Topology optimization of adhesive material in a single lap joint using an evolutionary structural optimization method and a cohesive zone model as failure criterion

This paper presents a study of the use of a structural optimization process coupled to a failure model in the adhesive material in single lap bonded joints. The critical point of these joints is in the region of the adhesive material, which performs the function of stress transmission between the structural elements. Owing to the single lap bonded joints shape, the applied loads are eccentric about the joint axis, resulting in a concentration of stress on the overlapping ends. In this study, numerical simulations in two and three dimensions were performed through finite element analysis to model an single lap bonded joints. An optimization procedure based on the bidirectional evolutionary structural optimization method was used to minimize the single lap bonded joints compliance under volume constraints. The design domain considered was restricted to the adhesive region. The cohesive zone model and the bidirectional evolutionary structural optimization method were simultaneously applied. The numerical results for two types of adhesives, with ductile and brittle failure behavior, enabled the establishment of mechanisms for determining the efficient positioning and quantity of adhesive materials.

Topology Optimization Methods for 3D Structural Problems: A Comparative Study

The work provides an exhaustive comparison of some representative families of topology optimization methods for 3D structural optimization, such as the Solid Isotropic Material with Penalization (SIMP), the Level-set, the Bidirectional Evolutionary Structural Optimization (BESO), and the Variational Topology Optimization (VARTOP) methods. The main differences and similarities of these approaches are then highlighted from an algorithmic standpoint. The comparison is carried out via the study of a set of numerical benchmark cases using industrial-like fine-discretization meshes (around 1 million finite elements), and Matlab as the common computational platform, to ensure fair comparisons. Then, the results obtained for every benchmark case with the different methods are compared in terms of computational cost, topology quality, achieved minimum value of the objective function, and robustness of the computations (convergence in objective function and topology). Finally, some quantitative and qualitative results are presented, from which, an attempt of qualification of the methods, in terms of their relative performance, is done.

A Hole Nucleation Method Combining BESO and Topological Sensitivity for Level Set Topology Optimization

As is known to all, the incapacity to nucleate holes automatically in the design domain is one of the main issues of the classical level set topology optimization method. To solve the issue of hole nucleation, this paper employs the bi-directional evolutionary structural optimization (BESO) method based on the material removal scheme and the frequently used topological sensitivity and proposes the combining BESO and topological sensitivity (CBT) method for level set topology optimization. This method can replace the existing hole nucleation method for level set topology optimization. First, the topological sensitivity is combined with BESO, and the BESO method based on topological sensitivity is proposed. Second, the method is integrated into level set topology optimization to solve the issue of hole nucleation. Two sensitivity thresholds are defined depending on the evolutionary volume ratio and boundary topological sensitivity, respectively, and the smaller one is used as the sensitivity threshold for hole nucleation. The material is removed from the design domain to nucleate holes based on this threshold. Three classical two-dimensional numerical examples are used to validate the proposed hole nucleation method.