{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,17]],"date-time":"2026-03-17T04:52:30Z","timestamp":1773723150064,"version":"3.50.1"},"reference-count":38,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2018,6,13]],"date-time":"2018-06-13T00:00:00Z","timestamp":1528848000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["51705422"],"award-info":[{"award-number":["51705422"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["11372246"],"award-info":[{"award-number":["11372246"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"China NSAF Project","award":["U1530139"],"award-info":[{"award-number":["U1530139"]}]},{"DOI":"10.13039\/501100012226","name":"Fundamental Research Funds for the Central Universities","doi-asserted-by":"publisher","award":["3102017OQD004"],"award-info":[{"award-number":["3102017OQD004"]}],"id":[{"id":"10.13039\/501100012226","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>L-shaped bolt lap joints are commonly used in aerospace and civil structures. However, bolt joints are frequently subjected to loosening, and this has a significant effect on the safety and reliability of these structures. Therefore, bolt preload monitoring is very important, especially at the early stage of loosening. In this paper, a virtual time reversal guided wave method is presented to monitor preload of bolted L-shaped lap joints accurately and simply. In this method, a referenced reemitting signal (RRS) is extracted from the bolted structure in fully tightened condition. Then the RRS is utilized as the excitation signal for the bolted structure in loosening states, and the normalized peak amplitude of refocused wave packet is used as the tightness index (TIA). The proposed method is experimentally validated by L-shaped bolt joints with single and multiple bolts. Moreover, the selections of guided wave frequency and tightness index are also discussed. The results demonstrate that the relationship between TIA and bolt preload is linear. The detection sensitivity is improved significantly compared with time reversal (TR) method, particularly when bolt loosening is at its embryo stage. The results also show that TR method is an effective method for detection of the number of loosening bolts.<\/jats:p>","DOI":"10.3390\/s18061928","type":"journal-article","created":{"date-parts":[[2018,6,15]],"date-time":"2018-06-15T10:15:14Z","timestamp":1529057714000},"page":"1928","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":33,"title":["Preload Monitoring of Bolted L-Shaped Lap Joints Using Virtual Time Reversal Method"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5073-4334","authenticated-orcid":false,"given":"Fei","family":"Du","sequence":"first","affiliation":[{"name":"School of Astronautics, Northwestern Polytechnical University, Xi\u2019an 710072, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3029-1657","authenticated-orcid":false,"given":"Chao","family":"Xu","sequence":"additional","affiliation":[{"name":"School of Astronautics, Northwestern Polytechnical University, Xi\u2019an 710072, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Guannan","family":"Wu","sequence":"additional","affiliation":[{"name":"School of Astronautics, Northwestern Polytechnical University, Xi\u2019an 710072, China"},{"name":"Mechanical Engineering Department, University of Maryland Baltimore County, Baltimore, MD 21250, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7886-5053","authenticated-orcid":false,"given":"Jie","family":"Zhang","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, University of Bristol, Bristol BS81TR, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2018,6,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"181","DOI":"10.1016\/j.triboint.2015.11.006","article-title":"On controlling preload and estimating anti-loosening performance in threaded fasteners based on accurate contact modeling","volume":"95","author":"Zhu","year":"2016","journal-title":"Tribol. Int."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1115\/1.4026973","article-title":"Detecting Loosening of Bolted Connections in a Pipeline Using Changes in Natural Frequencies","volume":"136","author":"He","year":"2014","journal-title":"J. Vib. Acoust."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1359","DOI":"10.1177\/1045389X11416029","article-title":"Space application of piezoelectric wafer active sensors for structural health monitoring","volume":"22","author":"Giurgiutiu","year":"2011","journal-title":"J. Intell. Mater. Syst. Struct."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"50","DOI":"10.1016\/j.ymssp.2011.11.016","article-title":"Integrated impedance and guided wave based damage detection","volume":"28","author":"An","year":"2012","journal-title":"Mech. Syst. Signal Process."