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1. In-situ process monitoring and adaptive quality enhancement in laser additive manufacturing: a critical review

Author

Chen, Lequn, Bi, Guijun, Yao, Xiling, Su, Jinlong, Tan, Chaolin, Feng, Wenhe, Benakis, Michalis, Chew, Youxiang, and Moon, Seung Ki

Subjects
Electrical Engineering and Systems Science - Signal Processing, Electrical Engineering and Systems Science - Systems and Control
Abstract

Laser Additive Manufacturing (LAM) presents unparalleled opportunities for fabricating complex, high-performance structures and components with unique material properties. Despite these advancements, achieving consistent part quality and process repeatability remains challenging. This paper provides a comprehensive review of various state-of-the-art in-situ process monitoring techniques, including optical-based monitoring, acoustic-based sensing, laser line scanning, and operando X-ray monitoring. These techniques are evaluated for their capabilities and limitations in detecting defects within Laser Powder Bed Fusion (LPBF) and Laser Directed Energy Deposition (LDED) processes. Furthermore, the review discusses emerging multisensor monitoring and machine learning (ML)-assisted defect detection methods, benchmarking ML models tailored for in-situ defect detection. The paper also discusses in-situ adaptive defect remediation strategies that advance LAM towards zero-defect autonomous operations, focusing on real-time closed-loop feedback control and defect correction methods. Research gaps such as the need for standardization, improved reliability and sensitivity, and decision-making strategies beyond early stopping are highlighted. Future directions are proposed, with an emphasis on multimodal sensor fusion for multiscale defect prediction and fault diagnosis, ultimately enabling self-adaptation in LAM processes. This paper aims to equip researchers and industry professionals with a holistic understanding of the current capabilities, limitations, and future directions in in-situ process monitoring and adaptive quality enhancement in LAM., Comment: 107 Pages, 29 Figures. Paper Accepted At Journal of Manufacturing Systems

Published
2024
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37. Microstructure and mechanical behavior of laser aided additive manufactured low carbon interstitial Fe₄₉.₅Mn₃₀Co₁₀Cr₁₀C₀.₅ multicomponent alloy

Author

Chew, Youxiang, Zhu, Zhiguang, Weng, Fei, Gao, Shubo, Ng, Fern Lan, Lee, Bing Yang, Bi, Guijun, School of Mechanical and Aerospace Engineering, and Singapore Institute of Manufacturing Technology

Subjects
Materials [Engineering], Additive Manufacturing, Multicomponent Alloys
Abstract

Laser aided additive manufacturing (LAAM) was used to fabricate bulk Fe49.5Mn30Co10Cr10C0.5 interstitial multicomponent alloy using pre-alloyed powder. The room temperature yield strength (σy), ultimate tensile strength (σUTS) and elongation (εUTS) were 645 MPa, 917 MPa and 27.0 % respectively. The as-built sample consisted of equiaxed and dendritic cellular structures formed by elemental segregation. These cellular structures together with oxide particle inclusions were deemed to strengthen the material. The other contributing components include dislocation strengthening, friction stress and grain boundary strengthening. The high εUTS was attributed to dislocation motion and activation of both twinning and transformation-induced plasticity (TWIP and TRIP). Tensile tests performed at −40 °C and −130 °C demonstrated superior tensile strength of 1041 MPa and 1267 MPa respectively. However, almost no twinning was observed in the fractured sample tested at −40 °C and −130 °C. Instead, higher fraction of strain-induced hexagonal close-packed (HCP) ε phase transformation of 21.2 % were observed for fractured sample tested at −40 °C, compared with 6.3 % in fractured room temperature sample. Agency for Science, Technology and Research (A*STAR) This research was supported by Agency for Science, Technology and Research (A*Star), Republic of Singapore, under the IAF-PP program “Integrated large format hybrid manufacturing using wire-fed and powder-blown technology for LAAM process”, Grant No: A1893a0031.

