K.-G. Eulitz

Betriebsfestigkeit in Germany — an overview ☆

Abstract The German word “Betriebsfestigkeit” can be translated into English with several terms. The best expression seems to be structural durability or structural integrity. This article gives a brief description of the efforts taken especially by the German automotive industry and its cooperating research institutes to improve the accuracy of life time prediction and to optimise the proof-out by usage of experimental and numerical procedures. The advantages of standardised load–time histories (SLHs) for the user particularly in the pre design stage are shown and an overview of the existing SLHs is given. At the end of the article some aspects of practical applications of “Betriebsfestigkeit” in the German automotive industry are presented.

Stress based fatigue life assessment of sintered steels and aluminium under variable amplitude loading

Abstract This paper aims to give an insight into the reliability of fatigue life assessment results for powder metallurgy (PM) components subjected to variable amplitude loading. In this study, notched specimens of two PM steel and two PM aluminium alloys are examined. As the experimental basis, constant amplitude tests with different stress amplitudes and stress ratios (to determine the S–N curves and mean stress sensitivities) as well as service load tests (variable amplitude loading) were carried out. The fatigue life was calculated, applying different modifications of the linear damage accumulation. The results of the experiments and calculations were compared and statistically evaluated. Regarding the resulting scatter, the fatigue life assessment with the modified damage accumulation by Zenner and Liu is recommended. Furthermore, mean relative damage sums are derived, which can be used to correct the fatigue life calculation. For PM steel, these values are very similar to compact steels, whereas they are higher for PM aluminium.