Title: Multi-objective optimisation of autofrettaged functionally graded thick spheres

Authors: Ali Asghar Atai; Saeed Farahmand

Addresses: School of Mechanical Engineering, College of Engineering, University of Tehran, North Kargar Ave., Tehran, Iran ' Young Researchers Club, Karaj Branch, Islamic Azad University, Karaj, Iran

Abstract: In this work, optimum configuration of autofrettaged FGM spherical pressure vessel is investigated. The objective functions of the optimisation problem are taken to be the pressure capacity of the FG vessel and its weight. The properties of FG vessel are taken to be radially varying. The residual stress after autofrettage is calculated in the absence of Bauschinger effect using variable material property (VMP) method. Assuming bilinear elastic-plastic behaviour for the metal and perfect elastic behaviour for ceramic, a bilinear behaviour is resulted for FGM based on the rule of mixture. In the autofrettage process, projection method is used to compute the distribution of stress. Also, isotropic hardening is assumed for unloading phase. The results illustrate significant effect of ceramic volume fraction used in FGM and autofrettage pressure on the residual stress and pressure capacity of the vessel.

Keywords: functionally graded; multi-objective optimisation; spherical vessel; variable material property method; autofrettage.

DOI: 10.1504/IJDE.2017.089651

International Journal of Design Engineering, 2017 Vol.7 No.2, pp.92 - 105

Received: 31 Mar 2017
Accepted: 26 Aug 2017
Published online: 05 Feb 2018 *

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