Numerical modeling of induction assisted subsurface heating technology

Zhang, Lei

Etd

Numerical modeling of induction assisted subsurface heating technology

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Nickel-based super alloys are widely employed in the aerospace industry due to their high- temperature strength and high corrosion resistance. Because of the special application, the superficial residual stress of the super alloy is mandatory to 100% compressive stress according to the Federal Aviation Administration (FAA) regulations. In manufacturing of nickel-based super alloy components, grinding processes are necessarily applied as the final material removal step for achieving the stringent tolerance and surface finish requirements. During the traditional grinding process of Nickel based alloy, due to the thermal effect, tensile residual stress might be generated on the surface of the alloy. It's critical to transfer the tensile residual stress to compressive one which benefits on the fatigue life of alloy. In the thesis, a novel technology is developed to generate the superficial compressive residual stress with the method of embed a subsurface heating layer inside the workpiece to regulate the distribution of temperature field very before mechanical process. The residual stress might be reduced much, even transfer to compressive stress after combining the thermal effect. The numerical model will be built in the thesis including the induction model, heat transfer model, grinding heat model. Effects of different parameters on final subsurface heating layer will be studied including the coil parameters, concentrator parameters, coolant parameters, feed rate and also electromagnetic field properties such as the skin effect, proximity effect and slot effect. The thesis creates a system combining induction heating and cooling processes to regulate the temperature distribution in subsurface area that will be used for further stress analysis.

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