An Ultrasonic Lamb Wave Method for Evaluating Fatigue Damage of Plate

An Ultrasonic Lamb Wave Method for Evaluating Fatigue Damage of Plate

Deng Mingxi Pei Junfeng

(College of Logistics Engineering, Chongqing 400016)

Abstract: Changes in the properties of solid plates caused by fatigue damage will affect the dispersion, attenuation and mode conversion properties of ultrasonic Lamb waves. This paper discusses the feasibility of using ultrasonic Lamb wave amplitude-frequency characteristics and stress wave factors to evaluate the fatigue damage of plates, and experimentally studies the relationship between ultrasonic Lamb wave amplitude-frequency characteristics and stress wave factors with the number of load cycles. The results show that the ultrasonic Lamb wave stress wave factor has a significant monotonous decrease law with the increase of the number of cycles. According to the corresponding relationship between the ultrasonic Lamb wave stress wave factor and the number of load cycles, it is expected to provide an effective way for the non-destructive evaluation of the fatigue damage of the plate.

Key words fatigue damage; plate; ultrasonic Lamb wave; stress wave factor

Evaluation of fatigue damage in a solid plate using ultrasonic Lamb waves

DENG Ming-xi PEI Jun-feng

(Logistics Engineering University, Chongqing 400016, China)

Abstract: Changes in the properties of a solid plate induced by fatigue damage will influence the features of Lamb wave propagation such as dispersion, attenuation and mode conversion. The feasibility of using the amplitude-frequency characteristics and the stress wave factors of Lamb wave propagation to evaluate fatigue damage of a solid plate has been analyzed in this paper. The relationships between the amplitude-frequency characteristics of Lamb waves and cycles of fatigue loading, as well as the ones between the stress wave factors of Lamb waves and cycles of fatigue loading, have been experimentally studied. The experimental results show that the stress wave factors of Lamb waves decrease obviously and monotonously with the increment of cycles of fatigue loading. Based on the relationships between the stress wave factors of Lamb waves and cycles of fatigue loading, it can be expected that an effective approach for evaluating fatigue damage in a solid plate may be provided.

Key words: fatigue damage; solid plate; ultrasonic Lamb wave; stress wave factor

1 Introduction

Due to the existence of fatigue loads, fatigue damage will occur to solid plates during use. The degree of fatigue damage of the solid plate determines the reliability and safety of the plate structure. It is of great practical significance to study the fatigue damage evaluation method of the solid plate. From the current research status and development level of fatigue, it is difficult to establish a damage evolution model and evaluate fatigue damage based on the damage mechanism of solid plates [1]. Focusing on the current detection methods and methods, it is of great practical significance to explore a non-destructive evaluation method for fatigue damage that can comprehensively describe the cumulative effect and overall effect of various forms of fatigue damage.

In recent years, in the monitoring and evaluation of solid plate fatigue damage, ultrasonic Lamb wave has been studied in depth as an effective method [2-7]. Literature [2] gives practical examples of rapid detection of the delamination of the rudder skin of the F-18 naval aircraft and the crack propagation of the transmission beam of the H-60 ​​helicopter using ultrasonic Lamb waves. Literature [3] reported the use of the Lamb wave method to monitor the development and growth of cracks in riveted aluminum parts under fatigue loading. Through the time-frequency analysis and Hilbert transform of the Lamb wave signal, the corresponding damage parameters were used. It can observe and monitor the formation, development and growth of cracks. Reference [4] used piezoelectric transducer arrays to excite and receive appropriate ultrasonic Lamb wave modes, and studied the crack growth monitoring of the structure during periodic loading. For some materials (such as Plexiglas), the changes in bulk wave sound velocity and sound attenuation coefficient after periodic loading (before the material fails) are very small (less than 0.6% for Plexiglas), but Lamb waves There is a certain correspondence between the propagation characteristics and the fatigue load. The propagation characteristics of the high-frequency Lamb wave mode can change by 10% after the fatigue load (before the material fails) [5]. Based on previous studies, this paper proposes and experimentally studies an ultrasonic Lamb wave evaluation method for fatigue damage of sheet metal. From the practical application point of view, in the process of applying fatigue load to the plate, the ultrasonic lamb wave is excited and received on the same side of the solid plate with the diagonal split ultrasonic transducer. Conveniently measure the amplitude-frequency characteristics of ultrasonic Lamb waves corresponding to different load cycles. Drawing on the concept of stress wave factor in acoustic-ultrasonic technology, the corresponding relationship between the ultrasonic Lamb wave stress wave factor and the number of load cycles can be obtained. The experimental results show that the corresponding relationship between the ultrasonic Lamb wave stress wave factor and the number of load cycles is expected to provide an effective way for the non-destructive evaluation of the fatigue damage of solid plates.

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