Showing papers by "Tetsuya Uchimoto published in 2019"

Magnetic incremental permeability non-destructive evaluation of 12 Cr-Mo-W-V steel creep test samples with varied ageing levels and thermal treatments

Abstract: Techniques based on Magnetic Incremental Permeability (MIP) measurements help to elucidate the physical/mechanical properties, which are correlated with the magnetic properties of the material. In this work, the MIP method was applied for the evaluation of creep-induced microstructural changes in a high-chromium steel subjected to different creep test conditions, such as stress and temperature treatments. Precipitations in the creep samples and recrystallization were investigated via Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD). The correlation between featured parameters in the MIP signature curve and the microstructural analysis of the creep samples was also investigated.

A novel frequency-band-selecting pulsed eddy current testing method for the detection of a certain depth range of defects

Abstract: Local wall thinning is one of the major defects in industrial structures and in some cases it generates in a certain depth range of the object structures. In this study, a novel nondestructive testing method called frequency-band-selecting pulsed eddy current testing (FSPECT) is proposed to detect a certain depth range of defects. This novel FSPECT method is based on the frequency-band-selecting strategy as well as the conventional square wave pulsed eddy current testing (PECT) method. In this study, FSPECT method is introduced and the frequency range selection principle of the excitation signal of FSPECT is explained in details at first. Then the simulation of FSPECT for detecting a certain depth range of defects has been performed. In addition, the sensitivities of the proposed FSPECT and the conventional PECT are compared and analyzed. Finally, a comparative experiment of FSPECT method and PECT method is implemented. The superiority of the proposed FSPECT method for detecting a certain depth range of defects is demonstrated through simulation and experiment.

A Fast Forward Simulation Scheme for Eddy Current Testing of Crack in a Structure of Carbon Fiber Reinforced Polymer Laminate

Abstract: High frequency Eddy Current Testing (ECT) is one of the key non-destructive testing techniques for ensuring integrity of a structure of Carbon Fiber Reinforced Polymer (CFRP) material. An efficient numerical simulator is indispensable to enhance the performance of quantitative ECT for CFRP structures from both point of view of probe optimization and defect sizing. In this paper, a fast forward simulation scheme based on the A-Φ formulation and databases approach is proposed, implemented and experimentally validated for the rapid and high precision simulation of ECT signals due to defects in a CFRP plate by updating an FEM-BEM hybrid code for ECT problem. Comparison of numerical results of the present method with those of the conventional full FEM-BEM code and the experimental results for artificial cracks in CFRP laminate plates indicates that the proposed novel fast forward scheme can predict ECT signals over 300 times faster but without worsening numerical accuracy, which enables it to be applied to efficient reconstruction of cracks in CFRP plates and for probe optimization.

Numerical model of the eddy current magnetic signature (EC-MS) non-destructive micro-magnetic technique

Abstract: Micro-magnetic nondestructive evaluation and testing techniques are particularly efficient for the evaluation of plastic strain in steel components. A new method derived from the magnetic incremental permeability experimental setup and called Eddy Current Magnetic Signature (EC-MS) seems to be the particularly adapted for such evaluation. Numerical simulation of EC-MS has never been done before. In this article, the EC-MS method is described first, then a lump scalar phenomenological model based on a modified Jiles-Atherton model and extended to dynamic behavior is proposed for its simulation. All the simulation details are exposed and justified with physical observations.Micro-magnetic nondestructive evaluation and testing techniques are particularly efficient for the evaluation of plastic strain in steel components. A new method derived from the magnetic incremental permeability experimental setup and called Eddy Current Magnetic Signature (EC-MS) seems to be the particularly adapted for such evaluation. Numerical simulation of EC-MS has never been done before. In this article, the EC-MS method is described first, then a lump scalar phenomenological model based on a modified Jiles-Atherton model and extended to dynamic behavior is proposed for its simulation. All the simulation details are exposed and justified with physical observations.

Investigation of Cast Iron Matrix Constituents by Magnetic Adaptive Testing

Abstract: Two types of cast iron materials—flake graphite cast iron and ductile cast iron—were investigated by the method of magnetic adaptive testing, which is based on the systematic measurement and the evaluation of minor magnetic hysteresis loops. In all cases, even within the same type of material rather big differences existed considering both the chemical composition and the material structure of the investigated sample series. The matrix structure was determined by traditional metallographic examination, and these values were compared with the non-destructively measured magnetic parameters. It was shown that the relative pearlite volume fraction of the metallic matrix of cast iron samples could be determined by this method with a good reliability. The same is true also for the relative chill content of the matrix, as long as the samples contain chill at all. A general expression was found to characterize those correlations, which do not depend on the actual sample and neither on the applied parameters of the concrete magnetic measurement.

Caution to Apply Magnetic Barkhausen Noise Method to Nondestructive Evaluation of Plastic Deformation in Some Ferromagnetic Materials

Abstract: Magnetic Barkhausen Noise (MBN) method is known as an effective nondestructive evaluation (NDE) method for evaluation of residual stress in ferromagnetic materials. Some studies on the feasibility of the MBN method for NDE of residual strains were also conducted and found applicable. However, these studies are mainly focused on the state of residual strains which were introduced through a one-cycle-loading process. In practice, however, structures may suffer from an unpredictable and complicated loading history, i.e., the final state of plastic strain may be induced by several times of large loads. Whether the loading history has influences on MBN signals or not is of great importance for the practical application of the MBN method. In this paper, several ferromagnetic specimens with the same final state of residual strain but of different loading history were fabricated and inspected by using a MBN testing system. The experimental results reveal that the loading history has a significant influence on the detected MBN signals especially for a residual strain in range less than 1%, which doubts the feasibility to apply the MBN method simply in the practical environment. In addition, micro-observations on the magnetic domain structures of the plastic damaged specimens were also carried out to clarify the influence mechanism of loading history on the MBN signals.