Research Initiation: Closed-loop Shape Control During Hot Isostatic Pressing Process

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An important problem with the hot isostatic pressing (HIP) process is the occurrence of shape distortion, which greatly limits the potential of HIP as a net or near net shape processing technology. The basic objective of the research is to explore the use of feedback control principles for reducing the unpredictable shape distortion due to model inaccuracy and process disturbance. The feedback compensation is achieved by adjusting the HIP temperature and pressure in real time based on the densification information provided by the in-situ eddy current sensors. Due to the multi-input multi-output, nonlinear and uncertain nature of the HIP process dynamics, a modified version of the model predictive control method will be used to design the computer control system. A state estimator will be constructed to estimate the densification status from the impedance values provided by the eddy current sensors. The research results from this project will not only lead to closed-loop computer control systems for improving HIP quality and productivity, but may also be useful for the development of real-time feedback control systems for other material processing systems. If successful, the research will allow the production of part from powdered metal with a high degree of consistency and shape accuracy, reducing scrap.