Characterization of material mechanical properties using strain correlation method combined with virtual fields method

The isotropic and anisotropic behaviors are considered as the important formats of the constitutive behaviors, and can also be called the global properties. To improve the identification ability of virtual fields method (VFM) when the global properties are unknown, this paper proposes the strain correlation method (SCM) to determine the global properties before the parameter identification using the VFM. Firstly, the basic principle of SCM is described in detail. Then, the feasibility and accuracy of SCM are verified through the numerical experiments based on the three-point bending configuration and the real experiment of polymethyl methacrylate (PMMA). The influence of the additive Gaussian white noise, local errors in the strain fields, and missing data at the specimen edges on the characterization results are evaluated. The results show that the SCM has good noise immunity and lower accuracy requirements for the strain fields. As an application, the mechanical properties of Ti-6Al-4V alloys fabricated by selective laser melting (SLM) are characterized by the SCM. The results show that the alloys are isotropic, and the isotropic VFM is utilized to determine the mechanical parameters. By using the SCM, the accuracy of identification results can be improved for the isotropic or bidirectional reinforced orthotropic materials when using VFM.