This paper reports a Genetic Algorithm (GA) based reconstruction procedure to determine the elastic constants of an orthotropic plate from ultrasonic velocity data. Phase velocity measurements are carried out using ultrasonic back-reflection technique on laminated unidirectional graphite-epoxy (0)16 and quasi-isotropic graphite-epoxy (+45, -45, 0, 90)7s fiber reinforced composite plates. A forward model to generate the slowness curves from elastic constants has been used to verify the quality of the reconstruction. The sensitivity of the chosen GA parameters is studied. As expected, out of 9 orthotropic elastic constants to be determined, the C23 and C44 found to be insensitive. The GA based reconstruction using data obtained from multiple planes were evaluated and it is shown that the single plane reconstruction at a non-symmetric plane was sufficient for the computation of the seven elastic constants. © 2006 Elsevier Ltd. All rights reserved.

Krishnan Balasubramaniam

Department of Mechanical Engineering

C V Krishnamurthy

Department Of Physics

J. Vishnuvardhan

ELASTICITY

Fiber reinforced materials

Genetic algorithms

Nondestructive examination

Ultrasonics

Velocity measurement

Fiber reinforced composites

Layered Structures

Orthotropic plates

PHASE VELOCITY MEASUREMENTS

Composite materials

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Composites Part B: Engineering

In this paper, an inversion method is proposed to determine simultaneously the electrical and the thermal properties of a given isotropic material from the time-temperature data obtained from tone-burst eddy current thermography (TBET). A multiphysics forward model for computing the surface temperature data was used in a genetic algorithm (GA) based inversion technique to determine the material properties such as electrical conductivity (σ), thermal conductivity (k), density (ρ), and specific heat (Cp) simultaneously. Different trials were carried out initially with simulated temperature data (with and without noise) and then validated with experiments. © 2011 IEEE.

IEEE Transactions on Magnetics

Simultaneous estimation of electrical and thermal properties of isotropic material from the tone-burst eddy current thermography (TBET) time-temperature data

Structural health monitoring of plate like structures, using transducer arrays located suitably on the structure, finds applications in monitoring aerospace structures. These plates are anisotropic, with wave propagation properties varying with direction. Single Transmitter Multiple Receiver (STMR) arrays have been shown before to have the ability to locally characterize the stiffness properties of a composite material with anisotropy. The STMR arrays have also been demonstrated for SHM applications using phase reconstruction techniques. The guided ultrasonic Lamb waves are used where the central piezoelectric wafer-active sensor (PWAS) emits the guided waves, and the other PWAS sensors receive the Lamb wave signals. In the current work, this technique has been extended to the determination of global elastic moduli using the Lamb wave S0 and A0 mode signals that are reflected from features in the structure such as edge of the plate, bolt holes, etc. that are known apriori using STMR array and then reconstruct the unknown defects present on the structure using the same sensor array. The reconstruction of elastic moduli is accomplished using a Genetic Algorithm (GA) based inversion algorithm that optimizes an objective function for a particular configuration of the STMR array and the elastic moduli of the component. The solution to this inversion is the global elastic moduli of the composite which is then used to determine the unknown defects in the test component. Simulations were carried out using S0 and A0 mode velocity data for composite layups such as unidirectional, cross-ply, and quasi-isotropic graphite-epoxy composite layups. The inversion algorithm was tested using the simulated edge reflector data and found to agree well with the expected values. Experimental validation has been performed on 3.15 mm quasi-isotropic graphite-epoxy composite. © 2010 American Institute of Physics.

AIP Conference Proceedings

Global material characterization of composite structures using lamb wave STMR array technique

Determination of the elastic moduli of polymer matrix based structural composite materials is necessary to characterize their strength after fabrication and while in service. This paper reports a modification to goniometry based ultrasonic through transmission data collection by using wide aperture low cost polyvinylidene fluoride (PVDF) based receiver. The use of PVDF based receiver more than satisfies the plane-wave conditions required from measurement. The use of a hybrid inversion technique which combines genetic algorithm based evolutionary approach, critical angle information and the use of stiffness invariants is implemented for determination of stiffness values from experimental transmission spectra measurements. Results for unidirectional and a multi-layered composite laminate are presented. © 2009 Elsevier Ltd. All rights reserved.

Hybrid inversion of elastic moduli of composite plates from ultrasonic transmission spectra using PVDF plane wave sensor

A novel blind inversion method using Lamb wave S0 and A0 mode velocities is proposed for the complete determination of elastic moduli, material symmetries, as well as principal plane orientations of anisotropic plates. The approach takes advantage of genetic algorithm, introduces the notion of "statistically significant" elastic moduli, and utilizes their sensitivities to velocity data to reconstruct the elastic moduli. The unknown material symmetry and the principal planes are then evaluated using the method proposed by Cowin and Mehrabadi [Q. J. Mech. Appl. Math. 40, 451-476 (1987)]. The blind inversion procedure was verified using simulated ultrasonic velocity data sets on materials with transversely isotropic, orthotropic, and monoclinic symmetries. A modified double ring configuration of the single transmitter and multiple receiver compact array was developed to experimentally validate the blind inversion approach on a quasi-isotropic graphite-epoxy composite plate. This technique finds application in the area of material characterization and structural health monitoring of anisotropic platelike structures. © 2009 Acoustical Society of America.

Journal of the Acoustical Society of America

Blind inversion method using Lamb waves for the complete elastic property characterization of anisotropic plates

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. © 2008 Elsevier Ltd. All rights reserved.

NDT and E International

Structural health monitoring of anisotropic plates using ultrasonic guided wave STMR array patches

Genetic algorithm reconstruction of orthotropic composite plate elastic constants from a single non-symmetric plane ultrasonic velocity data

Journal	Composites Part B: Engineering
ISSN	13598368
Open Access	No