, Rückschlüsse auf die innere Struktur eines Objektes zu ziehen. Bei Betonbauteilen sollen im Besonderen Verpressfehler, die dann zur Korrosion und damit zur einer Beeinträchtigung der Standsicherheit und Dauerhaftigkeit des Konstruktion (z. B. einer Spannbetonbrücke) führen können, schnell und mit einer hohen Sicherheit aus den Messdaten lokalisiert werden. Das konventionellen SAFT oder FT-SAFT-Verfahren liefern in Verbindung mit einer Phasenauswertung einen schnellen und sicheren Hinweis darauf, dass ein Lufteinschluss/Defekt vorliegt. Darüber hinaus können jedoch Rückausbreitungs-Verfahren, wenn ein gutes Geschwindigkeitsprofil vorliegt, eine wesentlich bessere Lokalisierung des Defekts bieten als SAFT-Verfahren, jedoch mit dem Nachteil, dass sie sehr zeit- und rechenintensiv sind, vor allem im Dreidimensionalen. Als Mittelweg kann hierzu die "One-Way"-Methode dienen. Diese Methode verwendet Pseudo-Differential-Operatoren und ist sehr robust auch bei relativ groben Geschwindigkeitsprofilen. Sie wird an Beispielen aus der Bauwerkdiagnose mit den konventionellen Verfahren verglichen.
Three new offset Delta11B isotope reference materials for environmental boron isotope studies
(2011)
The isotopic composition of boron is a well established tool in various areas of Science and industry. Boron isotope compositions are typically reported as 5nB values which indicate the isotopic difference of a sample relative to the isotope reference material NIST SRM 951.
A significant drawback of all of the available boron isotope reference materials is that none of them covers a natural boron isotope composition apart from NIST SRM 951. To fill this gap of required 5UB reference materials three new solution boric acid reference materials were produced, which cover 6096o of the natural boron isotope Variation (-20 to 40%oo B) of about 100%o. The new reference materials are certified for their B values and are commercially available through European Reference Materials® (http://wwrv.enn-cmi.org). The newly produced and certified boron isotope reference materials will allow straightforward method Validation and quality control of boron isotope data.
Eine stets optimale Nutzung von Anlagen, Rohstoffen und Energie in Verbindung mit einer guten Prozessführung sind die wichtigsten Voraussetzungen für globale Wettbewerbsvorteile der Chemisch Pharmazeutischen Industrie und für die Branchen Energieerzeugung, Petrochemie, Nahrungsmittel, Papier- und Zellstoff oder Wasserversorgung. Überlegene Verfahren erfordern die fortwährende Kontrolle der geforderten Produktqualität, ihre präventive Sicherstellung und eine ständige Verbesserung des Wissens über den Prozess. Sensoren helfen dabei, alle wichtigen Messgrößen an kritischen Stellen transparent zu machen.
Sie sind die 'Sinnesorgane der Prozessleittechnik' für automatisierte Verfahren. Allein aufgrund stetig wachsender Anforderungen an Sensoren ergibt sich für viele Messaufgaben die Notwendigkeit einer ständigen Verbesserung der Sensoren. Für völlig neue Aufgaben müssen jedoch neue Messprinzipien gefunden werden, weil heute noch keine Sensor-Technologie existiert oder die wachsenden Anforderungen nicht mehr allein durch Weiterentwicklung bestehender Technologien erfüllt werden können.
Ende 2009 wurden Anforderungen und Wege für die konsequente Weiterentwicklung und Verbesserung von Prozess-Sensoren aus Anwendersicht aufgeschrieben. Das Projekt wurde von NAMUR und GMA initiiert und gemeinsam mit Industrieanwendern und Geräteherstellern als Technologie-Roadmap 'Prozess-Sensoren 2015+' veröffentlicht.
Was ist aus den Wünschen seither geworden? Wie kann die Umsetzung dieser Entwicklungsziele von den Geräteherstellern wirtschaftlich und marktgängig erfolgen? Wie werden neuartige Forschungsziele mit der angemessenen Forschungsförderung am besten vorangebracht?
