Fatigue analysis of thermal shrink-fit autofrettage in pressure cylinder using finite element analysis

Abstract

Autofrettage is the process to find the residual stress properties of the thick cylinder under the high-pressure scenario. Due to the cost and material demands, the elastoplastic behaviour offers better durability result is increased resistance to cracking. One of the main parameters for the cause of cracking is the enormous level of pressure and with the autofrettage process, the durability of the material is boosted up and improves the corrosion cracking resistance. Another factor of autofrettage is the fatigue life of a thick cylinder under stress. The fatigue life of the material can be evaluated by a computerized method analysis to minimize the level of Von-Mises stress under the operating pressure condition. Conducting the computerized analysis by modelling the geometry of the model with frictionless support and acting pressure on the cylinder model. ANSYS finite element modelling is largely utilized tool in the material testing with an advantage of less computing time and cost. Since the results obtained from the simulation progress are actualized with the real-time condition by applying the real constraints in parametric setting and boundary conditions respectively. In this research work, the autofrettage of a thick cylinder is carried out in the finite element modelling using ANSYS workbench 18.1. The modelling is done for the boundary condition of pressure level of 45, 96, 110 and 134 MPa. A 3D model of cylinders is created with the dimension of the inner cylinder of inner radius 15mm, the outer cylinder of outer radius 35mm with the total cylinder wall thickness and length of 20 mm and 250mm respectively. Though the analysis is run for the different pressure limits and autofrettage on the thermal insulated thick cylinder is investigated for the stress parameters under shrink-fit pressure limits. The result from the analysis indicates that the autofrettage pressure at 159 MPa the cylinder withstand pressure beyond the limit it collapsed. Hence, it is evident from the result, the selected AISI 4630 steel material of thick cylinder can withstand the autofrettage under thermal shrink-fit condition under the maximum autofrettage pressure limit of 159 MPa respectively.