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Subsurface damage pattern and formation mechanism of monocrystalline -GaO in grinding process

《机械工程前沿（英文）》 2022年 第17卷 第2期 doi: 10.1007/s11465-022-0677-3

摘要： Monocrystalline beta-phase gallium oxide (β-Ga2O3) is a promising ultrawide bandgap semiconductor material. However, the deformation mechanism in ultraprecision machining has not yet been revealed. The aim of this study is to investigate the damage pattern and formation mechanism of monocrystalline β-Ga2O3 in different grinding processes. Transmission electron microscopy was used to observe the subsurface damage in rough, fine, and ultrafine grinding processes. Nanocrystals and stacking faults existed in all three processes, dislocations and twins were observed in the rough and fine grinding processes, cracks were also observed in the rough grinding process, and amorphous phase were only present in the ultrafine grinding process. The subsurface damage thickness of the samples decreased with the reduction in the grit radius and the grit depth of cut. Subsurface damage models for grinding process were established on the basis of the grinding principle, revealing the mechanism of the mechanical effect of grits on the damage pattern. The formation of nanocrystals and amorphous phase was related to the grinding conditions and material characteristics. It is important to investigate the ultraprecision grinding process of monocrystalline β-Ga2O3. The results in this work are supposed to provide guidance for the damage control of monocrystalline β-Ga2O3 grinding process.

关键词： monocrystalline beta-phase gallium oxide     grinding process     subsurface damage     nanocrystals     amorphous phase    

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Fiber-reinforced composites in milling and grinding: machining bottlenecks and advanced strategies

《机械工程前沿（英文）》 2022年 第17卷 第2期 doi: 10.1007/s11465-022-0680-8

摘要： Fiber-reinforced composites have become the preferred material in the fields of aviation and aerospace because of their high-strength performance in unit weight. The composite components are manufactured by near net-shape and only require finishing operations to achieve final dimensional and assembly tolerances. Milling and grinding arise as the preferred choices because of their precision processing. Nevertheless, given their laminated, anisotropic, and heterogeneous nature, these materials are considered difficult-to-machine. As undesirable results and challenging breakthroughs, the surface damage and integrity of these materials is a research hotspot with important engineering significance. This review summarizes an up-to-date progress of the damage formation mechanisms and suppression strategies in milling and grinding for the fiber-reinforced composites reported in the literature. First, the formation mechanisms of milling damage, including delamination, burr, and tear, are analyzed. Second, the grinding mechanisms, covering material removal mechanism, thermal mechanical behavior, surface integrity, and damage, are discussed. Third, suppression strategies are reviewed systematically from the aspects of advanced cutting tools and technologies, including ultrasonic vibration-assisted machining, cryogenic cooling, minimum quantity lubrication (MQL), and tool optimization design. Ultrasonic vibration shows the greatest advantage of restraining machining force, which can be reduced by approximately 60% compared with conventional machining. Cryogenic cooling is the most effective method to reduce temperature with a maximum reduction of approximately 60%. MQL shows its advantages in terms of reducing friction coefficient, force, temperature, and tool wear. Finally, research gaps and future exploration directions are prospected, giving researchers opportunity to deepen specific aspects and explore new area for achieving high precision surface machining of fiber-reinforced composites.

关键词： milling     grinding     fiber-reinforced composites     damage formation mechanism     delamination     material removal mechanism     surface integrity     minimum quantity lubrication    

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Formation mechanism and modeling of surface waviness in incremental sheet forming

《机械工程前沿（英文）》 2022年 第17卷 第2期 doi: 10.1007/s11465-022-0679-1

摘要： Improving and controlling surface quality has always been a challenge for incremental sheet forming (ISF), whereas the generation mechanism of waviness surface is still unknown, which impedes the widely application of ISF in the industrial field. In this paper, the formation mechanism and the prediction of waviness are both investigated through experiments, numerical simulation, and theoretical analysis. Based on a verified finite element model, the waviness topography is predicted numerically for the first time, and its generation is attributed to the residual bending deformation through deformation history analysis. For more efficient engineering application, a theoretical model for waviness height is proposed based on the generation mechanism, using a modified strain function considering deformation modes. This work is favorable for the perfection of formation mechanism and control of surface quality in ISF.

