Non-Destructive In-Process Determination of Hardness Values by Harmonic Analysis of Eddy Current Signals


The development of non-destructive hardness-test methods within a new innovative economic process chain based on precision forging technology for the mass production of high performance components is to be introduced. The project is integrated in the Collaborative Research Centre 489 (SFB 489) which has the aim to reduce the entire process chain by integrating the manufacturing steps. Therefore the precision forging process is combined with an integrated heat treatment. The high demands regarding the quality of precision forged high performance parts require local, process-integrated testing of the surface layer characteristics within the range of the functional surfaces. With the intention to build up a fast and highly exact in-process measuring system the harmonic analysis of eddy current signals for the integral and high resolution measuring of hardness values of helical gear wheels was developed further on. Presented will be the problem oriented developed integrated in-process measuring sensor technique for the determination of relevant tooth hardness values which are used for serving the automatic control of integrated heat treatment. A special, local measuring single tooth sensor was developed for high resolution determination of edge hardness and hardness penetration depth on tooth profiles caused by grinding errors. An exigency for the optimization of measuring sensor and technique were developments on the field of FEM-simulation to describe electromagnetic field changes in component and sensor. To rise up the accuracy of the in-process quality assurance best test parameters and optimized characteristic values were found out. Destructive analysing technique gave us the possibility to determine the edge hardness and hardness penetration depth of calibration samples. Computing multidimensional regressions leads us to correlations with high correlation coefficients and made possible to set up an inprocess measuring system with very high accuracy. These results create new possibilities for a fast automatic control of the hardening process and the determination of hardness values in the production line. 1. Nondestructive Testing of Components in the Process Chain "Precision-

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@inproceedings{BernardNonDestructiveID, title={Non-Destructive In-Process Determination of Hardness Values by Harmonic Analysis of Eddy Current Signals}, author={Martin Bernard and Wilfried Reimche} }