The traceabiiity requirements for certification analyses of reference materials are much more stringent than for routine analysis, where certified matrix reference materials (CRM) can be used for calibration and to establish traceabiiity. Although the ISO-Guides related to CRM production and certification are not fully clear concerning calibration, many established CRM-producers do not accept matrix-CRMs for calibration in case of certification analyses, e.g. to avoid circular reasoning. These requirements limit the methods used for certification to those that can be calibrated using Standards of known high purity and stoichiometry or mixtures of such Standards. Powerful solid sampling techniques such as glow discharge mass spectrometry (GD-MS) or spark-optical emission spectrometry (SOES), where usually compact CRMs are used for calibration, seem not be applicable for certification analyses. Especially GD-MS is a powerful tool for trace element determination of solid samples. Beside metallic impurities the use of specific gas mixtures enables also the determination of interesting nonmetallic impurities such as sulfur and phosphorus. Within BAM a calibration approach, was developed which enables to use mixtures of Standards of known high purity and stoichiometry also for GD-MS. Analogue to matrix adaption in solution based techniques, the calibration approach is based on doped pressed powder pellets.
Approach and application on the certification analyses of copper and Steel CRMs are presented.
Im Zuge des Forschungsvorhabens ENREA (Entwicklung rechnerischer Analysemethoden für stoßdämpfende Strukturen beim Anprall oder Absturz von Abfallgebinden) führt die BAM systematische Untersuchungen an stoßdämpfenden Werkstoffen, unter anderem an Fichtenholz, durch. Zweck der mit diesen Untersuchungen erzeugten Datenbasis ist die Erstellung und Parametrierung eines Finite-Elemente- (FE-) Materialmodells, das die Modellierung holzgefüllter stoßdämpfender Bauteile von Transportbehältern für radioaktive Stoffe in der FE-Simulation ermöglichen soll.
Anhand von Ergebnissen aus der ersten Versuchsphase werden der Einfluss der Dehnrate und der Faserorientierung auf das Kraft-Verformungs-Verhalten von Fichtenholz diskutiert. Anschließend wird die rechnerische Modellierung von Fichtenholz diskutiert und die Anforderungen an ein Materialmodell werden erläutert.
Während des Transportes sind Behälter für hoch radioaktive Abfälle durch stoßdämpfende Bauteile vor Einwirkungen, die aus Unfallszenarien gemäß den IAEA Regularien resultieren können, weitestgehend geschützt. Nach dem Entfernen dieser Komponenten im Rahmen der Einlagerung ins Zwischenlager müssen Vorkehrungen getroffen sein, um Beanspruchungen der Behälter aus möglichen Handhabungsunfällen im Empfangsbereich zu reduzieren. Die Maßnahmen müssen vor allem darauf abzielen, die stoßdämpfenden Eigenschaften der potentiellen Aufprallflächen zu optimieren. Da Standardmaterialien für Fundamente nur ein geringes Energieabsorptionsvermögen aufweisen, wurde durch die Firma HOCHTIEF eine neuartige Betonmixtur entwickelt, bei der ein spezieller Leichtzuschlag zum Einsatz kommen. Zur Charakterisierung dieses sogenannten Dämpferbetons liegen Standardkennwerte vor sowie Messwerte aus Eindringversuchen, die zur Qualitätssicherung für jede Produktcharge durchgeführt werden. Das stoßdämpfende Potential des neuen Werkstoffs kann jedoch nur dann vollkommen ausgeschöpft werden, wenn die Energieabsorption in numerischen Simulationen der Behälterabstürze über die gesamte Belastungsdauer zuverlässig wiedergegeben wird. Für die Implementierung und Anpassung eines entsprechenden Materialmodelis in einem Finite Elemente (FE) Programm
sind Daten aus systematischen Druckversuchen mit Variation der relevanten Einflussgrößen erforderlich. An der BAM werden daher im Rahmen eines werkstoffübergreifenden Forschungsvorhabens zur Untersuchung von stoßdämpfenden Strukturen auch die Eigenschaften von Dämpferbeton experimentell untersucht und zugehörige numerische Methoden entwickelt. Der aktuelle Beitrag behandelt die Ergebnisse der ersten Projektphase, in der kubische Probekörper mit der Kantenlänge 100mm bei unterschiedlichen Lagerungsbedingungen statisch und dynamisch gestaucht wurden. In nachfolgenden Versuchen wird der Einfluß der Probengröße ermittelt sowie die Eignung der verwendeten Materialmodelle anhand realistischer Belastungssituationen validiert.
