Influence of Bending Loads on Ultrasonic Guided-Waves Based Structural Health Monitoring of Laminated Composite Structures

Author(s):  
SURAJIT ROY ◽  
SKANDA RAI ◽  
MANOJ SAMPANGI RAM
Author(s):  
Victor Giurgiutiu

Piezoelectric wafer active sensors (PWAS) are lightweight and inexpensive transducers that enable a large class of structural health monitoring (SHM) applications such as: (a) embedded guided wave ultrasonics, i.e., pitch-catch, pulse-echo, phased arrays; (b) high-frequency modal sensing, i.e., the electro-mechanical (E/M) impedance method; and (c) passive detection (acoustic emission and impact detection). The focus of this paper is on the challenges posed by using PWAS transducers in the composite structures as different from the metallic structures on which this methodology was initially developed. After a brief introduction, the paper reviews the PWAS-based SHM principles. It follows with a discussion of guided wave propagation in composites and PWAS tuning effects. Then, it discusses damage modes in composites. Finally, the paper presents some experimental results with damage detection in composite specimens. Hole damage and impact damage were detected using pitch-catch method with tuned guided waves being sent between a transmitter PWAS and a received PWAS. Root mean square deviation (RMSD) damage index (DI) were shown to correlate well with hole size and impact intensity. The paper ends with summary and conclusion; suggestions for further work are also presented.


Author(s):  
Cliff J. Lissenden ◽  
James J. Blackshire ◽  
Padma K. Puthillath

Active structural health monitoring of plate-like structures can be performed with ultrasonic guided waves. The activation of ultrasonic guided waves from embedded piezoelectric fibers in carbon fiber reinforced polymer (CFRP) laminated plates is investigated. Finite element analysis simulations of wave propagation from an array of embedded parallel piezoelectric fibers are presented. A quasi-isotropic CFRP having piezoelectric fibers embedded at the midplane is studied. The number and spacing of piezoelectric fibers is varied in order to activate different modes at different frequencies. The simulation results (i) characterize the displacement profile through the thickness of the CFRP plate, (ii) enable visualization of mode excitability, and (iii) demonstrate the source influence. The results indicate that the embedded fibers have a strong potential for either hot spot monitoring or distributed monitoring of large areas. However, due to the size, spacing, and activation of embedded fibers the source influence causes the mode excitability to differ from that of a conventional comb transducer.


2020 ◽  
Vol 4 (1) ◽  
pp. 13 ◽  
Author(s):  
Alfredo Güemes ◽  
Antonio Fernandez-Lopez ◽  
Angel Renato Pozo ◽  
Julián Sierra-Pérez

Condition-based maintenance refers to the installation of permanent sensors on a structure/system. By means of early fault detection, severe damage can be avoided, allowing efficient timing of maintenance works and avoiding unnecessary inspections at the same time. These are the goals for structural health monitoring (SHM). The changes caused by incipient damage on raw data collected by sensors are quite small, and are usually contaminated by noise and varying environmental factors, so the algorithms used to extract information from sensor data need to focus on sensitive damage features. The developments of SHM techniques over the last 20 years have been more related to algorithm improvements than to sensor progress, which essentially have been maintained without major conceptual changes (with regards to accelerometers, piezoelectric wafers, and fiber optic sensors). The main different SHM systems (vibration methods, strain-based fiber optics methods, guided waves, acoustic emission, and nanoparticle-doped resins) are reviewed, and the main issues to be solved are identified. Reliability is the key question, and can only be demonstrated through a probability of detection (POD) analysis. Attention has only been paid to this issue over the last ten years, but now it is a growing trend. Simulation of the SHM system is needed in order to reduce the number of experiments.


2020 ◽  
pp. 147592172094740
Author(s):  
Valentin Serey ◽  
Nicolas Quaegebeur ◽  
Mathieu Renier ◽  
Philippe Micheau ◽  
Patrice Masson ◽  
...  

Ultrasonic guided waves are used in non-destructive testing and structural health monitoring solutions for long-range inspection, in applications ranging from Civil Engineering to Aerospace. In order to ease the inspection process, it is generally preferable to generate a carefully selected single mode. Although single mode Lamb wave generation is not difficult to achieve in infinite plate-like structures, with carefully polarized or sized piezoceramic elements, for example, such selective generation is much more difficult in a rectangular bar. In this article, we consider the propagation along a thin plate of finite rectangular cross section, which corresponds to a rectangular bar. The finite lateral width leads to a greater density of modes compared to an infinite plate. The authors have previously addressed this matter and developed a methodology for the selective generation of modes in the harmonic regime. This article extends this methodology to selective mode generation for finite time excitation, such as bursts. Results are presented for single mode generation of A0,0 and A0,1 in an aluminum bar instrumented with eight piezoelectric transducers. The waveguide modal basis is calculated with the two-dimensional semi-analytical finite element method, and measurements are conducted using a three-dimensional laser-Doppler vibrometer. To illustrate the potential of the method for structural health monitoring purposes, the detection of a defect simulated by a pair of magnets placed at various positions over the bar width is demonstrated.


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