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Fraktographischen Daten aus Schadensanalysen, Vergleichsversuchen und Vorhaben könnten der Fachöffentlichkeit im Bereich Fraktographie zur Verfügung gestellt werden, sofern das Urheberrecht es zulässt und außerdem ein geeignetes Medium existiert. Ein solches Medium könnte eine offene fraktographische online-Datenbank sein. Eine solche wird im Rahmen der AG Fraktographie im DVM-DGM Gemeinschaftsausschuss "Rasterelektronenmikroskopie in der Materialprüfung" zurzeit erarbeitet.
This study focuses on concrete flow in presence of obstacles and develops a mathematical model and a computational approach for SCC flow through reinforced formworks. In order to decrease high computational times needed to simulate castings through reinforced elements, an innovative approach to model the reinforced sections as porous media is proposed here. In the previous work, this numerical model is proved able to simulate the free-surface flow of non-Newtonian fluids through the reinforcement networks. In the present study, the applicability of the model on the concrete flow will finally be proved. The large-scale form-filling experiments with SCC will be conducted and the experiments will be simulated using the proposed numerical model. The numerical model will then be validated through the comparison of the experimental results and the results of the numerical simulations.
Computer modelling of non-destructive testing methods has come a long
way from the beginnings in the mid 90s to today. Radiographic modelling for
components with higher wall thicknesses, as they are typical for nuclear
applications, must include precise predictions of scattered radiation and its impact
in terms of contrast reduction. Dedicated or general purpose Monte Carlo methods
with the ability to calculate higher order scattering events are the state of the art for
these applications. Aerospace applications, on the other hand, have stronger
requirements on the modelling code's capabilities to import complex CAD
geometries, and can benefit from faster analytical scatter models, limited to first or
second order scattering events. Similar distinctions can be made for the various
approaches proposed to accurately model geometrical and film unsharpness, film
granularity, film responses, film/foil cartridges and photon noise. This article
presents a state-of-the-art review of radiographic modelling from the perspective of
two important application domains with very different requirements, nuclear and
aerospace.
Non-Destructive Evaluation (NDE) of structures is complex due to the uniqueness of almost all structures and their sizes. A single NDT method typically is not sufficient to meet the testing requirements, which cover different areas, such as material and structural properties. Measuring geometrical properties require other test methods than e.g. the detection of corrosion. Automation has proven to be necessary for aquiring large amounts a of high quality data in a short time. Examples of succesful method combinations from different areas of non-destructive testing in civil engineering are briefly described and their application is shown. Some of the examples also include automated inspection.
Ground penetrating radar (GPR) and infrared (IR) thermography techniques have been used in many civil engineering applications for the structural visualization and defect detection.
However, validation tests of the methods performance for the defection of defects in the nearsurface region with respect to the defects different material and depth below the surface are lacking. To overcome this, we performed GPR and IR thermography tests where the different material properties, shape and depth of defects were studied on concrete and the evaluation of seismic related damage propagation was assessed on stone masonry walls. The results showed that IR thermography, though being greatly affected by the presence of water in the specimen, outperformed GPR in the detection of defects very close to the surface. However, already at the depth of 3 cm and further up till almost 7.5 cm, the performance of GPR resembles the one of IR thermography for the detection of polystyrene (air) voids. On the plastered masonry walls, IR thermography could detect an air gap resulting from plaster delamination as small as 2 mm.
Moreover, structural cracking resulting from the induced lateral load could be detected at an early stage.
In Europa fallen jedes Jahr mehr als 10 Millionen Tonnen Klärschlamm an (Trockenmasse), etwa 2 Millionen davon in Deutschland, Bild 1 zeigt die Entwicklung der Klärschlammentsorgung in Deutschland. Nach dem Deponierungsverbot hat die Verbrennung des Klärschlamms stetig zugenommen. Die Verwendung im Landschaftsbau bzw. als Düngemittel ist nach einem Maximum um die Jahrtausendwende herum zugunsten der Verbrennung zurückgegangen, so dass heute jeweils etwa die Hälfte des Klärschlamms verbrannt und in der Landwirtschaft genutzt wird. Der Anteil an verbranntem Klärschlamm wird in Zukunft vermutlich weiter steigen. Ein wesentlicher Grund dafür ist die zunehmende Besorgnis über Schadstoffe im Klärschlamm, die Mensch und Umwelt schädigen könnten. Neben verschiedenen organischen und anorganischen Schadstoffen handelt es sich insbesondere um Emerging Pollutants of Concern (EMPOC) wie Antibiotika und Kosmetika.
In the context of national innovative project IMO-WIND, an integrated long term monitoring System was installed on a prototype of an offshore wind turbine System of 5 megawatt dass. The Federal Institute for Materials Research and Testing (BAM) was responsible for development of the SHM System. It consists of a signal acquisition System and a Signal processing and management System.