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Perera, R., P\u00e9rez, A., Garc\u00eda-Di\u00e9guez, M., and Zapico-Valle, J.L. (2017). Active Wireless System for Structural Health Monitoring Applications. Sensors, 17.","DOI":"10.3390\/s17122880"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"921","DOI":"10.1177\/1045389X10369850","article-title":"Piezoelectric wafer active sensor structural health monitoring of space structures","volume":"21","author":"Zagrai","year":"2010","journal-title":"J. Intell. Mater. Syst. Struct."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Lowe, P.S., Duan, W., Kanfoud, J., and Gan, T.H. (2017). Structural Health Monitoring of Above-Ground Storage Tank Floors by Ultrasonic Guided Wave Excitation on the Tank Wall. Sensors, 17.","DOI":"10.3390\/s17112542"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"581","DOI":"10.1088\/0964-1726\/15\/2\/041","article-title":"Detection of bolt loosening in C\u2013C composite thermal protection panels: I. Diagnostic principle","volume":"15","author":"Yang","year":"2006","journal-title":"Smart Mater. Struct."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Wang, T., Song, G., Wang, Z., and Li, Y. (2013). Proof-of-concept study of monitoring bolt connection status using a piezoelectric based active sensing method. Smart Mater. Struct., 22.","DOI":"10.1088\/0964-1726\/22\/8\/087001"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"659","DOI":"10.1177\/1475921710395810","article-title":"Structural health monitoring of bolted joints using linear and nonlinear acoustic\/ultrasound methods","volume":"10","author":"Amerini","year":"2011","journal-title":"Struct. Health Monit."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Yang, B., Xuan, F.Z., Xiang, Y., Li, D., Zhu, W., Tang, X., Xu, J., Yang, K., and Luo, C. (2017). Lamb Wave-Based Structural Health Monitoring on Composite Bolted Joints under Tensile Load. Materials, 10.","DOI":"10.3390\/ma10060652"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Haynes, C., Yeager, M., Todd, M., and Lee, J.-R. (2014). Health Monitoring of Structural and Biological Systems 2014. Monitoring Bolt Torque Levels through Signal Processing of Full-Field Ultrasonic Data, International Society for Optics and Photonics.","DOI":"10.1117\/12.2045024"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"328","DOI":"10.1016\/j.jsv.2016.06.038","article-title":"Multi-stage temperature compensation method for Lamb wave measurements","volume":"382","author":"Dworakowski","year":"2016","journal-title":"J. Sound Vib."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Kedra, R., and Rucka, M. (2015). Research on assessment of bolted joint state using elastic wave propagation. J. Phys. Conf. Ser., 628.","DOI":"10.1088\/1742-6596\/628\/1\/012025"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Zagrai, A., Doyle, D., and Arritt, B. (2008). Embedded nonlinear ultrasonics for structural health monitoring of satellite joints. Proc. SPIE, 6935.","DOI":"10.1117\/12.775766"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"251","DOI":"10.1177\/1045389X09354785","article-title":"Damage detection in bolted space structures","volume":"21","author":"Doyle","year":"2010","journal-title":"J. Intell. Mater. Syst. Struct."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Doyle, D., Zagrai, A., and Arritt, B. (2009, January 5). Bolted joint integrity for structural health monitoring of responsive space satellites. Proceedings of the 50th AIAA SDM Conference, Palm Springs, CA, USA.","DOI":"10.2514\/6.2009-2705"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Ing, R.K., and Fink, M. (1998). Time-reversed Lamb waves. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, IEEE.","DOI":"10.1109\/58.710586"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"345","DOI":"10.1016\/j.ymssp.2012.03.007","article-title":"A modified time reversal method for Lamb wave based diagnostics of composite structures","volume":"31","author":"Watkins","year":"2012","journal-title":"Mech. Syst. Signal Process."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Cai, J., Shi, L., Yuan, S., and Shao, Z. (2011). High spatial resolution imaging for structural health monitoring based on virtual time reversal. Smart Mater. Struct., 20.","DOI":"10.1088\/0964-1726\/20\/5\/055018"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Poddar, B., Kumar, A., Mitra, M., and Mujumdar, P.M. (2011). Time reversibility of a Lamb wave for damage detection in a metallic plate. Smart Mater. Struct., 20.","DOI":"10.1088\/0964-1726\/20\/2\/025001"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Zeng, L., Lin, J., Huang, L., and Zhao, M. (2016). Amplitude Dispersion Compensation for Damage Detection Using Ultrasonic Guided Waves. Sensors, 16.","DOI":"10.3390\/s16101623"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"50","DOI":"10.1016\/j.jsv.2006.10.044","article-title":"Time reversal active sensing for health monitoring of a composite plate","volume":"302","author":"Park","year":"2007","journal-title":"J. Sound Vib."