A Tension-Torsion Testing Technique
Although the creep behaviour of metals has been investigated since the beginning of the twentieth century (Andrade, 1910), a limited amount of data are available to describe this process, in the case of non-proportional, variable load conditions. The majority of tests have been performed under constant uniaxial load and do not coincide with those encountered in real components which operate under variable and complex states of stress. Such simple loading conditions do not show many of the effects found under complex stress states and which play an important role for some loading programmes (material softening observed after change in the principal component of the stress tensor, directional character of damage, etc.). So, because of modern design requirements for components such as nuclear power stations, chemical plants and so on, and due to the necessity of better knowledge of material behaviour and to the formulation of credible material models, it is necessary to obtain results of creep tests for complex stress state and variable loadings. Such experiments have not been carried out in a systematic way until relatively recently because of the technical difficulties in experimentation. Tests have been carried out basically for plane stress conditions (σ l≠0,σ4 2≠0,σ 3=0) using different test techniques.
KeywordsCreep Test Ball Bearing Knife Edge Complex Stress State Tubular Specimen
Unable to display preview. Download preview PDF.
- Andrade, E. N. DaCosta (1910), The viscous flow in metals and allied phenomena, Proc. Roy. Soc., 84.Google Scholar
- Findley, W. N. and Gjelsvik, A. G. (1962) A biaxial testing machine for plasticity, creep or relaxation under variable principal stress ratios. Proc. Am. Soc. Test. Materials, 62, 1103–18.Google Scholar
- Hostinsky, T. and Cadek, J. (1974) Stroj pro crepove zkousky w tahu pri konstantnim napeti. Kovove Materialy, 4, XII, Bratislava.Google Scholar
- Penny, R., Ellison, E. and Webster, G. (1966) Specimen alignment and strain measurement in axial creep tests, ASTM Mat. Res. Stand., 6, 76–84.Google Scholar
- Szczepinski, W. (1963) On the effect of plastic deformation on yield condition. Arch. Mech. Stosow., 2 (15), 275–93.Google Scholar
- Waniewski, M. (1983) Wpływ kierunku i wartości wstępnej deformacji plastycznej na pełzanie metali. Prace IPPT 34/1983.Google Scholar