Innovative mechanical characterization of materials by combining ESPI and numerical modelling

Mechanical characterization of materials allows measuring elastic constants (i.e. Young’s modulus, Poisson’s ratio, etc.). A complete experimental plan consists of several mechanical tests which may results expensive both in terms of time and costs. Particularly when manufacturing process itself is expensive or when controlling all parameters involved in the manufacturing process is complicated, only a limited number of specimens will be tested and so results risk to be unreliable. The procedure proposed in this work aims to simplify the traditional mechanical characterization of all materials and to obtain the elastic properties by carrying out a reduced number of non-destructive tests. This new methodology combines two techniques: Electronic Speckle Pattern Interferometry (ESPI) with Finite Element Model (FEM). It works iteratively and proposes to minimize the difference between the displacement fields, experimentally evaluated by ESPI in three-point-bending tests, and their counterpart computed by FEM analysis, applying the same loads and boundary conditions. In this way the approach could be defined as a hybrid procedure based on a combination of an optical interferometric technique, commonly used in experimental mechanics, having sub-micrometric sensitivity with a numerical procedure, which uses an optimization algorithm. Once the procedure has been validated on materials whose properties are known, the purpose of the paper is to accurately evaluate mechanical properties of new materials, today widely applied in numerous fields ranging from aerospace to biomedicine, allowing to deeply reduce experimentation time and costs.