The signal acquisition System is composed of 14 acceleration sensors, 110 strain gauges and 4 inclination sensors, installed at the tripod foundation and the tower. It began to work in August 2007. In order to investigate the structural dynamic properties, extract efficient damage index and manage huge amounts of Vibration Signals and analysis results, an automated signal processing and management Software System is developed in LabVIEW® environment. It includes functions such as automated Operational Modal Analysis (OMA) on the basis of Stochastic Subspace Identification (SSI) method and poly-reference Least-Squares Complex Frequency Domain (p-LSCF) approach, investigation of environmental/operational effects on structural dynamic properties under operational conditions, features extraction using Principal Component Regression (PCR) and Multiple Linear Regression (MLR) as well as data/result management and visualization.
Besides, this paper also presents variations of structural modal parameters of a wind turbine system under complex environmental/operational conditions. Comparison of modal parameters automatically extracted by SSI method and poly-reference p-LSCF approach indicates that the latter method provides more stable modal identification results ffom the viewpoint of long term OMA. Subsequently, the influences of temperature, wind velocity, rotation speed and nacelle direction on modal parameters are generally discussed. Finally, variations of indentified modal parameters during two years are presented.
The implementation of a continuous dynamic monitoring System in Pedro e Ines footbridge at Coimbra, Portugal, operating since June 2007, enabled to detect different environmental/operational effects on the modal properties, based on appropriate processing of monitoring data collected by a set of accelerometers and thermal sensors.
In order to remove or mitigate such environmental/operational effects with the purpose of damage detection, two different Statistical methods have been adopted, One of them consists in the multiple linear regression (MLR) by performing correlation analysis between measured modal properties and environmental/operational variables. Another is based on the identification of the linear subspace within the modal properties by applying principal component regression (PCR) without using measured values of environmental and operational variables.
This paper presents a comparison ofthe performance of these two alternative approaches on the basis of continuous monitoring data acquired front the instrumented Pedro e Ines footbridge.
The low-cycle fatigue behavior of cc-brass CuZn30 was irtvestigated in uniaxial (tension-compression and torional) and biaxial tests under total strain control at room temperature. Planar-biaxial fatigue tests were carried out on a servohydraulic tension-compression testing machine with and without phase shift using a cruciform specimen geometry with fixed principal stress axes. In phase and out of phase tensiontorsion tests were performed using tube shape specimens on a servohydraulic tensiontorsion testing machine. Microstructural investigations were performed by transmission electron microscopy as well as by scanning electron microscope. For all proportional load cases the equivalent strain amplitude based on a maximum shear strain energy criterion results in a similar hardening behavior and in fatigue life times within a scatter band of three. Out of phase loading results in additional cyclic hardening and reduced life time. Planar glide structures were observed in all tested cases as well as areas of pronounced strain localization in the torsional load cases. No evidence of transition to wavy glide behavior was observed.
The visualization of spatially resolved single Orientation data, e.g. collected by electron backscatter diffraction (EBSD) in the scanning electron microscope (SEM), is still a challenge since some Orientation coloring schemes have low color sensitivity, and/or specific color discontinuities. The latter appear even for crystal Orientations which are practically identical and characterized only by a tiny misorientation. Euler angle coloring schemes suffer from their lack of intuitiveness. The inverse pole figure (IPF) coloring that has been widely accepted does not display the real Orientation Information for each measurement point, but only the crystallographic description of a single reference direction. For the representation of the complete Orientation information at least a second IPF Orientation map must be shown which displays the crystallographic description for another reference direction. In this context it must be pointed out that the IPF coloring is also not immune to color discontinuities, which are visible as speckled grains (and usually misinterpreted as erroneous Orientation determinations by EBSD). However, a general analysis of the commonly used color keys shows that color discontinuities are a consequence of the crystal symmetry for 6 of the 11 centrosymmetric Laue groups. This means that the Orientation description is correct, but the representation tool is inappropriate for properly displaying the orientation information.
The calibration of the integrated sensors in a multisensor system has gained in interest over the last years. In this paper we introduce an enhanced calibration process, which is based on the preceding study described in. The enhancement consists of the integration of a gyroscope. So far only the accelerometer and the magnetic field sensor were taken into account for the calibration process. Due to this improvement we reach a better approximation of the accelerometer and the magnetic field sensor. Additionally, we minimize the standard
deviation of the single sensors and improve the accuracy of the positioning of a moving person.
A comparative study tested the performance of modern anti-corrosion Systems against that of traditional red lead Systems.
One aim of the research project was to find alternatives for the use of a red lead priming coat, the Standard anti-corrosive primer for iron and Steel in the past but a material which endangers health as well as environment. The investigation aimed to determine whether anti-corrosion Systems developed for industrial use were suitable for the Conservation of historic iron and cast iron objects.
Besides coatings containing red lead, several surface tolerant coatings with different anti-corrosion pigments were examined.
The modern anti-corrosion Systems examined were suitable for surfaces where Optimum surface preparation is not practical.
They were applied to both historical samples and to newly prepared model samples.
