Limit analysis-based approach to determine the material plastic properties with conical indentation

Representative strain plays an important role in indentation analysis; by using the representative strain and stress, the normalized indentation load becomes a function of one variable, which facilitates the reverse analysis of obtaining the material plastic properties. The accuracy of such function is critical to indentation analysis. Traditionally, polynomial functions are used to fit the function, which does not incorporate correct elastic/plastic limits and has no physical basis. In this paper, we have proposed a new limit analysis-based functional formulation based on the theoretical solutions of conical/ wedge indentation on elastic and rigid plastic solids. It is found that both limits agree well with numerical results, and the new approach involves no - or at most one - fitting parameter, which can be obtained with much less effort compare with the traditional polynomial approach. Reverse analyses on five different materials have shown that the new and simple limit analysis-based formulation works better than the traditional polynomial fit. The new technique may be used to quickly and effectively measure material plastic properties for any conical indenter if the elastic modulus is known a priori.