A new multi-objective robust optimisation methodology

Abstract

The important role of imperfections on decreasing the buckling load of structural cylinders has been investigated by scientists and engineers for the past century, yet there is currently no method that is able to stochastically replicate the full range of realistic imperfections for a full account of possible buckling loads. This drawback impairs optimised design as designers are restrained to using an outdated and conservative design philosophy which dates from 1968. Modern manufacturing methods and materials such as composites require new, optimised design measures to take full advantage of their efficiencies. Stochastic analyses can optimise and improve the reliability of such cylinders through accurate prediction of the range of conceivable buckling loads by realistic simulation and sensitivity analyses. A stochastic procedure which realistically models imperfection sensitive composite shells is investigated in this paper. Monte-Carlo simulations of axially compressed cylinders with the full range of imperfection types are performed to show that the stochastic methods described here are able to accurately capture the scatter in the buckling load introduced from the imperfections. The results from a sensitivity analysis indicate that loading imperfections play the largest role in reducing the buckling load knockdown factors of the shell.