Failure of Alumina in Torsion Tests
- Author: T. Schwind, S. Fuenfschilling, E. Kerscher, K.H. Lang, R. Oberacker, M.J. Hoffmann, T. Fett
- Source: ADVANCED ENGINEERING MATERIALS, 2010, Band 12, Heft 9, S. 942-947
Fatigue behavior under cyclic torsion loading shows a complicated dependency between the number of cycles to failure N-f and the height of the applied load sigma(appl). A recently published result is chosen for which three clearly different regions are observed in which the normally straight log(N-f)-log(sigma) plot shows different slopes. Whereas the high-stress region near the torsion strength can be interpreted as normal mode-I failure of randomly oriented surface cracks, the steep part may be understood as the consequence of friction degradation at grinding cracks which are under pure mode-II and mode-III loading. At lowest loads, quasi-static subcritical crack growth support has to be expected with its commonly higher load exponents.