{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,1]],"date-time":"2026-05-01T16:46:21Z","timestamp":1777653981980,"version":"3.51.4"},"reference-count":41,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2024,7,7]],"date-time":"2024-07-07T00:00:00Z","timestamp":1720310400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Key Research and Development Program of Jiangsu Province","award":["BE2022069-1"],"award-info":[{"award-number":["BE2022069-1"]}]},{"name":"Key Research and Development Program of Jiangsu Province","award":["BE2022069-2"],"award-info":[{"award-number":["BE2022069-2"]}]},{"name":"Key Research and Development Program of Jiangsu Province","award":["22KJB460030"],"award-info":[{"award-number":["22KJB460030"]}]},{"name":"Key Research and Development Program of Jiangsu Province","award":["22KJB460004"],"award-info":[{"award-number":["22KJB460004"]}]},{"name":"Natural Science Research Project of Jiangsu Higher Education Institutions","award":["BE2022069-1"],"award-info":[{"award-number":["BE2022069-1"]}]},{"name":"Natural Science Research Project of Jiangsu Higher Education Institutions","award":["BE2022069-2"],"award-info":[{"award-number":["BE2022069-2"]}]},{"name":"Natural Science Research Project of Jiangsu Higher Education Institutions","award":["22KJB460030"],"award-info":[{"award-number":["22KJB460030"]}]},{"name":"Natural Science Research Project of Jiangsu Higher Education Institutions","award":["22KJB460004"],"award-info":[{"award-number":["22KJB460004"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Several advantages of directed energy deposition-arc (DED-arc) have garnered considerable research attention including high deposition rates and low costs. However, defects such as discontinuity and pores may occur during the manufacturing process. Defect identification is the key to monitoring and quality assessments of the additive manufacturing process. This study proposes a novel acoustic signal-based defect identification method for DED-arc via wavelet time\u2013frequency diagrams. With the continuous wavelet transform, one-dimensional (1D) acoustic signals acquired in situ during manufacturing are converted into two-dimensional (2D) time\u2013frequency diagrams to train, validate, and test the convolutional neural network (CNN) models. In this study, several CNN models were examined and compared, including AlexNet, ResNet-18, VGG-16, and MobileNetV3. The accuracy of the models was 96.35%, 97.92%, 97.01%, and 98.31%, respectively. The findings demonstrate that the energy distribution of normal and abnormal acoustic signals has significant differences in both the time and frequency domains. The proposed method is verified to identify defects effectively in the manufacturing process and advance the identification time.<\/jats:p>","DOI":"10.3390\/s24134397","type":"journal-article","created":{"date-parts":[[2024,7,8]],"date-time":"2024-07-08T09:01:19Z","timestamp":1720429279000},"page":"4397","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":20,"title":["Acoustic Signal-Based Defect Identification for Directed Energy Deposition-Arc Using Wavelet Time\u2013Frequency Diagrams"],"prefix":"10.3390","volume":"24","author":[{"given":"Hui","family":"Zhang","sequence":"first","affiliation":[{"name":"Jiangsu Key Laboratory of 3D Printing Equipment & Manufacturing, School of Electrical and Automation Engineering, Nanjing Normal University, Nanjing 210023, China"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-7316-0457","authenticated-orcid":false,"given":"Qianru","family":"Wu","sequence":"additional","affiliation":[{"name":"Jiangsu Key Laboratory of 3D Printing Equipment & Manufacturing, School of Electrical and Automation Engineering, Nanjing Normal University, Nanjing 210023, China"}]},{"given":"Wenlai","family":"Tang","sequence":"additional","affiliation":[{"name":"Jiangsu Key Laboratory of 3D Printing Equipment & Manufacturing, School of Electrical and Automation Engineering, Nanjing Normal University, Nanjing 210023, China"}]},{"given":"Jiquan","family":"Yang","sequence":"additional","affiliation":[{"name":"Jiangsu Key Laboratory of 3D Printing Equipment & Manufacturing, School of Electrical and Automation Engineering, Nanjing Normal University, Nanjing 210023, China"}]}],"member":"1968","published-online":{"date-parts":[[2024,7,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Treutler, K., and Wesling, V. 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