Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7172091 | International Journal of Fatigue | 2015 | 6 Pages |
Abstract
Cyclic torsion fatigue tests with superimposed static torsion loads are performed with VDSiCr spring steel with shot-peened surface in the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) regime. Fatigue properties are investigated at load ratios RÂ =Â 0.1, RÂ =Â 0.35 and RÂ =Â 0.5 up to limiting lifetimes of 5Â ÃÂ 109Â cycles with a newly developed ultrasonic torsion testing method. Increasing the load ratio reduces the shear stress amplitude that the material can withstand without failure. Fatigue cracks are initiated at the surface in the HCF regime. In the VHCF regime, cracks are preferentially initiated internally in the matrix, below the surface layer with compression residual stresses, and less frequently at the surface. Cyclic and mean shear stresses with 50% survival probability in the VHCF regime are presented in a Haigh diagram. Linear line approximation delivers a mean stress sensitivity of MÂ =Â 0.33 for load ratios between RÂ =Â â1 and RÂ =Â 0.5.
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Authors
H. Mayer, R. Schuller, U. Karr, D. Irrasch, M. Fitzka, M. Hahn, M. Bacher-Höchst,