A Review on Energy Consumption and Efficiency of Selective Laser Melting Considering Support: Advances and Prospects

Qingyang Wang,Mengdi Gao,Qiang Li,Conghu Liu,Lei Li,Xinyu Li,Zhifeng Liu 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.1

Selective laser melting (SLM) exhibits excellent manufacturing accuracy and forming ability. However, the laser beam layering process is characterized by high specific energy consumption, long manufacturing cycle, and low energy efficiency. The use of supports increases the SLM building quality and eliminates defects caused by thermal and residual stresses; however, an improper support structural design increases the process energy consumption for manufactured parts. To control energy consumption and building quality during SLM, this study first discusses the main challenges related to energy saving and improving the building quality by performing an energy consumption analysis, process energy consumption optimization, and supporting structure optimization. The obtained results reveal that it is difficult to achieve high building quality only by controlling the process parameters and energy consumption by the SLM equipment. Next, the effect of supporting structures on the process energy consumption is examined to enable the construction of an SLM energy consumption model that considers the presence of supports. Finally, the effect of supports on the building quality is elucidated by studying the influence of supporting structures on thermal and residual stresses. By identifying the most energy-efficient support, the process energy efficiency and building quality may be simultaneously optimized. The proposed method represents a new approach to reducing energy consumption and improving the building quality during SLM. This study establishes a theoretical foundation for the subsequent industrial applications, providing a thorough literature review and describing the existing challenges in the SLM manufacturing field.

Analysis of Asymmetric Stress Ratio in Shallow Buried Tunnels

Qingyang Yu,Zeyu Song,Chao Du,Zhenxue Dai,Shangxian Yin,Mohamad Reza Soltanian,Mojtaba Soltanian,Wei Liu 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.6

Asymmetric stress occurs in shallow buried highways and railway tunnels. Due to asymmetricalloading, the design process of the tunnel is different from a regular tunnel. Chinese code for designing railway tunnel contains empirical values for different grounding rock to facilitate engineering judgement of asymmetrical loading tunnels based on the slope angle of surface and the burial depth of the tunnel. However, when calculating the asymmetric stress, there seem to be no quantitative criteria for estimating the asymmetric stress. Thus, in this work we create a numerical model to better evaluate the asymmetric stress ratios in different rock types. Our results demonstrate for surrounding rocks of grade V with poor stability, an asymmetrical loading conditions should be considered specifically when the stress ratio at the spandrel is higher than unity. For surrounding rock with grade IV in which stability slightly increases we found that the tunnel is asymmetrical once the stress ratio at the spandrel reaches to above 2 − 3. For the grade IV with a higher stability, an asymmetrical loading should be considered in the design when the stress ratio reaches to 3 − 4. For rock with grade III with the maximum stability only when the stress ratio is higher than 7 − 8, the asymmetrical loading conditions should be considered. We found that for grades III, IV, and V, the stress ratio of sidewall is about unity under various slope angles and burial depth. Importantly, we show that the stress ratio at the sidewall cannot be used to make judgements on whether the shallow buried tunnels are asymmetrical loading conditions. Our results have practical implications in design, safety, and risk analyses of tunnels.

Performance assessment and structural design of the atmospheric cutterhead of slurry shield machine

Feixiang Liu,Qingyang Wang,Zhiyong Ji,Laikuang Lin 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.11

The atmospheric cutterhead is a new type of cutterhead with high technical difficulty. Compared with the conventional cutterhead, the spatial structure of the atmospheric cutterhead is more complicated, and a mature design theory has not yet been formed. This paper presents an atmospheric cutterhead design method for slurry shield machines. The method was divided into three steps: (i) design load analysis; (ii) multiobjective topology optimization; and (iii) evaluation and selection of cutterhead structures. Based on topology optimization theory, four types of cutterhead structures with different numbers of radial arms are obtained. The performance of the cutterhead was evaluated by stress, deformation, vibration mode, opening situation and space complexity, and the five-radial arm cutterhead was determined to be the best solution. Analysing the actual tunnelling parameter data shows good engineering adaptability. This paper provides a reference for the optimal design of the atmospheric cutterhead of slurry shield machine.

