Structural Shape Optimisation by Iterative Finite Element Solution
DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION CANBERRA (AUSTRALIA)
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This report presents the development and automated numerical implementation of an iterative gradientless optimisation method for the analysis of problems relating to life extension of aircraft components. The method has been implemented to interface with the finite element code PAFEC, which does not normally have an optimisation capability. The key feature of the approach is to achieve constant boundary stresses, in regions of interest, by moving nodes on the stress concentrator boundary by an amount dependent on the sign and magnitude of the local hoop stress obtained from a previous iteration of a standard finite element analysis. The results of example problems are presented which include the optimisation of hole shapes in flat plates and the optimisation of the design of bonded reinforcements with a focus on minimising adhesive stress while maintaining the effectiveness of the reinforcement. In all cases significant stress reductions were achieved by way of the local shape changes. The method presented is considered a simple robust complementary method to the use of commercially available gradient based finite element optimisation software. It is also considered suitable for use with typical standard commercial finite element packages other than PAFEC.