thanks you. this is usermat original code I only add density to it. the problem is the density did not change during time steps. at the end i should hve plots of density vs time that density changes every step. the UPF ACT extension did not work with my academic version . i modeled in workbench and import the .inp fie to the APDL but it only solved the first time step . i use outres, all,all command.  i need the density  to change every time steps.