{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,7]],"date-time":"2026-05-07T03:27:18Z","timestamp":1778124438945,"version":"3.51.4"},"reference-count":63,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2017,12,9]],"date-time":"2017-12-09T00:00:00Z","timestamp":1512777600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This work proposes a novel hybrid signal processing technique to extract information on disbond-type defects from a single B-scan in the process of non-destructive testing (NDT) of glass fiber reinforced plastic (GFRP) material using ultrasonic guided waves (GW). The selected GFRP sample has been a segment of wind turbine blade, which possessed an aerodynamic shape. Two disbond type defects having diameters of 15 mm and 25 mm were artificially constructed on its trailing edge. The experiment has been performed using the low-frequency ultrasonic system developed at the Ultrasound Institute of Kaunas University of Technology and only one side of the sample was accessed. A special configuration of the transmitting and receiving transducers fixed on a movable panel with a separation distance of 50 mm was proposed for recording the ultrasonic guided wave signals at each one-millimeter step along the scanning distance up to 500 mm. Finally, the hybrid signal processing technique comprising the valuable features of the three most promising signal processing techniques: cross-correlation, wavelet transform, and Hilbert\u2013Huang transform has been applied to the received signals for the extraction of defects information from a single B-scan image. The wavelet transform and cross-correlation techniques have been combined in order to extract the approximated size and location of the defects and measurements of time delays. Thereafter, Hilbert\u2013Huang transform has been applied to the wavelet transformed signal to compare the variation of instantaneous frequencies and instantaneous amplitudes of the defect-free and defective signals.<\/jats:p>","DOI":"10.3390\/s17122858","type":"journal-article","created":{"date-parts":[[2017,12,11]],"date-time":"2017-12-11T12:26:37Z","timestamp":1512995197000},"page":"2858","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":80,"title":["Hybrid Signal Processing Technique to Improve the Defect Estimation in Ultrasonic Non-Destructive Testing of Composite Structures"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8937-3636","authenticated-orcid":false,"given":"Kumar","family":"Tiwari","sequence":"first","affiliation":[{"name":"Prof. K.Bar\u0161auskas Ultrasound Research Institute, Kaunas University of Technology, K. Bar\u0161ausko St. 59, LT-51423 Kaunas, Lithuania"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Renaldas","family":"Raisutis","sequence":"additional","affiliation":[{"name":"Prof. K.Bar\u0161auskas Ultrasound Research Institute, Kaunas University of Technology, K. Bar\u0161ausko St. 59, LT-51423 Kaunas, Lithuania"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Vykintas","family":"Samaitis","sequence":"additional","affiliation":[{"name":"Prof. K.Bar\u0161auskas Ultrasound Research Institute, Kaunas University of Technology, K. Bar\u0161ausko St. 59, LT-51423 Kaunas, Lithuania"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2017,12,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"413","DOI":"10.1179\/mst.1989.5.5.413","article-title":"Defect types and non-destructive testing techniques for composites and bonded joints","volume":"5","author":"Cawley","year":"1989","journal-title":"Mater. Sci. Technol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"139","DOI":"10.13111\/2066-8201.2013.5.3.14","article-title":"Advanced composite materials of the future in aerospace industry","volume":"5","author":"Maria","year":"2013","journal-title":"INCAS Bulletin"},{"key":"ref_3","unstructured":"Callister, W.D., and Rethwisch, D.G. (2007). Materials Science and Engineering: An Introduction, Wiley. [7th ed.]."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"846","DOI":"10.12955\/cbup.v4.863","article-title":"Comparative analysis of non-contact ultrasonic methods for defect estimation of composites in remote areas","volume":"4","author":"Tiwari","year":"2016","journal-title":"CBU Int. Conf. Proc."},{"key":"ref_5","unstructured":"Kudva, J.N., Grage, M.J., and Roberts, M.M. (1999, January 8\u201310). Aircraft structural health monitoring and other smart structures technologies-perspectives on development of smart aircraft. Proceedings of the 2nd International Work shop on Structural Health Monitoring, Stanford, CA, USA."},{"key":"ref_6","first-page":"141","article-title":"Emerging NDE technologies and challenges at the beginning of the 3rd millennium, Part 2","volume":"58","year":"2000","journal-title":"Mater. Eval."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.compstruct.2015.02.080","article-title":"Damage identification in aircraft composite structures: A case study using various non-destructive testing techniques","volume":"127","author":"Katunin","year":"2015","journal-title":"Compos. Struct."