Genetic algorithm based reconstruction of the elastic moduli of orthotropic plates using an ultrasonic guided wave single-transmitter-multiple-receiver SHM array
TL;DR: In this article, a single-transmitter-multiple-receiver (STMR) compact structural health monitoring (SHM) array is used to reconstruct the elastic moduli of orthotropic plate structures.
Abstract: The reconstruction of all nine unknown elastic moduli of orthotropic plate structures has been achieved using a single-transmitter-multiple-receiver (STMR) compact structural health monitoring (SHM) array. This method uses the velocity measurement of the fundamental guided Lamb wave modes (S0 and A0), generated from a central transmitter, and received by a sparse array of receivers that encircle the transmitter. The measured velocities are then used in an inversion algorithm based on genetic algorithms. A prototype compact STMR array was developed and used in the measurement. Simulated data were used to demonstrate the feasibility of the technique. Experiments were conducted on 3.15 mm graphite–epoxy composite plate using a PZT based STMR array as well as laser vibrometer based displacement measurement. Experimental Lamb wave velocity data were used to validate the present technique. This technique finds application in the areas of material characterization and SHM of anisotropic plate-like structures used in aerospace and automobile components made using fiber reinforced composites.
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TL;DR: In this article, an inverse procedure based on the propagation of guided ultrasonic waves is proposed for the characterization of the elastic material constants of plates, which consists of an optimization problem in which the discrepancy between the dispersion curves obtained through a semi analytical finite element (SAFE) formulation and numerical or experimental dispersion curve is minimized.
82 citations
TL;DR: In this article, two flexible printed circuit board (PCB)-based patches were developed for accomplishing both objectives, i.e. online material characterization (MC) and structural health monitoring (SHM) of anisotropic plate-like structures.
Abstract: Structural health monitoring (SHM) of plate-like structures used in aerospace industries, using transducer arrays located suitably on the structure, such as the single-transmitter multiple-receiver (STMR) array [Wilcox PD, Lowe M, Cawley P. Lamb and SH wave transducer arrays for the inspection of large areas of thick plates. Review of progress in quantitative nondestructive evaluation, vol. 19A. Melville, NY, USA: American Institute of Physics; 1999. p. 1049–56; Wilcox PD. Guided wave beam steering from omni-directional transducer arrays. Review of progress in quantitative nondestructive evaluation, vol. 22A. Melville, New York, USA: American Institute of Physics; 2002. p. 761–8], has been demonstrated here. The reconstruction of the material state was carried out by utilizing a phased addition reconstruction algorithm. In addition to the signals from damage sites, the ultrasonic guided wave-based reconstruction procedures also need the complete set of elastic moduli as a continuous input throughout the SHM process. In the present study, two flexible printed circuit board (PCB)-based patches: ((i). single-quadrant, double-ring STMR material characterization (MC) array and (ii). Full-ring STMR SHM array) were developed for accomplishing both objectives, i.e. (a) online MC and (b) SHM of anisotropic plate-like structures, respectively. Experiments were conducted on 3.15 mm graphite-epoxy composite plate using PCB-based STMR arrays, the feasibility of accomplishing both objectives was demonstrated.
48 citations
TL;DR: A review on the development of nondestructive vibrational evaluation approaches in identifying the elastic constants of composite plates, in experimental and numerical manners, in order to enlighten researchers with the current trends of nonsmooth vibrational approaches is presented in this article.
Abstract: Destructive identification approaches are no longer in favor since the advent of nondestructive evaluation approaches, as they are accurate, rapid, and cheap. Researchers are devoted to improving the accuracy, rate of convergence, and cost of such approaches, which depend greatly on the types of vibrational experiments conducted and the types of forward and inverse methods used in numerical section. Therefore, this article presents a review on the development of nondestructive vibrational evaluation approaches in identifying the elastic constants of composite plates, in experimental and numerical manners in order to enlighten researchers with the current trends of nondestructive vibrational approaches.
44 citations
TL;DR: An algorithm to compute specific parts of the dispersion curves for elastic waveguides based on an axisymmetric representation of the Scaled Boundary Finite Element Method.
43 citations
TL;DR: This paper introduces an efficient inversion method based on genetic algorithms using multimode guided waves, in which the mode-order is kept blind, and shows that the model parameters are in good agreement with the reference values derived from x-ray micro-computed tomography.