After uniform pre-corrosion, the model samples were coated and underwent two different ageing procedures: accelerated ageing in a climate chamber and outdoor weathering on a test site with moderate city climate. The specimens were exposed for more than two and a half years. Evaluation of the artificially aged samples was carried out under the aspect coating degradation, tensile strength test, cross-hatch test and Fourier-transform infrared microscope.
The results of the research with optical evaluation and test procedures will be presented. The two ageing methods will be discussed, with different results from the naturally and artificially aged samples. The results Show a similar eligibility of modern anti-corrosion Systems as compared with red lead Systems for the use in Conservation.
The mechanical and thermal loadings associated with the routine, normal and accident conditions of transport can have a significant effect on the leak tightness of the sealing system of transport casks for spent fuel and high radioactive waste.
Applicants are requested by BAM to provide test programmes for verification of design leakage rates of the sealing system under the possible loads.
Two test series initiated to clarify the dependency of the standard leakage rate on dynamic lid displacement as well as the dependency of the useful elastic recovery ru of a metallic seal on temperature and time, are outlined in this paper as examples of present investigations:
Sliding tests simulating a lid displacement possible by a horizontal drop of the cask are carried out at the controlled drop test facility of BAM with test flange pairs equipped with metallic Helicoflex seals.
For specification of covering values for the useful elastic recovery ru GNS has started a very comprehensive test programme with overall 70 metallic seals installed in test flanges which are stored for a period of one year at three different temperatures up to 150°C.
This paper gives an overview about the current approach of BAM in the assessment of cask tightness and informs about the status of the running test series.
Tunnel lining evaluation is performed in the Hanging Lake Tunnel near Glenwood Springs, Colorado, using variations of four nondestructive evaluation (NDE) methods: air- and ground-coupled ground penetrating radar (GPR), ultrasonic echo (US echo), ultrasonic tomography (UST), and impact echo (IE). Potential regions of interest are identified using high-speed air-coupled GPR and visual inspection. A robotic frame with pneumatically-operated vacuum plates was used to automate the ground-coupled GPR, US echo, and IE tests, while the UST technique was used manually. This study shows that a particular combination of NDE techniques is a powerful tool for assessing the condition of tunnel linings and can detect potential anomalies such as delamination, depth of surface cracks, reinforcement depth and layout, and lining thickness. By mapping the phase shift of the ultrasonic pulses at detected interface, the potential bonding of layer interfaces and reinforcement is assessed.
An in-depth investigation of tunnel linings is performed at Eisenhower Tunnel, 60 miles west of Denver, Colorado, using a combination of four nondestructive testing methods: air- and ground-coupled ground penetrating radar (GPR), ultrasonic echo (US echo), ultrasonic tomography (UST), and impact echo (IE). A robotic frame with pneumatically operated vacuum plates is used to automate GPR, US echo, and IE. UST was performed manually. These techniques are used to identify and locate the reinforcement mesh and structural steel ribs. Local changes in ultrasonic phase are calculated by phase analysis processing techniques and apparent relationships between positive and negative phase shifts and steel and air interfaces are observed. According to previous laboratory research, these relationships indicate the bonded state between the concrete and the embedded steel, but without ground truth verification this can only be suggested. It is shown that this combination of methods can be used synergistically to provide tunnel owners with the layout and possible condition of tunnel lining reinforcement and structural components.
Bottom ash from municipal solid waste incineration (MSWI) consists of elemental metals in considerable amounts. The fine fraction < 4 mm additionally contains chemically bound metals (oxides, carbonates, silicates). Separation prospects with techniques as in ore processing (flotation, density separation, bioleaching, hydrothermal solution) are discussed. During alteration after wet extraction mineral material with hydraulic properties form coatings on almost all particles of the bottom ash and complicate separation procedures. In addition bottom ash from MSWI is a heterogeneous material. For sufficient enrichment different concerted treatment steps seemed to be essential associated with an uncertainty of economic viability. The utilisation of metal compounds present in bottom ash as secondary raw material depends on the energy- and resource-efficiency of the enrichment processes. Therefore energy and material flow considerations are presented.
It is important to evaluate the effect of thermal ageing on the sealing performance of metal gaskets under high temperature for long-term usage. Therefore, in order to gain representative data for this kind of metal-sealed lid System, BAM is currently performing laboratory tests of different gasket types with aluminum and silver jackets at three different temperatures under static conditions up to four years so far, using test flanges for gaskets with full scale cross section diameter but much smaller outer diameter. On the other hand, in order to investigate the applicability of the numerical methodology to evaluate the long-term behavior of the metal gaskets, such as a correlation between seal pressure force and holding time, CRIEPI is developing a modeling method including material tests (tensile and creep tests) at high temperature. In this paper, the applicability of the finite element method (ABAQUS) to predict the recovery displacement and residual seal pressure force of the gasket complex was verified by comparing the calculated values with BAM’s laboratory test results under the joint research agreement between BAM and CRIEPI.
