Identification du comportement mécanique des matériaux à l'aide d'essais de micro-impact répétés

As constitutive laws reflect the mechanical properties of materials, they are an essential input for Finite Element Modelling software. In order to identify the behaviour of material, several techniques such as static tensile test, Hopkinson bars. . . can be used. However most of them tend to be expensive and require specific sample geometries. The objective of this study is to develop a method that provides a quick approach to the constitutive law of metals using micro-impact tests. This method is able to identify the stress-strain curve of material in compression and under high strain rate. In the first part, the experimental micro-impact device and the numerical model are presented then the inverse method is detailed. To launch the inverse method, a numerical finite element simulation of repeated impacts was created and a database has been developed from tens of simulations with several values of K and n parameters of the Hollomon constitutive law "σ = Kεⁿ". Based on these simulation results an inverse method was developed to identify a constitutive law by the comparison between the numerical (database) and experimental results of radius and loads. The first step of the method validation was performed using purely numerical tests on virtual materials with real and perfect constitutive laws, following a Hollomon model or not. Then, applications on virtual and industrial materials are presented.