Creep of autofrettaged thick-walled FGM cylindrical vessel

In this research work, the creep of thick-walled cylindrical vessels made of FGM with autofrettaged-treated was investigated using the analytical method. At different plastic depths and a variety of internal pressures for elastic modulus and yield stress constants (n(1) and n(4)), changes in residual creep strain rate (radial and circumferential) and final creep strain rate are investigated. The obtained results show that the circumferential stresses in the autofrettage have different values depending on the depth of the plastic. In the equivalent stress diagram, the resulting stress at the plastic points of the vessel reaches the yield stress of the FGM, and the stress decreases along the radius. If p over bar is increased from 1 to 1.8, the maximum creep strain rate decreases (for several n(4), the dimensionless plastic depth is equal to 1.8). The results show that up to a dimensionless plastic depth of 1.5, the change in residual strain rate is negligible. The slope of the graphs for the dimensionless depths above 1.6 increases sharply. A comparison of the maximum circumferential stress as a function of plastic depth for the present work and the study by Darijani shows very good agreement between the two studies.