Versuchsprogramm.
Metal seals are in common use as an essential component for the leak tight closure of transport and storage casks for spent fuel and vitrified high active waste from reprocessing. They are placed between the massive monolithic cask body made of ductile cast iron or forged steel and the primary and secondary lids, which are fixed with screws around the lid circumference, in order to ensure long term safe enclosure of the radioactive cask inventory. Hereby, long term reliable pressure forces in combination with a tight surface contact are as important as well maintained seal and surface qualities and dry and clean conditions during seal assembly and operation. A few years ago BAM started systematic investigation on the long term seal behavior with re-spect to longer storage periods and seal behavior in accidental cask scenarios with dynamic de-formations of the seal groove geometry or short term drop in pressure force up to lid lifting. BAM has developed test flanges for seals with full scale cross section diameter but much small-er outer diameter to gain representative data for metal-sealed lid systems. They are placed in appropriate testing machines for relevant mechanical loading under static and dynamic condi-tions with the ability to measure the standard helium leakage rate continuously during each test phase. This paper focuses on BAM long term tests of different seal types with aluminum and silver jackets at three different temperatures of +20°C, +100°C and +150°C under static conditions over longer periods of time. Due to creeping effects, a reduction of the pressure force does ap-pear during loading and unloading depending on prior holding times. So far, test results of up to 2 years indicate a clear correlation between seal pressure forces and holding time, temperature and seal type allowing for extrapolating to much longer periods of time. The paper presents basic correlations, test and evaluation procedures as well as important provisional results and gives an outlook on further investigations.
In Germany the concept of dry interim storage of spent fuel and vitrified high active waste in dual purpose metal casks is implemented (currently for periods of up to 40 years). The casks being used have an approved package design in accordance with the international transport regulations. The license for dry storage is granted on the German Atomic Energy Act with respect to the guidelines of the German Reactor Safety Commission for dry interim storage of spent fuel. Currently part of the assessment process of the cask design for transport on public routes is to evaluate the suitability of the used materials with respect to their properties and their compatibility for possible transport periods. For transport on public routes during or after long term interim storage periods, it has to be ensured that the transport and storage casks fulfill the specifications of the transport approval or other sufficient properties which satisfy the proofs for the compliance of the safety objectives at that time. This paper describes the state-of-the-art technology in Germany and points out arising prospective challenges and which related questions have to be answered in future. Present research and knowledge concerning the long term behavior of transport and storage cask components (such as gaskets and shielding components) have to be consulted as well as experiences from interim cask storage operations. Challenges in the safety assessment are therefore i.e. the behavior of aged metal and elastomeric gaskets under IAEA test conditions to ensure that the results of drop tests can be transferred to the compliance of the safety objectives at the time of transport after the interim storage period (aged package). Assessment methods for the material compatibility, the behavior of fuel assemblies and the aging behavior of shielding parts (e. g. influence of radiation) are further issues as well.
In Deutschland werden zwei Arten von radioaktiven Abfällen unterschieden: Wärme entwickelnde Abfälle und Abfälle mit vernachlässigbarer Wärmeentwicklung. Im Endlager Konrad werden ausschließlich radioaktive Abfälle mit vernachlässigbarer Wärmeentwicklung endgelagert (im internationalen Sprachgebrauch: schwach- und mittelradioaktive Abfälle). Solche Abfälle stammen zum Beispiel aus dem laufenden Betrieb, der Stilllegung und dem Rückbau von Kernkraftwerken, aus der Forschung, der Medizin oder von der Bundeswehr und beinhalten unter anderem kontaminierte Baustoffe, Schrott, Werkzeuge, Schutzkleidung, Schlämme und Suspensionen. Vor dem Endlagern dieser Abfälle werden sie konditioniert, d. h. die festen Abfälle werden teilweise zerkleinert, verpresst oder zementiert, flüssige eingedampft oder zementiert und häufig anschließend in Fässer verpackt. Im nächsten Schritt werden die konditionierten Abfälle in Abfallbehälter verpackt. Geeignete Behältertypen sind (gemäß IM, 121) kubische Container oder Rundbehälter mit definierten Abmaßen aus Stahlblech, Beton oder Gusseisen. Diese Abfallbehälter sind für die Endlagerung, für eine vorausgehende längerfristige Zwischenlagerung sowie ggf. für den Transport über öffentliche Verkehrswege zu qualifizieren.
