New User-Supplied Subroutines in DIANA have been proposed for the elastic matrix of rubber-like materials in this paper. When the first and second derivatives of the strain energy function are known, other information can be generated automatically in DIANA through the new User-Supplied Subroutines. Knowles’ and Gao’s constitutive laws for rubber-like materials have been implemented in DIANA by this means. Singular problems are described successfully by those constitutive laws. We demonstrate two representative examples: uniaxial and biaxial tension analyses of a rubber cube show that the DIANA finite element package provides data which are consistent with the analytical results. When a new strain energy function is proposed in the future, the new constitutive law could be more conveniently inserted into DIANA than before. The new User-Supplied Subroutines in DIANA render new possibilities to study mechanics of rubber-like materials.
