Nondestructive evaluation of a crack on austenitic stainless steel using a sheet type induced current and a Hall sensor array

Abstract

Austenitic stainless steels (hereafter A-STS) such as STS304 and STS316 are paramagnetic metals. However, a small amount of partial magnetization is generated in A-STS because of the imperfect final heat treatment and mechanical processing. Surface cracks on paramagnetic metal with a partially magnetized region (hereafter PMR) are difficult to inspect. In this paper, we propose a method for high speed inspection and evaluation of a crack on A-STS. Cracks can be inspected with high speed by using 64 arrayed Hall sensors (HSA) with 3.5 mm spatial resolution and a sheet type induced current (STIC). Then, a crack can be evaluated quantitatively by using the detailed distribution of the magnetic field obtained by using single Hall sensor scanning (SSS) around the inspected crack area. Several cracks on A-STS with partially magnetized areas were examined and the experimental formulas were derived.

Giant Magnetoresistance Sensors: A Review on Structures and Non-Destructive Eddy Current Testing Applications

“…The smart array probe is an improved version of the X-probe with the following characteristics that are different from the X-probe [ 37 , 38 ]: One transmitter and four receivers Every coil works in either excitation or detection mode Simple DAQ circuits Circumferential mode with higher resolutions No need for axial position correction Less time slots …”

Quantitative Nondestructive Evaluation of the Aluminum Alloy Using the Sheet Type Induced Current and the Single Sensor Scanning

“…Therefore, ∆l C 3.2 and ∆l C 25. 6 are approximately the same as the length of the crack in the case of 90° of θ TIP (No.1, 2, 3). Fig.…”

“…6 show larger values for rectangular cracks (No.1, 2, 3) compared to triangular cracks (No. 4,5,6) and circular arcs (No. 7,8).…”

“…The alternate MFL resulting from the DAC is detected using a Hall sensor. The RMS of the MFL obtained by using high pass filters after the use of the Hall sensor is converted to a digital signal by an analog-to-digital converter (ADC), stored in a computer, and processed by interface and operation software [6]. An algorithm for the quantitative nondestructive testing and evaluation of cracks of different shapes and sizes on the aluminum alloy, Al7075, is proposed in this paper.…”

Accurate 3D reconstruction of complex defects based on combined method of MFL and MFDs

“…Then the calibrated mapping model is used to estimate the actual size of the defect with measured MFL signals. The direct method can detect the defects of simple shapes (such as rectangular slits and cylindrical holes [14][15][16]) and is also applicable to reconstruct 3D morphology of complex defects if the mapping model has been well established by other technologies such as neural network technology [17,18]. The direct method can achieve the fast prediction of defect parameters, but its accuracy highly depends on the training samples (or finite element models) and the 3D morphology of actual defects.…”