Abstract
The incipient defect is difficult to be identified by ultrasonic signal analysis. The nonlinear ultrasonic method based on the nonlinear Lamb wave principle is proposed by establishing a nonlinear Lamb wave ultrasonic inspection platform. The optimal Lamb wave parameters are obtained for the incipient fatigue material defects. The aluminum alloy board with 3 mm thickness under the different fatigue tensile cycles is tested. The nonlinear ultrasonic signals are analyzed to obtain second harmonic signals. The intelligent diagnosis method for incipient material degrade is proposed based on the Sequential Probability Ratio Test (SPRT). The sequential probabilistic ratio test (SPRT) algorithm is carried out to classify and identify the second harmonics of four different fatigue damages. The results show that the method about with nonlinear Lamb wave analysis with SPRT is effective and reliable for the incipient material microdefect degradation.
Highlights
E research shows that the nonlinear ultrasonic testing technology overcomes the limits and deficiency of the traditional ultrasonic nondestructive testing, which is effective to detect the early damage of mechanical structural materials
The traditional linear Lamb wave detection technology is poor for the microdefect of the mechanical structural material identification, which inspired the nonlinear ultrasonic detection technology to be starting applications in the mechanical industry [2, 3]. erefore, the nonlinear Lamb wave detection technology [4–6] is introduced in the detection of the fatigue degradation of the mechanical structural material
For the second harmonic signals obtained in the experiment, fatigue stretching signals are recorded as normal signals S1, and 4,000, 8,000, and 12,000 fatigue damage signals are recorded as S2, S3, and S4, respectively
Summary
With the rapid development of the intelligent industry, the quick requirement for the quality control of the large scale mechanical system in the industrial areas of the transportation, energy, and chemical production is increased It is a great challenge for the nondestructive testing techniques such as ultrasonic methods to regularly maintain the reliability of the key equipment structures under the premise of considering the operation cost. Sequential probabilistic ratio test algorithm is proposed to classify the second harmonic signals extracted from nonlinear Lamb wave detection. According to the dispersion curve, four 2A12 aluminum alloy plates with different fatigue degrees were detected by selecting suitable modal Lamb waves, and the second harmonic signals were collected. E kurtosis value is extracted by time domain analysis method for sequential probabilistic ratio test, and the collected second harmonic signals with different fatigue degrees are classified effectively According to the dispersion curve, four 2A12 aluminum alloy plates with different fatigue degrees were detected by selecting suitable modal Lamb waves, and the second harmonic signals were collected. e kurtosis value is extracted by time domain analysis method for sequential probabilistic ratio test, and the collected second harmonic signals with different fatigue degrees are classified effectively
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