Elastoplastic Behavior of Case-Carburized 18Cr2Ni4WA Steel by Indenter Testing

Abstract

The mechanical behavior of case-carburized 18Cr2Ni4WA steel is investigated by an optimization method combined with finite-element simulation based on indentation tests. For a measured load-displacement curve, the uniqueness of the combination of the strain hardening exponent and yield stress of a material is discussed by analyzing their effects on the maximum reaction force and residual displacement. The result shows that the effects of yield stress on the load-displacement curve are more pronounced than those of the strain hardening exponent when the elastic modulus is prior known. An optimization model containing an equality constraint is constructed and carried out in every indentation location, and its results indicate that the strain hardening exponent may be constant with depth in the case-carburized steel. The conclusion is further verified through a modified optimization model proposed herein. Therefore, the gradient in the mechanical behavior for the carburized material is primarily reflected by the variation in yield stress with depth. The correlation between hardness and yield stress is established through the least squares method according to the results of the modified optimization model and should help predict the mechanical behavior of parts in the carburized material.