From an experimental data perspective, there is no difference between the uniaxial test data and uniaxial tension test data. However, which one you use does depend on the material model you chose. If you are going to perform a conventional hyperelastic curve fit with one of the several strain energy density functions, then input your test data as “Uniaxial Test Data”. If you are going to represent the hyperelastic material with the Response Function model, then the “Uniaxial Tension/Compression Test Data” must be defined instead. The Response Functions for the first and second strain invariants are determined from the experimental data from uniaxial, equibiaxial tension, or pure shear test data. Additionally, for incompressible materials, uniaxial compression experiments are equivalent to equibiaxial tension and can be used in place of equibiaxial data to determine the response functions. Refer also to // Theory Reference // 4. Structures with Material Nonlinearities // 4.6. Hyperelasticity for in the Help system for more information.