Ultrasonic Lamb wave tomography

Abstract

Nondestructive evaluation (NDE) of aerospace structures using traditional methods is a complex, time-consuming process critical to maintaining mission readiness and flight safety. Limited access to corrosion-prone structure and the restricted applicability of available NDE techniques for the detection of hidden corrosion or other damage often compound the challenge. In this paper we discuss our recent work using ultrasonic Lamb wave tomography to address this pressing NDE technology need. Lamb waves are ultrasonic guided waves, which allow large sections of aircraft structures to be rapidly inspected for structural flaws such as disbonds, corrosion and delaminations. Because the velocity of Lamb waves depends on thickness, for example, the travel times of the fundamental Lamb modes can be converted into a thickness map of the inspection region. However, extracting quantitative information from Lamb wave data has always involved highly trained personnel with a detailed knowledge of mechanical waveguide physics. Our work focuses on tomographic reconstruction to produce quantitative maps that can be easily interpreted by technicians or fed directly into structural integrity and lifetime prediction codes. Laboratory measurements discussed here demonstrate that Lamb wave tomography using a square perimeter array of transducers with algebraic reconstruction tomography is appropriate for detecting flaws in aircraft materials. The speed and fidelity of the reconstruction algorithms as well as practical considerations for person-portable array-based systems are discussed in this paper.

A two-stage approach for quantitative damage imaging in metallic plates using Lamb waves

“…A decade later, a research team led by Hinders carried out a number of studies in Lamb wave tomography. Malyarenko and Hinders (2000), Leonard et al (2002) studied a number of time-of-flight tomography algorithms using Lamb waves and provided an extensive bibliography of literature in this research area. Leonard and Hinders (2005) subsequently demonstrated that time-of-flight Lamb wave tomography could be used for inspecting curved panels.…”

Structural Health Monitoring for Composite Materials

“…A tomographic image can be reconstructed by using wave speed, waveform or amplitude as flaw-relevant features. The standard parallel projection, fan-beam or crosshole schemes are usually adopted in tomography technique [36]. The crosshole scheme with iterative nature and great flexibly is more suited for any geometry and incomplete data set.…”

Study on Guided Wave Imaging Methods for SOLID Rocket Motor Shell Material

“…In 2000, Malyarenko studied the filtered method for fan beam projection and double crosshole geometry [11]. In 2002, Leonard presented a sample of parallel projection and fan beam projection [12].…”