Embedded Non-destructive Evaluation for Structural Health Monitoring, Damage Detection, and Failure Prevention

Abstract

In this paper we review the state of the art in an emerging new technology: embedded ultrasonic non-destructive evaluation (NDE). Embedded ultrasonic NDE permits active structural health monitoring, i.e. the on-demand interrogation of the structure to determine its current state of structural health. The enabling element of embedded ultrasonic NDE is the piezoelectric wafer active sensor (PWAS). We begin by reviewing the guided wave theory in plate, tube, and shell structures, with special attention to Lamb waves. The mechanisms of Lamb wave excitation and detection with embeddable PWAS transducers is presented. It is shown analytically and verified experimentally that Lamb wave mode tuning can be achieved by the judicious combination of PWAS dimensions, frequency value, and Lamb mode characteristics. Subsequently, we address in turn the use of pitch-catch, pulse-echo, and phased array ultrasonic methods for Lambwave damage detection. In each case, the conventional ultrasonic NDE results are contrasted with embedded NDE results. Detection of cracks, disbonds, delaminations, and diffuse damage in metallic and composite structures are exemplified. Other techniques, such as the time reversal method and the migration technique, are also presented. The paper ends with conclusions and suggestions for further work.

Mechanical state assessment using lamb wave technique in static tensile tests

“…It is easily seen from the figure 2 that there are three main peaks of the maximum envelope corresponding to the frequencies of 60 kHz, 150 kHz and 350 kHz. The dispersion curves for aluminum plates obtained experimentally and theoretically [8][9][10] allow calculating the group velocities and the wavelengths of A0 and S0 modes for the specimens with thickness of 4 mm. Thus the first peak at 60 kHz corresponds to the high amplitude of A0 mode while the amplitude of S0 is negligible because it has long wavelength at this frequency.…”

Time Domain Strain/Stress Reconstruction Based on Empirical Mode Decomposition: Numerical Study and Experimental Validation

“…The sampling frequency is 1000 Hz. Strain responses are calculated using the strain-displacement matrix and Equation (9). The beam is modeled using Euler-Bernoulli beam theory and the 1 × 4 strain-displacement matrix is given by: where the superscript (k) denotes the kth element, L (k) is the length of the element, x (k) and y (k) are the horizontal and vertical locations (within the element dimension) that the strain is computed, respectively.…”

“…Due to the increasing complexity and high reliability demand of those systems, damage and system performance degradation need to be quantified accurately for maintenance purposes [5,6]. To monitor the status of a target system, measurements of system condition variables are taken either by sensors installed on the system or field non-destructive inspections [7][8][9]. In particular, using smart sensors for structural health monitoring has drawn a lot of attention in the SHM community due to flexibility of smart sensors and advances in composite materials [9][10][11][12].…”

“…To monitor the status of a target system, measurements of system condition variables are taken either by sensors installed on the system or field non-destructive inspections [7][8][9]. In particular, using smart sensors for structural health monitoring has drawn a lot of attention in the SHM community due to flexibility of smart sensors and advances in composite materials [9][10][11][12]. A commonly used classification system for damage identification methods defines four levels of damage identification: (1) determine the existence of the damage in a structure; (2) identify the location of the damage; (3) quantify the severity of the damage; and (4) estimate…”

Carbon Nanotube Sensing Skins for Spatial Strain and Impact Damage Identification

“…As opposed to relying on global-based SHM methods, guided-waves show tremendous promise for damage detection and localization in thin metallic structures [5,6]. With ultrasonic waves able to propagate over long distances, this sensing approach provides the sensor with a large interrogation zone.…”