Study on the Mechanism and Application of Applying Magnetic Barkhausen Noise to Evaluate Dislocation Density and Plastic Deformation

Seven specimens of 45 steel with different residual strains were prepared by homogeneous plastic tensile test. The microstructure of the specimens was observed by scanning electron microscopy and the texture characteristics of the specimens were studied by X-ray diffraction. The results showed that plastic deformation mainly leads to dislocation increment in the microstructure rather than obvious deformed grain morphology, texture and residual stress. Then the dislocation density of each sample was calculated by X-ray diffraction method. The MBN signals of the samples were tested by magnetic Barkhausen noise method and the corresponding RMS (root mean square) values were calculated. The results showed that the dislocation density increases and the RMS value decreases with the increase of plastic deformation magnitude, the phenomenon was explained deeply. By establishing the correlation between dislocation density and RMS value, it was found that there was a good linear relationship between dislocation density and RMS value. According to the formula provided by the fitting curve, the dislocation density can be predicted by measuring the RMS value of any degree of plastic deformation.

Instrumental Configuration of Electromagnetic Thermography and Optical Thermography

Electromagnetic thermography and optical thermography are both important non-destructive testing (NDT) methods that have been widely used in the fields of modern aerospace, renewable energy, nuclear industry, etc. The excitation modes are crucial whose performances have a decisive effect on the detection results. Previous studies mainly focused on the physics mechanism, applications, and signal processing algorithms. However, the instrument configuration is rarely presented. This paper is to introduces the recently designed excitation sources of electromagnetic thermography and optical thermography detection systems, respectively. These instruments involved L-shaped and Shuttle-shaped sensor structures for electromagnetic thermography and multi-modes excitation for optical thermography. Besides, the topologies and operating principles are shown in detail. Experimental results are carried out to verify the practicability and reliability of the proposed systems.

An Eddy Current Method to Evaluate Local Wall Thinning of Carbon Steel Pipe

This paper proposes to evaluate the local wall thinning of carbon steel pipe using an eddy current method. Firstly, the feature signals are determined by correlation analysis of the signals and the wall thinning sizes. Subsequently, the models for estimating the residual wall thickness rt is constructed using Gaussian process regression (GPR). Finally, the applicability of the models to the evaluation of local wall thinning is verified by simulation and experiment.

Data Analysis of Magnetic Flux Leakage Detection Based on Multi-Source Information Fusion

For the analysis of the magnetic flux leakage detection data in pipelines, a single information source data analysis method is used to determine the pipeline characteristics with uncertainty. A multi-source information fusion data analysis technology is proposed. This paper makes full use of the information collected by the multi-source sensors of the magnetic leakage internal detector, and adopts distributed and centralized multi-source information fusion analysis technology. First, pre-analyze and judge the information data of the auxiliary sensors (speed, pressure, temperature) of the internal magnetic flux leakage detector. Then, the data of the main sensor, ID / OD sensor, axial mileage sensor, and circumferential clock sensor of the magnetic flux leakage detector are analyzed separately. Finally, the RBF neural network + least squares support vector machine (LSSVM)fusion analysis technology is adopted to realize the fusion analysis of multi-source information. The results show that this method can effectively improve the quality and reliability of data analysis compared with traditional single information source data analysis.

An Investigation of Corrosion Progression Using Laser Profilometry

Atmospheric corrosion progression characterisation on metal substrates is a major problem in the field of corrosion science and Non-destructive Evaluation (NDE). A laser profilometry has been used to characterise the corrosion on the mild steel plate at a low cost and high resolution. Four mild steel samples have been measured which exposed to the marine environment from 1 month to 10 months. Two features have been developed to characterise thickness variation in the corrosion layer. These features have been used to characterise corrosion progression through experimental studies. The relationship between these features and corrosion progression has been derived which is useful for corrosion progression measurement, early-stage corrosion prediction, and monitoring areas.

