A REVISED APPROACH TO DAMAGE MEASUREMENT BASED ON STIFFNESS LOSS TECHNIQUE

In the last decades damage mechanics has received a lot of attention and has proved to be a powerful approach to describe the occurrence of failure in materials. In order to became an effective tool of practical application in the industrial design world, clear, reliable, and - when possible - simple procedures and practices, aimed to perform damage measures and to identified damage model parameters, are needed. In the literature, only a limited number of papers addresses the issue of the damage measurements. Among the possible different techniques, the measure of the progressive loss of stiffness as a function of the increasing inelastic strain level, is the most commonly used and referred. Even though this technique is conceptually simple, it can be affected by a number of error that can invalidated the measures. In this paper a clear and effective procedure based on the use of finite element simulation and experiments is presented. The proposed procedure allows one to correctly account for the geometry changes occurring in the sample even in the post necking regime where stresses and strain are no longer uniform along the section and the gauge length. The proposed methodology has been used to measure damage in 99.99% pure copper