Structural optimisation of 3D damage tolerant components comparing the biological and genetic algorithm solutions

This paper studies the 3D optimal design of two generic aircraft components and a rail component. Experimental studies of fatigue crack growth in aluminium alloys have shown that, at the low-to-mid stress intensity factor range; there is often a log-linear relationship between the crack length and the fatigue life. These observations have led to the development of the ‘generalised Frost–Dugdale’ crack growth law, which allowed the accurate prediction of fatigue crack growth from the low-to-mid stress intensity factor range. For this research paper the ‘generalised Frost–Dugdale’ law was used to perform the optimisation study of 7050-T7451 aluminium based structures. The optimal solutions produced by the biological and genetic algorithms are compared. The results indicated that the optimal geometrical shape and predicted fatigue life depended on the crack sizes and structural geometry. A comparison study between the solutions generated by the biological and genetic algorithms indicated that both algorithms produced similar solutions. As a result, this paper illustrates a procedure, based on the damage tolerance philosophy, for the design of light weight structures using fatigue based optimisation in conjunction with a genetic algorithm.