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Mean stress sensitivity and crack initiation mechanisms of spring steel for torsional and axial VHCF loading

Tuesday (27.09.2016)
17:00 - 17:15
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Shot peened VDSiCr spring steel has been investigated under cyclic torsional and axial loading at load ratios between R=-1 and R=0.5. The ultrasonic fatigue testing method is used to collect fatigue data in the range between 105 and 1010 cycles. Mean stress sensitivities and VHCF strengths are compared for both loading conditions. Damage mechanisms leading to failures in the VHCF regime are different for axial and torsional loading. Inclusions and fractured grain boundaries are preferential crack initiation sites under cyclic axial loading. VHCF cracks produced by cyclic torsion loading are mainly initiated internally by cyclic shear without the presence of a material inhomogeneity. The initial mode II / mode III cracks change their paths to mode I at a well defined stress intensity. Residual stresses are affected by cyclic torsion but not by axial VHCF loading.

Prof. Dr. Herwig Mayer
University of Natural Resources and Life Sciences
Additional Authors:
  • Reinhard Schuller
    Universität für Bodenkultur Wien
  • Ulrike Karr
    Universität für Bodenkultur Wien
  • Dr. Michael Fitzka
    Universität für Bodenkultur Wien
  • Daniel Irrasch
    Universität für Bodenkultur Wien
  • Dr. Malte Hahn
    Robert Bosch GmbH
  • Dr. Manfred Bacher Höchst
    Robert Bosch GmbH


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