Optimization of Autofrettage-Reautofgrettage Percent and Shrink-Fit Combination for Optimum Fatigue Life in Multilayer Pressure Vessels

摘要

With the increase in demand of materials for production, it is required to design an object such that consumption of material can be reduced for same working conditions or load carrying capacity can be enhanced for same consumption of material. In this paper, pressure vessel has been designed to withstand high internal pressure for same consumption of material. For this purpose, multilayer pressure vessel is constructed by shrink-fit of vessel, which has residual stress within it caused by pre-autofrettage, followed by autofrettage of the assembly. Thus,increase in the number of layers increases the number of ways to assemble and hence this analysis is limited to three-layered pressure vessel. Possible ways to assemble the three-layered vessel for different autofrettage or reautofrettage percent and radial interference for shrink-fit are discussed in this paper. Considering these parameters as design parameters and maximization of fatigue life as an objective function, optimization is carried out by Genetic Algorithm. For the optimum value of design variables, stress distribution for the assembled pressure vessel at design pressure is studied. It is observed that fatigue life of each case is different with little variation of maximum and minimum hoop stresses.