An accurate test method for measuring static compressive properties of a material

Abstract

In traditional uniaxial compression test, the friction between specimen and bearing plates during testing leads to non-uniform deformation of the specimen. Therefore, the compressive properties of a material may not be accurately measured. To improve the accuracy of measurement, a comprehensive testing scheme is developed in this report. In our method, both close range photogrammetry (CRP) and numerical inversion of the specimen deformation are introduced into a traditional compression test. Firstly, the surface deformation of a specimen during the testing is captured by CRP technique and measured using software Ncorr. Secondly, the mechanical properties of a material can be calculated using testing data. Thirdly, the numerical deformation of specimen under the same loads as those in testing is obtained by finite element method. There is a difference between the testing and numerical results. Minimizing the difference will provide optimal material properties. Finally, an inversion model is built, in which the mechanical properties are design variables. The objective is to minimize the difference between the testing deformation and numerical deformation. The consultant reaction along compression direction on a contact surface of specimen acts as a constraint function. Inversion results show that both the elastic modulus and Poisson’s ratio are modified.