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"2059","DOI":"10.1016\/j.compscitech.2005.04.010","article-title":"Non-destructive inspection of sandwich and repaired composite laminated structures","volume":"65","author":"Diamanti","year":"2005","journal-title":"Compos. Sci. Technol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"012056","DOI":"10.1088\/1757-899X\/87\/1\/012056","article-title":"Research on the defect types judgment in wind turbine blades using ultrasonic NDT","volume":"87","author":"Li","year":"2015","journal-title":"IOP Conf. Ser. Mater. Sci. Eng."},{"key":"ref_10","first-page":"1","article-title":"NDE of composite structures using ultrasonic guided waves","volume":"8695","author":"Mal","year":"2013","journal-title":"Health Monit. Struct. Biol. Syst."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"847","DOI":"10.4028\/www.scientific.net\/AMR.123-125.847","article-title":"Ultrasonic Propagation Imaging for Wind Turbine Blade Quality Evaluation","volume":"123","author":"Lee","year":"2010","journal-title":"Adv. Mater. Res."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"199","DOI":"10.1016\/j.compscitech.2005.04.027","article-title":"Assessment of NDT interferometric techniques for impact damage detection in composite laminates","volume":"66","author":"Ambu","year":"2006","journal-title":"Compos. Sci. Technol."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Nakamura, K. (2012). Ultrasonic Transducers, Woodhead Publishing. [1st ed.].","DOI":"10.1533\/9780857096302"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Jen, C.K., Wu, K.T., Kobayashi, M., and Blouin, A. (2008, January 2\u20135). NDE using laser generated ultrasound and integrated ultrasonic transducer receivers. Proceedings of the 2008 IEEE Ultrasonics Symposium, Beijing, China.","DOI":"10.1109\/ULTSYM.2008.0369"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1761","DOI":"10.1007\/s00542-016-2929-9","article-title":"Design of piezoelectric micromachined ultrasonic transducers (pMUTs) for high pressure output","volume":"23","author":"Wang","year":"2016","journal-title":"Microsys. Technol."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Kazys, R., Sliteris, R., and Sestoke, J. (2017). Air-Coupled Low Frequency Ultrasonic Transducers and Arrays with PMN-32% PT Piezoelectric Crystals. Sensors, 17.","DOI":"10.3390\/s17010095"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Haldar, A., Suwas, S., and Bhattacharjee, D. (2009). Non-Contact Non-Destructive Measurement of Texture Using an Electro-Magnetic Acoustic Transducer (EMAT) Sensor. Microstructure Texture in Steels, Springer.","DOI":"10.1007\/978-1-84882-454-6"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"50","DOI":"10.1016\/j.prostr.2016.02.008","article-title":"A review of non-destructive testing methods of composite materials","volume":"1","author":"Gholizadeh","year":"2016","journal-title":"Procedia Struct. Integr."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"431","DOI":"10.1016\/1359-8368(96)00009-1","article-title":"Scattering of waves by flaws in anisotropic laminated plates","volume":"27","author":"Liu","year":"1996","journal-title":"Compos. Part B Eng."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"2622","DOI":"10.1121\/1.1562913","article-title":"Guided waves propagating in sandwich structures made of anisotropic, viscoelastic, composite materials","volume":"113","author":"Castaings","year":"2003","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_21","first-page":"250","article-title":"Scattering of impact wave by a crack in composite plate","volume":"29","author":"Jung","year":"1996","journal-title":"NDT E Int."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"012005","DOI":"10.1088\/1757-899X\/42\/1\/012005","article-title":"An automated data processing method dedicated to 3D ultrasonic non destructive testing of composite pieces","volume":"42","author":"Osman","year":"2012","journal-title":"IOP Conf. Ser. Mater. Sci. Eng."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1840","DOI":"10.1063\/1.4865047","article-title":"Implementation of automated 3d defect detection for low signal-to noise features in nde data","volume":"1581","author":"Grandin","year":"2014","journal-title":"AIP Conf. Proc."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"181","DOI":"10.1016\/j.ndteint.2008.09.003","article-title":"Imaging of internal cracks in concrete structures using the surface rendering technique","volume":"42","author":"Yeh","year":"2009","journal-title":"NDT E Int."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1184","DOI":"10.1016\/j.prostr.2017.07.036","article-title":"Signal processing methods to improve the Signal-to-noise ratio (SNR) in ultrasonic non-destructive testing of wind turbine blade","volume":"5","author":"Tiwari","year":"2017","journal-title":"Procedia Struct. Integr."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1051\/epjap:2001161","article-title":"Using of a diverse field algorithm in ultrasonic signal processing for nondestructive testing","volume":"15","author":"Mahmud","year":"2001","journal-title":"Eur. Phys. J. Appl. Phys."