Within the framework of the G8 partnership, the German Ministry of Economics and Technology has been realizing a 300 EUR million project of the storage of decommissioned Russian nuclear submarines based on a German-Russian agreement. The main parts of the project are the construction of the long-term storage facility as well as a radioactive waste storage facility at Sayda Bay. Long-term interim storage facility for this particular case has a period of about 70 years. The Energiewerke Nord GmbH (EWN) under the technical controlling of BAM carried out the project management. Foremost in this presentation is the finalization of the long-term storage facility for nuclear submarine compartments and the planning and realization of the radioactive waste storage building with special emphases of the parts carried out by BAM. Because BAM staff cannot stay permanently on site, a random inspection of different topics was the bases for the activities of BAM. The key aspects of activities are the long-term storage of the nuclear compartments, maintenance building, the decommissioning of the compartments and the transportation of the very heavy weight compartments (1600 metric tons). Details relating of the progress of the construction work as well as information about technical recommendations will also be briefly illustrated. Within this scope, problems and difficulties during the construction of the storage facility as well as logistical challenges including transportation of the reactor compartments will also be discussed.
Die mechanische Beanspruchung von Transport- und Lagerbehältern für radioaktive Stoffe gemäß den durch die IAEA vorgegebenen Prüfszenarien oder bei Unfällen, die während der Handhabung in einer kerntechnischen Anlage auftreten können, wird maßgeblich durch das Design der Stoßdämpfer und die Eigenschaften des jeweiligen Untergrundes beeinflusst. Da der Nachweis der Behälterintegrität und -dichtheit häufig an numerische Simulationen gekoppelt ist, sind für die sicherheitstechnische Auslegung der Konstruktion zuverlässige Informationen über das Energieabsorptionsvermögen der Werkstoffe und eine geeignete Umsetzung dieser Daten in FEM - Programme erforderlich. Die im Rahmen von Falluntersuchungen bei der BAM festgestellten, teilweise erheblichen Abweichungen zwischen experimentellen und berechneten Größen sind entsprechend darauf zurückzuführen, dass die zur Verfügung stehenden numerischen Verfahren das komplexe Verhalten der stoßdämpfenden Strukturen
nicht ausreichend präzise wiedergeben. Hiervon besonders betroffen sind Bauteile aus Holz und Polyurethan-Schaum (PU-Schaum), die zur Konstruktion von Behälterstoßdämpfern für die Transportkonfiguration eingesetzt werden, sowie Dämpferbeton, der in ausgewählten Bereichen im Fundament von Standort-Zwischenlagern eingebaut wird. Um die zugehörigen Materialmodelle weiter zu entwickeln und die dafür erforderliche Datenbasis zu schaffen, hat die BAM vor knapp zwei Jahren das vom BMBF geförderte Forschungsvorhaben ENREA (Entwicklung rechnerischer Analysemethoden für stoßdämpfende Strukturen beim Anprall oder Absturz von Abfallgebinden) gestartet. Wesentlicher Bestandteil ist ein systematisches Versuchsprogramm, bei dem die drei genannten Werkstoffe statisch und dynamisch hohen Druckbelastungen ausgesetzt werden. Relevante Versuchsparameter sind, neben der Dehnrate, die Temperatur und Lagerungsbedingungen sowie die Orientierung des Werkstoffes hinsichtlich der Belastungsrichtung. Dieser Beitrag präsentiert die wichtigsten Ergebnisse aus der ersten Versuchsphase, die durch weggesteuerte Versuche mit konstanten Prüfgeschwindigkeiten von 0,02 mm/s und 3000 mm/s gekennzeichnet ist. Darüber hinaus wird die Verwertung dieser Daten zur Anpassung von Materialmodellen auf der Grundlage von Nachrechnungen gezeigt, wobei die Möglichkeiten und Grenzen der verwendeten Konzepte Umrissen werden. Aufgrund des Umfangs, den die Versuche mit Holzwerkstoffen einnehmen, und des erforderlichen Aufwandes für die numerische Modellierung werden die entsprechenden Maßnahmen und Ergebnisse in einem eigenständigen Beitrag auf der KONTEC vorgestellt.