Diffuse ultrasonic measurements are used to monitor progressive stress-induced damage in a number of concrete specimens. Each specimen was subjected to uniaxial compression, applied in small steps over one or several load cycles. At each step, the loading was held constant and a series of ultrasonic measurements parallel and perpendicular to the loading were obtained. The measurements were taken during both the loading and unloading phases. The time scale of the signals was chosen such that the diffuse ultrasonic regime could be recorded. Using Coda Wave Interferometry (CWI), the corresponding changes in the velocity of diffuse ultrasonic waves were monitored. The evolution of the slope of the CWI velocity-stress curve with the increased level of damage in concrete is demonstrated.
Temperature is an important parameter in weathering tests. In many (photo-)chemical degradation processes a Variation of the specimen temperature by A t = + 1 °C can cause a Variation of AP(property change) by ± 8%.
Since the early eighties it is well known that some types of black panel thermometers can show temperatures that are far below the maximum surface temperature of a black specimen. Although, there were precise requirements for the black coating of the BPT, a replacement by a white coating - depending on the design of the BPT - did not really change the temperature shown by the thermometer. There was no correlation between the BPT and the specimen surface temperature.
In Europe and later at ISO the so-called black- and white-standard thermometers BST/WST were introduced. Now, there are BST and WST (ISO) and there are thermally uninsulated and insulated BPT and WPT (ASTM), partly for artificial or for outdoor exposure. And there are other adventurous procedures to determine surface temperatures.
The different types of thermometers and different procedures will be discussed and it will be shown that there is no procedure which establishes a correlation between outdoor surface temperatures and surface temperatures in artificial exposure tests.
The tradition of discussing the newest achievements in the consideration of NDE reliability was continued with the 5th European American Workshop on Reliability of NDE (5th EAW) in Berlin in 2013. The focus of this workshop was to determine the “delta” between the laboratory- like conditions, in which reliability assessments are usually carried out, and the everyday field conditions. Which obstacles need to be still over- come and how do we get closer with our estimations to the real field re- liability? With the joint effort of international researchers and in-field practitioners the up-to-date research was presented and discussed, culminating in a half-a-day long “Open Space Technology” discussion. This paper presents the main conclusions of the workshop.
CFRP are more and more used in modern civil aircrafts hence the whole fuselage is made of this material (B787; A350). Due to strict certification Standards finally the normal in-service loading gives a low stress level compared to the static and even the fatigue strength of the material. Hence CFRP are assumed to have an infinite life. To evaluate this assumption, fatigue tests on CFRP-specimens were performed up to 108 load cycles. The first inter-fiber failure was evaluated non-destructively by the fatigue tests accompanying X-ray-refraction topography altemately and in-situ mechanical loading. The basic idea of the investigation is represented in fig. 1. At low load levels it could not be assumed the total failure of the samples. Hence accompanying non-destructive testing (NDT) is mandatory to get information about the damage state of the material.
The solid lubricant molybdenum disulfide is a well known material for extreme conditions where conventional oil or grease lubrication is not feasible (vacuum, high pressures). However, under reactive environments e.g. high humidity or hydrogen MoS2 is prone to premature failure. By using a PVD process, deposition parameters can be optimized to gain coatings with a more textured structure orienting the basal planes parallel to the Substrate surface, A similar concept has been used by Koch et al. for coatings developed to withstand the extreme operational conditions of the WENDELSTEIN W7-X fusion experiment. Therefore, an improved tribological behavior even under adverse conditions can be achieved.
The efficiency of gas sensor application for facilitating the safe use of hydrogen depends to a considerable extent on the response time of the sensor to change in hydrogen concentration. The response and recovery times have been measured for five different hydrogen sensors, three commercially available and two promising prototypes which operate at room temperature.
Experiments according to ISO 26142 show that most of the sensors surpass much for a concentration change from clean to hydrogen containing air the demands of the Standard for the response times t(90) and values of 2 to lös were estimated. For an opposite shift to clean air, the recovery times t(10) are from 7 to 70 s. Results of transient behaviour can be fitted with an exponential approach. It can be demonstrated that results on transient behaviour depend not only from investigation method, and the experimental conditions, like gas changing rate and concentration jump, as well as from operating
Parameters of sensors. In comparison to commercial MOS and MIS-FET hydrogen sensors new sensor prototypes operating at room temperature possesses in particular longer recovery times.
Gas sensors are applied for facilitating the safe use of hydrogen in, for example, fuel cell and hydrogen fuelled vehicles. New sensor developments, aimed at meeting the increasingly stringent performance requirements in emerging applications are presented based on in-house technical developments and a literature study. The strategy of combining different detection principles, i.e. sensors based on electrochemical cells, semiconductors or field effects in combination with thermal conductivity sensor or catalytic combustion elements, in one new measuring system is reported. This extends the dynamic measuring range of the sensor while improving sensor reliability to achieve higher safety integrity through diverse redundancy. The application of new nanoscaled materials, nano wires, carbon tubes and graphene as well as the improvements in electronic components of fieldeffect, resistive-type and optical systems are evaluated in view of key operating parameters such as sensor response time, low energy consumption and low working temperature.
