Generating Compressive Surface Residual Stresses Using Hydraulic Autofrettage Process With Heat Treatment

Abstract

Recently, a method of inducing compressive residual stresses in the vicinity of the walls of a thermally autofrettaged cylinder was proposed. In the proposed method, the thermally autofrettaged cylinder was heated in such a manner that its outer wall attained a temperature more than the lower critical temperature and the inner wall was at a sufficiently lower temperature. When the cylinder was quenched, compressive residual stresses were induced in the vicinity of the cylinder walls. This article investigates the feasibility of the same procedure for a hydraulic-autofrettaged cylinder made of AISI 1080 steel. A finite element method (FEM)-based analysis is carried out using commercial package abaqus by incorporating microstructure and temperature-dependent material properties. The results indicate that the heat treatment design proposed for the thermally autofrettaged cylinder to induce compressive residual stresses at the outer wall can also be adapted for a hydraulic-autofrettaged cylinder. However, for cylinders subjected to high percentage of autofrettage, heating of the outer wall needs to be carried out well below the lower critical temperature. In fact, this is an advantage in terms of energy saving and can be implemented even for cylinders subjected to a low percentage of autofrettage.