Laser thermal shock experiments - performance and evaluation on the basis of advanced ceramics
(2011)
The thermal shock behaviour in air and vacuum of three different advanced ceramics is investigated by introducing a new testing method. This thermal shock testing system permits the reproducible setting of defined temperature profiles in thin disks. In order to perform heating - up thermal shock experiments under reproducible conditions and to measure the transient temperature fields, a laser beam is directed spirally across the surface of the specimen. In this process, the specimen is heated up faster than the temperature gradient is compensated by thermal conductivity. Resulting temperature fields were recorded space and time resolved. Based on the knowledge of the local temperature distribution at the moment of failure, the critical fracture stress can be calculated. The scatter of thermal shock strength is quantitatively determined for the tested ceramics by using a improved statistical method.
Die steigenden Anforderungen im Schienenverkehr haben u. a. wachsende Betriebsbeanspruchungen für das Führungselement Schiene zur Folge. Auf Strecken mit hohen Belastungen wird dadurch die Entstehung von Rollkontaktermüdungsrissen, den sog. Head Checks, begünstigt. Für die Quantifizierung von Schäden im Hinblick auf eine optimierte Instandhaltung, setzt die DB AG daher seit einigen Jahren die Wirbelstromprüfung an Schienen ein. Es wurde ein Wirbelstromprüfsystem speziell für die Detektion und Bewertung von Head Checks auf der Schienenstahlsorte R260 entwickelt. Um den Instandhaltungsaufwand möglichst gering zu halten, unterliegen Eisenbahnschienen einer ständigen technologischen Weiterentwicklung durch die Hersteller. Durch Verbesserung der Schienenstahlsorten soll ein größerer Widerstand gegen die Bildung von Rollkontaktermüdungsrissen erreicht werden. Anhand von Streckenversuchen der DB AG in den letzten Jahren konnte festgestellt werden, dass tatsächlich eine Verminderung der Risswachstumsgeschwindigkeit erzielt wurde. Dafür zeigten sich im Vergleich zur Stahlsorte R260 abweichende Rissgeometrien, geringere Abstände zwischen den Ermüdungsrissen und somit eine größere Dichte des Rissfeldes. Die daraus resultierenden Folgen für die Ergebnisse der Wirbelstromprüfung werden hier erläutert. Praktische Prüferfahrungen an Schienenstahlsorten mit höherer Festigkeit werden vorgestellt.
Das Schienennetz der DB und anderer Bahngesellschaften wird regelmäßig mit Schienenprüfzügen inspiziert. Die mit den Prüfzügen aufgenommenen Messdaten werden offline zu einem späteren Zeitpunkt ausgewertet. Um Prüfbefunde manuell nachprüfen und ggf. Reparaturmaßnahmen einleiten zu können, ist eine möglichst exakte Zuordnung der Befunde zum Prüfort notwendig. Theoretisch ist jeder Ort des Schienennetzes durch Streckennummer, Richtungskennzahl und Kilometrierung exakt beschrieben. In der Praxis treten jedoch bei der Zuordnung diverse Probleme auf: Die Kilometrierung wird während der Prüfung manuell erfasst, indem die Beschriftung der Kilometer- bzw. Hektometertafeln in das Prüfsystem eingegeben und deren Position beim Vorbeifahren per Tastendruck in die Messdaten 'eingeblitzt' wird. Die Hektometertafeln stehen jedoch nicht an der aufgedruckten Position, sondern sind am nächstgelegenen Mast montiert. Dagegen ist die Ungenauigkeit des manuellen 'Einblitzens' vernachlässigbar. Außerdem ist die Kilometrierung nicht immer eindeutig, da nach Umbaumaßnahmen Kilometersprünge (sowohl fehlende als auch doppelte Kilometer) auftreten können. Abhilfe verspricht der Einsatz des satellitengestützten GPS, vorausgesetzt, die Strecken sind exakt vermessen. Um eine ausreichende Positionsgenauigkeit auch bei schlechten Empfangsbedingungen zu erreichen, ist jedoch ein erheblicher Aufwand notwendig. Die Positionsgenauigkeit eines Standard-GPS-Empfängers genügt hier nicht. Es wird ein Verortungssystem hoher Positionsgenauigkeit auf der Basis des GPS vorgestellt, das sich derzeit in der Erprobung befindet.
