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Advances in polishing of internal structures on parts made by laser-based powder bed fusion

《机械工程前沿（英文）》 2023年 第18卷 第1期 doi: 10.1007/s11465-022-0724-0

摘要： The internal structures of metallic products are important in realizing functional applications. Considering the manufacturing of inner structures, laser-based powder bed fusion (L-PBF) is an attractive approach because its layering principle enables the fabrication of parts with customized interior structures. However, the inferior surface quality of L-PBF components hinders its productization progress seriously. In this article, process, basic forms, and applications relevant to L-PBF internal structures are reviewed comprehensively. The causes of poor surface quality and differences in the microstructure and property of the surface features of L-PBF inner structures are presented to provide a perspective of their surface characteristics. Various polishing technologies for L-PBF components with inner structures are presented, whereas their strengths and weaknesses are summarized along with a discussion on the challenges and prospects for improving the interior surface quality of L-PBF parts.

关键词： laser-based powder bed fusion     polishing     internal structures     surface quality     surface features     post process     additive manufacturing    

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Orientation effect of electropolishing characteristics of 316L stainless steel fabricated by laser powderbed fusion

《机械工程前沿（英文）》 2021年 第16卷 第3期   页码 580-592 doi: 10.1007/s11465-021-0633-7

摘要： 3D metal printing process has attracted increasing attention in recent years due to advantages, such as flexibility and rapid prototyping. This study aims to investigate the orientation effect of electropolishing characteristics on different surfaces of 316L stainless steel fabricated by laser powder bed fusion (L-PBF), considering that the rough surface of 3D printed parts is a key factor limiting its applications in the industry. The electropolishing characteristics on the different surfaces corresponding to the building orientation in selective laser melting are studied. Experimental results show that electrolyte temperature has critical importance on the electropolishing, especially for the vertical direction to the layering plane. The finish of electropolished surfaces is affected by the defects generated during L-PBF process. Thus, the electropolished vertical surface has higher surface roughness Sa than the horizontal surface. The X-ray photoelectron spectroscopy spectra show that the electropolished horizontal surface has higher Cr/Fe element ratio than the vertical surface. The electropolished horizontal surface presents higher corrosion resistance than the vertical surface by measuring the anodic polarization curves and fitting the equivalent circuit of experimental electrochemical impedance spectroscopy.

关键词： electropolishing     laser powder bed fusion     316L stainless steel     corrosion resistance     microstructure    

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of CoCrFeMnNi high-entropy alloy from elemental feedstock toward high-throughput synthesis via laser powderbed fusion

《机械工程前沿（英文）》 2023年 第18卷 第1期 doi: 10.1007/s11465-022-0727-x

摘要： High-entropy alloys (HEAs) are considered alternatives to traditional structural materials because of their superior mechanical, physical, and chemical properties. However, alloy composition combinations are too numerous to explore. Finding a rapid synthesis method to accelerate the development of HEA bulks is imperative. Existing in situ synthesis methods based on additive manufacturing are insufficient for efficiently controlling the uniformity and accuracy of components. In this work, laser powder bed fusion (L-PBF) is adopted for the in situ synthesis of equiatomic CoCrFeMnNi HEA from elemental powder mixtures. High composition accuracy is achieved in parallel with ensuring internal density. The L-PBF-based process parameters are optimized; and two different methods, namely, a multi-melting process and homogenization heat treatment, are adopted to address the problem of incompletely melted Cr particles in the single-melted samples. X-ray diffraction indicates that HEA microstructure can be obtained from elemental powders via L-PBF. In the triple-melted samples, a strong crystallographic texture can be observed through electron backscatter diffraction, with a maximum polar density of 9.92 and a high ultimate tensile strength (UTS) of (735.3 ± 14.1) MPa. The homogenization heat-treated samples appear more like coarse equiaxed grains, with a UTS of (650.8 ± 16.1) MPa and an elongation of (40.2% ± 1.3%). Cellular substructures are also observed in the triple-melted samples, but not in the homogenization heat-treated samples. The differences in mechanical properties primarily originate from the changes in strengthening mechanism. The even and flat fractographic morphologies of the homogenization heat-treated samples represent a more uniform internal microstructure that is different from the complex morphologies of the triple-melted samples. Relative to the multi-melted samples, the homogenization heat-treated samples exhibit better processability, with a smaller composition deviation, i.e., ≤ 0.32 at.%. The two methods presented in this study are expected to have considerable potential for developing HEAs with high composition accuracy and composition flexibility.

