The Experts below are selected from a list of 81 Experts worldwide ranked by ideXlab platform
Wieslaw Ostachowicz - One of the best experts on this subject based on the ideXlab platform.
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Analysis of S0/A0 elastic wave mode conversion phenomenon in glass fibre reinforced polymers
MATEC Web of Conferences, 2018Co-Authors: Tomasz Wandowski, Pawel Malinowski, Wieslaw OstachowiczAbstract:In this paper results of experimental analysis of elastic guided wave mode conversion phenomenon in glass fibre reinforced polymers GFRP are presented. Results of research presented in this paper are strictly focused on S0/A0' mode conversion caused by discontinuities in the form of circular Teflon Insert simulating damage and impact damage. Experimental research is based on non-contact elastic wave sensing with utilisation of scanning laser Doppler vibrometer SLDV and full wave-field measurements. In presented research influence of location of circular Teflon Insert on S0/A0' mode conversion is investigated. Teflon Inserts were located between layers of composite material at different depth. Moreover influence of impact damage with different energy on S0/A0' mode conversion is investigated. Analysis of influence of investigated discontinuities on S0/A0' mode conversion are based on the elastic wave mode filtration in frequency-wavenumber domain. Mode filtration process allows to remove effects of unwanted type of mode propagation in forward or backward direction. Effects of S0/A0' mode conversion are characterise by mode conversion indicator based on amplitude of new mode A0'.
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Impact induced damage assessment by means of Lamb wave image processing
Mechanical Systems and Signal Processing, 2018Co-Authors: Pawel Kudela, Maciej Radzieński, Wieslaw OstachowiczAbstract:Abstract The aim of this research is an analysis of full wavefield Lamb wave interaction with impact-induced damage at various impact energies in order to find out the limitation of the wavenumber adaptive image filtering method. In other words, the relation between impact energy and damage detectability will be shown. A numerical model based on the time domain spectral element method is used for modeling of Lamb wave propagation and interaction with barely visible impact damage in a carbon-epoxy laminate. Numerical studies are followed by experimental research on the same material with an impact damage induced by various energy and also a Teflon Insert simulating delamination. Wavenumber adaptive image filtering and signal processing are used for damage visualization and assessment for both numerical and experimental full wavefield data. It is shown that it is possible to visualize and assess the impact damage location, size and to some extent severity by using the proposed technique.
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Impact Induced Delamination Detection by Application of Full Wavefield Analysis
Structural Health Monitoring-an International Journal, 2017Co-Authors: Wieslaw Ostachowicz, Maciej Radzieński, Pawel KudelaAbstract:Comprehensive numerical studies of elastic wave interaction with damage of various sizes and severities which resembles impact damage were performed. Full wavefield signal processing allowed to visualize damaged area and quantify its size by the thresholding damage maps. It was shown that the severity of damage can be quantified by relation of damage map energy in relation to Young’s modulus reduction. It enables to make a step towards damage prognosis. Experimental data of propagating waves in carbon/epoxy laminate acquired by a scanning laser vibrometer revealed that the wave attenuation is highly dependent on angle of propagation. Such behavior strongly affects damage visualization algorithms which are based on a wavenumber filtering. It was shown that this effect can be reduced by the proposed weighting method utilizing propagating elastic wave energy spread. It was also shown that the damage caused by the low impact energy is more difficult to detect and quantify than a delamination simulated by the Teflon Insert.
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Application of scanning laser Doppler vibrometry for delamination detection in composite structures
Optics and Lasers in Engineering, 2017Co-Authors: Pawel Kudela, Tomasz Wandowski, Pawel Malinowski, Wieslaw OstachowiczAbstract:In this paper application of scanning laser Doppler vibrometry for delamination detection in composite structures was presented. Delamination detection was based on a guided wave propagation method. In this papers results from numerical and experimental research were presented. In the case of numerical research, the Spectral Element Method (SEM) was utilized, in which a mesh was composed of 3D spectral elements. SEM model included also a piezoelectric transducer. In the experimental research guided waves were excited using the piezoelectric transducer whereas the sensing process was conducted using scanning laser Doppler vibrometer (SLDV). Analysis of guided wave propagation and its interaction with delamination was based on a full wavefield approach. Attention was focused on interactions of guided waves with delamination manifested by A0 mode reflection, A0 mode entrapment, and S0/A0 mode conversion. Delamination was simulated by a Teflon Insert located between plies of composite material. Results of interaction with symmetrically and nonsymmetrical placed delamination (in respect to the composite sample thickness) were presented. Moreover, the authors investigated different size of delaminations. Damage detection was based on a new signal processing algorithm proposed by the authors. In this approach the weighted RMS was utilized selectively. It means that the summation in RMS formula was performed only for a specially selected time instances. Results for simple composite panels, panel with honeycomb core, and real stiffened composite panel from the aircraft were presented.