Formic and acetic acids are often responsible for damage of cultural objects, e. g. glass and metal corrosion or changing and fading of colours. Museums all around the world are equipped with different show cases. Display cases should protect cultural objects from dust as well as from mechanical damage. Several construction materials which are used for display cases, including wood, glue and coatings, are possible sources of very volatile organic compounds (VVOCs), volatile organic compounds (VOCs) and semi volatile organic compounds (SVOCs). These construction products can emit formic and acetic acids into the indoor or display case air. Modern display cases with small air change rates can cause higher concentrations of formic and acetic acids if any source is installed in the display case (Salthammer and Uhde, 2009). To minimize the risk of damage emissions from building products must be quantified. There is a need for a method for identification and quantification of acetic and formic acid. Some possibilities for the identification of acetic acid exist. The quantification of acetic acid for example after sampling on TENAX® or CARBOTRAP and thermal desorption-GC in accordance with ISO 16000-6 and ISO 16017-1 results in very low recovery rates. A new method should be stabile, robust, reproducible and comparable, with an easy local sampling and determination in laboratories. Miniaturised emission test chambers and model display cases were used to study the recovery rates.
VOC emissions from building materials accompanying sensory tests for different evaluation schemes
(2011)
Within a follow up project of a former study (Horn et al. 2005) emissions and odor from different types of construction products were investigated (financed by the German Federal Environmental Agency - FKZ 37 07 62 300).
The tested materials were mainly those used for construction of floors indoors. For this type of materials in Germany several labeling procedures exist which are based on Emission chamber testing. Two important labeling procedures in Germany are based on the AgBBevaluation scheme (Däumling et al. 2005). For some applications (flooring material) it is the mandatory Ü-mark of DIBt (German Institute for Construction Technology). Furthermore for carpets, adhesives and many other products, like sealants, mattresses, furniture and so on the voluntary blue angel mark exist. Within this scheme the volatile organic compounds (VOC) compounds are measured with well established procedures and are evaluated with LCI-values which were derived from health information.
Beyond that many complaints according to building products are caused by odors. Therefore an evaluation procedure for the odor is very important and should be implemented into all of the mentioned labeling schemes.
Quality and trueness of results received from measurements are very important for all involved parties, producers and consumers as well; for instance, if the results were used for acceptance of a product within a labeling procedure. Based on an inter-laboratory study with many German, European and US-American laboratories an extemal quality assurance System for the analysis of VOC emitting from products or the measurement in indoor air should be implemented (financed by the German Federal Environmental Agency).
A focus was set on the emission test chamber experiments and the connected analytical procedure. VOC have a dominating influence when applying the German AgBB scheme for health evaluation of building products.
Therefore it is necessary to ensure that the results between the testing laboratories are comparable. The successful participation to such round robin tests is offen essential for the acceptance of results given by an analytical laboratory.
The labelling of construction products or building materials as “low-emitting” is based on measurements using third-party emission test chambers. Unfortunately there is no method to validate the performance of such test chamber measurements. This might give a Variation of results when testing one material at different laboratories. Therefore it is necessary to hold round robin tests as part of the quality management System to ensure comparable results.
A research project financed by the Federal Environmental Agency focused on the development of an external quality management System for the detection of relevant Chemical compounds from products and in ambient air. The project was structured in four phases (Horn et al., 2009 and 2011; Wilke et al., 2009a) This paper shows results of the fourth phase of the project, which was an inter-laboratory study for VOC-emission testing by means of emission test chambers.