关键词： surface waviness     incremental sheet forming     numerical simulation     formation mechanism     deformation history    

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The formation mechanism and the influence factor of residual stress in machining

null

《机械工程前沿（英文）》 2014年 第9卷 第3期   页码 265-269 doi: 10.1007/s11465-014-0311-0

摘要：

Residual stresses generated in cutting process have important influences on workpiece performance. The paper presents a method of theoretical analysis in order to explicate the formation mechanism of residual stresses in cutting. An important conclusion is drawn that the accumulated plastic strain is the main factor which determines the nature and the magnitude of surface residual stresses in the workpiece. On the basis of the analytical model for residual stress, a series of simulations for residual stress prediction during cutting AISI 1045 steel are implemented in order to obtain the influences of cutting speed, depth of cut and tool edge radius on surface residual stress in the workpiece. And these influences are explained from the perspective of formation mechanism of residual stress in cutting. The conclusions have good applicability and can be used to guide the parameters selection in actual production.

关键词： residual stress     analytical model     strain     plastic     cutting parameter    

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Reduced kinetic mechanism of -heptane oxidation in modeling polycyclic aromatic hydrocarbon formation

ZHONG Beijing, XI Jun

《能源前沿（英文）》 2008年 第2卷 第3期   页码 326-332 doi: 10.1007/s11708-008-0047-9

摘要： A reduced mechanism, which could couple with the multidimensional computational fluid dynamics code for quantitative description of a reacting flow, was developed for chemical kinetic modeling of polycyclic aromatic hydrocarbon formation in an opposed-flow diffusion flame. The complete kinetic mechanism, which comprises 572 reactions and 108 species, was reduced to a simplified mechanism that includes only 83 reactions and 56 species through sensitivity analysis. The results computed via this reduced mechanism are nearly indistinguishable from those via the detailed mechanism, which demonstrate that the model based on this reduced mechanism can properly describe -heptane oxidation chemistry and quantitatively predict polycyclic aromatic hydrocarbon (such as benzene, naphthalene, phenanthrene and pyrene) formation in opposed-flow diffusion flames.

关键词： phenanthrene     multidimensional computational     sensitivity analysis     polycyclic     mechanism    

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Influence of construction-induced damage on the degradation of freeze–thawed lightweight cellular concrete

《结构与土木工程前沿（英文）》 2021年 第15卷 第3期   页码 781-792 doi: 10.1007/s11709-021-0733-9

摘要： During the construction of lightweight cellular concrete (LCC), material damage frequently occurs, causing the degradation and deterioration of the mechanical performance, durability, and subgrade quality of LCC. The construction-induced damage can be more significant than those from the service environment of LCC, such as freeze–thaw (F–T) action in cold regions. However, the effect of construction-induced damage on LCC during F–T cycles is often ignored and the deterioration mechanisms are not yet clarified. In this study, we investigated the factors causing damage during construction using a sample preparation method established to simulate the damage in the laboratory setting. We conducted F–T cycle tests and microstructural characterization to study the effect of microstructural damage on the overall strength of LCC with different water contents under F–T actions. We established the relationship between the pore-area ratio and F–T cycle times, pore-area ratio, and strength, as well as the F–T cycle times and strength under different damage forms. The damage evolution is provided with the rationality of the damage equation, verified by comparing the measured and predicted damage variables. This study would serve as a guide for the construction and performance of LCC in cold regions.

关键词： lightweight cellular concrete     construction-induced damage     freeze-thaw action     microstructure     degradation mechanism    

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Impact and inhibitory mechanism of phenolic compounds on the formation of toxic Maillard reaction products

