Study on the element rejection and addition strategies of discrete topology methods

The discrete methods such as ESO/AESO/BESO/SERA methods are some of the topology optimization methods that contributed to the rapid expansion of the optimization field. Between the different approaches, an issue that remains unstudied is the key difference between the two strategies to add and remove material that can be found in the literature for discrete topology optimization methods. They can be differentiated in two groups: 1) ne criterion Topology methods that consider one criterion to add and remove material (hard and soft kill BESO); 2) wo criteria Topology methods that consider two separate criteria to add and remove material (original BESO, SERA). In this paper, a study of the two strategies using examples of structural and compliant mechanisms design is performed to understand the implications of each option. This analysis shows that the elements that are added and removed are not the same in the two strategies, especially in compliant mechanisms design. In addition, the study concludes that with the ne criterion-strategy there is no control in the process as the method does not consider the current material status in order to select which elements to add and remove from the design domain.