I want to create a new material ( say similar to SA 516 gr 70 ) but with other allowable stresses (versus temperature and ALSO versus thickness)

1/-Could you please tell me the steps
I would like to start from SA 516 gr 70 , make a copy and modify the stresses .

2/-Please tell where and how to check the material ( I mean in which directory of PV elite is it stored ?

thanks