Sensitivity Analysis for the Inverse Problems of Electromagnetic Nondestructive Evaluation

Sensitivity analysis of the model-based inverse problem associated to electromagnetic nondestructive evaluation is dealt with. Some uncertainty of the arrangement is inevitable present (imprecise host material parameters, sensor mispositioning, etc.), and this induces uncertainty on the reconstructed defect parameters. The aim of this work is to present a methodology for the ranking of the different sources of random error according to their contribution to the reconstruction uncertainty. To this end, state-of-art mathematical tools of sensitivity analysis are applied, including Sobol’ indices, and a polynomial chaos expansion surrogate model to reduce the computational burden of the method. A numerical example drawn from magnetic flux leakage nondestructive evaluation is presented to illustrate the proposed methodology.

Study on Effect of Electromagnetic Characteristics of Deformed 304 Stainless Steel on Eddy Current Testing

The induced ferrite and other high magnetic microstructures content changes are studied when 304 austenitic stainless steel stripe specimens are tested under different uniaxial tension deformation, namely its deformation less than 50%. Furtherly, the correlation is plotted between the resulting magnetic permeability or coercivity caused by these microstructures and deformation. Meanwhile, the optimal eddy current excitation frequency under different deformation was obtained, which was consistent with 3-D finite element analysis (FEA). Besides, other various factors affecting the quality of eddy current testing (ECT), such as temperature and conductivity, are also considered comprehensively during the tensile test. The results of the experiment and simulation calculation show that when the deformation is within 50% that necking deformation has occurred, the magnetic permeability of specimens increases with deformation, and gradually begin to have the magnetic properties of weak ferromagnetic materials, which also changes the optimal excitation frequency, which varies from 60 kHz to 110 kHz. Because of the electromagnetic response noise increase, the impedance plane diagrams of defects distort simultaneously, which leads to the quantitative evaluation error of defects.

Simulation and Experimental Study of Closed Crack Detection by Ultrasonic Nonlinearity Under Electromagnetic Loading

The reliability of micro-damage detection of metal materials plays a crucial role in the safe and reliable operation of large equipment. In recent years, nonlinear ultrasonic nondestructive testing technology has achieved good development in closed cracks detection, but the problem of nonlinear ultrasonic detection of closed cracks is weak response signal and vulnerable to external interference. This paper realizes the modulation of the ultrasonic wave by electromagnetic loading at the closed cracks, which can effectively enrich the frequency components of nonlinear ultrasonic and magnify the amplitude. This lays a foundation for further research on nonlinear ultrasonic detection of closed cracks under electromagnetic loading.

Design and Application of a Magnetoelectric Composite Sensor for Pipeline Defect Detection

Nowadays, there are 160000 kilometers of pipelines in China. How to get more pipeline information in pipeline integrity management is a vitally important research topic. This paper designs a magnetoelectric composite sensor which is suitable for the non-destructive detection of the buried pipeline. according to the defect characteristics. this paper introduces the working principle, structure and characteristics of the composite sensor. Combined with the advantages of the magnetic sensor which is sensitive to the volume defects of the tube wall and the high frequency eddy current sensor which is sensitive to the near-surface defects of the tube wall on the principle of magnetic flux leakage, it realizes the identification and evaluation of the inner and outer wall defects of the tube wall. In this paper, the pipeline in the traction test field is taken as the test object. The test results show that there are 37 defects picked up by the magnetic sensor and 19 defects judged by the eddy current sensor.

Investigation of Beam Features of Unidirectional Rayleigh Waves Electromagnetic Acoustic Transducers (EMATs) by a Wholly Analytical Solution

Electromagnetic acoustic transducers (EMATs) are widely used in industries due to its non-contact nature. This paper investigates the beam features of unidirectional Rayleigh waves EMATs, especially the effect of the wire length on beam directivity. A wholly analytical model is developed to calculate the Lorentz force distribution and ultrasound displacement distribution. The modelling results indicate that, compared to the coil consists of shorter wires, the coil consists of longer wires results in a narrower bandwidth of main lobe of unidirectional Rayleigh waves, which means the ultrasound are more concentrated. This study can be used for unidirectional Rayleigh waves EMATs design and optimization.