Characterisation of hyper-elastic materials by non-equibiaxial extension test based on dual-variable method

ABSTRACTThis paper presents a dual-variable test method for material constants calibration in hyper-elasticity. By ‘dual-variable’, we mean that two deformation parameters, axial stretching ratio λ1 and hoop extension ratio λ2, vary independently during the tests so that the measured strain invariants display a scattered two-dimensional distribution rather than one-dimensional variation along certain lines. Suggestions are made on testpiece design and test set-up. Deformation and stress analysis are conducted to provide equations and methods used for data processing. Effectiveness of the present method is verified by a case study of finite element method numerical simulation. The proposed method has the advantage of removing errors caused by uncertain non-homogeneous strain zones without complicated and expensive testing machines.