Load attachment points, consisting of the lifting component and corresponding bolt connections, and lid systems, consisting of a lid, gaskets and bolt connections, are usually analyzed numerically using the Finite Element Method. Reasons for applying the FEM are complex geometry, specific load distribution and the violation of application criteria for analytical approaches. For example the elementary beam theory is not suitable for the calculation of compact trunnions and the Kirchhoff plate theory is not suitable for the calculation of lids with a large thickness to diameter ratio because the Bernoulli-hypothesis is violated. In addition for structural integrity assessments often local stress and for the evaluation of lid systems tightness local contact opening are needed, which can be obtained only through accurately discretized numerical models.
Independent comparative calculations are essential for complex calculations. Simplified but appropriate analytical approaches are an efficient way of examination. Is it possible to provide conservative analytical estimates of such kind of analysis problems? Are analytical calculations an appropriate approach in today's authority assessment business? Using the example of bolted trunnion and lid systems of a heavy package the possibilities and limits of analytical comparative calculations are shown.
In context with new cask designs and their approval procedure, the experimental testing of impact limiters under drop test conditions becomes more and more important in order to assess the damage mechanics behaviour and safety margins for validation reasons. In recent years, various designs of impact limiters have been tested by the Federal Institute for Materials Research and Testing within specific component testing and particularly with regard to type B package design approval procedures. The paper focuses on the experimental realisation of impact limiter tests and presents implemented measurement techniques to determine the amount of deformation and to explain the impact behaviour by means of photogrammetric metrology and three-dimensional fringe projection method, high speed motion analysis and adjusted deceleration measurements.
Ensuring a sustainable energy supply is currently one of the most important areas for industry and research institutions. Hydrogen technology is a promising candidate, but its broad extension requires extremely high reliability and safety in all areas for common applications as automobiles and stationary fuel cells. Particularly components containing tribosystems are critical parts.
Superconducting magnets are susceptible to quenching, even with the smallest amounts of energy disturbances due to the extremely low thermal capacity of materials at 4.2 K. Hence, small mechanical disturbances resulting in frictional heating can be sufficient to exceed the wire’s critical temperature, causing it to quench. Unfortunately, relative motion between surfaces in the magnet System is inevitable due to various forces present in the System, including winding pretension, differences in material thermal contraction and the large electromagnetic forces. Typically insulating polymers are present at this interface to achieve the required electrical insulation requirements.
During the last three decades concrete has emerged from a rather simple mass construction material based on only the three components cement, water, and aggregates towards a high performance material, which can be adjusted for high performance applications and according to ultimate user specifications. The reason for the rapid evolvement was the increasing awareness about how the rheology of concrete can be improved without negatively affecting the mechanical properties of concrete. Hence, mineral additions and in particular Chemical admixtures have been the most influential factors for the technological boost since approximately the 1980s.
The incorporation of superplasticizers into concrete mixture compositions eventually facilitated concrete engineers to improve the workability properties without need to increase the water-cement-ratio (w/c) and furthermore to significantly reduce the w/c without loss of workability. This finally resulted in concrete with higher performance and specified properties. Fillers are basically used to improve the particle packing of cementitious Systems, but they can also be used beneficially to support the rheology, since they modify the water demand and may interact with superplasticizers as well.
Finally, supplementary admixtures like polysaccharides have become more populär in the field of mortar, plaster, and grout technology. They can have a variety of rheological effects on cementitious Systems, which can be used to individually adjust their performance.
The possibility to control the rheology and the significantly widened ränge of consistencies that can be adjusted opened up the gates for modern concrete and any type of high performance concrete. Therefore, without doubt, it can be concluded that the capability to control the rheology of concrete Systems can be considered as the catalyst for the invention of the many recent mortar and concrete innovations such as polymer modified cementitious composites (PCC) self-compacting concrete (SCC), high-performance concrete (HPC), ultra-high performance concrete (UHPC) or engineered cementitious composites (ECC).
Therefore, understanding the rheology of cementitious Systems and how to control the workability by the use of Chemical admixtures is the key to innovations in concrete technology.
However, the other side of the coin of versatility is that sophisticated cementitious Systems have become more sensitive. Hence, concrete mixture composition with admixtures demands for a high level of expertise and often there is lack of awareness about the mode of Operation of rheology modifying admixtures among concrete technoiogists. The paper gives a comprehensive overview about rheology modifying constituents such as superplasticizers, stabilising agents, and mineral fillers, and how they can be used depending upon the application in the most favourable way.
