On the mechanical behavior at sharp indentation of materials with compressive residual stresses

The correlation between residual stresses and the global properties, i.e. hardness and size of the contact area, given by a sharp indentation test have been studied quite frequently in recent years. The investigations presented have been based on experimental, theoretical and numerical methods and as a result, the basic features of the problem are now well understood. Furthermore, in this context quantitative relations, for the determination of residual stresses using sharp indentation, have been presented. Such relations have proven to be reliable in case of predominantly tensile residual stresses while the accuracy of predictions is much worse at compressive stress states. It is therefore the aim of the present study to investigate this matter in some detail and to present possible mechanisms for the difference in indentation behavior between tension and compression. Accordingly, the results are essentially qualitative but necessary and detailed investigations needed for a quantitative understanding are suggested. The present analysis is based on theoretical and numerical methods and in the latter case, the finite element method (FEM) is relied upon. Classical Mises elastoplastic material behavior is assumed throughout the investigation.