Evaluation of finite element analysis on topology optimized direct metal laser sintered TI6Al4V structures

Abstract

The problem under investigation in this dissertation is the validity of Finite Element Analysis (FEA) when applied to topology optimized Direct Metal Laser Sintering (DMLS) structures manufactured from Ti6AL4V with the assumption that the weakest material properties are homogeneous. In order to address the problem under investigation a verifiable topology optimized test specimen is generated. DMLS is an additive or layered manufacturing process used to melt metal powder with a high powered laser to produce customised components. Finite element strength analysis is the practical application of FEM (Finite Element Modelling) and entails the virtual modelling of products and systems for the purpose of finding and solving potential structural issues. Topology optimization is a type of structural optimization that uses a mathematical method to optimize a defined problem within a design domain with fixed boundary conditions, and the optimization is done for appropriate objective conditions that satisfy the defined constraints. The mechanical properties of DMLS Ti6Al4V are investigated, and the weakest material properties are identified. These material properties are assigned to the design space identified, and the topology optimized model is generated in solidThinking Inspire™. The topology optimized model is validated by comparing the stress induced by the complex loads on the initial model and topology optimized model as well as weight reduction of the topology optimized model. An FEA is performed on the validated topology optimized model. This FEA strives to mimic the conditions of the practical test performed on the topology optimized model. The FEA is performed in more than one software package in order to compare the simulations for verification. Two practical tests were performed on the topology optimized model. The von Mises stress for different loads is determined from the virtual strain rosette and obtained from the FEA. These simulated von Mises stress and practically obtained von Mises stresses are compared in an attempt to validate the simulation. An excellent linear correlation between the practical results and simulated results were found, with the practically obtained results being consistently lower than the simulated results. The reason given for this phenomenon is the use of the weakest material properties as though they are homogeneous. A verifiable conclusion is drawn, and the problem under investigation is addressed.