TY - JOUR A1 - Gaal, Mate A1 - Bovtun, Viktor A1 - Stark, Wolfgang A1 - Erhard, Anton A1 - Yakymenko, Y. A1 - Kreutzbruck, Marc T1 - Viscoelastic properties of cellular polypropylene ferroelectrets N2 - Viscoelastic properties of cellular polypropylene ferroelectrets (PP FEs) were studied at low frequencies (0.3–33 Hz) by dynamic mechanical analysis and at high frequencies (250 kHz) by laser Doppler vibrometry. Relaxation behavior of the in-plane Young’s modulus (Y´ 11~1500 MPa at room temperature) was observed and attributed to the viscoelastic response of polypropylene matrix. The out-of-plane Young’s modulus is very small (Y´33≈0.1 MPa) at low frequencies, frequency- and stress-dependent, evidencing nonlinear viscoelastic response of PP FEs. The highfrequency mechanical response of PP FEs is shown to be linear viscoelastic with Y´33≈0.8 MPa. It is described by thickness vibration mode and modeled as a damped harmonic oscillator with one degree of freedom. Frequency dependence of Y*33 in the large dynamic strain regime is described by the broad Cole-Cole relaxation with a mean frequency in kHz range attributed to the Dynamics of the air flow between partially closed air-filled voids in PP FEs. Switching-off the relaxation contribution causes dynamic crossover from the nonlinear viscoelastic regime at low frequencies to the linear viscoelastic regime at high frequencies. In the small strain regime, contribution of the air flow seems to be insignificant and the power-law response, attributed to the mechanics of polypropylene cell walls and closed air voids, dominates in a broad frequency range. Mechanical Relaxation caused by the air flow mechanism takes place in the sound and ultrasound frequency range (10 Hz–1MHz) and, therefore, should be taken into account in ultrasonic applications of the PP FEs deal with strong exciting or receiving signals. KW - Viscoelastic KW - Cellular polypropylene KW - Ferroelectret PY - 2016 U6 - https://doi.org/10.1063/1.4944798 SN - 0021-8979 SN - 1089-7550 SN - 1520-8850 VL - 119 SP - Article Number: 125101 PB - AIP Publishing AN - OPUS4-35956 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Iancu, O.T. A1 - Erhard, Anton A1 - Otremba, Frank A1 - Sklorz, Christian T1 - Consistency between analytical and finite element predictions for safety of cylindrical pressure vessels at higher temperatures N2 - Die Vorhersage der Beanspruchung bei plastischem Versagen von zylindrischen Druckbehältern wird häufig mittels Finite Elemente Berechnungen durchgeführt. Die Berechnung der zulässigen Beanspruchung erfordert ein elastisch-plastisches Werkstoffmodell und die Berücksichtigung von nichtlinearen geometrischen Effekten. Das plastische Versagen verursacht eine gesamte Strukturinstabilität und kann nicht direkt aus der Finite Elemente Analyse bestimmt werden. In dem vorliegenden Beitrag wird die Beanspruchung für plastisches Versagen eines zylindrischen Druckbehälters mittels eines analytischen Verfahrens basierend auf einem linear elastischen ideal-plastischen Materialmodell bestimmt. Wenn Plastizität auftritt, wird zum einen der Werkstoff als inkompressibel und zum anderen der Tensor der plastischen Dehnungen als parallel zum Spannungsabweichungstensor angenommen. In diesem Fall kann die Spannungs-Dehnungs-Beziehung von Henkel angewendet werden, um den Druck zu berechnen, bei dem plastisches Fließen und Versagen eintritt. Die analytischen Ergebnisse werden von den Finite Elemente Berechnungen vollkommen bestätigt. KW - Materials testing KW - FEM KW - Plastic instability KW - Limit load analysis KW - Pressure vessel KW - Analytical solution PY - 2014 SN - 0025-5300 VL - 56 IS - 4 SP - 274 EP - 278 PB - Hanser CY - München AN - OPUS4-30722 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erhard, Anton A1 - Otremba, Frank T1 - Nondestructive testing and fracture mechanics N2 - Nondestructive Testing (NDT) and fracture mechanics are two different disciplines in applied engineering science. Both areas are very important for the evaluation of the component integrity. Unfortunately the technical understanding in both disciplines is not identically, what lead to misunderstandings. In the present paper, the basic ideas about fracture mechanics and the input parameters coming from the NDT side are explained, concerning the integrity evaluation of the components. The widely used NDT methods are magnetic particle, dye penetrant, electrical eddy currents, radiography and ultrasonics. But not all of these common NDT methods can deliver parameters satisfy the fracture mechanics requirements. The first two can detect only surface-breaking or immediately sub-surface defects. Eddy current can also find defects in deeper sub-surface layers, while radiography and ultrasonics can also find embedded, remote defects. These three methods have furthermore a high potential for defect sizing and are therefore predestined to provide fracture mechanics input parameters. At the example of steam generator tube inspection the interplay of eddy current and fracture mechanics as related to tube integrity will be explained. T2 - 5th International CANDU In-Service inspection workshop and NDT in Canada 2014 conference CY - Toronto, Ontario, Canada DA - 16.06.2014 KW - Eddy current KW - Steam generator tube inspection KW - Component integrity KW - Fracture mechanics PY - 2014 SP - 1 EP - 12 AN - OPUS4-30907 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Ono, K. A1 - Erhard, Anton T1 - Nondestructive testing, 3. Ultrasonics N2 - The field of acoustics deals with sound Propagation in solids, liquids, and gases, whereby the frequencies may lie above or below the Audio band, that is, infrasound (<16 Hz) and ultrasound (>16 kHz), respectively. The speed of sound