Abstract
Bars are significant load-carrying components in engineering structures. In particular, L-bars are typical structural components commonly used in truss structures and have typical irregular asymmetric cross-sections. To ensure the safety of load-carrying bars, much research has been done for non-destructive testing (NDT). Ultrasonic guided waves have been widely applied in various NDT techniques for bars as a result of the long-range propagation, low attenuation, and high sensitivity to damages. Though good for inspection of ultrasonic guided waves in symmetric cross-section bar-like structures, the application in asymmetric ones lacks further research. Moreover, traditional damage detection in bars using ultrasonic guided waves usually depends on a single-mode at a lower frequency with lower sensitivity and accuracy. To make full use of all frequencies and modes, a multi-mode characteristic-based damage detection method is presented with the sum of multiple signals (SoM) strategy for L-bars with asymmetric cross-section. To control the desired mode in multi-mode ultrasonic guided waves, excitation optimization and weighted gathering are carried out by the analysis of the semi-analytical finite element (SAFE) method and the normal mode expansion (NME) method. An L-bar example with the asymmetric cross-section of 35 mm × 20 mm × 3 mm is used to specialize the proposed method, and some finite element (FE) models have been simulated to validate the mode control. In addition, one PZT is applied as a contrast in order to validate the multielement mode control. Then, more FE simulations experiments for damage detection have been performed to validate the damage detection method and verify the improvement in detection accuracy and damage sensitivity.
Highlights
The occurrence of structural damage is able to threaten the safety of structures and further lead to unacceptable catastrophic consequences, calling for the development of non-destructive testing (NDT) [1] and structural health monitoring (SHM) [2]
The results indicate that the multi piezoelectric transducers (PZT) applied for excitation optimization and weighted gathering can avoid low energy and proportion of the desired mode
This paper presents a damage detection method using multi-mode ultrasonic guided waves for L-bars with asymmetric cross-sections
Summary
Guided wave technology has been widely utilized because of the excellent stability over long propagation and high sensitivity to damage initiation [4,5]. Ultrasonic guided waves have been applied for the rapid long-range damage detection in common structures such as plates [6], pipes [7] and composite [8]. Giurgiutiu et al [10] described a model of the ultrasonic guided waves generation and detection mechanism with PZTs in plate-like structures, which was utilized to design excitation for mode selection. Raghavan et al [2,11] modeled transient ultrasonic guided wavefields excited by differently shaped PZTs and developed the rigorous analytical solutions based on Considering the strong material damping and anisotropic characteristic, Mei et al [12]
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