Experimental and numerical validation of guided wave phased arrays integrated within standard data acquisition systems for structural health monitoring

Abstract

Summary Phased array methods are a promising approach to damage detection by enabling guided wave steering and beam focusing leading to improved localization and sizing of structural damage. Due to the costs and challenges to addressing piezoelectric arrays in parallel, most phased array methods actuate piezoelectric elements one at a time in round‐robin fashion with postprocessing algorithms used to synthetically steer and focus the guided waves. In this study, true parallel excitation and sensing of ceramic piezoelectric actuators is implemented in a standard structural health monitoring data acquisition system without requiring highly specialized and expensive ultrasonic data acquisition equipment. The study performs both numerical simulation and laboratory experiments to illustrate the damage detection capabilities of a piezoelectric phased array. Laboratory experiments are first performed using the high‐speed data acquisition system to actuate and sense piezoelectric elements bonded in a linear array on an aluminum plate. To visualize the direction and focal point of the guided waves, a laser Doppler vibrometer triggered by the data acquisition system is adopted to scan the surface displacements of the plate. The study verifies that the location and size of damage can be accurately detected in the plate using the phased array operated by the structural health monitoring data acquisition system. To explore the capabilities of the system to detect different damage cases, the computationally efficient local interaction simulation approach is implemented on a graphic processing unit to simulate the performance of a linear phased array to steer and focus Lamb waves for damage detection.

Phase symmetry analysis for nonlinear ultrasonic modulated signals

“…A single frequency excitation method was also conducted for the aluminium sample from Tx 1 (116 kHz) and captured at Rx 1 (see Table 1). In order to evaluate the effects of the excitation amplitude on the production of sidebands, the composite sample tests were conducted at multiple voltages (5,20,40,60, and 80 V). Nonlinearities are only generated once a minimum energy threshold is applied to the damage region; thus, generally high voltage (high energy) excitation of the structure is required.…”

“…The need for NDT/E methods has increased dramatically in recent years due to the high demand from end users for product safety, in‐line diagnostics, quality control, health monitoring, and secure testing. Moreover, due to the high cost of inspection in both metallic and composite materials, development of reliable and effective NDT/E methods to detect the occurrence of critical failure modes has been pursued . For this scope, numerous ultrasonic inspection techniques have been developed over the past 20 years to detect and localise material defects such as microcracks, delamination, and weak adhesive bonds …”

“…Moreover, due to the high cost of inspection in both metallic and composite materials, development of reliable and effective NDT/E methods to detect the occurrence of critical failure modes has been pursued. [2][3][4][5] For this scope, numerous ultrasonic inspection techniques have been developed over the past 20 years to detect and localise material defects such as microcracks, delamination, and weak adhesive bonds. [6][7][8] Early work, focusing on single frequency excitation, by Breazeale and Thompson, 9 Suzuki et al, 10 and Gauster and Breazeale 11 relate the production of higher order harmonics to the deviation of Hooke's law in a nonlinear medium, which forms the foundation for damage detection using nonlinear ultrasound methods.…”

Nondestructive Ultrasonic Inspection of Composite Materials: A Comparative Advantage of Phased Array Ultrasonic

“…This capability assists in generating the desired type of ultrasonic signal and improving the wave characteristics in comparison to the conventional single-element ultrasonic transducer. The PAUT method can also be used to generate guided waves [22][23][24][25][26]. Guided waves are another type of ultrasonic wave, which provide useable features for inspection of plate type structures.…”

Calculation of Guided Wave Dispersion Characteristics Using a Three-Transducer Measurement System

“…Dispersion curves show the relation of phase and group velocities against frequency, for a particular geometry and material. Determination of dispersion curves is important for any guided wave application; accurate dispersion curves enable wave modes of received wavepackets to be distinguished, specific wave modes to be cancelled to clean the acquired signal, the propagation of wave modes in a particular direction using phased arrays [3] and the spatial location of damage in the structure to be determined based on time-of-flight measurements [4]. Guided waves are being used in commercial products, for instance to detect wall thickness losses due to corrosion for pipeline inspection in the oil and gas industry.…”