Comparison of stress rate and strain rate methods in timedependent creep evolution analysis of FGM structures

The stress rate and strain rate methods in creep evolution analysis are compared. For this purpose a thick-walled sphere made of functionally graded material (FGM) subjected to an internal pressure is studied. All of the material properties except the Poisson’s ratio have been expressed as a power function of the sphere radius. It has been concluded from the present study that, the stress rate method has a good adoption with the strain rate method for lower time increments, however by increasing time intervals the agreement between stress rate and strain rate methods decreases. It has also been found that the stress rate method is faster than strain rate method.