Yes, there is a difference in the formula used: In ANSYS Mechanical, the Williams-Landau-Ferry Equation is described as log(a_T) = C1 * (T – T_ref)/(C2 + (T – T_ref)) . However, in Workbench LS-DYNA, the WLF Equation is described as: O(T) = exp( -A * (T – T_ref)/(B + (T – T_ref)) . Hence, the conversion is A = C1 / log10(e), B = C2 It is important to keep this in mind while specifying the material parameters in both codes.