Magneto-inductive test method
The magneto-inductive test method is a non-destructive procedure for determining material properties such as hardness, alloy composition, and microstructure. It uses electromagnetic induction to evaluate magnetic and electric parameters that characterize the tested material.
In magneto-inductive testing, the part to be examined passes through a test coil containing an exciter and a measuring coil. An alternating current applied to the exciter coil generates a magnetic alternating field, which induces eddy currents in the material. The measuring coil records the resulting voltage, which depends on both the electrical conductivity and the magnetic properties of the material.
Because the magnetic hysteresis curve is influenced by technological parameters such as hardness, heat treatment, and alloy composition, these properties can be determined with high sensitivity. By adjusting the excitation field strength and frequency, the test can be targeted to specific areas of the hysteresis curve, enabling selective analysis of surface and core properties. The magneto-inductive method is particularly well suited for automated material and structure testing of steels and non-ferrous metals.
Application Examples
Crack and Structure Testing
Eddy current testing can be divided into two complementary areas: high-frequency crack testing and low-frequency magneto-inductive structure testing. At high frequencies, surface defects such as cracks, pores, or overlaps are detected contact-free and without coupling media – even on delicate surfaces. Distance compensation ensures stable results despite probe lift-off variations.
In the lower frequency range, the magneto-inductive method evaluates the material’s magnetic and electrical properties to detect differences in hardness, alloy composition, or heat treatment. The test voltage, represented as a point in the complex plane, reflects these properties and enables precise material classification. By defining sorting limits during calibration, serial testing can automatically assess each part. Modern FOERSTER systems combine multi-frequency operation with harmonic analysis and intelligent signal evaluation – ensuring reproducible, high-precision results.
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