关键词： laser powder bed fusion (L-PBF)     in situ alloying     high-entropy alloys     heat treatment     rapid synthesis    

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Manufacturing cost constrained topology optimization for additive manufacturing

Jikai LIU, Qian CHEN, Xuan LIANG, Albert C. TO

《机械工程前沿（英文）》 2019年 第14卷 第2期   页码 213-221 doi: 10.1007/s11465-019-0536-z

摘要： This paper presents a manufacturing cost constrained topology optimization algorithm considering the laser powder bed additive manufacturing process. Topology optimization for additive manufacturing was recently extensively studied, and many related topics have been addressed. However, metal additive manufacturing is an expensive process, and the high manufacturing cost severely hinders the widespread use of this technology. Therefore, the proposed algorithm in this research would provide an opportunity to balance the manufacturing cost while pursuing the superior structural performance through topology optimization. Technically, the additive manufacturing cost model for laser powder bed-based process is established in this paper and real data is collected to support this model. Then, this cost model is transformed into a level set function-based expression, which is integrated into the level set topology optimization problem as a constraint. Therefore, by properly developing the sensitivity result, the metallic additive manufacturing part can be optimized with strictly constrained manufacturing cost. Effectiveness of the proposed algorithm is proved by numerical design examples.

关键词： topology optimization     manufacturing cost     additive manufacturing     powder bed    

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用于粉末床增材制造的铬镍铁合金粉末特征研究

Quy Bau Nguyen, Mui Ling Sharon Nai, Zhiguang Zhu, Chen-Nan Sun, Jun Wei, Wei Zhou

《工程（英文）》 2017年 第3卷 第5期   页码 695-700 doi: 10.1016/J.ENG.2017.05.012

摘要：

本研究中使用不同的粉末表征技术对铬镍铁合金的原始粉末和回收粉末在粉末床增材制造（AM）上的流动特性、行为特征进行研究。结果发现，选择性激光熔化（SLM）工艺的粒径分布（PSD）范围通常在15 ～ 63 μm 之间。原始的铬镍铁合粉末的流量约为28 s·(50 g)–1，组装密度是60%。流变测试结果表明，原始粉末与回收粉末相比具有更好的流动性。讨论了两种粉末之间的相互关系。运用铬镍铁合金粉末已经成功打印出了螺旋桨。实验结果表明铬镍铁合金粉末适用于增材制造（AM），本研究为生产增材制造粉末提供参考。

关键词： 增材制造     粉末特征     气体雾化     微观结构     铬镍铁合金    

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微观选择性激光熔化技术发展的现状及未来展望 Review

Balasubramanian Nagarajan, Zhiheng Hu, Xu Song, Wei Zhai, Jun Wei

《工程（英文）》 2019年 第5卷 第4期   页码 702-720 doi: 10.1016/j.eng.2019.07.002

摘要：

增材制造（AM）能将各种材料制成形状复杂的部件，因此在制造业中越来越受到青睐。选择性激光熔化（SLM）是一种常见的AM技术，它基于粉床熔融法（PBF）来处理金属，但目前只专注于大中型元件的制作。本文综述了微型金属材料SLM的研究现状。与通常用于微观AM的直接写入技术相比，微观SLM由于许多因素而更加具有吸引力，包括更快的周期时间、流程简单性和材料通用性。此外，本文综合评价了利用SLM和选择性激光烧结（SLS）制造微尺度零件的各种研究工作和商业系统，不仅从微观尺度上找出了SLM存在的问题，包括粉末重涂、激光光学和粉末粒度等， 还详细阐述了SLM未来的发展方向。文章详细回顾了粉床技术中现有的粉末重涂方法，并描述了在AM领域实施干粉分配方法的新进展。对AM部件的一些二次整理技术进行了回顾，重点介绍了细微加工特征的应用以及与微观SLM系统的结合。

关键词： 增材制造     选择性激光熔化     微细加工     混合处理     粉床重涂    

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Assessment of glass fiber-reinforced polyester pipe powder in soil improvement

《结构与土木工程前沿（英文）》 2021年 第15卷 第3期   页码 742-753 doi: 10.1007/s11709-021-0732-x

摘要： This study investigates the use of glass fiber-reinforced polyester (GRP) pipe powder (PP) for improving the bearing capacity of sandy soils. After a series of direct share tests, the optimum PP addition for improving the bearing capacity of soils was found to be 12%. Then, using the optimum PP addition, the bearing capacity of the soil was estimated through a series of loading tests on a shallow foundation model placed in a test box. The bearing capacity of sandy soil was improved by up to 30.7%. The ratio of the depth of the PP-reinforced soil to the diameter of the foundation model (H/D) of 1.25 could sufficiently strengthen sandy soil when the optimum PP ratio was used. Microstructural analyses showed that the increase in the bearing capacity can be attributed to the chopped fibers in the PP and their multiaxial distribution in the soil. Besides improving the engineering properties of soils, using PP as an additive in soils would reduce the accumulation of the industrial waste, thus providing a twofold benefit.

