Filtern
Erscheinungsjahr
- 2011 (194) (entfernen)
Dokumenttyp
- Beitrag zu einem Tagungsband (194) (entfernen)
Sprache
- Englisch (194) (entfernen)
Schlagworte
- CCS (7)
- Corrosion (7)
- Steel (7)
- Concrete (6)
- Strain sensor (6)
- Computed tomography (5)
- Structural health monitoring (5)
- CO2-storage (4)
- Emission (4)
- Fibre optic sensors (4)
A multi-sensor system for 3D localization was developed and named BodyGuard. It combines body movement sensing and a guard system for the tracking and recording of the status of persons. BodyGuard was designed to monitor and transmit the movement of a person radio-based and to transform that data into a spatial coordinate. This paper describes how the BodyGuard system works, what components the system consists of, how the individual sensor data is converted into 3D motion data, with which algorithms the individual sensors are processed, how individual errors are compensated and how the sensor data are fused into a 3D Model.
BAM (Federal Institute for Material Research and Testing) is the competent authority for mechanical and thermal safety assessment of transport packages for spent fuel and high level waste (HLW) in Germany. In context with package design approval of the new German HLW cask CASTOR HAW28M, BAM performed several drop tests with a half-scale model of the CASTOR HAW/TB2. The test model was manufactured by GNS (Gesellschaft fur Nuklear Service mbH) and tested under accident transport conditions on the 200 tons BAM drop test facility at the BAM Test Site Technical Safety. For this comprehensive test program the test specimen CASTOR HAW/TB2 was instrumented at 21 measurement planes with altogether 23 piezo-resistive accelerometers, five temperature sensors and 131 tri-axial strain gauges in the container interior and exterior, respectively. The strains of four representative lid bolts were recorded by four uniaxial strain gauges per each bolt. Helium leakage rate measurements were performed before and after each test in the above noted testing sequence. The paper presents some experimental results of the half-scale CASTOR HAW/TB2 prototype (14,500 kg) and measurement data logging.
A novel approach to strongly suppress artifacts in radiography and computed tomography caused by the effect of diffuse background Signals (backlight) of 2D X-ray detectors is suggested. Depending on the detector geometry the mechanism may be different, either based on the optical scattering of the fluorescent screen materials into optical detection devices or Compton or X-ray fluorescence scattering by the detector components. Consequently, these erroneous intensity portions result in locally different violations of Lambert Beers law in single projections (radiographs).
When used as input data for computed tomography these violations are directly observed via modulation of the projected mass as a function of the rotation Phase and the samples aspect ratio (dynamics). The magnitude of the diffuse Background signal depends on the detector area covered by the projected sample. They are more pronounced the smaller the shaded area and the stronger the total attenuation.
Moreover, the local intensity mismatch depends on the attenuation of the sample.
We present very basic reference data measured with multiple metal foils at a synchrotron radiation source. Beam hardening artifacts can be excluded due to the monochromatic radiation. The proposed correction procedure assumes a constant (non-local) scattering mechanism.
The present investigations cover different relevant influences on the numerical calculation of welding-induced distortion. Therefore, a single-layer pulsed gas metal arc (GMA) weld of structural Steel S355J2+N with a thickness Öf5 mm is experimentally and numerically investigated. The influences of mesh density, tack-welds, and continuous cooling transformation (CCT) diagrams on welding-induced distortion are studied. The quality and quantity of These effects are clarified based on the used experimental and numerical set up. The occurring differences between the investigated cases achieve significant values. Consequently, prediction of welding-induced distortion can be improved considering the present investigations.
A dynamic and quasi-distributed sensor principle for simultaneous measurement of length changes and optical power changes between reflection points in an optical fiber is presented. The technique is based on the incoherent optical frequency domain reflectometry (I-OFDR). Length change resolutions < 1 µm and measurement repetition rates up to 2 kHz can be achieved using standard single-mode and multi-mode optical fibers. Simultaneous length change and refractive index measurement as well as field test results showing the deformation of a masonry building under seismic load are presented. Promising fields of application for this technique are the structural health monitoring sector and chemical process control.
