Code for Cowper-Symonds material deformation law ?

I am working on Cowper-Symonds material deformation law and i wanted your help. I have already done i big part from my code but i wanted to know if anyone else has a "ready to play" code so i can use that as an example to correct my code and help me to proceed to the end. Also a analytic "step by step" answer for how to create the code will be also very helpfull. ( I have also all the data with the different speed of the tests that were made.) Any suggestions? Thanks for your time !

[LOKANATH BARIK]

Can you please share the constitutive matrix for the model in order to determine the stiffness matrix.