Automatic implementation of finite strain anisotropic hyperelastic models using hyper-dual numbers

The main aim of this paper is to automate the implementation of finite strain anisotropic hyperelastic models into a general finite element framework. The automation presented in this paper enables the end-user to implement a hyperelastic model by programming its Helmholtz free energy function alone. The automation is achieved by employing hyper-dual number system to evaluate analytical quality derivatives. New perturbation techniques are introduced and are employed to extend the hyper-dual numbers system to evaluate tensor derivatives. The capability of the proposed automation scheme is demonstrated by implementing five finite strain anisotropic hyperelastic models. The merits and demerits of the proposed automation scheme are compared to an automation scheme based on the central difference method.