Determination of the material constants of creep damage constitutive equations using Matlab optimization procedure

Creep damage constitutive equations based in continuum damage mechanics are characterized by their complexity due to the coupled form of the multi-damage state variables over a wide range of stresses. Thus, the determination of the material constants involved in these equations requires the application of an optimization technique. A new objective function was designed where the errors between the predicted and experimental normalized deformation and lifetime were used in conjunction of the minimal nonlinear least square method from Matlab. Its use is simpler, more compact, and less uncertain and is able to obtain an accurate solution for a sample material (0.5Cr 0.5Mo 0.25V ferritic steel) at the range of 560-590°C. The specific experimental data, the material constants, and all the factors needed are provided as a comparison with the existent investigation of this material. Future works should aim at to further establish the reliability and user-friendness of the method.