The Band Offset at CdS/Cu2ZnSnS4 Heterojunction Interface

Ji Li,Qingyang Du,Weifeng Liu,Guoshun Jiang,Xuefei Feng,Wenhua Zhang,Junfa Zhu,Changfei Zhu 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.4

The band offset at the CdS/Cu2ZnSnS4 heterojunction interface is studied by measuring the valence band spectra using synchrotron radiation photoemission spectroscopy. The Cu2ZnSnS4 thin films are prepared by the sulfurization of electrodeposited Cu-Zn-Sn precursors. A CdS overlayer is sequentially grown on the Cu2ZnSnS4 thin films from a chemical bath deposition process. Valence band spectra were obtained before and after each period of growth to study the electronic structure at the heterojunction interface. The valence band offset was determined to be 0.96 eV, and the conduction band offset was determined to be .0.06 eV. This means that the CdS/Cu2ZnSnS4 hetrojunction has a ‘type II’ band alignment which will cause largescale recombination at the interfaces and will not be suitable for solar cells fabrication.

Integration of Additive Manufacturing in Casting: Advances, Challenges, and Prospects

Mengdi Gao,Lei Li,Qingyang Wang,Zhilin Ma,Xinyu Li,Zhifeng Liu 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.1

Additive manufacturing (AM) is a novel manufacturing technology that can create highly customized products with more complex geometries than traditional techniques. Despite its significant advantages, including the freedom of design, mass customization, and ability to produce complex structures, AM consumes a large amount of energy and incurs high costs. In addition, AM suffers from long production cycles and low production efficiency in the large-scale manufacturing of metal structures. This study offers a review of the existing literature focused on metal AM technology. To avoid the shortcomings of AM and highlight its bene fits, which are widely used for manufacturing in combination with casting. The current combination application of AM and casting is reviewed to provide solutions to the problem of manufacturing large metal components from the perspective of the use of different AM technology and quality control in casting. However, such integration is insufficient for producing large castings with complex shapes, structures, or multiple features. Therefore, a novel method for integrating AM into casting to enable the manufacture of large scale metal parts with complex shapes is introduced as a topic for possible future research. This method divides complex castings with multiple features into an AM processing part and the casting substrate. The complex features were processed by AM on the fabricated casting substrate. This study provides a review of the application of AM into casting and presents a novel idea for the integration application of AM and other processes. This promising method has significant value for future study.

Performance of corrosion inhibitor extracted from enzymatic hydrolysate of waste Platanus acerifolia leaves

Zijian Song,Huanchun Cai,Qingyang Liu,Linhua Jiang,Hongqiang Chu 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.111 No.-

In this study, an ultrasound-assisted enzymatic extraction (UEE) method was proposed to augment theanti-corrosion performance of the green inhibitor extracted from waste Platanus acerifolia leaves. Chemical compositions and anticorrosive properties of UEE extract were characterized via multiple technologies. The adsorption film on the steel surface was characterized via X-ray photoelectron spectroscopy(XPS). The surface information of corroded steel was also analyzed. Results showed that, compared withthe ultrasound-assisted alkali extraction (UAE), UEE increased the utilization rate of raw plant materialsby 22%39%. After optimized via response surface methodology, the maximum yield of UEE extract couldreach 27.081 mg/g. Electrochemical results showed, compared with 3% UAE extract, the inhibition efficiencyof 3% UEE extract after 72 h in 0.5 M NaCl was increased by 22% while the extraction time wassaved by 90%. Microscopic observations also proved that UEE extract can effectively mitigate the corrosiondegree where the roughness of steel surface decreased by 63.67%. XPS results revealed that a carbonaceousprotecting layer was formed on steel surfaces. The inhibition mechanism analysis suggestedthat flavonoids and their derivatives were apt to adsorb on the steel surface via chelation and surfacephysical adsorption, which could block the pathway of chloride attack.

