Detection and characterisation of defects in directed energy deposited multi-material components using full waveform inversion and reverse time migration

ABSTRACT

Directed energy deposition (DED) is capable in producing complex or high-value components with good mechanical properties. Despite these potential advantages, the quality and integrity of multi-material DED parts, remains a challenging issue that limits its wide applications. Material porosity in multi-material components is detrimental since it may lead to premature structural failure. This paper proposes a two-stage ultrasonic method to characterise the internal structure to enhance the understanding of the process parameters on material porosity. In this method, the low-frequency model building aims at reconstructing background structure and the high-frequency imaging targets at small defects. The first stage is based on the gradient sampling full-waveform inversion for the estimation of the velocity model, which is then used as the initial model for the reverse time migration for reflectivity. The experimental results show that accurate reconstructions of the interface between two materials and defects in multi-material DED components can be achieved.

KEYWORDS:

• Additive manufacturing
• multi-material components
• directed energy deposition
• defect characterisation
• non-destructive evaluation

Acknowledgments

We are grateful to Abhishek Saini for data acquisition. We would also like to express gratitude for the support from the Advanced Remanufacturing and Technology Centre (ARTC) and NAMIC Singapore.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

Jing Rao was supported by the start-up grant from UNSW Canberra [grant number PS63396]. Jizhong Yang was supported by the National Natural Science Foundation of China [grant number 42004096] and the Fundamental Research Funds for the Central Universities.

Notes on contributors

Jing Rao

Jing Rao received the Ph.D. degree with the focus on quantitative ultrasonic tomography from Nanyang Technological University, Singapore. After completing her Ph.D., she was a Humboldt Research Fellowship holder in the Chair of Computational Modeling and Simulation at the Technical University of Munich, Munich, Germany. She is currently a Lecturer with the School of Engineering and Information Technology, The University of New South Wales, Canberra, ACT, Australia. Her research interests include ultrasonic guided wave tomography, structural health monitoring, and quantitative imaging.

Swee Leong Sing

Dr Swee Leong Sing is an Assistant Professor at the Department of Mechanical Engineering, National University of Singapore (NUS), Singapore. Prior to joining NUS, he was a Presidential Postdoctoral Fellow at the Singapore Centre for 3D Printing and School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore after receiving the prestigious fellowship in 2020. His research interest is enabling material development and creating strategic values for Industry 4.0 and beyond through the use and integration of advanced manufacturing. As of May 2022, he has co-authored 53 peer reviewed articles in the field of additive manufacturing or 3D printing. He currently has a h-index of 30, with more than 4500 citations based on statistics from Web of Science. Swee Leong is also the co-inventor for three patents in additive manufacturing.

Joel Choon Wee Lim

Joel Choon Wee Lim is currently a Ph.D. student at Nanyang Technological University. His area of focus is on the research of DED technology. He is also involved with various industry translational projects and has an interest in hybrid manufacturing.

Wai Yee Yeong

Prof Wai Yee Yeong is the winner of the TCT Women in 3D Printing Innovator Award 2019 and named as one of the Singapore 100 Women in Tech List 2021. Her work is well-recognized, with H-index of 56 and more than 12000 citations on Google Scholar. She has filed multiple patents and knowhows, with key interest in Bioprinting and 3D printing of new materials. On academic fronts, she is the Associate Editor for 2 international journals and authored 3 textbooks on 3D printing. Prof Yeong serves as Program Director in the Singapore Centre for 3D Printing and HP-NTU Digital Manufacturing Corp Lab. Prof Yeong was awarded the NRF Investigatorship (Class of 2022) in her pursuit for groundbreaking and high-risk research.

Jizhong Yang

Dr. Jizhong Yang is a Research Professor at Tongji University since 2021, where he served as an Associate Research Professor for one year. From 2017 to 2020, he was a Research Fellow at National University of Singapore. He received his Ph.D. and B.S. degrees in Geophysics from Tongji University in 2016 and 2010, respectively. His research interests include exploration geophysics, borehole geophysics, distributed fiber-optic sensing, and AI in geophysical application. He is an Associate Editor of Geophysics since 2022.

Zheng Fan

Zheng Fan received the Ph.D. degree from Imperial College London, London, U.K., in 2010, specialized in ultrasonic nondestructive evaluation. He is currently an Associate Professor with the School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore, leading a research team to develop novel techniques for metal and composite inspection, structural health monitoring, and material characterization, by integrating physics and modeling techniques with the development of rapidly exploitable technologies.

Paul Hazell

Paul Hazell received his Eng.D. from Cranfield University, UK in 1999. After completing his doctoral degree he took up a position as Lecturer in Terminal Ballistics for Cranfield University at what was then called the Royal Military College of Science (which is now part of the Defence Academy of the United Kingdom). He was promoted to Senior Lecturer in 2006 and Reader in 2011 and subsequently took up the position of Professor of Impact Dynamics at The University of New South Wales in Canberra, Australia in 2012. His research interests include shock, penetration mechanics, biomimicry, and in particular using additive manufacturing techniques to develop structures that are tuned to mitigate the effects of impact and penetration.