Nondestructive Testing with 3MA—An Overview of Principles and Applications

Abstract

More than three decades ago, at Fraunhofer IZFP, research activities that were related to the application of micromagnetic methods for nondestructive testing (NDT) of the microstructure and the properties of ferrous materials commenced. Soon, it was observed that it is beneficial to combine the measuring information from several micromagnetic methods and measuring parameters. This was the birth of 3MA-the micromagnetic multi-parametric microstructure and stress analysis. Since then, 3MA has undergone a remarkable development. It has proven to be one of the most valuable testing techniques for the nondestructive characterization of metallic materials. Nowadays, 3MA is well accepted in industrial production and material research. Over the years, several equipment variants and a wide range of probe heads have been developed, ranging from magnetic microscopes with µm resolution up to large inspection systems for in-line strip steel inspection. 3MA is extremely versatile, as proved by a huge amount of reported applications, such as the quantitative determination of hardness, hardening depth, residual stress, and other material parameters. Today, specialized 3MA systems are available for manual or automated testing of various materials, semi-finished goods, and final products that are made of steel, cast iron, or other ferromagnetic materials. This paper will provide an overview of the historical development, the basic principles, and the main applications of 3MA.

A Method of Barkhausen Noise Feature Extraction Based on an Adaptive Threshold

“…However, the linearity and dispersion of the pulse count feature are closely related to the choice of threshold. Similarly, MBN features extracted by the commercial non-destructive testing instrument 3MA are full width at 25, 50 and 75% of the maximum amplitude [2,3], which is shown in Figure 2. These three thresholds are not necessarily the best choice for stress detection or other parameter measurements.…”

“…The magnetic Barkhausen noise (MBN) as a non-destructive evaluation method is mainly used to detect stress of ferromagnetic materials [1][2][3]. Feature extraction of MBN signals is important for stress detection of ferromagnetic materials.…”

“…The new method proposed in the paper can be used for other feature extraction situations where thresholds need be selected. For an incremental permeability (IP) signal, curve width at the certain percentage of µMAX can be selected optimally [3]. For multi-frequency eddy current testing, the appropriate excitation frequency also can be chosen optimally.…”

Characterization of Damage Evolution on Hot Flat Rolled Mild Steel Sheets by Means of Micromagnetic Parameters and Fatigue Strength Determination

“…The highest density of these pulses is present on the coercivity point (C). This defines two important measuring parameters: the maximum of the M(H) curve, M max , and its corresponding magnetic field strength called the coercive magnetic field H cm [9,42]. During the cyclic process of magnetization, the Bloch walls can collide with obstacles like lattice defects, voids, dislocations, and grain boundaries, which produce sudden jumps on the hysteresis curve, called Barkhausen noises.…”

“…The highest density of these pulses is present on the coercivity point (C). This defines two important measuring parameters: the maximum of the M(H) curve, Mmax, and its corresponding magnetic field strength called the coercive magnetic field Hcm [9,42].…”