Reaction mechanisms for dithiothreitol as a measure of particulate matter induced oxidative potential activity by density functional theory

Yi-ling Bei,Qingyang Liu 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.7

The measurement of particulate matter induced oxidative potential activity by dithiothreitol (DTT) as analternative quantitative method has been of recent interest. The mechanism of this process is not well understood. Proposedmechanisms often involve formation of the hydrogen peroxide as the final step. Evidence suggests that this maynot be the dominant route. We applied computational methods to determine a possible alternative mechanism in thepresence of •OH radical production. An energetically favored mechanism was found for DTT-chemical reactivity reactionwhich is consistent with previously reported experimental results.

Energy Efficiency and Dynamic Analysis of a Novel Hydraulic System with Double Actuator

Mengdi Gao,Lei Li,Qingyang Wang,Conghu Liu 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.7 No.3

At present, increased attention has been given to energy effi ciency promotion and energy saving of manufacturing equipment and systems. Hydraulic system is widely used in engineering machinery industries; however, the high energy consumption and low energy effi ciency of which limit its development and application. On the basis of previous research on hydraulic system, an energy-effi cient hydraulic system with double actuator is proposed in this study. This hydraulic system can reduce the energy consumption by reusing the potential energy loss of the system. In this novel hydraulic system, the chambers of two actuators are connected with rod by pipes and valves. During the operating processes, the falling operation of one cylinder and the returning operation of the other are synchronized. That is, one actuator remains at the top point performing the demanded operation, whereas the other one remains at the bottom performing the corresponding operation. System models are developed to address the energy consumption and dynamic performance of the proposed hydraulic system. This hydraulic system is applied into a press to study its energy-saving mechanism and dynamic performance during transient under various working conditions. On the basis of the simulation and experimental results, energy and production effi ciency are compared and discussed. Results show that in comparison with the energy and time consumption of the original 630 kN hydraulic press, the energy-saving potential has reached 17.34%, and the production effi ciency can be improved by 18.85%.

Electronic spin transition in FeO2 : Evidence for Fe(II) with peroxide O22−

Jang, Bo Gyu,Liu, Jin,Hu, Qingyang,Haule, Kristjan,Mao, Ho-Kwang,Mao, Wendy L.,Kim, Duck Young,Shim, Ji Hoon American Physical Society 2019 Physical Review B Vol.100 No.1

Analysis and Optimization of Energy Consumption for Multi-part Printing Using Selective Laser Melting and Considering the Support Structure

Zhilin Ma,Mengdi Gao,Kai Guo,Qingyang Wang,Lei Li,Conghu Liu,Guang Zhu,Zhifeng Liu 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.3

Selective laser melting (SLM) can form complex and precise metal parts simultaneously and is widely used in medical and aerospace fields. The support structure plays an important role in SLM process, including supporting the overhanging structure, dissipating heat, and minimizing geometric deformation caused by internal stress. However, a non-optimal support structure causes increased energy and material consumption during processing and must be removed afterward to allow for utilization of the parts. Existing support structure design methods only consider reducing the support of a single part, and research on the support and energy consumption of simultaneous multi-part printing is lacking. Therefore, to reduce the energy and material consumption of simultaneous multi-part printing by SLM and improve processing efficiency, an energy consumption analysis and optimization method is proposed in this study from the perspective of the support structure. Based on previous studies on energy consumption distribution of the additive manufacturing process, a multi-component SLM energy consumption and material consumption model was established. Furthermore, a shared-support optimization strategy for simultaneous multi-part processing is proposed. For optimization, the method selects the appropriate printing direction of one part, and then combines multiple parts to form a shared support structure to minimize energy consumption. Finally, under the constraint of minimizing the mass, an optimization strategy of the SLM multi-part shared support combination is established, and the purpose of reducing the energy consumption and material consumption of the SLM is achieved under the premise of ensuring the geometric accuracy of the parts. The method was applied to the manufacturing process of a group of parts with a beam structure. Compared with the printing method using independent support, the shared support structure method reduced energy consumption more than 5.5%, material consumption for the support structure more than 17.2%, and printing time to a certain extent. This method effectively improves SLM production efficiency and sustainability and provides strategic support for additive manufacturing designers and producers.