Wood and wood products are often used as construction material for buildings and even more for furniture and indoor decoration. Therefore Chemical emissions from wood have an influence on the indoor air quality. A research project financed by the Federal Environmental Agency focused on VOC emissions from oriented Strand boards (OSB) and also from plywood made from pine and spruce (Wilke et al., 2011a). This paper shows results of the plywood testing because only little information is available about plywood emission behaviour and its impact on indoor air quality.
The fire behaviour of composites clearly differs in comparison to polymers. Even though fibres and inorganic particles may be inert with respect to pyrolysis, they are clearly not with respect to fire behaviour. They change heat absorption and transfer within the Condensed phase, the melt flow/dripping behaviour of pyrolysing melts, the amount and properties of the fire residue and so on. Flame retardancy concepts tailored to composites are needed. Furthermore tasks that are specific for composites such as the structural integrity in fire get into the focus. Thus understanding of fire behaviour and flame retardancy mechanisms in composites is a key for target-oriented future development. The field is illuminated by Spotlights on different length scales. The examples are taken from different projects carried out in the group of the authors in the recent years. Flame retardancy mechanisms in nanocomposites are discussed, advanced halogen-free flame retardants for carbon and glass fibre composites presented as well as an approach to mechanical intermediate scale testing of carbon fibre composites under fire.
Wann ist es sinnvoll ein Biozid in ein synthetisches Material einzubringen? Wenn dadurch ein Problem gelöst wird. Deshalb sollte bei jeder Versuchsplanung die Frage stehen: Was ist das Problem, das man durch Biozieinsatz lösen will? Wie kann es im Laborversuch dargestellt werden? Konnte der Laborversuch zeigen, dass bei Biozideinsatz das Problem kleiner wird, beziehungsweise nicht mehr existiert? Je höher die Teststufe ist, umso mehr muss der Prüfablauf auf die Praxisbedingungen in der Gebrauchsphase des biozidhaltigen Erzeugnisses abgestimmt werden. Auf Stufe 1 werden in der Regel einzelne Wirkstoffe getestet. Ziel ist, die prinzipielle Wirksamkeit nachzuweisen, um die Ergebnisse für die Zulassung auf die Positivliste biozider Wirkstoffe der Biozidrichtlinie einzureichen. Während auf Stufe 1 bereits Normmethoden unter Einbeziehung einer relevanten Materialmatrix angewendet oder für die Fragestellung adaptiert werden können, ist dies für Stufe 2 oftmals nicht gegeben. Stufe 2 zeichnet sich durch Prüfmethodik mit praxisrelevanten Belastungen zur zeitraffenden Alterung des Biozids in seiner Materialmatrix aus. Hier stellt sich auch die Frage zur Langzeitwirksamkeit. Anstelle eines einzelnen Wirkstoffs wird oftmals ein Gemisch verschiedener Wirkstoffe und zusätzlichen Additiven, die wiederum Einfluss auf beispielsweise die Verteilbarkeit, Stabilität und Bioverfügbarkeit haben können. Es wird also kein Wirkstoff, sondern ein Biozidprodukt geprüft. In dem Biozidprodukt dürfen aber nur Wirkstoffe eingesetzt werden, die im Rahmen der Biozidrichtlinie bereits zugelassen sind und auf der Positivliste zu finden sind. Stufe 3 wird diskutiert im Zusammenhang mit Biozidprodukten mit Außeneffekt. Sie beschäftigt sich mit dem Nachweis von Vorteilen durch die Biozidnutzung. Hier gilt es den Verbraucher- und Umweltschutz gegen den Nutzen der möglichen Wertschöpfung oder auch den Gesundheitsschutz durch Biozideinsatz abzuwägen.
