Hyperelastic constants from a modified hardness test using energy balance obtained from FE-analysis

In order to simplify the hyperelastic characterisation of rubber materials, an extension of the standard hardness test is proposed. A number of indentation depths are chosen for the hardness test and the indentation forces for these depths are recorded. By this modification, hyperelastic constants can be derived from the test, providing more information from the test by a small extra effort. Equivalence of the work done by the external force of the indenter and the strain energy stored in the rubber material, together with displacement control and the incompressible nature of rubber, reduce the problem of determining the hyperelastic constants to finding a solution to a system of equations with these constants as unknowns. The method is theoretically evaluated using finite element analysis, using hyperelastic constants from three real rubber materials with hardness from 40 to 78 IRHD. Hyperelastic constants with good accuracy are obtained using this simple method.