The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

Nonlinear Oscillations: Exact Solutions and their Approximations

Non-destructive techniques are used widely in the metal industry in order to control the quality of materials. Eddy current testing is one of the most extensively used non-destructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor. This paper includes an overview of the fundamentals and main variables of eddy current testing. It also describes the state-of-the-art sensors and modern techniques such as multi-frequency and pulsed systems. Recent advances in complex models towards solving crack-sensor interaction, developments in instrumentation due to advances in electronic devices, and the evolution of data processing suggest that eddy current testing systems will be increasingly used in the future.

/pdf/non-destructive-techniques-based-on-eddy-current-testing-ekomtngkyg.pdf

Non-Destructive Techniques Based on Eddy Current Testing

The Journal of the Acoustical Society of America

Magnetic flux leakage (MFL) detection is one of the most popular methods of pipeline inspection. It is a nondestructive testing technique which uses magnetic sensitive sensors to detect the magnetic leakage field of defects on both the internal and external surfaces of pipelines. This paper introduces the main principles, measurement and processing of MFL data. As the key point of a quantitative analysis of MFL detection, the identification of the leakage magnetic signal is also discussed. In addition, the advantages and disadvantages of different identification methods are analyzed. Then the paper briefly introduces the expert systems used. At the end of this paper, future developments in pipeline MFL detection are predicted.

https://www.mdpi.com/1424-8220/15/12/29845/pdf

Theory and Application of Magnetic Flux Leakage Pipeline Detection

This paper proposes a new omni-directional electromagnetic acoustic transducer (EMAT) for the ultrasonic Lamb wave (ULW) tomography imaging (TI) of defects in metallic plates. The proposed EMAT is composed of a permanent magnet and a coil with a contra-flexure structure. This new EMAT coil structure is used for omni-directional ULW transmission and reception and ULW TI for the first time. The theoretical background and the working principles of this EMAT are presented and analyzed. The experimental results of its use on a 3 mm thick aluminum plate indicate that the EMAT with a contra-flexure coil (CFC) can transmit and receive a pure single A0 mode ULW with a high signal-to-noise ratio (SNR). Thus, the extraction of the projection data used for ULW TI may be performed accurately. The circumferential consistency of the projection data is only slightly influenced by the distortion of the eddy current field that is induced by the new CFC with an irregular shape. When the new EMAT array is used for ULW TI using the cross-hole method and SIRT arithmetic, a desirable imaging quality can be achieved, and the estimated size of an artificial corrosion defect agreed well with its actual value. The relation between the reconstruction resolution and the number of the new EMATs used is analyzed. More TI experiments are carried out when the aluminum plate defect is in two different locations relative to the EMAT array, for the further investigation of the performances of the new EMATs.

A new omni-directional EMAT for ultrasonic Lamb wave tomography imaging of metallic plate defects.

Defect inversion is of special interest to magnetic flux leakage (MFL) inspection in industry. This study proposes an iterative neural network to reconstruct three-dimensional defect profiles from three-axial MFL signals in pipeline inspection. A radial basis function neural network is utilised as the forward model to predict the MFL signals given a defect profile, and the defect profile gets updated based on a combination of gradient descent and simulated annealing in the iterative inversion procedure. Accuracy of the proposed inversion procedure is demonstrated in estimating the profile of different defects in steel pipes. Experimental result based on three-axial simulated MFL data also shows that the proposed inversion approach is robust even in presence of reasonable noise.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-smt.2014.0173

Three-dimensional defect inversion from magnetic flux leakage signals using iterative neural network

Laser based measurement for the monitoring of shaft misalignment.

We propose a new unidirectional point focusing shear horizontal (SH) guided wave electromagnetic ultrasonic transducer (EMAT) with an angled periodic permanent magnet (PPM) in this work. The angled PPM developed here provides an angled bias magnetic field to achieve the EMAT’s unidirectional focusing capability. The characteristics of the magnetic field distribution are analyzed by numerical and theoretical calculations. The simulation and experimental results are proven to be in good agreement when studying the bidirectional normalized amplitudes of the displacement of the single-coil SH-guided EMAT with oblique permanent magnets. Both the proposed angled transducer structure and the traditional paralleled transducer structure are performed and simulated using the three-dimensional Finite Element Method (FEM) to compare their unidirectional focusing capabilities. The results show that the SH guided wave EMAT of the focusing coils with an oblique permanent magnet enhances the signal on the focusing side and weakens the signal on the other side effectively. This performance can suppress the influence of the reflected signal from the unfocused side and further improve the ultrasonic signal’s resolution. Moreover, it is shown in the study that increasing the oblique angle of the PPM makes it difficult to increase the signal strength at the focal point when the angle reaches a certain value, but it is still effective at weakening the signal on the unfocused side.

/pdf/improvement-of-unidirectional-focusing-periodic-permanent-1f2wk3sxsr.pdf

Improvement of unidirectional focusing periodic permanent magnet shear-horizontal wave electromagnetic acoustic transducer by oblique bias magnetic field

The defect opening profile recognition is of great concern in the magnetic flux leakage (MFL) measurement technique. The detected spatial MFL signal has three components: horizontal, vertical, and normal components. Horizontal and normal component signals are commonly used to estimate the defect profile, while the vertical component has always been neglected. With the development of the high resolution and the 3-D MFL testing techniques, the vertical component signal is becoming more available. This paper analyzes the essential right-angle features of the vertical component signal, which is useful for the defect opening profile recognition. After obtaining the initial profile from the horizontal or normal component, the types of the right angle is identified from the vertical component, and the opening profile is further optimized based on these right-angle features. The opening profile recognition method is put forward in this paper to improve the accuracy of the recognition result of the defect. Both simulation and experimental tests are conducted to verify the good performance of the proposed method. Compared with the opening profiles recognized merely by the horizontal component signal, the proposed method shows better recognition results, which also validates that the vertical component signal can also be a useful information for the defect estimation.

/pdf/an-opening-profile-recognition-method-for-magnetic-flux-2habw14sgx.pdf

Wei Zhao

Papers

A new omni-directional EMAT for ultrasonic Lamb wave tomography imaging of metallic plate defects.

Three-dimensional defect inversion from magnetic flux leakage signals using iterative neural network

Laser based measurement for the monitoring of shaft misalignment.

Improvement of unidirectional focusing periodic permanent magnet shear-horizontal wave electromagnetic acoustic transducer by oblique bias magnetic field

An Opening Profile Recognition Method for Magnetic Flux Leakage Signals of Defect