Abstract: Recent progress in quantitative ultrasound has exploited the multimode waveguide response of long bones. Measurements of the guided modes, along with suitable waveguide modeling, have the potential to infer strength-related factors such as stiffness (mainly determined by cortical porosity) and cortical thickness. However, the development of such model-based approaches is challenging, in particular because of the multiparametric nature of the inverse problem. Current estimation methods in the bone field rely on a number of assumptions for pairing the incomplete experimental data with the theoretical guided modes (e.g. semi-automatic selection and classification of the data). The availability of an alternative inversion scheme that is user-independent is highly desirable. Thus, this paper introduces an efficient inversion method based on genetic algorithms using multimode guided waves, in which the mode-order is kept blind. Prior to its evaluation on bone, our proposal is validated using laboratory-controlled measurements on isotropic plates and bone-mimicking phantoms. The results show that the model parameters (i.e. cortical thickness and porosity) estimated from measurements on a few ex vivo human radii are in good agreement with the reference values derived from x-ray micro-computed tomography. Further, the cortical thickness estimated from in vivo measurements at the third from the distal end of the radius is in good agreement with the values delivered by site-matched high-resolution x-ray peripheral computed tomography.
38 citations
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TL;DR: In this paper, the elastic constants of an anisotropic material are determined from ultrasonic measurements made in non-principal directions of a specimen using a pulsed laser as a source and a miniature, point-like transducer as a receiver.
Abstract: This paper presents the solution of the materials characterization problem in which the elastic constants of an anisotropic material are determined from ultrasonic wavespeed measurements made in nonprincipal directions of a specimen. The ultrasonic waves were generated via the point‐source/point‐receiver technique using a pulsed laser as a source and a miniature, point‐like transducer as a receiver. Data were acquired during a scan of the source along one of the principal acoustic axes of symmetry of the material. In each waveform the arrivals of the quasi‐longitudinal and the two quasi‐shear bulk modes were measured and the elastic constants of the material were then recovered using an optimization algorithm. Experimental results are presented for a transversely isotropic, unidirectional fiberglass/polyester and a single crystal specimen of silicon. It was found that the nonlinear fit between the measured and the recovered longitudinal slowness values is excellent. Some discrepancies are observed in the ...
67 citations
TL;DR: In this paper, the use of embedded piezoelectric-wafer active-sensors for in-situ structural health monitoring of thin-wall structures is presented, and experiments performed on aircraft-grade metallic specimens of various complexities exemplified the detection procedures for near-field and far-field damage.
Abstract: The use of embedded piezoelectric-wafer active-sensors for in-situ structural health monitoring of thin-wall structures is presented. Experiments performed on aircraft-grade metallic specimens of various complexities exemplified the detection procedures for near-field and far-field damage. For near-field damage detection, the electro-mechanical (E/M) impedance method was used. Systematic experiments conducted on statistical samples of incrementally damaged specimens were followed by illustrative experiments on realistic aging aircraft panels. For far-field damage detection, guided ultrasonic Lamb waves were utilized in conjunction with the pulse-echo technique. Systematic experiments conducted on aircraft-grade metallic plates were used to develop the method, while experiments performed on realistic aging-aircraft panels exemplified the crack detection procedure.
65 citations
01 Jan 2002
64 citations
22 Nov 2017
TL;DR: In this paper, the basic governing equations of wave surfaces and energy propagation in anisotropic media have been studied, including phase velocity vs group velocity, elastic modulus reconstruction from ultrasonic data and composite microstructure characterization.
Abstract: Introduction - Basic Governing Equations - Wave Surfaces - Energy Propagation - Bulk Wave Propagation Anisotropic Media - Guided Waves - Ultrasonic Measurements - Elastic Modulus Reconstruction from Ultrasonic Data - Dynamic Modulus Measurement in Anisotropic Media: Phase Velocity vs Group Velocity - Ultrasonic Modulus Measurements - Composite Microstructure Characterization
64 citations
TL;DR: In this paper, the authors used the displacement polarization factors to define the degree of material anisotropy and represent solutions of the Christoffel equation, and then derived simple expressions for coefficients describing the sensitivity of ultrasonic waves to different elastic constants.
Abstract: The determination of elastic constants from ultrasonic bulk wave velocity data taken in a plane of symmetry is studied. It is shown that the problem is well‐posed, i.e., the solution is unique and stable. The displacement polarization factors are used to define the degree of material anisotropy and represent solutions of the Christoffel equation. Such a representation in a rotated coordinate system helps to derive simple expressions for coefficients describing the sensitivity of ultrasonic waves to different elastic constants. Thus the optimal refraction angles for velocity measurement can be determined simply. The analysis performed shows that the elastic constants reconstructed from velocity data are not affected by the selection of initial guesses used in a nonlinear least‐square optimization (the solution is unique). The solution stability is validated by performing reconstruction with different levels of random scatter in the velocity data. The effect of the angle range used for velocity measurements...
62 citations