A new burner concept (PEROXY-BAM®) for the combustion of liquid organic peroxides (Peroxy-fuels) is presented. As peroxy-fuels are thermally unstable the design of burners for them should be accordingly modified ensuring a safe operation. It is found that 10 to 100 time less amounts of peroxy fuels are required for the same heat flux or output in comparison to hydrocarbons. Correspondingly, the fuel pump power and the volume of combustion chamber (furnace) are also reduced. As a result of less amount of fuel the emissions will also be stepped down and oxygen in the molecule helps to establish conditons like in an oxy-fuel combustion process. The advantages of using peroxy-fuels over hydrocarbons inside a model combustion chamber are also investigated with the help of CFD (Computational Fluid Dynamics) simulations.
X-ray computed tomography (CT) is a volumetric (3D) Imaging diagnostic method, well established in the medical field, and in industrial NDE as well. Developments in industrial CT aim to extent the applicability to complex structures, which do not allow the access of all directions. This are e.g. limited view, data and angle CT applications. New reconstruction algorithms are required on one
side, and the accuracy has to be improved on the other side. Numerical Simulation can support such developments by providing well defined data sets for the testing of reconstruction algorithms. This approach of virtual CT is realized within the radiographic simulator aRTist, developed by BAM. The poster shows the possibilities of this tool to consider complex scan paths. Simulated data sets have been reconstructed by an versatile backprojection algorithm.
To determine a polymer’s spectral response of photo degradation, two main methods have been established. The so-called “filter technique” uses polychromatic radiation, which is filtered by a set of various sharp cut-on filters. This procedure provides separated reading points of an activation spectrum of the investigated material. With the "spectrographic technique” a specimen is irradiated with pectrally dispersed radiation, locally quasi monochromatically, and the local property changes.are related to the radiant exposure at the respective wavelengths. A third method, the irradiation of specimens with quasi monochromatic radiation behind interference filters, is rarely used.
These methods have advantages and disadvantages and therefore, there are limits for conclusions from these spectral data. Concerning the quasi monochromatic Irradiation of specimens the development of new UV radiation sources looks promising.
With the rapid development of inexpensive UV Light-emitting diodes (LEDs), new : sources of nearly monochromatic radiation in the UV ränge are available, even down to about 250 nm. To determine the spectral response, the use of such UV-LEDs in TO-18 ) and TO-39 metal cases combines the advantages of low cost and energy efficiency, stable spectral irradiance, temperature.and humidity control, larger specimen areas, and an easy and stable analysis.
Combinations of different UV LEDs are also discussed as replacement for xenon arc ' radiation sources, see patent application EP01528388A1.
Experimental investigation of the laser-plume interaction during high power fiber laser welding
(2011)
The effect of the well-known plasma absorption and refraction in CO2-laser metal welding plumes is in case of high power solid state laser welding negligibly small. By contrast, the diffraction effects of shorter wavelength laser radiation are considerable. According
to the results of preliminary studies, the fine condensed metal particles in the welding plume can lead to essential worsening of the laser beam quality.
This work is devoted to the investigation of the lasermatter interaction during up to 20 kW ytterbium fiber laser welding of thick mild steel plates. The plume attenuation of a probe 1.3 µm wavelength diode laser beam as well as of continuous radiation in 250-600 nm
wavelength range was measured during welding with and without Ar shielding gas supply. The measured results allow it to calculate average size and concentration of fine condensed metal particles in
different plume areas using the multi-wavelength method and the Mie scattering theory. The plume temperature, which determines the condensation conditions, was measured by means of Fe I atom
spectral line emission registration.
The obtained results can be also of interest for remote metal treatment with high-power fiber or disc lasers.