Jing TENG, Xiaoqian HU, Ningping TAO, Mingfu WANG

《农业科学与工程前沿（英文）》 2018年 第5卷 第3期   页码 321-329 doi: 10.15302/J-FASE-2017182

摘要：

As one of the dominant reactions occurring during thermal treatment of food, the Maillard reaction not only leads to the formation of aroma, browning color and taste compounds, but also contributes to the formation of some unpleasant toxic substances including acrylamide, heterocyclic amines and advanced glycation end products. Polyphenols, one of the most abundant antioxidants in the human diet, are contained in different kinds of foods. In this review, some recent studies on the impact of dietary polyphenols on the formation of acrylamide, heterocyclic amines and advanced glycation end products formed during the Maillard reaction are summarized, including the research work conducted with both chemical model systems and real food model systems; the possible inhibitory mechanisms of different polyphenols are also summarized and discussed in this review. Basically we found that some dietary polyphenols not only scavenge free radicals, but also react with reactive carbonyl species, thus lowering the formation of toxic Maillard reaction products. This review provides a useful theoretical foundation for the application of polyphenols in food safety, and suggests some directions for further study of natural products as inhibitors against the formation of toxic substances in thermally processed food.

关键词： advanced glycation end products     acrylamide     food safety     heterocyclic amine     Maillard reaction     polyphenols    

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锌液冷却管损坏机理的研究

袁望姣,何将三

《中国工程科学》 2005年 第7卷 第9期   页码 56-60

摘要：

炼锌工业中广泛使用由无缝钢管冷弯而成的冷却管来实现锌液的冷却。冷却管的使用寿命非常短，消耗量相当大。锌液的表面张力小，渗透性强，腐蚀性强，能与冷却管中的铁元素生成铁-锌合金，能溶解冷却管中碳、硅等元素，锌液对冷却管的强腐蚀性，是影响锌液冷却管使用寿命的决定性因素；锌液冷却管的损坏是高温腐蚀和应力腐蚀共同作用的结果，热应力和残余应力促使其损坏由高温腐蚀向应力腐蚀发展；冷却管损坏位置由热应力和残余应力共同决定，其中热应力起主导作用。

关键词： 锌液     冷却管     损坏机理     高温腐蚀     应力腐蚀    

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Damage mechanism and evaluation model of compressor impeller remanufacturing blanks: A review

Haiyang LU, Yanle LI, Fangyi LI, Xingyi ZHANG, Chuanwei ZHANG, Jiyu DU, Zhen LI, Xueju RAN, Jianfeng LI, Weiqiang WANG

《机械工程前沿（英文）》 2019年 第14卷 第4期   页码 402-411 doi: 10.1007/s11465-019-0548-8

摘要： The theoretical and technological achievements in the damage mechanism and evaluation model obtained through the national basic research program “Key Fundamental Scientific Problems on Mechanical Equipment Remanufacturing” are reviewed in this work. Large centrifugal compressor impeller blanks were used as the study object. The materials of the blanks were FV520B and KMN. The mechanism and evaluation model of ultra-high cycle fatigue, erosion wear, and corrosion damage were studied via theoretical calculation, finite element simulation, and experimentation. For ultra-high cycle fatigue damage, the characteristics of ultra-high cycle fatigue of the impeller material were clarified, and prediction models of ultra-high cycle fatigue strength were established. A residual life evaluation technique based on the “ - - ” (where was the nonlinear parameter, was the Vickers hardness, and was the fatigue life) double criterion method was proposed. For erosion wear, the flow field of gas-solid two-phase flow inside the impeller was simulated, and the erosion wear law was clarified. Two models for erosion rate and erosion depth calculation were established. For corrosion damage, the electrochemical and stress corrosion behaviors of the impeller material and welded joints in H S/CO environment were investigated. (critical stress intensity factor) and d /d (crack growth rate, where is the total crack length and is time) varied with H S concentration and temperature, and their variation laws were revealed. Through this research, the key scientific problems of the damage behavior and mechanism of remanufacturing objects in the multi-strength field and cross-scale were solved. The findings provide theoretical and evaluation model support for the analysis and evaluation of large centrifugal compressor impellers before remanufacturing.

关键词： remanufacturing     centrifugal compressor impeller     remanufacturing blank     damage mechanism     evaluation model    

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重大建设工程技术创新网络形成机理与运行机制分析

王孟钧,张镇森

《中国工程科学》 2011年 第13卷 第8期   页码 62-66

摘要：

笔者从重大建设工程技术创新的特点和现状分析入手，剖析制约重大建设工程技术创新的核心障碍，建立面向重大建设工程技术创新网络的基本架构，分析其形成起点、演化路径和整合方式，探讨技术创新网络的动力机制、协同机制和学习机制，为建立跨组织协同的新型技术创新模式，提高重大建设工程技术创新效率和水平提供理论依据。

关键词： 重大建设工程     技术创新网络     形成机理     运行机制    

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Mechanism insight into the formation of HS from thiophene pyrolysis: A theoretical study

《环境科学与工程前沿（英文）》 2021年 第15卷 第6期 doi: 10.1007/s11783-021-1404-8

摘要：

• Possible formation pathways of H2S were revealed in thiophene pyrolysis.