In modernen Schweißkonstruktionen des Stahl- und Ingenieurbaus werden zunehmend hochfeste Feinkornbaustähle eingesetzt. Grundsätzlich sind während der schweißtechnischen Verarbeitung hochfester Stahlgüten aufgrund ihres speziellen Gefüges und wegen ihres vergleichweise hohen Streckgrenzenverhältnisses engere Verfahrensgrenzen einzuhalten, als bei Stählen mit niedrigerer Festigkeit. Die Sicherheit von hochfesten Schweißverbindungen erfordert präzise Kenntnisse über die Höhe und Verteilung der schweißbedingten Beanspruchungen, da sie die erreichbare Tragfähigkeit unmittelbar beeinflussen. In den Untersuchungen wurde der Einfluss der Wärmeführung in Form der Zwischenlagentemperatur und Streckenenergie auf die Eigenspannungsausbildung und Gesamtbeanspruchung in hochfesten Schweißverbindungen ermittelt. Zur Berücksichtigung einer äußeren Bauteilsteifigkeit wurden die Proben in Nahtquerrichtung unter einem definierten Einspanngrad in einer speziellen Prüfanlage (CTW-Test) mehrlagig geschweißt. Es zeigte sich beispielsweise, dass insbesondere die Zwischenlagentemperatur einen direkten Einfluss auf die globalen Reaktionsspannungen hat. Ferner bedingt die Erhöhung der Wärmeführung ein deutliches Anheben der Zugeigenspannungen im Bereich des Schweißgutes.
Für die rechnerische Dimensionierung der Betondecken im Oberbau von Verkehrsflächen für den Neubau sowie die Erneuerung nach RDO Beton 09 ist die statische Spaltzugfestigkeit an der unteren bzw. unteren und oberen Scheibe des Betonzylinders bzw. Bohrkerns entsprechend der Vorgaben der AL Sp-Beton zu bestimmen. Aufgrund der unzureichenden Kenntnis der Präzision dieses Prüfverfahrens wurden mit einem breit aufgestellten Ringversuch die statistischen Kennwerte an Labor- und Bestandsbetonen unter Vergleich- und Wiederholbedingungen auf der Grundlage des „Merkblatts über die statistische Auswertung von Prüfergebnissen" ermittelt. Für eine möglichst gute statistische Absicherung nahmen an dem Ringversuch 13 erfahrene Prüfstellen teil. Zur Abdeckung des vielschichtigen Einsatzes des Prüfverfahrens erfolgte der Ringversuch an acht Prüflosen. Dabei berücksichtigen einerseits die Prüf lose 1 und 2 mit den im Transportbetonwerk hergestellten Betonzylindern die Erst-/Eignungsprüfung und das darauf aufbauende Prüflos 3 mit Bohrkernen aus einer im Feldversuch hergestellten Fahrbahnplatte mit gleicher Betonrezeptur die Übereinstimmungskontrolle bei Neubaumaßnahmen. Andererseits findet der Einsatz des Prüfverfahrens bei der Restsubstanzbewertung von Betonfahrbahnplatten bei den Prüflosen 4 bis 7 mit den Bohrkernen aus vier in Waschbetonbauweise ausgeführten Fahrbahnplatten Berücksichtigung. Das zusätzlich aufgenommene Prüflos 8 mit einem Labormörtel dient der Herausarbeitung des Materialeinflusses auf die Präzision der Spaltzugfestigkeitsprüfung. Zusammenfassend kann festgestellt werden, dass die Präzision der in der AL SP-Beton beschriebenen Spaltzugfestigkeitsprüfung mit einem Variationskoeffizienten von weniger als 10 % unter Wiederhol- und Vergleichbedingungen hinreichend genau ist. Der geringe Unterschied zwischen den Variationskoeffizienten unter Wiederhol- und Vergleichbedingungen lässt zusätzlich den Schluss zu, dass der Einfluss des unterschiedlichen Personals und der verschiedenartigen Prüftechniken bei den einzelnen Prüfstellen relativ gering ist. Die im Rahmen des Ringversuchs gewonnenen Erkenntnisse haben bereits partiell Eingang in die Normung gefunden.
A management system based on international, national or other standards acceptable to the competent authority shall be established and implemented for all activities including design, manufacture, testing, documentation, use, maintenance, inspection in accordance with IAEA SSR-6. Hereby, quality assured testing and documentation can substantially contribute to the demonstration of package design compliance with the regulations. Nowadays, a drop test campaign within the approval process of packages for radioactive materials can be a very complex and extensive project including various test and measurement techniques. On this basis of procedures and documents the experimental tests of packages and containers are performed with quality proofed results and a high reliability. A complete traceability and direct transferability of package design test results can give particular importance to the type approval procedure.
Operational modal analysis and vibration based damage detection of engineering
structures have become important issues for Structural Health Monitoring (SHM) and
maintenance operations, e.g. on transport infrastructure. Methods from control
engineering have been adopted and converted for the application on civil structures.
Approaches like subspace-based system identification combine excellent theoretical
properties under the unknown excitation properties of a structure with practical
usefulness.
In this paper, the implementation of covariance-driven stochastic subspace
identification (SSI) on the smart wireless sensor platform PEGASE is described.
