Interaction of guided lamb waves with delaminations and discontinuities in composite plate‐like structures
21 Jun 2011-Vol. 1335, Iss: 1, pp 1483-1490
TL;DR: In this paper, the length and width of interface delamination in composite T-joint have been worked out using Dscan and B-scan, respectively, through numerical simulations and experimental verifications through Non Contact Ultrasound (NCU) technique.
Abstract: Delamination is one of the critical failure modes that laminated composites structures encounter during their fabrication and/or in‐service. When guided Lamb wave (Ao) is employed for sizing of delamination, it is necessary to understand the wave interaction with the defect. Studies were carried out on the interaction of Ao mode with symmetric and asymmetric delaminations and transmission of turning modes in the sub‐laminates. An attempt was also made to understand the propagation of Ao mode in composite structural T‐joint. During the interaction of Ao mode with structural discontinuity in a T‐joint, generation of a new mode, So, and propagation of turning modes were observed. Length and width of interface delamination in composite T‐joint have been worked out using D‐scan and B‐scan respectively. All studied were carried out through numerical simulations and experimental verifications through Non‐ Contact Ultrasound (NCU) technique.
Citations
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01 Oct 2011
TL;DR: In this article, the authors studied the reflection from axi-symmetric tapered steps and notches in pipes and found that the peak of the reflection coefficient from a defect is linearly dependent on the circumferential extent of the defect and is independent of its shape.
Abstract: The presence of defects in pipelines is a concern especially in petrochemical applications where the service integrity of pipes is a fundamental requirement to avoid process interruptions and to fulfil safety standards. Guided wave inspection is now routinely used in industry for screening long lengths of pipe for corrosion, any suspect areas then being followed up with conventional ultrasonic thickness gauging. However, this is difficult in cases where the suspect area is inaccessible (e.g. buried pipelines or pipes passing though walls), so it would be very useful to apply guided wave techniques for sizing as well as the detection and location of defects. This target is challenging due to the complexity of the profiles encountered in practice. The present work aims to improve the understanding of the scattering of the fundamental torsional mode T(0, 1) from complex shaped discontinuities and to determine the controlling parameters of this phenomenon. The overall analysis starts with a study of the reflection from axi-symmetric tapered steps and notches in pipes. After that the scattering from three dimensional (3D) defects with different shapes has been studied. Firstly, flat-bottomed defects with different surface profiles have been analyzed, and then the study of the reflection behavior from 3D defects with varying depth profile has been carried out. All of the work presented here uses the T(0,1) mode for inspection. It is revealed that the reflection coefficient maxima from axi-symmetric tapered defects decrease with increasing frequency as the slope of the taper becomes more gradual, this effect being more pronounced when the ratio of the average defect length to the wavelength increases. Tapered defects are therefore expected to be more difficult to detect at higher inspection frequencies; this effect is more evident for shallower tapers. It is also found that at a given maximum depth of a finite discontinuity, the peak of the reflection coefficient from a defect is linearly dependent on the circumferential extent of the defect, and is independent of its shape. The results from these analyses have been used to propose a practical approach to determine the maximum depth of a complex discontinuity from the reflection coefficient
8 citations
Cites background from "Interaction of guided lamb waves wi..."
...The significance of the non-propagating modes in the reflection from discontinuities has been analyzed in [71]....
[...]
Dissertation•
01 Jan 2014
TL;DR: Guided wave propagation and damage interaction in Isotropic and Composite Structures by Matthew Bridger Obenchain Chair: Professor Carlos E. S. Cesnik as discussed by the authors explores several key aspects of guided wave propagation in both isotropic and composite structures.