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1902","DOI":"10.1109\/TUFFC.2006.123","article-title":"Blind multiridge detection for automatic nondestructive testing using ultrasonic signals","volume":"53","author":"Wu","year":"2006","journal-title":"IEEE Trans. Ultrason. Ferroelectr. Freq. Control"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"185","DOI":"10.1016\/j.tafmec.2007.11.004","article-title":"Inverse method for detection and sizing of cracks in thin sections using a hybrid genetic algorithm based signal parametrisation","volume":"49","author":"Satyanarayan","year":"2008","journal-title":"Theor. Appl. Frac. Mech."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1177\/0583102406075428","article-title":"Review of guided-wave structural health monitoring","volume":"39","author":"Raghavan","year":"2007","journal-title":"Shock Vibr. Digest"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"979","DOI":"10.1109\/58.535502","article-title":"Order selection criteria for detecting mean scatterer spacings with the AR model","volume":"43","author":"Varghese","year":"1996","journal-title":"IEEE Trans. Ultrason. Ferroelectr. Freq. Control"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"14","DOI":"10.1109\/58.585186","article-title":"Signal detection and noise suppression using a wavelet transform signal processor: Application to ultrasonic flaw detection","volume":"44","author":"Abbate","year":"1997","journal-title":"IEEE Trans. Ultrason. Ferroelectr. Freq. Control"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1109\/58.16976","article-title":"Split-spectrum processing: Analysis of polarity threshold algorithm for improvement of signal-to-noise ratio and detectability in ultrasonic signals","volume":"36","author":"Shankar","year":"1989","journal-title":"IEEE Trans. Ultrason. Ferroelectr. Freq. Control"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"350","DOI":"10.1784\/insi.2007.49.6.350","article-title":"Analysis of cross-correlation and wavelet de-noising for the reduction of the effects of dispersion in long-range ultrasonic testing","volume":"49","author":"Mallett","year":"2007","journal-title":"Insight Non-Destr. Test. Condition Monit."},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Bouden, T., Dib, S., Aissaous, K., and Grimes, M. (2009, January 20\u201323). Signal processing methods for materials defects detection. Proceedings of the IEEE International Ultrasonics Symposium, Rome, Italy.","DOI":"10.1109\/ULTSYM.2009.5441482"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"628","DOI":"10.1784\/insi.2008.50.11.628","article-title":"A comparative study of time-frequency analysis techniques in the case of signal processing for ultrasonic NDT","volume":"50","year":"2008","journal-title":"Insight Non-Destr. Test. Condition Monit."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Huang, N.E., and Shen, S.S. (2014). Hilbert\u2013Huang Transform and Its Applications, World Scientific Publishing Company. [2nd ed.].","DOI":"10.1142\/8804"},{"key":"ref_37","unstructured":"Horton, M., and Clark, E. (1999). Discrete-Time Signals and Systems. Discrete-Time Signal Processing, Prentice-Hall, Inc.. [2nd ed.]."},{"key":"ref_38","first-page":"101","article-title":"Multiresolution imaging in elastography","volume":"36","author":"Varghese","year":"1989","journal-title":"IEEE Trans. Ultrason. Ferroelectr. Freq. Control"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"847","DOI":"10.1016\/j.ultras.2004.01.063","article-title":"Ultrasonic flaw detection in NDE of highly scattering materials using wavelet and Wigner\u2013Ville transform processing","volume":"42","author":"Emeterio","year":"2004","journal-title":"Ultrasonics"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1155\/2016\/9794723","article-title":"Using the Dual-Tree Complex Wavelet Transform for Improved Fabric Defect Detection","volume":"2016","author":"Vermaak","year":"2016","journal-title":"J. Sens."},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Yu, G., and Wang, X. (2016, January 30\u201331). Ultrasonic signal processing using wavelet transform for automatic rail defect detection. Proceedings of the 2016 International Forum on Management, Education and Information Technology Application, Guangzhou, China.","DOI":"10.2991\/ifmeita-16.2016.124"},{"key":"ref_42","unstructured":"(2017, March 03). The Engineer\u2019s Ultimate Guide to Wavelet Analysis-the Wavelet Tutorial. Available online: http:\/\/users.rowan.edu\/%7Epolikar\/WAVELETS\/WTtutorial.html."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"674","DOI":"10.1109\/34.192463","article-title":"A Theory for Multiresolution Signal Decomposition: The Wavelet Representation","volume":"11","author":"Mallat","year":"1989","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"263","DOI":"10.1016\/S0041-624X(02)00149-X","article-title":"Influence of thresholding procedures in ultrasonic grain noise reduction using wavelets","volume":"40","author":"Emeterio","year":"2002","journal-title":"Ultrasonics."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"319","DOI":"10.1111\/1467-9868.00071","article-title":"Wavelet Threshold Estimators for Data with Correlated Noise","volume":"59","author":"Johnstone","year":"1997","journal-title":"J. R. Stat. Soc. Ser. B (Stat. Method.)"},{"key":"ref_46","unstructured":"(2017, June 17). Modelling Wind Forcing in Phase Resolving Simulation of Nonlinear Wind Waves. Available online: http:\/\/hdl.handle.net\/1721.1\/57791."