Special care is taken about the fast implementation of this technique since the
computations are embedded on the platform and perform in real-time. The most
efficient and current version of subspace algorithms has been implemented. Efficiency
and memory consumption are primary criteria in this implementation.
First validated results will be given for each step of the algorithms: crosscorrelation
on natural inputs signal from sensors; Hankel matrix output; SSI
implementation using the LAPACK library to get a SVD, pseudo-inverse, eigenvalues
etc. Results validation has been correlated between PEGASE implementation and the
previous processing in static situation: the same data was collected by wired sensors
and data-loggers, then, later, processed on a PC using traditional Matlab software.
In parallel, from an engineering point of view, a description of the PEGASE
wireless platform will be given: generic usage, wide capacities, embedded Digital
Signal Processing (DSP) processor and Library over a small embedded Linux
Operating System, a very accurate synchronization principle based on a GPS/PPS
principle, etc. Perspectives about a complete technical in-situ installation will also be
given.
A theorem on damage localization from flexibility changes has been proven recently,
where it has been shown that the image of the change in flexibility δF between
damaged and reference states of a structure is a basis for the influence lines of stress
resultants at the damaged locations. This damage localization approach can operate on
output-only vibration measurements from damaged and reference states, and a finite
element model of the structure in reference state is required. While the localization
approach is based on purely mechanical principles, an estimate of the image of δF is
required from the data that is subject to statistical uncertainty due to unknown noise
excitation and finite data length. In this paper, this uncertainty is quantified from the
measurements and a statistical framework is added for the decision about damaged
elements. The combined approach is successfully applied to a numerical simulation
and to a cantilever beam in a lab experiment.
The high demand for sustainable and durable building materials requires profound knowledge on the material properties. In this respect, the phenomena occurring at nano-level are of crucial importance for the design of new building materials. Therefore, all around the world, increasing amounts of funding are being directed to research projects dealing with material properties on nano-level, which is claimed to have tremendous potential for the future. One of the most referred to and used cementitious nano-material is amorphous silica with a particle size in the nano-range, even though its application and effects on concrete have not been fully understood yet. Olivine (Mg,Fe)2Si04 is the fastest weathering siiicate mineral dissolving easily in acid. Düring dissolution in acid the metallic ions (Mg2+,Fe2+) are replaced by H+, yielding Si(OH)4 monomers and metallic ions in solution. After cleaning treatments an amorphous nano-silica is obtained. The produced olivine nano-silica (OnS) has a specific surface area between 100 and 400 m2/g, the size of the primary particles, which are agglomerated in Clusters, ranges from 10 to 25 nm and the impurity content is below 5 % IV. Literature related with the application of OnS in cement based materials is scarce; only one research work performed by Justnes and Ostnor 121 is available. Thus, the effect of adding OnS in cement based Systems has been not studied. Based on this, the present research aims on elucidating the effects of OnS in the fresh and hardened state of cement pastes and mortars.
Rubbers are widely used as main sealing materials for containers for low and intermediate level radioactive waste and as additional component to metal seals in spent fuel and high active waste containers. According to appropriate guidelines and regulations safe enclosure of the radioactive container contents has to be guaranteed for long storage periods as well as down to temperatures of -40 °C for transportation. Therefore the understanding of seal behavior is of high importance.
In this paper we focus on the behavior of elastomer seals at low temperatures with regard to poten-tial decrease of leak-tightness. In addition, changes in material properties due to aging effects over long periods of time and their influence on the seal performance is investigated.
It is known that material properties of rubbers are strongly temperature dependent. At low tempera-tures this is caused by the rubber-glass transition (abbr. glass transition). During continuous cool-ing, the material changes from rubber-like entropy-elastic to stiff energy-elastic behavior, that al-lows nearly no strain or retraction due to the glass transition. Hence rubbers are normally used above their glass transition but the minimum working temperature limit is not defined precisely.
Aging of elastomer seals is important, as possible dynamic loads may have to be considered during the whole interim storage period (so far approved in Germany for up to 40 years) and for transporta-tion after storage.
For the investigations, fluorocarbon (FKM) and ethylene-propylene-diene (EPDM) rubbers were selected as they are often used in radioactive waste containers. Some materials were purchased from a commercial seal producer and some materials were compounded and cured at BAM. The elastom-ers where studied by several thermo-analytical methods and compression set to characterize the material behavior at low temperatures. Additionally component tests were performed to determine the breakdown temperature of the sealing function of complete elastomer O-rings.
We base our paper on data from a global company survey of certified companies carried out by the International Accreditation Forum (IAF) in 2010/11. We use multivariate Probit and ordered Probit models to analyze how company internal and external factors influence the perception of benefits from accredited certification. Benefits from accredited certification are divided into added value for the organization, increased sales and regulatory compliance. As for company external factors, we find that benefits from certification are higher for companies that went through a challenging certification process, had a competent certification body team, and are aware of the importance of accreditation. Internal factors are related to different motives for seeking certification. We find that the benefits from accredited certification are largest when companies become certified in order to improve their own business performance. Dividing our sample in high-income and middle income countries shows that the latter put more emphasis on company internal improvement through certification and are more likely to benefit from certification when they employ an external consultant. Finally, we can show that benefits are unequally distributed among companies. That is, smaller companies have a lower probability to benefit from certification compared to larger companies.
