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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 interaction of the signals.
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sensors-15-17420-f002: The interaction of the signals.

Mentions: According to the description of the testing process of the EMAT, the interaction of the signals can be simplified as in Figure 2. When the pulsed current is sent through the coil, the exciting signal A is generated in the probe. There is a distance between the transmitting probe and the sample, namely the lift-off ht. The signal A transforms into signal B. Signal C is obtained after the wave is blocked by the surface crack d. Through the lift-off hr between the receiving probe and the sample, the receiving signal D is picked up in the coil. The above processes can be expressed in Equations (3)–(5).


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 interaction of the signals.
© Copyright Policy
Related In: Results  -  Collection

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

sensors-15-17420-f002: The interaction of the signals.
Mentions: According to the description of the testing process of the EMAT, the interaction of the signals can be simplified as in Figure 2. When the pulsed current is sent through the coil, the exciting signal A is generated in the probe. There is a distance between the transmitting probe and the sample, namely the lift-off ht. The signal A transforms into signal B. Signal C is obtained after the wave is blocked by the surface crack d. Through the lift-off hr between the receiving probe and the sample, the receiving signal D is picked up in the coil. The above processes can be expressed in Equations (3)–(5).

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