Pawel Kudela - One of the best experts on this subject based on the ideXlab platform.
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Impact induced damage assessment by means of Lamb wave image processing
Mechanical Systems and Signal Processing, 2018Co-Authors: Pawel Kudela, Maciej Radzieński, Wieslaw OstachowiczAbstract:Abstract The aim of this research is an analysis of full wavefield Lamb wave interaction with impact-induced damage at various impact energies in order to find out the limitation of the wavenumber adaptive image filtering method. In other words, the relation between impact energy and damage detectability will be shown. A numerical model based on the time domain spectral element method is used for modeling of Lamb wave propagation and interaction with barely visible impact damage in a carbon-epoxy laminate. Numerical studies are followed by experimental research on the same material with an impact damage induced by various energy and also a Teflon Insert simulating delamination. Wavenumber adaptive image filtering and signal processing are used for damage visualization and assessment for both numerical and experimental full wavefield data. It is shown that it is possible to visualize and assess the impact damage location, size and to some extent severity by using the proposed technique.
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Impact Induced Delamination Detection by Application of Full Wavefield Analysis
Structural Health Monitoring-an International Journal, 2017Co-Authors: Wieslaw Ostachowicz, Maciej Radzieński, Pawel KudelaAbstract:Comprehensive numerical studies of elastic wave interaction with damage of various sizes and severities which resembles impact damage were performed. Full wavefield signal processing allowed to visualize damaged area and quantify its size by the thresholding damage maps. It was shown that the severity of damage can be quantified by relation of damage map energy in relation to Young’s modulus reduction. It enables to make a step towards damage prognosis. Experimental data of propagating waves in carbon/epoxy laminate acquired by a scanning laser vibrometer revealed that the wave attenuation is highly dependent on angle of propagation. Such behavior strongly affects damage visualization algorithms which are based on a wavenumber filtering. It was shown that this effect can be reduced by the proposed weighting method utilizing propagating elastic wave energy spread. It was also shown that the damage caused by the low impact energy is more difficult to detect and quantify than a delamination simulated by the Teflon Insert.
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Application of scanning laser Doppler vibrometry for delamination detection in composite structures
Optics and Lasers in Engineering, 2017Co-Authors: Pawel Kudela, Tomasz Wandowski, Pawel Malinowski, Wieslaw OstachowiczAbstract:In this paper application of scanning laser Doppler vibrometry for delamination detection in composite structures was presented. Delamination detection was based on a guided wave propagation method. In this papers results from numerical and experimental research were presented. In the case of numerical research, the Spectral Element Method (SEM) was utilized, in which a mesh was composed of 3D spectral elements. SEM model included also a piezoelectric transducer. In the experimental research guided waves were excited using the piezoelectric transducer whereas the sensing process was conducted using scanning laser Doppler vibrometer (SLDV). Analysis of guided wave propagation and its interaction with delamination was based on a full wavefield approach. Attention was focused on interactions of guided waves with delamination manifested by A0 mode reflection, A0 mode entrapment, and S0/A0 mode conversion. Delamination was simulated by a Teflon Insert located between plies of composite material. Results of interaction with symmetrically and nonsymmetrical placed delamination (in respect to the composite sample thickness) were presented. Moreover, the authors investigated different size of delaminations. Damage detection was based on a new signal processing algorithm proposed by the authors. In this approach the weighted RMS was utilized selectively. It means that the summation in RMS formula was performed only for a specially selected time instances. Results for simple composite panels, panel with honeycomb core, and real stiffened composite panel from the aircraft were presented.
