The development of an optimisation algorithm based on fatigue life

A new structural optimisation algorithm based on fatigue life is introduced. The two key decisions in implementing this algorithm are firstly what assumption about the stress state (uniaxial or multiaxial proportional or non-proportional) should be made and secondly what method of stress calculation should be used (quasi-static, transient dynamic or harmonic modal stress analysis). The paper investigates the effects of different assessment strategies on the predicted fatigue life of a lower suspension arm, the properties of which are modified to generate different degrees of interaction between the arm natural frequencies and the frequency range of the applied forcing functions. The results of this investigation are used to derive a new form of structural optimisation algorithm which is more robust and efficient than the original.