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- Absorbed energy (1)
- Axial Compression (1)
- Axial compression variation (1)
- Bewertung (1)
- Charpy pendulum impact test (1)
- Conversion of results (1)
- Curve fitting (1)
- Cyclic load (1)
- Cycling Tests (1)
- Ductile cast iron (1)
Organisationseinheit der BAM
Casks for the transport and storage of heat generating radioactive waste in Germany are normally provided with screwed lid systems, which are in most cases equipped with double jacket metal seals with an inner spring wire to provide long term resistance to the seal compression force. Preservation of the high sealing quality of those seals under operational and accidental stress conditions is essentially important to the safety of those casks. Relative displacements of the lid system surfaces caused by specific impact scenarios cannot be excluded and have to be evaluated with respect to a possible increase in the leakage rate.
To get representative data for such metal sealed lid systems, BAM has developed a special conceptualised flange system placed in an appropriate testing machine for relevant mechanical loading of the metal seals under static and cyclic conditions. Furthermore, the flange system enables continuous measurement of the standard helium leakage rate during each test.
The primary aim of the investigation is to identify the correlation between variation of installation conditions (axial displacements) caused by external loads and the standard helium leakage rate. An essential parameter in this case is the useable resilience ru of a metal seal under relevant stress conditions. The useable resilience ru is the vertical difference in the cross-section between the seal's assembling status and the point where the leakage rate, by means of external load relieving, exceeds the quality criterion of 10-8 Pa m3 s-1. Load relieving can instantly occur due to modification of the seal groove dimension caused by accident impacts and deformation of the lid system. Furthermore, component specific basis data for the development of finite element calculation models should be collected. In the tests, seals are subjected to static and cyclic loads. All tests are performed at ambient temperature.
This paper presents the test configuration, different test series and results of the current experiments. Typical load-displacement-leakage rate correlations are presented and discussed.
This paper is focused on the approximation of absorbed Charpy impact energy-temperature curves (KV-T) and the management of sub-size test piece results in Charpy pendulum impact tests. Both subjects are frequently underestimated but may have a strong impact on the assessment of product quality and structural integrity. The status of related test standards, product standards, structural integrity assessment procedures and corresponding research is reviewed.
It is concluded that the state of regulation is partly insufficient and wrong. There is a wide gap between the state of knowledge in the field of materials testing and the requirements of product standards and structural integrity assessment procedures. The present paper aims at boosting and supporting the necessary discussion among the parties involved to raise the level of technical safety. Correspondingly, a large experimental database was created by Charpy impact testing of popular modern structural Steels with nominal yield strength from 235 MPa to 960 MPa. KV-T data were generated using test pieces with thicknesses between 2.5 mm and 10 mm. Different strategies for KV-T curve fitting, definition of transition temperatures, as well as upper and lower shelf energy levels were followed, and different scaling procedures were applied to the sub-size test piece results. The results show that proportional scaling of sub-size to full-size test piece results in terms of KV should be disallowed because it is a wrong approach.
Regulations still incorporating such procedures should be revised as soon as possible. Existing nonproportional scaling and conversion procedures were applied. The results obtained illustrate that neither an overall nor consistent conservatism nor an adequate conservatism level can be achieved. In summary, the standardizing bodies should enforce the discussion to revise relevant test standards considering more precise specifications on Charpy data fitting. Furthermore, proposals are made for an improved management of sub-size test piece results.
Large scale testing and statistical analysis of dynamic fracture toughness of ductile cast iron
(2009)
Der Kerbschlagbiegeversuch ist als Prüfverfahren seit langem international genormt. Zu garantierende Kerbschlagarbeitswerte sind in Produktnormen weltweit festgelegt. Gleichwohl enthalten ganze Normenreihen für Stähle falsche Festlegungen zur Verwendung von Untermaßprobenergebnissen. Im Mittelpunkt der vorliegenden Studie stehen die Auswertung von KV-T-Daten und die Skalierung von Untermaßprobenergebnissen. Hierzu wurden an ISO-V-Proben der Breiten 2,5; 5; 7,5 und 10 mm aus vier Baustählen im Streckgrenzenbereich von 235 bis 960 MPa dicht belegte KV-T-Kurven ermittelt. Es wurden unterschiedliche Vorgehensweisen zur Kurvenanpassung und Festlegung von Übergangstemperaturen wie auch der Hoch- bzw. Tieflagenarbeit untersucht. Die Ergebnisse unterstreichen unter anderem, dass die in festgelegte Vorgehensweise, nach der Untermaßprobenergebnisse proportional auf Normprobenmaße zu skalieren sind, nicht nur zu falschen, sondern auch nicht-konservativen Kerbschlagarbeitswerten führen kann. Das Ausmaß dieses Probenbreiteneffektes ist Werkstoff- und temperaturabhängig. Da die Kerbschlagarbeit als Abnahmekriterium verwendet wird, ergeben sich unmittelbare wirtschaftliche und sicherheitstechnische Konsequenzen. Es ist zu schlussfolgern, dass die entsprechenden Produktnormenreihen dringend zu überarbeiten sind.