An algorithm for obtaining real stress field of hyperelastic materials based on digital image correlation system

Abstract

Soft matter with hyperelastic behavior may be harnessed for novel applications. However, it is not achievable if the mechanical behaviors of soft matter are not well understood. At present, various traditional extensometers have been used to measure the engineering strain of materials to determine the mechanical properties. The basic assumption of extensometers is that the strain is assumed to be uniform over the gage length. However, this assumption does not hold good in case of experimental specimens having significant nonuniform strain distribution, for example, tensile tests on notched specimens or materials that undergo localized deformations. Hence, it is imperative to adopt a new method which enables us to capture the actual strain field on the surface of a material. Digital image correlation (DIC) technique is an adequate approach that has been widely used in many fields of science and engineering. In this paper, we have presented a mapping algorithm for hyperelastic materials, translating the strain field provided by DIC to the stress field based on continuum mechanics. It overcomes the limitation of extensometers and captures the real stress field for such materials. This method will not only improve the measuring accuracy of stress and strain fields in current experiments, but also greatly promote the study of the localized characteristic for nonlinear and inhomogeneous materials.