Dr. Zhifen Zhang is Associate Professor in Department of Mechanical Engineering, Xi’an Jiaotong University (XJTU), Shaanxi, China. She has authored more than ten magazine articles, including those published in IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS, Mechanical Systems and Signal Processing, and Journal of Materials Processing Technology. Her research interests include intelligent manufacturing, monitoring and defect prediction of the welding process, laser shock peening, multisensory data fusion and modeling, mechanical Fault detection and detection. Dr. Guangrui Wen is currently a Full Professor of the School of Mechanical Engineering and the Executive Dean of the School of International Education in XJTU, China. He is also the Vice Dean of the Key Laboratory of Education Ministry for Modern Design & Rotor-Bearing System, and the Vice Dean of National & Local Joint Engineering Research Center for Equipment Operation Safety Assurance and Intelligent Monitoring, China. Dr. Wen is a member of IEEE, the Chinese Mechanical Engineering Society (CIME), the Chinese Society for Vibration Engineering (CSVE), and the Executive Director and Deputy Secretary-General of the Dynamic Test Professional Committee of CSVE. Dr.Wenjing Ren is currently an associate researcher at the School of Materials Science and Engineering, Tianjin University, Tianjin, China. She has published more than 30 academic papers in journals including IEEE Transactions on Industrial Informatics, Additive Manufacturing, Materials Science and Engineering: A. Her research interests include automatic welding, in-situ monitoring and defect prediction of welding, and metal additive manufacturing.

• 1. Introduction.- 2. Arc sound and its application on penetration detection for GTAW.- 3 Optical spectroscopy-based inner porosity monitoring for GTAW.- 4. Optical spectroscopy-based multiple defects detection for GTAW.- 5. Optical spectroscopy-based real-time seam strength prediction for laser beam welding (LBW).- 6. Optical spectroscopy-based intelligent defect detections for laser AM.- 7. Summary and Conclusions.

Dr. Zhifen Zhang is Associate Professor in Department of Mechanical Engineering, Xi’an Jiaotong University (XJTU), Shaanxi, China. She has authored more than ten magazine articles, including those published in IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS, Mechanical Systems and Signal Processing, and Journal of Materials Processing Technology. Her research interests include intelligent manufacturing, monitoring and defect prediction of the welding process, laser shock peening, multisensory data fusion and modeling, mechanical Fault detection and detection. Dr. Guangrui Wen is currently a Full Professor of the School of Mechanical Engineering and the Executive Dean of the School of International Education in XJTU, China. He is also the Vice Dean of the Key Laboratory of Education Ministry for Modern Design & Rotor-Bearing System, and the Vice Dean of National & Local Joint Engineering Research Center for Equipment Operation Safety Assurance and Intelligent Monitoring, China. Dr. Wen is a member of IEEE, the Chinese Mechanical Engineering Society (CIME), the Chinese Society for Vibration Engineering (CSVE), and the Executive Director and Deputy Secretary-General of the Dynamic Test Professional Committee of CSVE. Dr.Wenjing Ren is currently an associate researcher at the School of Materials Science and Engineering, Tianjin University, Tianjin, China. She has published more than 30 academic papers in journals including IEEE Transactions on Industrial Informatics, Additive Manufacturing, Materials Science and Engineering: A. Her research interests include automatic welding, in-situ monitoring and defect prediction of welding, and metal additive manufacturing.

• 1. Introduction.- 2. Arc sound and its application on penetration detection for GTAW.- 3 Optical spectroscopy-based inner porosity monitoring for GTAW.- 4. Optical spectroscopy-based multiple defects detection for GTAW.- 5. Optical spectroscopy-based real-time seam strength prediction for laser beam welding (LBW).- 6. Optical spectroscopy-based intelligent defect detections for laser AM.- 7. Summary and Conclusions.

Dr. Zhifen Zhang is Associate Professor in Department of Mechanical Engineering, Xi’an Jiaotong University (XJTU), Shaanxi, China. She has authored more than ten magazine articles, including those published in IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS, Mechanical Systems and Signal Processing, and Journal of Materials Processing Technology. Her research interests include intelligent manufacturing, monitoring and defect prediction of the welding process, laser shock peening, multisensory data fusion and modeling, mechanical Fault detection and detection. Dr. Guangrui Wen is currently a Full Professor of the School of Mechanical Engineering and the Executive Dean of the School of International Education in XJTU, China. He is also the Vice Dean of the Key Laboratory of Education Ministry for Modern Design & Rotor-Bearing System, and the Vice Dean of National & Local Joint Engineering Research Center for Equipment Operation Safety Assurance and Intelligent Monitoring, China. Dr. Wen is a member of IEEE, the Chinese Mechanical Engineering Society (CIME), the Chinese Society for Vibration Engineering (CSVE), and the Executive Director and Deputy Secretary-General of the Dynamic Test Professional Committee of CSVE. Dr.Wenjing Ren is currently an associate researcher at the School of Materials Science and Engineering, Tianjin University, Tianjin, China. She has published more than 30 academic papers in journals including IEEE Transactions on Industrial Informatics, Additive Manufacturing, Materials Science and Engineering: A. Her research interests include automatic welding, in-situ monitoring and defect prediction of welding, and metal additive manufacturing.

• 1. Introduction.- 2. Arc sound and its application on penetration detection for GTAW.- 3 Optical spectroscopy-based inner porosity monitoring for GTAW.- 4. Optical spectroscopy-based multiple defects detection for GTAW.- 5. Optical spectroscopy-based real-time seam strength prediction for laser beam welding (LBW).- 6. Optical spectroscopy-based intelligent defect detections for laser AM.- 7. Summary and Conclusions.