关键词： shallow foundation     sandy soil     bearing capacity     soil improvement     pipe powder    

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Experimental study and assessment of thermal energy storage mortar with paraffin/recycled brick powder

Luchen HAO; Jianzhuang XIAO; Wanzhi CAO; Jingting SUN

《结构与土木工程前沿（英文）》 2022年 第16卷 第10期   页码 1301-1314 doi: 10.1007/s11709-022-0883-4

摘要： Thermal energy storage recycled powder mortar (TESRM) was developed in this study by incorporating paraffin/recycled brick powder (paraffin/BP) composite phase change materials (PCM). Fourier transform infrared and thermogravimetric analysis results showed that paraffin/BP composite PCM had good chemical and thermal stability. The onset melting temperature and latent heat of the composite PCM were 46.49 °C and 30.1 J·g−1. The fresh mortar properties and hardened properties were also investigated in this study. Paraffin/BP composite PCM with replacement ratio of 0%, 10%, 20%, and 30% by weight of cement were studied. The results showed that the static and dynamic yield stresses of TESRM were 699.4% and 172.9% higher than those of normal mortar, respectively. The addition of paraffin/BP composite PCM had a positive impact on the mechanical properties of mortar at later ages, and could also reduce the dry shrinkage of mortar. The dry shrinkage of TESRM had a maximum reduction about 26.15% at 120 d. The thermal properties of TESRM were better than those of normal mortar. The thermal conductivity of TESRM was 36.3% less than that of normal mortar and the heating test results showed that TESRM had good thermal energy storage performance.

关键词： recycled powder mortar     recycled brick powder     thermal energy storage     paraffin     phase change material    

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Aging properties and aging mechanism of activated waste rubber powder modified asphalt binder based on

《结构与土木工程前沿（英文）》 2023年 第17卷 第4期   页码 625-636 doi: 10.1007/s11709-023-0938-1

摘要： The research and development of high-performance pavement materials has been intensified owing to the demand for long-life pavements. This study is performed to develop a novel pavement material using waste rubber powder, waste lubricating by-product (LBP), and asphalt. Subsequently, the aging properties and aging mechanism of activated waste rubber powder modified asphalt (ARMA) are investigated based on its rheological properties and micro-characterization. The rheological results show that, compared with waste rubber powder modified asphalt (RMA), ARMA offers a higher aging resistance and a longer fatigue life. A comparison and analysis of the rheological aging parameters of ARMA and RMA show that LBP activation diminishes the aging sensitivity of ARMA. The micro-characterization result shows that the aging of ARMA may be caused by the fact that LBP-activated waste rubber powder is more reactive and can form a dense colloidal structure with asphalt. Therefore, the evaporation loss of asphalt light components by heat and the damage to the colloidal structure by oxygen during the aging process are impeded, and the thermal-oxidative aging resistance of ARMA is improved.

关键词： rubber powder modified asphalt     aging     mechanism     rheological     characterization    

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Preparation of adsorptive nanoporous membrane using powder activated carbon: Isotherm and thermodynamic

Majid Peyravi

《化学科学与工程前沿（英文）》 2020年 第14卷 第4期   页码 673-687 doi: 10.1007/s11705-019-1800-9

摘要： Adsorptive polyethesulfone (PES) membranes were prepared by intercalation of powder activated carbon (PAC) with and without functionalization. Accordingly, PAC was aminated with 1,5-diamino-2-methylpentane, and the physicochemical properties of the functionalized PAC were analyzed. Intercalation of PAC within the PES scaffold changed the porosity and mean pore size of the aminated membrane (AC-NH ) from 52.6% to 92.5% and from 22.6 nm to 3.5 nm, respectively. The effect of temperature on the performance of the modified membranes was monitored by the flux and chemical oxygen demand (COD) removal of leachate. At ambient temperature, the COD removal of the neat, AC-containing, and AC-NH membranes was 47%, 52%, and 58.5%, respectively. A similar increment was obtained for the membrane flux, which was due to the synergistic effect of the high porosity and large number of hydrophilic functional groups. The experimental leachate adsorption data were analyzed by Langmuir, Freundlich, and Dubinin- Radushkevich isotherm models. For all membranes, the significant thermodynamic parameters ( , , and ) were calculated and compared. The isosteric heat of adsorption was lower than 80 kJ∙mol , indicating that the interaction between the membranes and the leachate is mainly physical, involving weak van der Waals forces.

