Shape optimization of damage tolerant structures for static strength and fatigue life

This paper presents a methodology for shape optimization of 2D plane structures using damage tolerance objective functions. Damage tolerant structures require consideration of small cracks that can be present at a range of fracture critical locations. An innovative new method to automate and visualize damage tolerance calculations, such as static strength or fatigue life, is described which uses CAD-based software with the efficient Finite Element Alternating Method FEAM. This is used to perform shape optimization to maximize static strength. This is demonstrated by two example structures using a biological gradientless method. The results of stress and static strength shape optimization are compared and show that the optimum shape for fracture parameters is not necessarily the same for minimum peak stress. This work is currently being extended to use fatigue life for curved crack growth as an objective function.