Guided Lamb waves for identification of damage in composite structures: A review

The capability of embedded piezoelectric wafer active sensors (PWAS) to excite and detect tuned Lamb waves for structural health monitoring is explored. First, a brief review of Lamb waves theory is presented. Second, the PWAS operating principles and their structural coupling through a thin adhesive layer are analyzed. Then, a model of the Lamb waves tuning mechanism with PWAS transducers is described. The model uses the space domain Fourier transform. The analysis is performed in the wavenumber space. The inverse Fourier transform is used to return into the physical space. The integrals are evaluated with the residues theorem. A general solution is obtained for a generic expression of the interface shear stress distribution. The general solution is reduced to a closed-form expression for the case of ideal bonding which admits a closed-form Fourier transform of the interfacial shear stress. It is shown that the strain wave response varies like sin a, whereas the displacement response varies like sinc a. ...

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Tuned Lamb-Wave Excitation and Detection with Piezoelectric Wafer Active Sensors for Structural Health Monitoring

Cost-effective and reliable damage detection is critical for the utilization of composite materials. This paper presents part of an experimental and analytical survey of candidate methods for in situ damage detection of composite materials. Experimental results are presented for the application of Lamb wave techniques to quasi-isotropic graphite/epoxy test specimens containing representative damage modes, including delamination, transverse ply cracks and through-holes. Linear wave scans were performed on narrow laminated specimens and sandwich beams with various cores by monitoring the transmitted waves with piezoceramic sensors. Optimal actuator and sensor configurations were devised through experimentation, and various types of driving signal were explored. These experiments provided a procedure capable of easily and accurately determining the time of flight of a Lamb wave pulse between an actuator and sensor. Lamb wave techniques provide more information about damage presence and severity than previously tested methods (frequency response techniques), and provide the possibility of determining damage location due to their local response nature. These methods may prove suitable for structural health monitoring applications since they travel long distances and can be applied with conformable piezoelectric actuators and sensors that require little power.

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Damage detection in composite materials using lamb wave methods

Renewable energy sources have gained much attention due to the recent energy crisis and the urge to get clean energy. Among the main options being studied, wind energy is a strong contender because of its reliability due to the maturity of the technology, good infrastructure and relative cost competitiveness. In order to harvest wind energy more efficiently, the size of wind turbines has become physically larger, making maintenance and repair works difficult. In order to improve safety considerations, to minimize down time, to lower the frequency of sudden breakdowns and associated huge maintenance and logistic costs and to provide reliable power generation, the wind turbines must be monitored from time to time to ensure that they are in good condition. Among all the monitoring systems, the structural health monitoring (SHM) system is of primary importance because it is the structure that provides the integrity of the system. SHM systems and the related non-destructive test and evaluation methods are discussed in this review. As many of the methods function on local damage, the types of damage that occur commonly in relation to wind turbines, as well as the damage hot spots, are also included in this review.

https://iopscience.iop.org/article/10.1088/0957-0233/19/12/122001/pdf

Structural health monitoring for a wind turbine system: a review of damage detection methods

Fatigue damage assessment by nonlinear ultrasonic materials characterization

Health monitoring of aerospace structures can be done passively by listening for acoustic waves generated by cracks, impact damage and delaminations, or actively by propagating diagnostic stress waves and interpreting the parameters that characterize the wave travel. This paper investigates modeling of flexural wave propagation in a plate and the design of sensors to detect damage in plates based on stress wave parameters. To increase understanding of the actual physical process of wave propagation, a simple model is developed to simulate wave propagation in a plate with boundaries. The waves can be simulated by applied forces and moments in the model either to represent passive damage growth or active wave generation using piezoceramic actuators. For active wave generation, the model considers a piezoceramic patch bonded perfectly to a quasi-isotropic glass-epoxy composite plate. Distributed sensors are used on the plate and are modeled as being constructed using active fiber composite and piezoceramic materials. For active wave generation, a moment impulse is generated by the actuation of a piezoceramic patch. The waves generated from the patch are detected by the distributed sensor. For passive sensing of acoustic waves, a step function is used to simulate an acoustic emission from a propagating damage. The resulting acoustic wave is measured by the distributed sensor and produces micro-strains in the sensor nodes. The strains produce a single voltage signal output from the distributed sensor. Computational simulations and animations of acoustic wave propagation in a plate are discussed in the paper. A new method to locate the source of an acoustic emission using the time history of the dominant lower frequency components of the flexural wave mode detected by continuous sensors is also presented.

Wave propagation sensing for damage detection in plates

Modeling delamination in composite structures by incorporating the Fermi-Dirac distribution function and hybrid damage indicators

Studies of the acoustic signals originating from impact damage on Space Shuttle components were undertaken Sprayed on foam insulation and small aluminum spheres were used as impactors Shuttle reinforced carbon‐carbon panels, panels with Shuttle thermal protection tiles, and Shuttle main landing gear doors with tiles were targets Ballistic speed and hypervelocity impacts over a wide range of impactor sizes, energies, and angles were tested Additional tests were conducted to correlate the acoustic response of the test articles to actual Shuttle structures

Detection of Impact Damage on Space Shuttle Structures Using Acoustic Emission

Finite Element and Plate Theory Methods for Modeling Acoustic Emission Waveforms

One effect of nonlinear elasticity on elastic wave propagation is that the velocity of the elastic wave is a function of the applied stress on the material. This effect has been used to characterize the nonlinear elastic properties of numerous materials and is also important in attempts to nondestructively characterize residual and applied stress in materials. In addition, investigations have established a possible correlation between the nonlinear elastic properties and ultimate strength in conventional materials such as aluminum [1] and carbon steel [2].

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=2257&context=qnde

William H. Prosser

Papers

Wave propagation sensing for damage detection in plates

Modeling delamination in composite structures by incorporating the Fermi-Dirac distribution function and hybrid damage indicators

Detection of Impact Damage on Space Shuttle Structures Using Acoustic Emission

Finite Element and Plate Theory Methods for Modeling Acoustic Emission Waveforms

Stress dependence of ultrasonic velocity in unidirectional graphite/epoxy composites for longitudinal waves propagating along the direction of stress