C. M. Manjunatha - One of the best experts on this subject based on the ideXlab platform.
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Prediction of Mode II Delamination Onset Life Under Spectrum Fatigue Loads Using Equivalent Strain Energy Release Rate Concept
Advances in Structural Integrity, 2017Co-Authors: A. R. Anilchandra, Ramesh Bojja, N. Jagannathan, M. Seshagirachari, C. M. ManjunathaAbstract:End notched flexure (ENF) test specimens of unidirectional IMA/M21 carbon fiber composite (CFC) were fabricated using standard autoclave process. A Teflon Insert was used to simulate a delamination at the midplane. Three-point bend setup tests were conducted at an average frequency of 2 Hz using a 25 kN servo-hydraulic test machine in room temperature conditions. Constant amplitude fatigue tests were done at three different stress ratios, viz. R = 0.0, 0.5, and −1.0 to construct the standard G-N onset diagram, similar to S–N curve in its usefulness. N onset was identified as 5% change in initial compliance value. Using an equivalent energy release rate parameter, G eq, all the curves were collapsed into a single curve in the form of Basquin’s equation. The equation was subsequently used in predicting the delamination onset-of-growth life under a standard mini-FALSTAFF spectrum load sequence. A fairly good correlation was found between the predicted and experimental mode II onset-of-growth behavior.
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Variable Amplitude Fatigue Testing to Characterize Mode II Delamination in a Polymer Composite
Transactions of The Indian Institute of Metals, 2015Co-Authors: A. R. Anilchandra, Ramesh Bojja, N. Jagannathan, C. M. ManjunathaAbstract:In this study, the mode II delamination behavior in terms of onset-of-growth and propagation characteristics under a standard variable amplitude (VA) fatigue load sequence was investigated. A special three point bend test fixture was designed and fabricated to perform fatigue tests under VA loads. Standard end notched flexure test specimens of unidirectional IMA/M21 carbon fiber composite were fabricated. A Teflon Insert was used to simulate a delamination at the mid plane. The fatigue tests were conducted under a standard mini FALSTAFF VA load sequence. Tests were carried out with different reference values of loads to determine the onset-of-growth, Nonset. Decreasing the reference load was observed to increase the Nonset. Further, the delamination propagation under the mini FALSTAFF load sequence was determined in the same test set-up. It is successfully demonstrated that the test fixture could be used to apply both negative and positive fatigue loads to simulate the service loads.
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Onset-of-growth behavior of mode II delamination in a carbon fiber composite under spectrum fatigue loads
Composite Structures, 2015Co-Authors: N. Jagannathan, A.r. Anil Chandra, C. M. ManjunathaAbstract:End notched flexure (ENF) test specimens of unidirectional IMA/M21 carbon fiber composite were fabricated using standard autoclave process. A Teflon Insert was used to simulate a delamination at the mid plane. Three point bend tests were conducted under a modified mini-FALSTAFF spectrum load sequence with various reference strain energy release rate, Gref to determine the onset-of-growth of mode II delamination. The onset life was identified as 5% increase in compliance during the fatigue test. Onset fatigue life was observed to increase with decreasing, Gref. Further, the onset-of-growth was predicted using empirical models. For this purpose, the mode II fracture toughness, GIIc and the constant amplitude fatigue data, Gmax–Nonset curves at two different stress ratios were determined and used to construct a constant onset life diagram (COLD). Following the general procedure of damage estimation, the onset-of-growth was predicted using the COLD and compared with experimental results.
Jeffrey P. Seebo - One of the best experts on this subject based on the ideXlab platform.
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Guided wave imaging for detection and evaluation of impact-induced delamination in composites
Smart Materials and Structures, 2015Co-Authors: Zhenhua Tian, Lingyu Yu, Cara A. C. Leckey, Jeffrey P. SeeboAbstract:In this paper, guided wavefield interactions with delamination damage in laminated composite panels are investigated. The frequency–wavenumber representations of the guided wavefields show that different wavenumbers are present in the delaminated plate, compared to a pristine case. The wavenumbers are correlated to trapped waves in the delamination region. Novel approaches for imaging the composite panels using guided waves are discussed and demonstrated for quantitative evaluation of the delamination damage. A filter reconstruction imaging method is shown to provide a rapid technique to locate delamination damage by showing where guided wave energy is trapped. A spatial wavenumber-based imaging algorithm is applied to calculate wavenumber values at each spatial location and highlights the delamination damage as regions with larger wavenumber values. The imaging approaches are demonstrated using experimental data from a plate with a simulated delamination (Teflon Insert) and from a plate containing impact-induced delamination damage. The methods are also applied to a multiple mode guided wave case to demonstrate application to complex wave cases.