关键词： Density functional theory     Waste rubber     Thiophene     H2S     Pyrolysis    

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Atomistic understanding of interfacial processing mechanism of silicon in water environment: A ReaxFF

《机械工程前沿（英文）》 2021年 第16卷 第3期   页码 570-579 doi: 10.1007/s11465-021-0642-6

摘要： The interfacial wear between silicon and amorphous silica in water environment is critical in numerous applications. However, the understanding regarding the micro dynamic process is still unclear due to the limitations of apparatus. Herein, reactive force field simulations are utilized to study the interfacial process between silicon and amorphous silica in water environment, exploring the removal and damage mechanism caused by pressure, velocity, and humidity. Moreover, the reasons for high removal rate under high pressure and high velocity are elucidated from an atomic perspective. Simulation results show that the substrate is highly passivated under high humidity, and the passivation layer could alleviate the contact between the abrasive and the substrate, thus reducing the damage and wear. In addition to more Si-O-Si bridge bonds formed between the abrasive and the substrate, new removal pathways such as multibridge bonds and chain removal appear under high pressure, which cause higher removal rate and severer damage. At a higher velocity, the abrasive can induce extended tribochemical reactions and form more interfacial Si-O-Si bridge bonds, hence increasing removal rate. These results reveal the internal cause of the discrepancy in damage and removal rate under different conditions from an atomic level.

关键词： silicon     ReaxFF     molecular dynamics     friction     damage    

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Hierarchical ZSM-5 zeolite with radial mesopores: Preparation, formation mechanism and application for

Darui Wang, Hongmin Sun, Wei Liu, Zhenhao Shen, Weimin Yang

《化学科学与工程前沿（英文）》 2020年 第14卷 第2期   页码 248-257 doi: 10.1007/s11705-019-1853-9

摘要： Hierarchical ZSM-5 zeolite with radial mesopores is controllably synthesized using piperidine in a NaOH solution. The piperidine molecules enter the zeolite micropores and protect the zeolite framework from extensive desilication. The areas containing fewer aluminum atoms contain fewer piperidine protectant molecules and so they dissolve first. Small amounts of mesopores are then gradually generated in areas with more aluminum atoms and more piperidine protectant. In this manner, radial mesopores are formed in the ZSM-5 zeolite with a maximal preservation of the micropores and active sites. The optimal hierarchical ZSM-5 zeolite, prepared with a molar ratio of piperidine to zeolite of 0.03, had a mesopore surface area of 136 m ·g and a solid yield of 80%. The incorporation of the radial mesopores results in micropores that are interconnected which shortened the average diffusion path length. Compared to the parent zeolite, the hierarchical ZSM-5 zeolite possesses more accessible acid sites and has a higher catalytic activity and a longer lifetime for the alkylation of benzene.

关键词： hierarchical ZSM-5 zeolite     protective desilication     piperidine     radial mesopores     benzene alkylation    

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Mechanism of hepatocellular damage in rat caused by low serum selenium

LU Yi, QU Bo, LIU Chang, YU Liang, Liu Xuemin, WANG Haohua, JIANG An, ZHANG Xiaogang

《医学前沿（英文）》 2008年 第2卷 第3期   页码 255-258 doi: 10.1007/s11684-008-0048-4

摘要： The aim of this paper is to investigate the mechanism of hepatocellular damage in rats caused by low serum selenium. Thirty six rats were randomly divided into 2 groups: group A (fed with low-selenium diet from the Keshan Disease area with the content of selenium being 0.017 mg/kg); group B [fed with selenium-supplemented diet and 0.3 mg/L selenium (NaSeO) was added to the drinking water]. Both were respectively fed for 12 weeks. At the end of the 12 week, the levels of serum selenium, glutathione peroxidase (GPX) and malondialdehyde (MDA) in hepatic tissue were measured; the hepatocellular ultrastructure and apoptosis were observed as well. The levels of serum selenium and GPX in group A were markedly lower than those in group B. MDA level in group A was significantly higher than that in group B. Under the electron microscope (EM), the mitochondria were remarkably changed in group A. The rate of liver cell apoptosis appeared much higher in group A as well. It indicated that the damage caused by selenium deficiency was through the process of oxidation. Selenium deficiency led to apoptosis of hepatocytes where oxidative damage to mitochondria might be the cause.

