Prediction of the Elastic Response of TPMS Cellular Lattice Structures Using Finite Element Method

Cellular lattice structures are a group of porous materials in which the cells are regularly distributed. Since the morphology of the cells is complicated, the fabrication of them is challenging using conventional methods. However, with the advent of additive manufacturing technology, more attention is focused on these classes of materials because the regular geometry makes it possible to tailor the mechanical response of the structure. Among all kinds of cellular lattice structures, those based on triply periodic minimal surfaces are of great importance due to mechanical and biological properties. Since the fabrication of such structures is challenging and expensive, it is desirable to predict their mechanical response before fabrication. In this paper, finite element approach is employed to predict the elastic response of two well-known Schwarz minimal surfaces named P-Type and G-Type. To do so, first, the cloud points of the surfaces are generated using the implicit equation of the surface and are converted into solid finite element models. The results show that at the same value of porosity, the P-Type specimen provides a higher value of elastic modulus than G-Type one.Mechanical Engineerin

A Heuristic Algorithm Based on Line-up Competition and Generalized Pattern Search for Solving Integer and Mixed Integer Non-linear Optimization Problems

Abstract The global optimization of integer and mixed integer non-linear problems has a lot of applications in engineering. In this paper a heuristic algorithm is developed using line-up competition and generalized pattern search to solve integer and mixed integer non-linear optimization problems subjected to various linear or nonlinear constraints. Due to its ability to find more than one local or global optimal points, the proposed algorithm is more beneficial for multi-modal problems. The performance of this algorithm is demonstrated through several non-convex integer and mixed integer optimization problems exhibiting good agreement with those reported in the literature. In addition, the convergence time is compared with LCAs' one demonstrating the efficiency and speed of the algorithm. Meanwhile, the constraints are satisfied after passing only a few iterations

Modeling of the Mechanical Behavior of 3D Bioplotted Scaffolds Considering the Penetration in Interlocked Strands

Three-dimensional (3D) bioplotting has been widely used to print hydrogel scaffolds for tissue engineering applications. One issue involved in 3D bioplotting is to achieve the scaffold structure with the desired mechanical properties. To overcome this issue, various numerical methods have been developed to predict the mechanical properties of scaffolds, but limited by the imperfect representation of one key feature of scaffolds fabricated by 3D bioplotting, i.e., the penetration or fusion of strands in one layer into the previous layer. This paper presents our study on the development of a novel numerical model to predict the elastic modulus (one important index of mechanical properties) of 3D bioplotted scaffolds considering the aforementioned strand penetration. For this, the finite element method was used for the model development, while medium-viscosity alginate was selected for scaffold fabrication by the 3D bioplotting technique. The elastic modulus of the bioplotted scaffolds was characterized using mechanical testing and results were compared with those predicted from the developed model, demonstrating a strong congruity between them. Once validated, the developed model was also used to investigate the effect of other geometrical features on the mechanical behavior of bioplotted scaffolds. Our results show that the penetration, pore size, and number of printed layers have significant effects on the elastic modulus of bioplotted scaffolds; and also suggest that the developed model can be used as a powerful tool to modulate the mechanical behavior of bioplotted scaffolds