The cement and concrete market in East, Central and Southern Africa is highly fragmented. The concrete industry in this area consists of multiple parties, including producers and suppliers of construction materials, formal and informal contractors, engineers and architects, unions of trades persons and workmen, governmental bodies and formal institutions of research and education. All these institutions mostly do not interact adequately, which makes building with cementitious materials susceptible to damage and failures. Completely opposed to the situation in Europe or North America, cement in Africa is often unaffordable, while manpower is cheap, which results in a questionable economisation of cement. Typically, there is not sufficient awareness of methods to sensibly reducing the cement content in concrete or replace Ordinary Portland Cement by adequate alternative materials. Research activities in this field of technology are often missing completely. Only few countries in the area, such as South Africa, are exempted from these issues.
This paper presents the SPIN project, which is a joint project of a consortium of 8 African and 3 European partners within the ACP Science and Technology Programme. The project is funded by the EC and ACP Secretariat is the project body. The main objective of the current project is to strengthen the cement and concrete industry in the East and Central African regions. The project shall generate reasonable solution strategies to implement clean, safe and sustainable cement and concrete technology on the African continent, including general and specific guidelines for sensible application. Furthermore it shall be the kick-off for future projects, research activities and the world-wide expansion of a European-African network.
The paper addresses special problems the cement and concrete market in Eastern, Central and Southern African countries has to face. Several options are presented in detail, which shall help overcoming the current situation. Customized solutions for the African market include rational methods for reducing the amount of cement used and the replacement of Ordinary Portland Cement with cheaper alternatives. The use of recycled concrete through a new and economically effective method, as well as the opportunity of using locally available resources is also discussed.
Concrete technology was exposed to a rapid development during the last three decades. For the longest time in its history, concrete was considered as a three component System consisting of aggregates, which are bound by the hardened cement paste consisting of hydrated cement. Traditionally, the only way of adjusting the consistency of concrete was using well adjusted aggregates and grading curves and adding excess water to the concrete, accepting that the latter in return reduces strength and durability. During the last three decades, however, concrete has developed further from a three component System towards an (at least) five component system, since the use of mineral additions and Chemical admixtures has become state of the art. Both components are able to enhance the workability, the compactability, and the density of the microstructure with effects on strength, ductility and durability, while cement can be saved in parallel. Due to reasonable use of admixtures and additions, concrete can be designed to match mechanically high performance specifications. Traditionally, cement paste was considered the weakest component in concrete. Flowever, in modern concrete a good paste composition can yield highest performance, passing the role of the mechanical bottleneck towards the aggregates.
Today polycarboxylate ether based superplasticizer (PCE) is commonly used in concrete technology when high flow properties and water reduction are specified. The ionic strength of the polymers’ backbones determines the adsorption behaviour of polymers on clinker and early hydration products. The amount of required polymers for specified flow properties and the performance over the time of casting is thus determined by the molecular structure of the superplasticizer. The time depending consumption of polycarboxylate ether polymers strongly affects the reaction of aluminates and sulphate ions as well as the hydration process in general. Hence, the choice of polymers for particular flow properties greatly affects the very early properties of cementitious materials such as setting, heat evolution and autogenous deformations.
In order to better understand how PCEs influence the early properties, mixes from cement, limestone filler, viscosity modifying agent and water were varied with a high and a low charge density superplasticizer in differing amounts. Results are presented from measurements with an automatic Vicat device, an isothermal heat flow calorimeter, and shrinkage cones. Tests were conducted at 5, 20, and 30 °C.
It is shown that in presence of PCE the final set correlates well with the inflexion point of the heat flow curve, which emphasises the interrelation between C-S-H formation and setting. No such clear correlation can be found for the initial set, which is attributed to the fact that the initial set is rather a rheological than a structural phenomenon, so that other effects overlap with C-S-H formation. The results demonstrate that for a given polymer concentration low charge density polymers yield earlier setting than high charge polymers. However, this influence is overridden by the influence of the total amount of polymers in a cementitious system. Since PCE is typically added according to rheological specifications, and low charge PCE typically requires higher amounts of polymers than high charge PCE for comparable flow performance, low charge PCE retards setting more than high charge PCE.
The paper furthermore points out that there is no significant influence of the polymer type or amount on the early deformations. Since type and amount strongly affect the hydration, it is demonstrated that early setting causes higher strain after the final set. It is hence concluded that higher PCE solid contents reduce the risk of early cracks that occur at time of setting, when a solid structure has already been formed but without resistance against cracks yet.