关键词： process     glutathione peroxidase     hepatocellular damage     group     Keshan Disease    

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Review of the damage mechanism in wind turbine gearbox bearings under rolling contact fatigue

Yun-Shuai SU, Shu-Rong YU, Shu-Xin LI, Yan-Ni HE

《机械工程前沿（英文）》 2019年 第14卷 第4期   页码 434-441 doi: 10.1007/s11465-018-0474-1

摘要： Wind turbine gearbox bearings fail with the service life is much shorter than the designed life. Gearbox bearings are subjected to rolling contact fatigue (RCF) and they are observed to fail due to axial cracking, surface flaking, and the formation of white etching areas (WEAs). The current study reviewed these three typical failure modes. The underlying dominant mechanisms were discussed with emphasis on the formation mechanism of WEAs. Although numerous studies have been carried out, the formation of WEAs remains unclear. The prevailing mechanism of the rubbing of crack faces that generates WEAs was questioned by the authors. WEAs were compared with adiabatic shear bands (ASBs) generated in the high strain rate deformation in terms of microstructural compositions, grain refinement, and formation mechanism. Results indicate that a number of similarities exist between them. However, substantial evidence is required to verify whether or not WEAs and ASBs are the same matters.

关键词： rolling contact fatigue (RCF)     white etching area (WEA)     white etching crack (WEC)     adiabatic shear band (ASB)    

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标题 作者 时间 类型 操作

Subsurface damage pattern and formation mechanism of monocrystalline -GaO in grinding process

期刊论文

Fiber-reinforced composites in milling and grinding: machining bottlenecks and advanced strategies

期刊论文

Formation mechanism and modeling of surface waviness in incremental sheet forming

期刊论文

The formation mechanism and the influence factor of residual stress in machining

null

期刊论文

Reduced kinetic mechanism of -heptane oxidation in modeling polycyclic aromatic hydrocarbon formation

ZHONG Beijing, XI Jun

期刊论文

Influence of construction-induced damage on the degradation of freeze–thawed lightweight cellular concrete

期刊论文

Impact and inhibitory mechanism of phenolic compounds on the formation of toxic Maillard reaction products

Jing TENG, Xiaoqian HU, Ningping TAO, Mingfu WANG

期刊论文

锌液冷却管损坏机理的研究

袁望姣,何将三

期刊论文

Damage mechanism and evaluation model of compressor impeller remanufacturing blanks: A review

Haiyang LU, Yanle LI, Fangyi LI, Xingyi ZHANG, Chuanwei ZHANG, Jiyu DU, Zhen LI, Xueju RAN, Jianfeng LI, Weiqiang WANG

期刊论文

重大建设工程技术创新网络形成机理与运行机制分析

王孟钧,张镇森

期刊论文

Mechanism insight into the formation of HS from thiophene pyrolysis: A theoretical study

期刊论文

Atomistic understanding of interfacial processing mechanism of silicon in water environment: A ReaxFF

期刊论文

Hierarchical ZSM-5 zeolite with radial mesopores: Preparation, formation mechanism and application for

Darui Wang, Hongmin Sun, Wei Liu, Zhenhao Shen, Weimin Yang

期刊论文

Mechanism of hepatocellular damage in rat caused by low serum selenium

LU Yi, QU Bo, LIU Chang, YU Liang, Liu Xuemin, WANG Haohua, JIANG An, ZHANG Xiaogang

期刊论文

Review of the damage mechanism in wind turbine gearbox bearings under rolling contact fatigue

Yun-Shuai SU, Shu-Rong YU, Shu-Xin LI, Yan-Ni HE

期刊论文