Analysis of thermal stresses in shape deposition manufacturing of metal parts

Shape Deposition Manufacturing (SDM) is a Layered Manufacturing process where objects are constructed by sequential deposition and machining of material layers. When the deposition process involves temperature gradients, thermal stresses develop. These stresses cause distortions and can lead to part failure due to cracking. This research investigated thermal stresses in SDM using a combination of analytical modeling, finite element modeling, and experiments. Initially an analytical model was developed to predict the overall part warpage. Then both finite element modeling and experiments were used to investigate how the deposition pattern influences the substrate warpage and to investigate the inter-layer surface defect known as the Christmas Tree Step.; This research began by first developing an analytical model to predict substrate warpage. Both elastic and elastic-perfectly plastic models were investigated. This model was used to examine how the deposit thickness and the number of layers used to produce the deposit affects the warpage of the part.; In SDM the pattern used to deposit a layer has a significant effect on the substrate warpage. This effect was investigated using both finite element modeling and experiments. From the finite element observations the optimal deposition pattern for both the beam and plate substrates was determined. To check the validity of the finite element results, the calculated values for deflection were compared to experimentally determined values.; The local defect known as the Christmas Tree Step was also investigated. This step is found at the layer interface and results in poor surface quality and part inaccuracy. The step was investigated using both a finite element model and experiments. The investigation showed that the surface defect develops when material is deposited on top of previously machined layers. The step is a local edge effect and does not significantly depend on the deposition pattern.; This research deepened the understanding of residual stress accumulation in the Layered Manufacturing process Shape Deposition Manufacturing. The combination of analytical modeling, finite element modeling and experiments was used to predict overall part deflection, to understand the effect of deposition patterns on part warpage, and to understand the development of the Christmas Tree Step.