Abstract: Guided Wave Propagation and Damage Interaction in Isotropic and Composite Structures by Matthew Bridger Obenchain Chair: Professor Carlos E. S. Cesnik Guided wave structural health monitoring methods offer many of the capabilities needed to move from a schedule-based maintenance paradigm to a more cost-effective condition-based system. This dissertation explores several key aspects of guided wave propagation and damage interaction in both isotropic and composite structures. First, a reliable method of computing displacement time histories from guided wave excitation is presented. This formulation, based on the Global Matrix Method, is directly applicable to composite laminates. It improves upon previous methods that were unable to properly separate inbound and outbound wave solutions. Second, a comprehensive wave propagation simulation tool is presented that combines the best features of the Global Matrix Method and the recently developed local interaction simulation approach (LISA). This LISA hybrid model accurately captures guided wave generation from both piezoceramic and piezocomposite actuators. Wave propagation results from the new model compare favorably with semi-analytical models for both isotropic plates and composite laminates. Following that, the dissertation describes the application of the LISA hybrid model to examine guided xviii wave interaction with holes in plate structures. Simulations are used to analyze the influence of various damage parameters, such as hole radius and depth, and the results are compared with experimental measurements. The effect of hole orientation relative to fiber direction in composite laminates is also explored. Subsequently, the dissertation examines guided wave interaction with low-velocity impact damage in composite laminates. Diagnostic imagery of laboratory-produced impact damage is presented to help characterize the size, shape, and composition of the damage. Experimental results from guided wave interrogation of the damage region are also presented. Together, these are used to evaluate various methods to model the impact damage in LISA. Finally, this dissertation introduces a damage characterization tool based on the matching pursuit method. The new algorithm uses a library of LISA simulations that capture the effects of various damage sizes and locations. The ability of the algorithm to locate damage is demonstrated in both 1-D and 2-D scenarios.
5 citations
Cites background from "Interaction of guided lamb waves wi..."
...[121] experimentally characterized the propagation of Lamb waves in T-joint structures composed of glass fiber reinforced sublayers....
[...]
01 Apr 2019
TL;DR: In this article, the results of an experimental study of guided ultrasonic wave interaction with damage in an alpine ski are described. But the results indicate further study is required to fully understand how the lateral boundaries of the structure affect the signals obtained from damaged configurations.
Abstract: This paper describes the results of an experimental study of guided ultrasonic wave interaction with damage in an alpine ski. The ski is chosen to act as a surrogate for built-up composite structures commonly used in aerospace and many other engineering applications. The study begins by characterizing the optimal actuation signal to generate observable guided wave signals in sensors located along the ski. Using this frequency, the experiment continues by determining the effect of through-thickness hole damage. The damage is located between the sensors to allow for both pitch-catch and pulse-echo approaches to be considered. Data were collected for various hole diameters to determine the sensors’ ability to detect worsening damage in the ski. Interestingly, results showed the damage difference signals collected by comparing damaged and pristine cases actually decreased in value as the diameter of the hole increased. These results indicate further study is required to fully understand how the lateral boundaries of the structure affect the signals obtained from damaged configurations.
1 citations
References
More filters
01 Oct 2011
TL;DR: In this article, the authors studied the reflection from axi-symmetric tapered steps and notches in pipes and found that the peak of the reflection coefficient from a defect is linearly dependent on the circumferential extent of the defect and is independent of its shape.