Structural performances of earthen building materials. A comparison between different typologies
(2011)
Traditional construction techniques utilizing earthen materials are often seen as inferior compared to modern ways of building. Structural earthen elements are perceived as vulnerable towards environmental influences (moisture, frost) and in particular towards the load scenarios during earthquakes. In comparison to the recent advances in research on stone and brick masonry, knowledge on the structural performance of earthen building construction is limited and scattered. Consequently the confidence in the performance of these earthen buildings constructed in the traditional techniques during earthquakes is fairly low. The research presented here aims to make a comparison of mechanical behavior between different earth masonry material typologies, consisting of earth block masonry, rammed earth and cob. The paper has been developed in the framework of a larger research program called NIKER. BAM and other seventeen research partners from the Mediterrean area are jointly involved to develop and validate innovative materials and technologies for the systemic improvement of the seismic behavior of Cultural Heritage assets
In connection with the use of chemically unstable gases (especially acetylene and ethylene oxide) accidents keep on happening - amongst them also quite serious ones. These gases are known to be chemically unstable. A chemically unstable sas is a flammable gas that is able to react exolosivelv even in the absence of air or oxveen. The investigation of accidents showed that the Chemical instability of flammable gases played an important role in the severity of accidents. Therefore, this hazardous property was included in the global harmonizatiön of the Classification of Chemicals. The Classification of chemically unstable flammable gases and mixtures is an amendment to Chapter 2.2 “Flammable gases” of the UN Globally Harmonized System of Classification and Labelling of Chemicals (GHS), because most chemically unstable gases are flammable as well. The proposal to add them to the GHS originated from the experts of an informal working group of the UN Sub-Committee of Expert on the GHS (UNSCEGHS) headed by BAM, Germany. The UNSCEGHS has decided to include it in the Fourth Revised Edition of the GHS. The respective method for determining whether a gas is chemically unstable or not, is included in the UN Manual of Tests and Criteria. This paper presents some experimental investigations of these gases, the test methods, examples of new classifications and results from CHEMSAFE
Cementitious materials, in particular concrete, are durable materials if prepared appropriately and the Service life of concrete structures is now often required to last 120 years or more. Concrete durability depends strongly on intrinsic (e.g. composition, porosity) and exterior factors (e.g. moisture condition and composition, frost cycles, load pattem). Deleterious actions leading to concrete degradation are often created by the environment. Extemal sulfate attack is one of the more spectacular damage scenarios for concrete structures caused by the ingress of sulfate ions into the pore System of the material and successive formation of expanding phases. Though in recent years well studied there are still many questions remaining conceming the mechanisms of sulfate attack. In particular over the last ten years, with the increased utilization of blended cements, new questions arose concerning the sulfate resistance of those binder Systems. In the presented study therefore a method was developed to analyze the changes of the phase composition within the micro structure due to sulfate attack. The analytical method was based on pX-Ray diffraction (pXRD) using Synchrotron radiation in Debye-Scherrer (transmission) geometry. The spatial resolution of the method is ca. 10 pm and allows the characterization of phase transformations in the wake of damaging processes in more detail compared to other techniques. Furthermore, the experimental setup provides the possibility for analyzing the phase assemblage of a given sample without destroying the micro structure. This is possible because the specimens for phase analysis consists of thick sections, which can be used for further microscopic analysis of the micro structure and micro chemistry (e.g. by SEM-EDX). Samples containing supplementary cementitious materials were measured in comparison and to reconstruct the influence of the degradation process in detail. Additionally, reaction ffonts within the samples were localized by micro x-ray fluorescence analysis (MXRF).
Biocompatible materials such as titanium are regularly applied in oral surgery. Titanium-based implants for the replacement of missing teeth demand a high mechanical precision in order to minimize micro-bacterial leakage, especially when two-piece concepts are used. Synchrotron-based hard x-ray radiography, unlike conventional laboratory radiography, allows high spatial resolution in combination with high contrast even when micro-sized features in such highly attenuating objects are visualized. Therefore, micro-gap formation at interfaces in two-piece dental implants with the sample under different mechanical loads can be studied. We show the existence of micro-gaps in implants with conical connections and study the mechanical behavior of the mating zone of conical implants during loading. The micro-gap is a potential source of implant failure, i.e., bacterial leakage, which can be a stimulus for an inflammatory process.
new burner concept for peroxy-fuels is proposed. The performance of the proposed peroxy-fuel burner is predicted with the help of Computational Fluid Dynamics (CFD) simulation. It is found that peroxy-fuel burner not only requires considerable less amount of fuel for the same output/power but also at the same time the overall size of the processing unit can be reduced. As peroxy-fuels contain oxygen atoms within the molecule itself a similar to oxy-fuel combustion environment is created without even supplying pure oxygen. CFD simulations also support the above facts and demonstrate the existence of less favorable conditions to form NOx.
Cathodic protection (CP) is a common method for rehabilitation of reinforced concrete structures suffering from Chloride induced corrosion. A sufficient protection of the corroding rebar can be ensured by use of several protection criteria. The use of these assessment criteria, in particular the so called 100 mV-criterion, can lead to erroneous resuits for certain unconventional arrangements of rebar and cp anode.
