New measurement method for process control of inductive heating operations of metals into the semi-solid state

在触变成形中，加热后的半固相工件被成形。半固态材料具有有利于成型的特殊性能。触变成形的工件通常是感应加热的，因为这种类型的加热可以实现高输出和效率以及感应功率的精确控制。由于集肤效应导致的热输入不均匀，对感应加热提出了挑战。这使得很难在工件中获得均匀的液相分数，特别是在高加热速率下。对于液相分数的测量，在已知的时间常数测量的基础上，开发了一种基于电感记录电流的电流测量方法。由于趋肤效应，负责加热的电流集中在工件的边缘区域。这带来了熔化边缘区域的风险，而工件的中心尚未达到成形过程所需的液相分数。虽然可以通过测量值的采集和监测来防止边缘区域的熔化，但不知道工件内部何时由于热传导效应而发生了调整。在工件边缘区域可测量的液相分数值的基础上，根据加热模型确定工件内部的液相分数。该模型由已开发的测量的测量值支持，以便对工件中的热能传播和相关的熔化过程做出尽可能准确的陈述。本研究项目将对该加热模型进行研究和实施。加热模型将首先通过离线评估与开发的基于电流的测量一起进行测试。随后，在控制硬件上实现测量量的采集和加热模型。

In thixoforming, heated workpieces in a semi-solid phase are formed. Semi-solid materials have special properties which are positive for forming. Workpieces for thixoforming are often heated inductively, as this type of heating enables high outputs and efficiencies as well as precise control of the inducted power. Challenges in inductive heating arise due to the uneven heat input due to the skin effect. This makes it difficult to obtain a homogeneous liquid phase fraction in the workpiece, especially at high heating rates.For the measurement of the liquid phase fraction, a current measurement based on the recorded currents at the inductor was developed, which is based on the already known time constant measurement. Due to the skin effect, the currents responsible for heating are concentrated in the edge area of the workpiece. This carries the risk of melting off the edge areas, while the center of the workpiece has not yet reached the liquid phase fraction required for the forming process. Although the melting of the edge areas can be prevented by measured value acquisition and monitoring, but it is not known when the inside of the workpiece has adjusted due to heat conduction effects.On the basis of the values for the liquid phase fraction that can be measured in the edge area of the workpiece, the liquid phase fraction inside the workpiece is to be determined on the basis of a heating model. The model is supported by the measured values of the developed measuring in order to make as accurate a statement as possible about the propagation of the heat energy in the workpiece and the associated melting processes. This heating model will be investigated and implemented in this research project.The heating model will first be tested together with the developed current-based measurement by offline evaluation. Subsequently, the measured quantity acquisition and the heating model will be implemented on the control hardware.