Lehrstuhl für Fertigungstechnologie, Universität Erlangen-Nürnberg

Nondestructive determination of mechanical properties of sheet metal using the eddy current method

Datum: 22.07.1997



  • Prof. Dr.-Ing. Dr. h.c. M. Geiger
  • Prof.-Dr.-Ing. A. Weckenmann

The aim of this thesis was to develop an eddy current testing system capable of determining mechanical properties of sheet metal nondestructively. The intention is to check the sheet quality directly prior to the forming process. Inadmissible deviations from desired values can be recognized and disturbances of the production process avoided. For this purpose a flexible, modular and automated testing device has been built up. Multiple regression methods and neural networks have been applied to evaluate the measurement data. The results show that the eddy current method in connection with complex data evaluation methods is capable of determining quantities relevant for metal forming nondestructively. Investigations on deep drawing steel show that the tensile strength and yield strength can be determined with deviations <±5% and <±10% respectively. Testing time in the range of two seconds could be realized by optimizing the evaluation algorithms. Thus a flexible, cheap and precise testing system is available that enables to check mechanical properties very fast and can be applied for increasing the process performance.