Nondestructive material characterization and component identification in sheet metal processing with electromagnetic methods

Abstract

Electromagnetic methods for non-destructive evaluation (NDE) are presented, with which sheet metal components can be identified and their material properties can be characterized. The latter is possible with 3MA, the Micromagnetic Multiparametric Microstructure and stress Analyser. This is a combination of several micromagnetic NDE methods that make it possible to analyse the microstructure in a ferromagnetic material and to determine quantitative values of the mechanical material properties or the stress state. In the case of cold forming, the 3MA application for pre-process testing of sheet metal is discussed. Based on the 3MA information, the formability of the sheets can be predicted. To apply 3MA in-line, the influence of the relative speed and the relative distance between the 3MA probe head and the sheet was investigated. In a second study, a spatially resolved eddy current (EC) method was used to create an image of the intrinsic material microstructure of a component for its identification and traceability. It turned out, that these intrinsic fingerprint images can still be recognized even after subsequent plastic deformation or coating of the surface. This enabled the development of a marker-free traceability method for sheet metal processing. It is based on a low-cost array sensor and a specimen identification using robust and partly redundant features of the fingerprint images processed by machine learning (ML).

Past, Present, and Future of New Applications in Utilization of Eddy Currents

“…EC-NDE systems not only detect the geometric features of metals, but can be used to detect and estimate different magnitudes of the material. Wolter et al [33] presented a combination of NDE methods that allows the microstructure of ferromagnetic metals to be analyzed. It obtains a 2D image of the material structure by using the proposed system.…”

“…In addition to applications that directly use eddy currents, different studies [32][33][34][35] have shown that some materials exhibit a high-frequency diamagnetic response due to the reverse magnetic field induced by them. These investigations demonstrate that diamagnetic materials have great potential to be used in electromagnetic shielding and attenuation systems.…”