关键词： amine functionality     nanoporous membrane     adsorption isotherm     thermodynamic parameters     landfill leachate    

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Global warming potential associated with Irish milk powder production

William Finnegan, Jamie Goggins, Aksana Chyzheuskaya, Xinmin Zhan

《环境科学与工程前沿（英文）》 2017年 第11卷 第3期 doi: 10.1007/s11783-017-0949-z

摘要： Climate change is an ever growing issue and a major concern worldwide. Both producers and processors need to address the issue now by reducing their carbon footprint. Additionally, if Ireland is to meet their climate and energy targets, as outlined in Food Harvest 2020, which outlines a range of objectives for the Irish agricultural sector, the efficient use of resources and fuels within the industry will need to be increased. In Ireland, agriculture accounts for 29.2% of the total greenhouse gas emissions (58.5 million tonnes CO eq). Therefore, in this paper, a single agri-food product, milk powder, is examined in order to estimate the global warming potential (GWP) associated with its manufacture using life cycle assessment. A cradle-to-processing factory gate analysis, which includes raw milk production, raw milk transportation to the processing factory, its processing into each product and product packaging, is assessed in this study using data collected circa 2013. The factories surveyed processed approximately 24% of the total raw milk processed in the Republic of Ireland in 2013, which was 5.83 billion liters. The average total GWP associated with the manufacture of milk powder is 9.731 kg CO eq·kg milk powder, which has a standard deviation of 2.26 kg CO eq·kg milk powder, for the life cycle stages analyzed in this study. The most significant contributor to GWP is raw milk production (84%), followed by dairy processing (14%), with the remainder of the life cycle stages contributing approximately 2%.

关键词： Dairy     Global warming potential     Ireland     Life cycle assessment     Milk powder     Milk production    

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Prediction of bed load sediments using different artificial neural network models

Reza ASHEGHI, Seyed Abbas HOSSEINI

《结构与土木工程前沿（英文）》 2020年 第14卷 第2期   页码 374-386 doi: 10.1007/s11709-019-0600-0

摘要： Modeling and prediction of bed loads is an important but difficult issue in river engineering. The introduced empirical equations due to restricted applicability even in similar conditions provide different accuracies with each other and measured data. In this paper, three different artificial neural networks (ANNs) including multilayer percepterons, radial based function (RBF), and generalized feed forward neural network using five dominant parameters of bed load transport formulas for the Main Fork Red River in Idaho-USA were developed. The optimum models were found through 102 data sets of flow discharge, flow velocity, water surface slopes, flow depth, and mean grain size. The deficiency of empirical equations for this river by conducted comparison between measured and predicted values was approved where the ANN models presented more consistence and closer estimation to observed data. The coefficient of determination between measured and predicted values for empirical equations varied from 0.10 to 0.21 against the 0.93 to 0.98 in ANN models. The accuracy performance of all models was evaluated and interpreted using different statistical error criteria, analytical graphs and confusion matrixes. Although the ANN models predicted compatible outputs but the RBF with 79% correct classification rate corresponding to 0.191 network error was outperform than others.

关键词： bed load prediction     artificial neural network     modeling     empirical equations    

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Experimental study on shear behavior of prestressed reactive powder concrete I-girders

Hui ZHENG, Zhi FANG, Bin CHEN

《结构与土木工程前沿（英文）》 2019年 第13卷 第3期   页码 618-627 doi: 10.1007/s11709-018-0500-8

摘要： As a new generation of concrete, RPC(Reactive Powder Concrete) has attracted great research attention for its ultra-high strength and high durability. In the present paper, experimental results from tests on eight prestressed RPC I-section girders failing in shear are reported herein. The beams with RPC of 120 MPa in compression were designed to assess the ability to carry shear stress in thin webbed prestressed beams with stirrups. The test variables were the level of prestressing, shear span-depth ratio ( / ) and stirrup ratio. Shear deformation, shear capacity and crack pattern were experimentally investigated in detail. With regard to the shear resistance of the test beams, the predictions from three standards (AFGC, JSCE and SIA) on the design of UHPC structures were compared with the experimental result suggesting that the experimental strength is almost always higher than predicted. RPC, as a new concrete, was different from normal concrete and fiber reinforced concrete. Further study should be needed to develop an analytical method and computation model for shear strength of RPC beams.

