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Multiaxial fatigue behaviour of sintered steels under combined in and out of phase bending and torsion.

Festigkeitsverhalten von Sinterstählen unter kombinierter phasengleicher und phasenverschobener Biegung und Torsion
: Grubisic, V.; Sonsino, C.M.

Zeitschrift für Werkstofftechnik 18 (1987), No.5, pp.148-157 : Abb.,Tab.,Lit.
ISSN: 0049-8688
Journal Article
Fraunhofer LBF ()
Festigkeitsverhalten; mehrachsige Beanspruchung; Rundprobe; Sinterstahl; Zeitfestigkeitsversuch

This paper discusses the fatigue behaviour of sintered steels under multiaxial loading. These steels are the Fe-1.5%Cu and the Fe-2.0%Cu-2.5%Ni, sintered at low and high temperatures, in the densities 7.1 and 7.4 g/cubicmeter, which are used in the production of several ready to assemble automotive parts. Fully reversed or pulsating combined loading with constant frequency and amplitudes acting in and out of phase, was applied to round notched specimens (K sub tb=1.49, K sub tt=1.24) in the finite fatigue life region (10E4 smaller N sub f smaller 2.10E6). The mechanics of crack initiation and propagation as well as rupture were studied using fractography and microfractography. These analyses led to a mechanical model based on local normal stresses for the fatigue life evaluation. The fatigue life evaluation on the base of the local bending stress obtained under uniaxial loading describes the test results for in phase combined bending and torsion satisfactory. But the increase of fatigu e strength and life by out of phase loading is overestimated in the case of fully reversed loading. However for design purposes the out of phase loading can be neglected because of its beneficial effect in increasing fatigue life for this type of material. If the dependence of the different stress concentrations under combined in and out of phase loading on the supportable local bending stress obtained under uniaxial loading is considered, then the calculation procedure covers all test results. (LBF)