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"903","DOI":"10.1098\/rspa.1998.0193","article-title":"The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis","volume":"454","author":"Huang","year":"1971","journal-title":"Proc. R. Soc. A Math. Phys. Eng. Sci."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"417","DOI":"10.1146\/annurev.fluid.31.1.417","article-title":"A new view of nonlinear water waves: The Hilbert Spectrum","volume":"31","author":"Huang","year":"1999","journal-title":"Annu. Rev. Fluid Mech."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"171","DOI":"10.2113\/JEEG14.4.171","article-title":"Improved Hydrogeophysical Parameter Estimation from Empirical Mode Decomposition Processed Ground Penetrating Radar Data","volume":"14","author":"Addison","year":"2009","journal-title":"J. Environ. Eng. Geophys."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"2317","DOI":"10.1098\/rspa.2003.1123","article-title":"A confidence limit for the empirical mode decomposition and Hilbert spectral analysis","volume":"459","author":"Huang","year":"2003","journal-title":"Proc. R. Soc. London Ser. A Math. Phys. Eng. Sci."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1142\/S1793536909000047","article-title":"Ensemble Empirical Mode Decomposition: A Noise-Assisted Data Analysis Method","volume":"1","author":"Wu","year":"2009","journal-title":"Adv. Adapt. Data Anal."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"937","DOI":"10.1002\/stc.1506","article-title":"Evaluation of instantaneous characteristics of guided ultrasonic waves for structural quality and health monitoring","volume":"20","author":"Pavlopoulou","year":"2012","journal-title":"Struct. Control Health Monit."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1016\/j.jappgeo.2012.05.002","article-title":"Comparing the applications of EMD and EEMD on time\u2013frequency analysis of seismic signal","volume":"83","author":"Wang","year":"2012","journal-title":"J. Appl. Geophys."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"539","DOI":"10.4028\/www.scientific.net\/KEM.324-325.539","article-title":"Vibration-Based Damage Detection of Composite Wingbox Structures Using Improved Hilbert\u2013Huang Transform","volume":"324","author":"Chen","year":"2006","journal-title":"Key Eng. Mater."},{"key":"ref_55","doi-asserted-by":"crossref","unstructured":"Torres, M.E., Colominas, M.A., Schlotthauer, G., and Flandrin, P. (2011, January 22\u201327). A complete ensemble empirical mode decomposition with adaptive noise. Proceedings of the IEEE International Conference Acoustic Speech Signal Processing (ICASSP), Prague, Czech Czech.","DOI":"10.1109\/ICASSP.2011.5947265"},{"key":"ref_56","doi-asserted-by":"crossref","unstructured":"Boller, C., Chang, F.K., and Fujino, Y. (2009). Hilbert transform, envelope, instantaneous phase, and frequency. Encyclopedia of Structural Health Monitoring, John Wiley & Sons.","DOI":"10.1002\/9780470061626"},{"key":"ref_57","unstructured":"Saliu, S. (2000, January 4\u20138). Definition of instantaneous frequency on real signals. Proceedings of the European Signal Processing Conference, Tampere, Finland."},{"key":"ref_58","first-page":"30","article-title":"Contact ultrasonic transducers for mechanical scanning systems","volume":"65","year":"2010","journal-title":"Ultrasound"},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"753","DOI":"10.1016\/j.jsv.2006.01.020","article-title":"Guided Lamb waves for identification of damage in composite structures: A review","volume":"295","author":"Su","year":"2006","journal-title":"J. Sound Vib."},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"1159","DOI":"10.1121\/1.400530","article-title":"A two-dimensional Fourier transform method for the measurement of propagating multimode signals","volume":"89","author":"Alleyne","year":"1991","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_61","doi-asserted-by":"crossref","first-page":"50","DOI":"10.1109\/99.388960","article-title":"An introduction to wavelets","volume":"2","author":"Graps","year":"1995","journal-title":"IEEE Comput. Sci. Eng."},{"key":"ref_62","first-page":"68","article-title":"Comparison between haar and daubechies wavelet transformions on FPGA technology","volume":"26","author":"Mahmoud","year":"2007","journal-title":"Int. J. Electron. Commun. Eng."},{"key":"ref_63","doi-asserted-by":"crossref","first-page":"275","DOI":"10.1016\/j.dsp.2005.12.003","article-title":"Optimal selection of wavelet basis function applied to ECG signal denoising","volume":"16","author":"Singh","year":"2006","journal-title":"Digit. Signal Process."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/12\/2858\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T18:53:20Z","timestamp":1760208800000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/12\/2858"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017,12,9]]},"references-count":63,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2017,12]]}},"alternative-id":["s17122858"],"URL":"https:\/\/doi.org\/10.3390\/s17122858","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2017,12,9]]}}}