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Thermal mechanical analysis of wheel deformation induced from quenching Estey, Christina Michelle

Abstract

The focus of this present investigation was to develop a mathematical model capable of predicting the evolution of temperature, formation of thermal strains and stresses and resulting displacements within a die cast aluminum wheel during the quenching stage of the T6 heat treatment process. The development of this model will aid in understanding the mechanisms associated with wheel deformation and the factors that influence wheel deformation. A sequentially coupled finite element based thermal-mechanical model was developed using the commercial finite element software ABAQUS. The model consisted of a heat transfer model to predict the evolution of temperature and a mechanical model to predict the formation of strains and stresses within a die-cast aluminum wheel during quenching. The thermal model was validated against industrial temperature measurements acquired at Canadian Autoparts Toyota Inc. using embedded thermocouples throughout the wheel. The parameters describing the thermal boundary conditions were systematically adjusted until an acceptable agreement was obtained with the measured data. The temperature-time predictions within a 180° section of the wheel obtained from the thermal model were used as input for the mechanical model. The mechanical analysis revealed that the quenching process induces a high state of compressive residual stresses on the surface and a high state of residual tensile stresses in the interior of the wheel. The mechanical model was validated against industrial wheel deformation results obtained at Canadian Autoparts Toyota Inc, which proved to be in good qualitative agreement at some locations and in good quantitative agreement in others. This model revealed that temperature differences occurring in a circumferential direction around the wheel play a more significant role in influencing the degree of wheel deformation as compared to higher quenching rates. Therefore, to minimize the amount of wheel deformation induced from quenching, a reduction in the thermal gradients around the wheel would be required, in which a better design of the quenching system should be implemented. Overall, the stress and displacement predictions obtained from the thermal-mechanical analysis revealed that this finite element based mathematical model can be used as a powerful tool to predict overall wheel deformation. Based on an understanding of the mechanism associated with wheel deformation, the quench conditions can be optimized to reduce wheel deformation while meeting the industry standards for strength and fatigue performance.

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