Therefore a joint research project of the Institute for Building Materials Research, RWTH-Aachen University, Germany, (ibac) and the Federal Institute for Materials Research and Testing, Berlin, Germany, (BAM) has been set up to determine the applicability of CP under arbitrary geometrical conditions. A special focus was set on the applicability of surface applied anode Systems for protection of the reinforcement of structures opposite to the accessible side (e.g. outer side of tunnel Shell, Bridge deck protected from inside a box girder) In this paper, the impact of the time dependent changes of the Polarisation behaviour of the rebar on the current and potential distribution is shown by means of parametric studies using the FEM method.
This contribution describes a computationally efficient ray tracing algorithm for evaluating transducer generated ultrasonic wave fields in anisotropic materials such as austenitic cladded and austenitic weld components. According to this algorithm, ray paths are traced during its propagation through various layers of the material and at each Interface the problem of reflection and transmission is solved. The presented algorithm evaluates the transducer generated ultrasonic fields accurately by taking in to account the directivity, divergence, density of rays, phase relations as well as transmission coefficients. The ray tracing algorithm is able to calculate the ultrasonic wave fields generated by a point source as well as a finite dimension transducer. The simulation results are compared quantitatively with the results obtained from Elastodynamic Finite Integration Technique (EFIT) on several configurations generally occuring in the ultrasonic non destructive testing of anisotropic materials. The excellent agreement between both models confirms the validity of the presented ray tracing algorithm. Finally, the ray tracing model results are also validated by means of experiments.
It has been shown in fire tests that polypropylene fibres reduce or avoid explosive spalling of high performance concrete. In the critical temperature ränge up to 300 °C the permeability of HPC increases by using polypropylene fibre. Due to this the water vapour, which is the main reason for explosive spalling, can escape. There exist different theories in the literature conceming the micro structural mechanisms, which cause an increase in the permeability. Within the framework of an internal research project at BAM an innovative methodology was developed for experimental verifying of existing theories and to get new insights into this problem The methodology used is unique and has been undertaken here for the first time. This consists of the combination of acoustic emission and ultrasonic measurement during temperature loading and the non-destructive micro structural analysis of cooled down samples with the aid of micro X-ray computed tomography. For the validation of the nondestructive test methods scanning electron microscopic images of prepared samples were undertaken. The results show that due to the thermal decomposition of the polypropylene fibres micro canals emerge. These are connected due to a simultaneous micro cack formation.
The paper has been developed in the framework of a larger EC‐research program called NIKER, in which BAM and other seventeen research partners from the Mediterrean area are jointly involved. It aims to develop and validate innovative materials and technologies for the systemic improvement of the seismic behavior of Cultural Heritage assets. The death tolls brought about by recent catastrophes in
developing countries where many inhabitants lived in earthen dwellings (Gujarat, India 2001, Bam, Iran 2003 and Concepción, Chile 2010 Earthquakes, Tamil Nadu 2004 Tsunami) have brought about research studies aimed at improving earth construction in terms of strength, seismic resistance and speed of construction.
In comparison to the recent advances in research on stone and brick masonry, knowledge on the material properties and failure mechanisms of earthen Building construction is limited and scattered.
The research presented here by aims making a comparison of mechanical behaviour between different earth masonry material typologies, consisting of earth block masonry, rammed earth and cob.
Whenever the preservation of original substance obtains priority in a restoration task, reprofiling techniques using repair mortars are a welcome solution. For ordinary concrete repair aesthetic aspects are of minor importance whereas for the restoration of natural stone elements they come to the fore. Especially for listed buildings and monuments, historico-cultural and aesthetical interests become the ruling Parameters for planning and execution of restoration tasks. Nevertheless the technical and constructive requirements have to be considered and deterioration processes have to be understood to ensure sustainability and durability of the repair task. Due o differences in the Chemical and mineralogical composition, natural stone provides a vast variety of texture and colour. Also the range of different mechanical and durability related properties is far wider than found with concrete for example. A research project dealing with the development of a modular repair mortar System for natural stone is currently set up at the BAM. To provide the conservator with the best possible options to match colour, texture and technical requirements, the System will be setup on a modular basis. Several different binder Systems on basis of cement, lime and sodium Silicate as well as polymer based Systems are planned, which can be combined with different aggregate compositions and different pigments. To evaluate the mortar performance, test procedures will be defined for tests on mortar samples and on composite specimens. In the paper the experimental Programme will be explained and first results will be presented and discussed.