Optimum structures design study of a large plastic container based on variable density method

Large plastic container may induce large deformation of its body when it fills a great deal of substances. In order to make the deformation reduced, more thick of the plastic container wall may be used, but it will make the container heavier. Another way to make the deformation reduced efficiently is to construct some ribs around the container body surface, but where to put the ribs is hard to design. Based on the variable density method, a topological optimum design method is presented in this paper to solve problem of how to distribute the ribs and size its sections. Combined with the structural finite element analysis of the plastic container and the material density change according to the stress-strain energy values operated on the elements, optimization variable density is achieved with the rule of more stress-strain energy win more material density and less stress-strain energy accepting less material density. With the OptiStruct software tool, the reality boundary conditions are defined and then the topology optimization technology is utilized to seek the best materials layout of container in the optimization space. The plastic container stiffeners are designed with the ribs forming around the body surface according to the optimal iso-surface map of material. The finite element analysis results of the optimizing constructed model show that the maximum deformation of the redesigned plastic container has a decrease of 91.1%, at the same time the maximum element stress has a decrease of 65.3%. For the comparison purpose, another finite element analysis is applied to the same container with the double thickness of the container wall. Results show that the maximum displacement is twice more than the optimizing redesigned plastic container; the volume increase is also twice more. The works bring forward a novel method to avoid injection molding process issues due to the excessive thick of plastic container wall, and thereby a great lot material is saved. And the method can also be applied to various types of plastic containers.