Abstract: The presence of defects in pipelines is a concern especially in petrochemical applications where the service integrity of pipes is a fundamental requirement to avoid process interruptions and to fulfil safety standards. Guided wave inspection is now routinely used in industry for screening long lengths of pipe for corrosion, any suspect areas then being followed up with conventional ultrasonic thickness gauging. However, this is difficult in cases where the suspect area is inaccessible (e.g. buried pipelines or pipes passing though walls), so it would be very useful to apply guided wave techniques for sizing as well as the detection and location of defects. This target is challenging due to the complexity of the profiles encountered in practice. The present work aims to improve the understanding of the scattering of the fundamental torsional mode T(0, 1) from complex shaped discontinuities and to determine the controlling parameters of this phenomenon. The overall analysis starts with a study of the reflection from axi-symmetric tapered steps and notches in pipes. After that the scattering from three dimensional (3D) defects with different shapes has been studied. Firstly, flat-bottomed defects with different surface profiles have been analyzed, and then the study of the reflection behavior from 3D defects with varying depth profile has been carried out. All of the work presented here uses the T(0,1) mode for inspection. It is revealed that the reflection coefficient maxima from axi-symmetric tapered defects decrease with increasing frequency as the slope of the taper becomes more gradual, this effect being more pronounced when the ratio of the average defect length to the wavelength increases. Tapered defects are therefore expected to be more difficult to detect at higher inspection frequencies; this effect is more evident for shallower tapers. It is also found that at a given maximum depth of a finite discontinuity, the peak of the reflection coefficient from a defect is linearly dependent on the circumferential extent of the defect, and is independent of its shape. The results from these analyses have been used to propose a practical approach to determine the maximum depth of a complex discontinuity from the reflection coefficient
8 citations
Dissertation•
01 Jan 2014
TL;DR: Guided wave propagation and damage interaction in Isotropic and Composite Structures by Matthew Bridger Obenchain Chair: Professor Carlos E. S. Cesnik as discussed by the authors explores several key aspects of guided wave propagation in both isotropic and composite structures.
Abstract: Guided Wave Propagation and Damage Interaction in Isotropic and Composite Structures by Matthew Bridger Obenchain Chair: Professor Carlos E. S. Cesnik Guided wave structural health monitoring methods offer many of the capabilities needed to move from a schedule-based maintenance paradigm to a more cost-effective condition-based system. This dissertation explores several key aspects of guided wave propagation and damage interaction in both isotropic and composite structures. First, a reliable method of computing displacement time histories from guided wave excitation is presented. This formulation, based on the Global Matrix Method, is directly applicable to composite laminates. It improves upon previous methods that were unable to properly separate inbound and outbound wave solutions. Second, a comprehensive wave propagation simulation tool is presented that combines the best features of the Global Matrix Method and the recently developed local interaction simulation approach (LISA). This LISA hybrid model accurately captures guided wave generation from both piezoceramic and piezocomposite actuators. Wave propagation results from the new model compare favorably with semi-analytical models for both isotropic plates and composite laminates. Following that, the dissertation describes the application of the LISA hybrid model to examine guided xviii wave interaction with holes in plate structures. Simulations are used to analyze the influence of various damage parameters, such as hole radius and depth, and the results are compared with experimental measurements. The effect of hole orientation relative to fiber direction in composite laminates is also explored. Subsequently, the dissertation examines guided wave interaction with low-velocity impact damage in composite laminates. Diagnostic imagery of laboratory-produced impact damage is presented to help characterize the size, shape, and composition of the damage. Experimental results from guided wave interrogation of the damage region are also presented. Together, these are used to evaluate various methods to model the impact damage in LISA. Finally, this dissertation introduces a damage characterization tool based on the matching pursuit method. The new algorithm uses a library of LISA simulations that capture the effects of various damage sizes and locations. The ability of the algorithm to locate damage is demonstrated in both 1-D and 2-D scenarios.
5 citations
01 Apr 2019
TL;DR: In this article, the results of an experimental study of guided ultrasonic wave interaction with damage in an alpine ski are described. But the results indicate further study is required to fully understand how the lateral boundaries of the structure affect the signals obtained from damaged configurations.
Abstract: This paper describes the results of an experimental study of guided ultrasonic wave interaction with damage in an alpine ski. The ski is chosen to act as a surrogate for built-up composite structures commonly used in aerospace and many other engineering applications. The study begins by characterizing the optimal actuation signal to generate observable guided wave signals in sensors located along the ski. Using this frequency, the experiment continues by determining the effect of through-thickness hole damage. The damage is located between the sensors to allow for both pitch-catch and pulse-echo approaches to be considered. Data were collected for various hole diameters to determine the sensors’ ability to detect worsening damage in the ski. Interestingly, results showed the damage difference signals collected by comparing damaged and pristine cases actually decreased in value as the diameter of the hole increased. These results indicate further study is required to fully understand how the lateral boundaries of the structure affect the signals obtained from damaged configurations.
1 citations