Structural optimization and fatigue simulation became standard applications in the various phases of design development processes within the last years. Introducing fatigue simulation into the optimization procedure enables to use all the available methods from the field of fatigue also for structural optimization. This means, beside correct consideration and combination of static and dynamic load portions, also the option for assessing different joining technologies like spot welds.
Beside gaining better performance of spot welded structures, economic aspects drive the development of optimization in the field of spot welds. Therefore different methods like sensitivity based approaches or genetic algorithms have been used for some time.
The application of standard software for topology optimization was investigated for the purpose of automated finding optimal spot weld distributions. Beside optimizations regarding stiffness, optimizations using fatigue life as objective were performed too. The used method and according results will be shown in this paper.
In case of rearranging the original number of joints, stiffness and fatigue based optimization lead to an increase of stiffness of the structures compared to the baseline. Structures with fatigue based optimized spot weld distributions show an advantage compared to stiffness oriented optimized ones. The load distribution among spot welds optimized regarding fatigue is more uniform than in case of stiffness optimized spot weld patterns.
The number of required analysis runs is only a fraction of the one necessary working with genetic algorithms. The presented approach does not need any preprocessing for the introduction of design variables. So this approach results in an efficient way of finding improved spot weld distributions regarding stiffness and/or fatigue behavior. Small examples and real world structures are provided to demonstrate the method.