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A New Method to Evaluate Surface Defects with an Electromagnetic Acoustic Transducer.

Zhang K, Yi P, Li Y, Hui B, Zhang X - Sensors (Basel) (2015)

Bottom Line: Moreover, it can also reduce the influence of other factors, such as the lift-off, during the testing.Compared with other features, the theoretical and experimental results show that the feature lift-off slope has many advantages prior to the other features for evaluating the surface defect with the EMAT.Meanwhile, it is not essential to measure the signal without defects.

View Article: PubMed Central - PubMed

Affiliation: School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074, China. zhangkang@hust.edu.cn.

ABSTRACT
Characterizing a surface defect is very crucial in non-destructive testing (NDT). We employ an electromagnetic acoustic transducer (EMAT) to detect the surface defect of a nonmagnetic material. An appropriate feature that can avoid the interference of the human factor is vital for evaluating the crack quantitatively. Moreover, it can also reduce the influence of other factors, such as the lift-off, during the testing. In this paper, we conduct experiments at various depths of surface cracks in an aluminum plate, and a new feature, lift-off slope (LOS), is put forward for the theoretical and experimental analyses of the lift-off effect on the receiving signals. Besides, by changing the lift-off between the receiving probe and the sample for testing, a new method is adopted to evaluate surface defects with the EMAT. Compared with other features, the theoretical and experimental results show that the feature lift-off slope has many advantages prior to the other features for evaluating the surface defect with the EMAT. This can reduce the lift-off effect of one probe. Meanwhile, it is not essential to measure the signal without defects.

No MeSH data available.


Related in: MedlinePlus

The process of the new method with the lift-off slope (LOS) for characterizing the defect.
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sensors-15-17420-f009: The process of the new method with the lift-off slope (LOS) for characterizing the defect.

Mentions: Based on the above results, a new method is proposed to characterize the defect quantitatively through the EMAT. The method is described in Figure 9. We measure the signals at different lift-offs under different depths. Firstly, the signals are linearized to calculate the slope T, and the exponents e(T*hr), namely the independent variables f3, are obtained. Then, the data (e(T*hr), D) are linearized to get the feature, LOS K, corresponding to the depth d. On the basis of the fitting to the data (K, d), a calibration f(K,d) can be obtained. The same as the method for an unknown depth dj of the crack, we can get the LOS Kj. Comparing this value Kj with the calibration f(K,d), the depth dj can be found.


A New Method to Evaluate Surface Defects with an Electromagnetic Acoustic Transducer.

Zhang K, Yi P, Li Y, Hui B, Zhang X - Sensors (Basel) (2015)

The process of the new method with the lift-off slope (LOS) for characterizing the defect.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541941&req=5

sensors-15-17420-f009: The process of the new method with the lift-off slope (LOS) for characterizing the defect.
Mentions: Based on the above results, a new method is proposed to characterize the defect quantitatively through the EMAT. The method is described in Figure 9. We measure the signals at different lift-offs under different depths. Firstly, the signals are linearized to calculate the slope T, and the exponents e(T*hr), namely the independent variables f3, are obtained. Then, the data (e(T*hr), D) are linearized to get the feature, LOS K, corresponding to the depth d. On the basis of the fitting to the data (K, d), a calibration f(K,d) can be obtained. The same as the method for an unknown depth dj of the crack, we can get the LOS Kj. Comparing this value Kj with the calibration f(K,d), the depth dj can be found.

Bottom Line: Moreover, it can also reduce the influence of other factors, such as the lift-off, during the testing.Compared with other features, the theoretical and experimental results show that the feature lift-off slope has many advantages prior to the other features for evaluating the surface defect with the EMAT.Meanwhile, it is not essential to measure the signal without defects.

View Article: PubMed Central - PubMed

Affiliation: School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074, China. zhangkang@hust.edu.cn.

ABSTRACT
Characterizing a surface defect is very crucial in non-destructive testing (NDT). We employ an electromagnetic acoustic transducer (EMAT) to detect the surface defect of a nonmagnetic material. An appropriate feature that can avoid the interference of the human factor is vital for evaluating the crack quantitatively. Moreover, it can also reduce the influence of other factors, such as the lift-off, during the testing. In this paper, we conduct experiments at various depths of surface cracks in an aluminum plate, and a new feature, lift-off slope (LOS), is put forward for the theoretical and experimental analyses of the lift-off effect on the receiving signals. Besides, by changing the lift-off between the receiving probe and the sample for testing, a new method is adopted to evaluate surface defects with the EMAT. Compared with other features, the theoretical and experimental results show that the feature lift-off slope has many advantages prior to the other features for evaluating the surface defect with the EMAT. This can reduce the lift-off effect of one probe. Meanwhile, it is not essential to measure the signal without defects.

No MeSH data available.


Related in: MedlinePlus