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Impact induced delamination detection and quantification with guided wavefield analysis
Proceedings of SPIE, 2015Co-Authors: Zhenhua Tian, Lingyu Yu, Cara A. C. Leckey, Jeffrey P. SeeboAbstract:This paper studies impact induced delamination detection and quantification methods via guided wavefield data and spatial wavenumber imaging. In this study, the complex geometry impact-like delamination damage in a composite laminate is created through the quasi-static indention technique. To detect and quantify the delamination damage, the guided ultrasonic waves are excited through a piezoelectric actuator, and the guided wavefields are measured by a scanning laser Doppler vibrometer. The acquired guided wavefields contain a wealth of information regarding the wave propagation in the composite plate and complex wave interaction at the delamination region. To process the wavefield data and evaluate the delamination damage, the measured wavefields are analyzed through the spatial wavenumber imaging method which can generate an image containing the dominant local wavenumber at each spatial location. For a proof of concept, the approach is first applied to a single Teflon Insert simulating a delamination, and then to the complex geometry impact-like delamination damage. The results show that the spatial wavenumber imaging can not only determine the delamination location, but also provide quantitative information regarding the delamination size and shape. The detection results for the impact induced delamination are compared to an ultrasonic C-scan image and wavenumber images are studied for two different excitation frequencies. Fairly good agreement is observed for portions of the delamination, and differences in wavenumber are observed at the two different frequencies. Results demonstrate that the spatial wavenumber imaging is a promising technique for yielding delamination location and size information.
N. Jagannathan - One of the best experts on this subject based on the ideXlab platform.
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Prediction of Mode II Delamination Onset Life Under Spectrum Fatigue Loads Using Equivalent Strain Energy Release Rate Concept
Advances in Structural Integrity, 2017Co-Authors: A. R. Anilchandra, Ramesh Bojja, N. Jagannathan, M. Seshagirachari, C. M. ManjunathaAbstract:End notched flexure (ENF) test specimens of unidirectional IMA/M21 carbon fiber composite (CFC) were fabricated using standard autoclave process. A Teflon Insert was used to simulate a delamination at the midplane. Three-point bend setup tests were conducted at an average frequency of 2 Hz using a 25 kN servo-hydraulic test machine in room temperature conditions. Constant amplitude fatigue tests were done at three different stress ratios, viz. R = 0.0, 0.5, and −1.0 to construct the standard G-N onset diagram, similar to S–N curve in its usefulness. N onset was identified as 5% change in initial compliance value. Using an equivalent energy release rate parameter, G eq, all the curves were collapsed into a single curve in the form of Basquin’s equation. The equation was subsequently used in predicting the delamination onset-of-growth life under a standard mini-FALSTAFF spectrum load sequence. A fairly good correlation was found between the predicted and experimental mode II onset-of-growth behavior.
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Variable Amplitude Fatigue Testing to Characterize Mode II Delamination in a Polymer Composite
Transactions of The Indian Institute of Metals, 2015Co-Authors: A. R. Anilchandra, Ramesh Bojja, N. Jagannathan, C. M. ManjunathaAbstract:In this study, the mode II delamination behavior in terms of onset-of-growth and propagation characteristics under a standard variable amplitude (VA) fatigue load sequence was investigated. A special three point bend test fixture was designed and fabricated to perform fatigue tests under VA loads. Standard end notched flexure test specimens of unidirectional IMA/M21 carbon fiber composite were fabricated. A Teflon Insert was used to simulate a delamination at the mid plane. The fatigue tests were conducted under a standard mini FALSTAFF VA load sequence. Tests were carried out with different reference values of loads to determine the onset-of-growth, Nonset. Decreasing the reference load was observed to increase the Nonset. Further, the delamination propagation under the mini FALSTAFF load sequence was determined in the same test set-up. It is successfully demonstrated that the test fixture could be used to apply both negative and positive fatigue loads to simulate the service loads.
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Onset-of-growth behavior of mode II delamination in a carbon fiber composite under spectrum fatigue loads
Composite Structures, 2015Co-Authors: N. Jagannathan, A.r. Anil Chandra, C. M. ManjunathaAbstract:End notched flexure (ENF) test specimens of unidirectional IMA/M21 carbon fiber composite were fabricated using standard autoclave process. A Teflon Insert was used to simulate a delamination at the mid plane. Three point bend tests were conducted under a modified mini-FALSTAFF spectrum load sequence with various reference strain energy release rate, Gref to determine the onset-of-growth of mode II delamination. The onset life was identified as 5% increase in compliance during the fatigue test. Onset fatigue life was observed to increase with decreasing, Gref. Further, the onset-of-growth was predicted using empirical models. For this purpose, the mode II fracture toughness, GIIc and the constant amplitude fatigue data, Gmax–Nonset curves at two different stress ratios were determined and used to construct a constant onset life diagram (COLD). Following the general procedure of damage estimation, the onset-of-growth was predicted using the COLD and compared with experimental results.
