Grade: Master
Thesis Title:
Three-Dimensional Finite Element Simulation and Experimental Analysis FDM Process in Order to Control Residual Stress and Distortion of Products
Year: Sept. 2012- Jan. 2015.
Abstract:
Fused deposition modelling (FDM) is a layer-manufacturing technology that has been increasingly popular in last years. This increment can be explained due to their Ability in field of manufacturing in order to allow us to make any kind of geometry in a satisfactory time. This method is based on using heat extrusion of thermoplastics wire. FDM process involve heat and mass transfer, rapid cooling, repetitive heating and cooling coupled with mechanical loading and phase changes, Thus, parts made by FDM process deviate from the designed geometry. Most severe form inaccuracies such as curl and warping are attributed to the residual stress accumulations during prototype fabrications. During this process, the ABS polymer, experiencing different phases, solid, melting and re-solidification. Because of the viscoelastic nature of the polymer, the effect of temperature and time on their properties is very high compared to other materials. In the transition temperature range where ABS behavior is viscoelastic. These properties are determined by tensile test. Using experimental data obtained from tensile test, the constants of elasticity modulus in Prony series model can be extracted. The coefficient of bulk and shear modulus of ABS are obtained by non-linear curve fitting in MATLAB. In continuous, the obtained data were used in FDM simulation using ANSYS software. A finite element analysis model using element activations has been developed to simulate the mechanical and thermal phenomena in FDM and further used for temperature distribution, residual stress and part distortion simulations. Validation of Simulated temperature distribution and distortion model has been compared with the results of experiments and good agreement was observed. This correspondence shows that the model correctly describes the behavior of matter. Since the distortion is caused by the accumulation of residual stress, this model can be used to predict the residual stress.
Keywords: Additive manufacturing, FDM, Viscoelastic, Prony Serious, Finite element simulation, Residual stress, Distortion