Published
2021

42. Effects of High-Concentration CO2 on Ignition Delay Time of 70% n-Heptane/30% Toluene Mixtures.

Author

Yao, Shengzhuo, Zhang, Yuewei, Liu, Yongfeng, Bi, Guijun, Zhang, Lu, Wei, Ping, Song, Jinou, and Sun, Hua

Subjects
COMBUSTION chambers, GAS as fuel, IGNITION temperature, DIESEL fuels, CHEMICAL models, TOLUENE
Abstract

In order to research the high-concentration CO2 effects on ignition delay time (IDT) of diesel surrogate fuel (70% n-heptane/30% toluene), a carbon dioxide effect (CDE) model is established, which considers fuel and ambient gas concentration, density, and temperature influence on autoignition under CO2/O2 atmosphere. Firstly, a chemical model of n-heptane/toluene is established, and the coupling, reduction, and simulation processes are carried out in chemical kinetic software with the IDT as the target parameter. Secondly, a constant volume combustion chamber (CVCC) visualization platform is built by incorporating a high-speed camera system and different working conditions are set in the CO2 volume fraction range (40%-70%) at 3.0 MPa and 850 K for an autoignition experiment. Thirdly, experiment and simulation results are discussed in air, 60% CO2/40% O2, 50% CO2/50% O2, and 40% CO2/60% O2 atmospheres, including the IDT, CO2 effects, temperature sensitivity, and OH radical rate of production (ROP). The results show that the CDE model well predicts the 70% n-heptane/30% toluene IDT under the CO2/O2 atmosphere and the average error in 60% CO2/40% O2 atmosphere is 5.29%. Besides, when the CO2 volume fraction increases from 40% to 60%, the CO2 thermal effect plays a leading role in the IDT prolongation and the OH radical ROP peak of R4 (O+H2O⟶2OH) decreases by 180%. [ABSTRACT FROM AUTHOR]

Published
2022
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44. Ultrasonic welding aluminium alloy 7075 to titanium alloy Ti-6Al-4V: parameter optimization and mechanical property

Author

Pan Dayou, Liu Shibo, Cheng Chek Kweng, Sun Xianchong, Lee Bing Yang, Bi Guijun, and Man Yijun

Subjects
Ultrasonic welding, Mechanical property, Materials science, visual_art, Metallurgy, Aluminium alloy, visual_art.visual_art_medium, Titanium alloy, Ti 6al 4v
Abstract

The demand for lightweight materials has increased for automobile and airplane industry. Traditional fusion welding techniques always generate brittle intermetallic compound (IMC). Ultrasonic spot welding (USW) is a promising technique to joint dissimilar metals and suppress IMC formation. This study aims to investigate the role of process parameters as well as surface roughness on the joint shear strength of titanium alloy Ti-6Al-4V and aluminium alloy 7075. Process parameters namely penetration depth, welding time and pressure were varied and the joint shear strength obtained was investigated. Results obtained were indicative that penetration depth and pressure should be used with highest values and surface roughness with lowest. In summary, optimal parameters are USW penetration depth 0.7mm, welding time 1.8s, pressure 0.7 MPa and surface roughness of AA7075 0.1457 Ra µm and Ti-6Al-4V 0.0651 Ra µm (both ground by P1200 SiC paper) in this study.

Published
2020

45. Experimental Research on Humping Bead of Vertical High-speed GMAW

Author

Guo Zhen, BI Guijun, Han Bing, Zhou Wei, and Zhang Li

Subjects
Bead (woodworking), Materials science, Applied Mathematics, Mechanical Engineering, Composite material, Experimental research, Computer Science Applications, Gas metal arc welding
Published
2020

47. Abrasive Surface Finishing on SLM 316L Parts Fabricated with Recycled Powder.

Author

Mesicek, Jakub, Ma, Quoc-Phu, Hajnys, Jiri, Zelinka, Jan, Pagac, Marek, Petru, Jana, Mizera, Ondrej, and Bi, Guijun

Subjects
SURFACE finishing, FINISHES & finishing, SURFACE roughness, POWDERS, STAINLESS steel
Abstract

Improving the surface roughness quality of 3D printed components, especially metallic ones, which are fabricated from the selective laser melting (SLM) method, has drawn enormous attention from the research community. It should be noted that various studies on this topic have reported that precise surface roughness results can be obtained with various techniques that are indeed not cost-effective. Differing itself from these studies, this manuscript investigates an economical solution for fabricating and surface treating SLM components. Specifically, the inspected specimens were printed with recycled 316L stainless steel powder and treated solely with two abrasive surface finishing methods. In the manuscript, two scanning strategies namely meander and stripes, and three types of surfaces were investigated. Subsequently, their 2D and 3D surface roughness results were elaborated. After the proposed herein abrasive treatment, 3D surface roughness arithmetical mean height of a surface (Sa) value of 0.9 µm can be achieved. [ABSTRACT FROM AUTHOR]

Published
2021
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