Analytical Investigations on Stress Relaxation at Elevated Temperature

Stress relaxation is a phenomenon which occurs for components subjected to stress and temperature and natural creep is some how arrested. That the natural creep gets arrested due to prevailing constraints is a common experience and stress relaxation is almost always present. This subject of stress relaxation which is of concern in design of high temperature components is the theme of this research. Relaxation is studied next using these creep laws and a relaxation model. Five different relaxation models are considered and uniaxial (pure) relaxation is studied. A typical bolt material (x 22 crMo V 121) is used for analysis. The experimentally observed relaxation is used to evaluate various relaxation models. Larsen Miller parameter (LMP) which is quite commonly used in creep calculations is advantageously used to evaluate self-consistency of various creep laws and the relaxations derived there from. Practical cases of stress relaxation like relaxation under stress gradient and temperature gradient & pre tensioned bolt are studied. Some programs in the form of spread-sheet, Fortran, and ANSYS macros are also developed.