关键词： prestressed concrete     RPC(Reactive Powder Concrete)     concrete beams     shear strength     experimental study    

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Liquefaction and impurity separation of oxygen-bearing coal-bed methane

Qiuying LI, Yonglin JU, Li WANG,

《能源前沿（英文）》 2010年 第4卷 第3期   页码 319-325 doi: 10.1007/s11708-010-0115-9

摘要： Coal-bed methane (CBM) is a type of clean energy. However, most oxygen-bearing CBM have not yet to be utilized due to limited techniques, and when utilized, the discharged gas leads to resource wastage and environment pollution. In this paper, a liquefaction process is proposed and designed for the specified oxygen-bearing CBM obtained from the Daqing Qingshen gas field. The distillation column is employed to separate the oxygen and nitrogen components present in the CBM. HYSYS software is adopted to simulate the process, and the results reveal that the energy consumption of the whole liquefaction process is low. Moreover, oxygen and nitrogen are nearly removed completely, achieving a high-purity liquefied natural gas product with a high methane recovery rate. The applicability and safety of the liquefaction process are also analyzed. The simulation results can offer references for the separation of the oxygen component from CBM.

关键词： coal bed methane     oxygen-bearing     liquefaction     distillation    

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铁矿粉熔态还原冶炼的新流程

许志宏,王立新,杨章远,谢裕生,胥昌第,招冀

《中国工程科学》 1999年 第1卷 第3期   页码 69-74

摘要：

提出了一种直接用粉矿和煤的熔态还原炼铁新流程，其最大特点是消除污染产生源。为解决过去流化床铁矿粉还原技术中的粘结问题，提出了非等温渗碳的流化移动床的新方法。建议放弃一些工业化国家在熔化气化炉中发展二次燃烧率的指导思想，代之以系统的能量最佳利用原理。提出直接采用粉矿、综合利用尾气和利用高炉下部还原机制的具体建议，用以实现冶金与化工系统的集成，保证系统在技术和经济上成功。为了适应经济全球化的形势发展，建议以自力更生和引进国外技术与资金相结合的方式，促进熔态还原和其他冶金新技术在我国早日成功。

关键词： 熔态还原     粉末     流化移动床     环境保护     技术改造    

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标题 作者 时间 类型 操作

Advances in polishing of internal structures on parts made by laser-based powder bed fusion

期刊论文

Orientation effect of electropolishing characteristics of 316L stainless steel fabricated by laser powderbed fusion

期刊论文

of CoCrFeMnNi high-entropy alloy from elemental feedstock toward high-throughput synthesis via laser powderbed fusion

期刊论文

Manufacturing cost constrained topology optimization for additive manufacturing

Jikai LIU, Qian CHEN, Xuan LIANG, Albert C. TO

期刊论文

用于粉末床增材制造的铬镍铁合金粉末特征研究

Quy Bau Nguyen, Mui Ling Sharon Nai, Zhiguang Zhu, Chen-Nan Sun, Jun Wei, Wei Zhou

期刊论文

微观选择性激光熔化技术发展的现状及未来展望

Balasubramanian Nagarajan, Zhiheng Hu, Xu Song, Wei Zhai, Jun Wei

期刊论文

Assessment of glass fiber-reinforced polyester pipe powder in soil improvement

期刊论文

Experimental study and assessment of thermal energy storage mortar with paraffin/recycled brick powder

Luchen HAO; Jianzhuang XIAO; Wanzhi CAO; Jingting SUN

期刊论文

Aging properties and aging mechanism of activated waste rubber powder modified asphalt binder based on

期刊论文

Preparation of adsorptive nanoporous membrane using powder activated carbon: Isotherm and thermodynamic

Majid Peyravi

期刊论文

Global warming potential associated with Irish milk powder production

William Finnegan, Jamie Goggins, Aksana Chyzheuskaya, Xinmin Zhan

期刊论文

Prediction of bed load sediments using different artificial neural network models

Reza ASHEGHI, Seyed Abbas HOSSEINI

期刊论文

Experimental study on shear behavior of prestressed reactive powder concrete I-girders

Hui ZHENG, Zhi FANG, Bin CHEN

期刊论文

Liquefaction and impurity separation of oxygen-bearing coal-bed methane

Qiuying LI, Yonglin JU, Li WANG,

期刊论文

铁矿粉熔态还原冶炼的新流程

许志宏,王立新,杨章远,谢裕生,胥昌第,招冀

期刊论文