SEDL / STP / STP1387-EB / STP13507S

Fatigue of the Quenched and Tempered Steel 42CrMo4 (SAE 4140) under Combined In- and Out-of-Phase Tension and Torsion

Löwisch, G
Research engineer, senior research engineer, and managing director, Stiftung Institut fuer Werkstofflechnik, Bremen,

Bomas, H
Research engineer, senior research engineer, and managing director, Stiftung Institut fuer Werkstofflechnik, Bremen,

Mayr, P
Research engineer, senior research engineer, and managing director, Stiftung Institut fuer Werkstofflechnik, Bremen,

Pages: 14    Published: Jan 2000

Download this paper for $25 PDF (228K)          View License Agreement
Abstract

Two types of specimens of the quenched and hardened steel 42CrMo4 (similar to SAE 4140) that differed in their residual stress state were tested by combined tension-torsion in- and out-of-phase loading. Under cyclic, stress controlled loading an elastic behavior is registered until 50% of the lifetime. Then a continuous softening occurs, the velocity of which correlates with the von-Mises equivalent stress in the case of in-phase loading. The residual stresses have no influence on the lifetime when cyclic softening occurs. Analytically, the lifetime is best described by the fatigue criterion of Zenner which considers the integral average of the stress state in every plane. This stress state is described by a function of the shear stress amplitude and the normal stress amplitude. Below the cyclic yield strength, the residual stresses must be taken into account as static stresses. The comparison of the local residual stress distributions is possible by using the weakest link model of Heckel.