Influence of surface hardening on low cycle tension-compression and bending durability in stress concentration zones

Abstract

This paper provides experimental and analytical
evaluation of durability of nonhardened and hardened by
EMT specimens of grade 45 steel with stress concentrators,
under low cycle tension-compression and pure bending.
For both types of loading modes durability analysis was
carried out, taking into account fatigue and quasi-static
damage depending on loading level and the number of
semicycles. Stress and strain concentration coefficients
were calculated by analytical and finite element methods
(FEM) under elastic plastic cyclic loading. It was determined,
that in specimens with the stress concentrators under
low cycle pure bending, hardened surface has nonsignificant
influence on the durability, while under low cycle
tension-compression the positive influence starts when
stress amplitude is max 1.3 σ ≤ . The performed analyticalinvestigation showed, that the suggested method for quasistatic
and fatigue damage summation, when accumulated
plastic strain and the width of hysteresis loop are taken into
account, provides a very good agreement with the experimental
results in stress concentration zones of surfacehardened
parts under tension-compression and bending.