A STUDY OF THE DEFORMATION-BEHAVIOR UNDER MULTIAXIAL LOADING

Biaxial tests have been carried out on tubular specimens of En15R steel at room temperature, covering both proportional and non-proportional loading. Tests were conducted on a tension-torsion fatigue machine with a computer system for control and data acquisition. An integral form of hysteresis strain hardening rule and a memory rule are presented for proportional loading, from which the stress-strain response under proportional variable amplitude loading can be predicted. Both the hysteresis hardening rule and the memory rule have been generalized to extrapolate from proportional loading to the case of non-proportional random loading. The hysteresis hardening rule is interrelated to a scalar memory; this enables the dependence of strain hardening behaviour on loading history to be characterized. The predictions of the proposed model are compared with experimental data for proportional and non-proportional variable amplitude loading paths, showing good agreement and demonstrating the capability of the present model.