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Zeng, L., Lin, J., and Huang, L. (2017). A Modified Lamb Wave Time-Reversal Method for Health Monitoring of Composite Structures. Sensors, 17.","DOI":"10.3390\/s17050955"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Parvasi, S.M., Ho, S.C.M., Kong, Q., Mousavi, R., and Song, G. (2016). Real time bolt preload monitoring using piezoceramic transducers and time reversal technique\u2014A numerical study with experimental verification. Smart Mater. Struct., 25.","DOI":"10.1088\/0964-1726\/25\/8\/085015"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Wang, T., Liu, S., Shao, J., and Li, Y. (2016). Health monitoring of bolted joints using the time reversal method and piezoelectric transducers. Smart Mater. Struct., 25.","DOI":"10.1088\/0964-1726\/25\/2\/025010"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Jalalpour, M., El-Osery, A.I., Austin, E.M., and Reda Taha, M.M. (2014). Health monitoring of 90\u00b0 bolted joints using fuzzy pattern recognition of ultrasonic signals. Smart Mater. Struct., 23.","DOI":"10.1088\/0964-1726\/23\/1\/015017"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"781","DOI":"10.1115\/1.4001840","article-title":"Finite Element Modeling of Structures with L-Shaped Beams and Bolted Joints","volume":"133","author":"He","year":"2011","journal-title":"J. Vib. Acoust."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"122","DOI":"10.1007\/s10921-011-0098-4","article-title":"An Assessment of Joint Rigidity with Ultrasonic Wave Energy","volume":"30","author":"Montoya","year":"2011","journal-title":"J. Nondestruct. Eval."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"44","DOI":"10.1080\/09349847.2013.824632","article-title":"Ultrasonic Evaluation of Bolted Connections in Satellites","volume":"25","author":"Montoya","year":"2014","journal-title":"Res. Nondestruct. Eval."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"451","DOI":"10.1016\/j.wavemoti.2009.04.004","article-title":"Understanding a time reversal process in Lamb wave propagation","volume":"46","author":"Park","year":"2009","journal-title":"Wave Motion"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"123","DOI":"10.1007\/s10921-007-0027-8","article-title":"Single Mode Tuning Effects on Lamb Wave Time Reversal with Piezoelectric Wafer Active Sensors for Structural Health Monitoring","volume":"26","author":"Xu","year":"2007","journal-title":"J. Nondestruct. Eval."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"130","DOI":"10.1016\/j.jsv.2017.01.031","article-title":"Spatial resolution improvement for Lamb wave-based damage detection using frequency dependency compensation","volume":"394","author":"Zeng","year":"2017","journal-title":"J. Sound Vib."},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Lin, Q., and Li, B. (2015). Comparison of the influences of surface texture and boundary slip on tribological performances. Math. Probl. Eng.","DOI":"10.1155\/2015\/126824"},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Herdovics, B., and Cegla, F. (2018). Compensation of phase response changes in ultrasonic transducers caused by temperature variations. Struct. Health Monit.","DOI":"10.1177\/1475921718759272"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"5708","DOI":"10.1080\/00207543.2016.1158881","article-title":"Integration of geometric variation and part deformation into variation propagation of 3-D. assemblies","volume":"54","author":"Guo","year":"2016","journal-title":"Int. J. Prod. Res."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Du, F., Li, B., and Hong, J. (2015). Application of ultrasound technique to evaluate contact condition on the faying surface of riveted joints. J. Eng. Tribol., 229.","DOI":"10.1177\/1350650115574536"},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Sevillano, E., Sun, R., and Perera, R. (2016). Damage detection based on power dissipation measured with PZT sensors through the combination of electro-mechanical impedances and guided waves. Sensors, 16.","DOI":"10.3390\/s16050639"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/18\/6\/1928\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T15:08:36Z","timestamp":1760195316000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/18\/6\/1928"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,6,13]]},"references-count":38,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2018,6]]}},"alternative-id":["s18061928"],"URL":"https:\/\/doi.org\/10.3390\/s18061928","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,6,13]]}}}