Leakage testing during lateral displacement of metallic seals under mechanical accident impact
(2013)
TN®24 E, a new package design, was developed and applied for by Areva TN for German transport approval certificate. The certificate was issued by BfS, Federal Office for Radiation Protection, on 24th of July 2013. The package is designed as a dual purpose cask for transport and storage of up to 21 PWR spent fuel assemblies from German NPPs. BAM is the German competent authority responsible for the design assessment of RAM packages regarding mechanical and thermal safety cases, activity release analysis and all issues of quality assurance during manufacturing and operation of packages. Certain assessment experiences as well as new developments resulting from the BAM TN®24E approval procedure are presented. The mechanical safety case of the TN®24E is based mainly on finite element calculations, which were verified by the TN®81 1/3 scale drop test program performed at BAM. Thermal analyses rely upon calculations, while the activity release criterion is based upon leakage rate results of TN®81 drop tests. The BAM-GGR 012 guideline for the analysis of bolted lid and trunnion systems has been fully implemented. Due to requirements by BAM, AREVA TN developed a new assessment strategy for fracture mechanical evaluation of welding seams. The material qualification and documentation is also an important aspect of BAM assessment; the qualification of borated aluminum basket material, the determination of strength values for thermal aged hardened aluminum alloys for the basket or consideration of high burn-up fuel assemblies are remarkable issues in this context. In addition, the consideration of the material compatibility, especially taking into account a transport after 40 years of dry interim storage in German facilities, has gained significant importance in the licensing process of the TN®24E. Next to obvious mechanical issues such as the assessment of shell ovalization under 9 m drop test scenario and its impact on basket load, thermo-mechanical interactions had to be addressed in the safety case. Due to BAM requirements, AREVA TN performed a full thermo-mechanical analysis of the cask behavior under fire test conditions.
New sensors for the detection of partial discharges (PDs) in high-voltage (HV) cable accessories are being de-veloped consisting of a fluorescent polymer optical fiber (F-POF) as sensing element. Depending on the fiber material F-POFs can be attached to and even integrated into the translucent silicone rubber insulation of HV cable terminations. As the embedment into the insulation material plays an important role, the sensor should not weaken the dielectric strength of the insulation material and should not be the origin of PD incidents. A sensor consisting of a commercial F-POF has been tested in the high-voltage lab regarding its PD detection ability un-der AC in comparison to a conventional electrical sensor. New silicone rubber F-POF (Si-F-POF) fiber models functionalized with coumarin dyes have been produced. The optical properties of these dye functionalized silox-anes are presented. These potential sensor fibers are highly flexible and might be embeddable at medium to high-voltage level. An additional way to further improve the level of PD light detection is to modify the translucent type of silicone rubber used in HV cable accessories in terms of optical transparency. In this context we present our first results of the optical and mechanical properties of new elastomeric transparent silicone materials specif-ically designed for the application as HV insulation materials in stress cones.
Existing spent nuclear fuel (SF) and high active waste (HAW) management policies and practices worldwide are the result of past presumptions that sufficient reprocessing and/or disposal capacity would be available in the near term. Consequently, in the past many countries have developed specific solutions for different periods of time due to their individual national nuclear policies.
In Germany the concept of dry interim storage in dual purpose metal casks before disposal is being pursued for SF and HAW management and transport and storage licenses have been issued accordingly. The current operation licenses for existing storage facilities have been granted for a storage period of up to 40 years. This concept has demonstrated its suitability for over 20 years so far. Relevant safety requirements haven been assessed for the short-term as well as for the long-term for site-specific operational and accidental storage conditions. But in the meantime significant delays in the national repository siting procedure occured which will make extended storage periods necessary in the future.
This paper describes the current situation in Germany with regard to dry cask storage and focuses on current perspectives considering regulatory, technical, and scientific aspects for storage license renewal. Since there is one case of a storage license limitation to only 20 years due to administrative reasons, first experience is currently gathered in case of an expiring storage license. Subsequent license options have been pursued intensively including the extension of the initial storage license as well as shipping all casks to another storage facility considering an extended storage period at that storage facility as well. All safety relevant aspects have to be reviewed on basis of the current state-of-the-art which might be different from the initial safety demonstrations. That includes new safety assessment standards as well as improved knowledge base. Major issues are e.g. improved accident scenario analyses, assessment methods, and consideration of aging effects from previous operation periods. Inspection programs with respect, e.g. to bolts and seals to verify leak-tightness and lid screw pre-stress have been initiated to demonstrate proper cask conditions for extended storage as well as transportation to another storage facility.