Our work will show that complex transient coupled problems can be formulated
and solved effectively with AceGen and AceFEM using an automatic differentiation
based formulation (ADB-formulation). From scalar pseudo-potential function consistent
tangent matrix for strongly coupled problems can be derived, leading to quadratically
convergent Newton-Raphson type procedure. Another problem considered is the implementation
of finite element. Typically, all equations are written inside a single finite
element and a single pseudo-potential is defined. Such implementation is efficient but
rigid, therefore, a different implementation was considered. Within the second approach
we wrote a separate finite element for each field, but in a way that quadratic convergent
Newton-Raphson procedure is preserved. The paper presents examples where unified and
field-by-field implementations are compared according to computational efficiency. The
results show that with increasing ratio between the complexity of constitutive equations
and discretization, generated code size and evaluation time of implementations become
comparable