Eddy Current and Micro Magnetic On-Line Prediction of Mechanical Properties

Non-destructive characterization (NDC) of materials is a technology of increasing application by industrial users for process monitoring and control. The main reason for this fact in materials processing is the need for a better process understanding and mastering in order to produce quality according to a zero-defect-principle and the objective to reduce non-conformities compared with a given quality specification. This means, integration of NDC by use of intelligent sensors into monitoring and control systems to predict mechanic properties and to detect and document their discontinuities (hardness, hardness depth, yield strenght, deep drawability, residual stresses, etc.). NDT-technology, which in the last two decades was mainly pushed by research and development in different national and international programm [1] now, is matured for a wider range of applications. The special emphasis of the contribution is to give characteristic examples, which illuminate mainly the gain in economical benefit. Eddy current and micro magnetic techniques have a special advantage to be applied for the mentioned objectives, because electrical and micro magnetic intrinsic properties and mechanic properties are influenced by the same microstructure parameters and their changes during material processing and material degradation. Furthermore they are sensitive for load-induced and residual stresses. However, their application is restricted to ferromagnetic materials and material phases