depends on mechanical properties of the material like elastic constants and compressibility. Interaction of imperfections such as grains, cracks, pores, and inclusions with sound waves results in reflection, refraction, scattering, and attenuation due to discontinuities in elastic moduli and density. By sending a pulse and receiving its reflection, the presence and Location of defects can be determined (pulse-echo technique). Ultrasound was applied in nondestructive testing (NDT) earlier than in medicine, but visualization of the data in a unicolor-scale image was first used in medical ultrasound diagnostics. The principle of ultrasonic testing, for example, the wave types that are suitable for different applications, the frequency ränge employed, reflectivity behavior, mode conversions, probe types, and so on are described in various publications, and a newer ultrasonic method, namely, the phased array technique, is treated in. KW - Ultrasonic waves KW - Piezocomposite materials for ultrasound generation KW - Phased array technique PY - 2011 SN - 978-3-52730-673-2 U6 - https://doi.org/10.1002/14356007.o17_o02 SP - 1 EP - 17 PB - Wiley-VCH AN - OPUS4-24090 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erhard, Anton A1 - Noack, Volker A1 - Völzke, Holger T1 - Storage facilities at Sayda Bay N2 - 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. T2 - 52nd INMM Annual meeting CY - Palm Desert, CA, USA DA - 17.07.2011 KW - Storage facility KW - Nuclear reactor compartments PY - 2011 SP - 1 EP - 7 AN - OPUS4-26197 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Erhard, Anton A1 - Völzke, Holger A1 - Probst, Ulrich A1 - Wolff, Dietmar T1 - Aging management for long-term interim storage casks N2 - The aging management system for the mechanical components of nuclear power plants (NPPs) must be established and used by the licensee in such a way that the quality of safety relevant components is guaranteed for the completely designed lifetime of the NPP. This demands an extensive plant life management with special emphases on the knowledge of the degradation in material properties. The basic safety concept in Germany observes this circumstance. Lifetime extension of the German NPPs is an aim of the current valid coalition agreement of the German government. Operational extension of interim storage facilities requires, in comparison to the aging management system for NPP, an aging management system adapted to the Special circumstances of spent fuel storage casks. Extension of interim storage periods for spent fuel casks beyond the designed lifetime requires, in comparison to the components of an NPP, an increasing knowledge of material degradation with potential impact on cask integrity, e.g. leak tightness. Dry interim storage in Germany has been approved for 40 years. After that time, according to the present strategy, a final repository should be available. However, until now, such a final facility still does not exist, and the German exploration and licensing process is heavily delayed. Currently, discussions are continuing regarding further exploration of the Gorleben salt mine. There is willingness to overcome this situation that is clearly described in the available coalition agreement of the federal government. Anyway, however, the prediction is viewed; a repository for heat generating radioactive waste in Germany will not be available in the near future and may not be available when first storage facilities and casks reach their 40 years of approved lifetime, which will occur in ~25 years starting from now. Therefore, the question must be asked: what has to be done with the existing storage casks in the interim facilities? May these casks be fit for continued use, with an extension of the storage period? One option is to have an aging management system, which creates enough information about the technical condition of safety relevant cask properties. This is the basis for safety evaluation for extended storage periods. In the present paper, possible aging mechanisms for high level waste storage casks are discussed, as well as the influence of the time dependent changes of the component properties. KW - Long term interim storage KW - Storage casks KW - Aging mechanisms KW - Degradation mechanisms KW - Metal seals KW - Larson-Miller parameter PY - 2011 U6 - https://doi.org/10.1179/1746510910Y.0000000013 SN - 1746-5095 SN - 1746-5109 SN - 0957-476X VL - 22 IS - 1 SP - 46 EP - 53 PB - Ramtrans Publ. CY - Ashford AN - OPUS4-23890 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brekow, Gerhard A1 - Erhard, Anton T1 - Untersuchungen mit TOFD an geschweißten Längsnahtproben N2 - Im Gegensatz zur Impuls-Echo-Technik, die im Wesentlichen auf der Anton Erhard, Berlin Reflexion am Fehler basiert, wird bei der Time-Of-Flight Diffraction Technique (TOFD-Technik) die Beugung der Schallwellen am Fehler zum Nachweis genutzt. Zwei Winkelprüfköpfe für Longitudinalwellen sind in V-Durchschallung angeordnet. Die Prüfköpfe befinden sich jeweils auf einer Seite der Schweißnaht und werden bei der Messung parallel zur Schweißnaht verschoben. Das ausgesandte Schallbündel trifft auf Fehlerränder, an denen gebeugte Wellenanteile entstehen, die je nach Entstehungsort mit unterschiedlichen Schalllaufzeiten empfangen, in hochfrequenten A-Bildern abgespeichert und für die Auswertung in B-Bildern dargestellt werden. Die Untersuchungen zeigen, dass die TOFD-Technik Beiträge zur Fehlergrößenabschätzung liefert, aber keinesfalls die Impuls-Echo- Technik mit nachgeschalteter Röntgenprüfung ersetzen kann. PY - 2000 SN - 0025-5300 VL - 42 IS - 11-12 SP - 437 EP - 443 PB - Carl Hanser Verlag CY - München AN - OPUS4-963 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -