The paper discusses the problem of boundary conditions formulation in FEA-based design procedures of load-carrying parts driven by topology optimization. The emphasis is on the correct formulation of boundary conditions and the definition of corresponding load cases so that topology optimization will deliver a usable design. It demonstrates that inadequate preparation of load cases may lead to a result that seems to be reasonable, but may behave badly in practical application due to possible lack of robustness and reliability. To illustrate this, an example study is performed for a load-carrying bracket that is fastened by four screws. Namely, in such situations it may quickly happen that one or more screws become at least slightly loose. This changes the stress fields in the part dramatically. If this is not captured correctly in the applied load cases, this means that the topology optimizer will deliver some design that might be extremely sensitive to a loose-screw situation. Such a design may fail very quickly during normal operation.
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