A Sensitivity Mapping Technique for Tensile Force and Case Depth Characterization Based on Magnetic Minor Hysteresis Loops

Cunfu He,Ruifang Zhang,Meng Yang,Xiucheng Liu,Wenqiao Dou

doi:10.1186/s10033-020-00508-5

Cunfu He, Ruifang Zhang + Show 3 more

Open Access

https://doi.org/10.1186/s10033-020-00508-5

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Abstract

In the nondestructive testing and evaluation area, magnetic major hysteresis loop measurement technology are widely applied for ferromagnetic material evaluation. However the characterization ability of major hysteresis loop measurement technology greatly varies as the evaluated target properties. To solve this limitation, magnetic minor hysteresis loops, which reflect the responses of ferromagnetic material magnetization in a systematic way, is recommend. Inspired by plenty of information carried by the minor loops, the sensitivity mapping technique was developed to achieve the highest sensitivity of minor-loop parameters to the nondestructively evaluated targets. In this study, for the first time, the sensitivity mapping technique is used to measure the tensile force in a steel strand and evaluate the effective case depth in induction-hardened steel rods. The method and procedures for the sensitivity mapping technique are given before experimental detection. The obtained experimental results indicate that the linear correlation between the induced voltage (or the magnetic induction intensity) and the tensile force (or effective case depth) exists at most of the locations in the cluster of minor loops. The obtained sensitivity maps can be used to optimize the applied magnetic field (or excitation current) and the analyzed locations at the minor loops for achieving the highest sensitivity. For the purpose of tensile force measurement, it is suggested that the strand should be firstly magnetized to the near-saturation state and then restored to the remanent state. In this way, the highest sensitivity is obtained as about 15.26 mV/kN. As for the induction-hardened steel rods, the highest sensitivity of magnetic induction intensity to the effective case depth occurs under low magnetic field conditions and the absolute value of the highest sensitivity is about 0.1110 T/mm. This indicates that if the highest sensitivity is required in the case depth evaluation, the induction-hardened steel rods are only required to be weakly magnetized. The proposed sensitivity mapping technique shows the good performance in the high-sensitivity evaluation of tensile force and case depth in ferromagnetic materials and its application scope can be extended to other nondestructive detection fields.

Highlights

The measurement of the magnetic hysteresis curves is a promising pathway to achieve the nondestructive evaluation (NDE) of the properties of ferromagnetic materials [1]
5 Conclusions Magnetic minor hysteresis loop measurement and sensitivity mapping technique are applied in the measurements of tensile force in steel strand and effective case depth in induction-hardened steel rods for the first time
To achieve high-sensitivity and nondestructive measurement of target properties, the excitation current and the analyzed locations in the minor loops are optimized based on the sensitivity map

Summary

Introduction

The measurement of the magnetic hysteresis curves is a promising pathway to achieve the nondestructive evaluation (NDE) of the properties of ferromagnetic materials [1]. The traditional feature parameters are extracted and can well reflect the magnetic property of ferromagnetic materials. (2020) 33:84 the sensitivity of the traditional feature parameters to the target properties is not necessarily the highest. Due to the diversity of target properties in NDE applications, the universality of the frequently used major loop measurement method is debatable [5]. To clarify the two questions, the systematic measurement methods of magnetic minor hysteresis loops are suggested for NDE applications. Multiple candidate parameters are extracted from the measured cluster of minor loops for the characterization of target properties and the performances of the extracted candidate parameters are discussed in the space made of minor loops [6, 7]

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Conclusion