检索结果-南通市图书馆

Friction 2024年第6期12卷 1119-1132页

作者： Song YUAN Xiaoguang GUO Hao WANG renke kang Shang GAO State Key Laboratory of High-performance Precision Manufacturing Dalian University of TechnologyDalian 116024China

The roughness of the contact surface exerts a vital role in rubbing.It is still a significant challenge to understand the microscopic contact of the rough surface at the atomic level.Herein,the rough surface with a special root mean square(RMS)value is constructed by multivariate Weierstrass–Mandelbrot(W–M)function and the rubbing process during that the chemical mechanical polishing(CMP)process of diamond is mimicked utilizing the reactive force field molecular dynamics(ReaxFF MD)simulation.It is found that the contact area A/A0 is positively related with the load,and the friction force F depends on the number of interfacial bridge bonds.Increasing the surface roughness will increase the friction force and friction coefficient.The model with low roughness and high lubrication has less friction force,and the presence of polishing liquid molecules can decrease the friction force and friction coefficient.The RMS value and the degree of damage show a functional relationship with the applied load and lubrication,i.e.,the RMS value decreases more under larger load and higher lubrication,and the diamond substrate occurs severer damage under larger load and lower lubrication.This work will generate fresh insight into the understanding of the microscopic contact of the rough surface at the atomic level.

关键词： diamond random roughness reactive force field molecular dynamics(ReaxFF MD) friction Weierstrass-Mandelbrot(W-M)function chemical mechanical polishing(CMP)

Laser-assisted grinding of RB-SiC composites:Laser ablation behavior and mechanism

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第1期37卷 362-376页

作者： Zhigang DONG Wenchao SUN Xintong CAI Feng YANG Yan BAO renke kang Dongjiang WU Guangyi MA Fangyong NIU Key Laboratory for Precision and Non-traditional Machining Technology of the Ministry of Education School of Mechanical EngineeringDalian University of TechnologyDalian 116024China

Laser ablation is an important process during Laser-Assisted Grinding(LAG)of hard and brittle materials.To realize controllable material removal during laser ablation of RB-SiC composites,ablation experiments under different Laser Energy Density(LAED)and LAG experiments are conducted.Evolution rules and mechanism of physical phase,ablation morphology and crack characteristics caused by laser irradiation are investigated.The forces of LAG and Conventional Grinding(CG)are compared.The results show that ablation surface changes from slight oxidation to obvious material removal with LAED increasing,and ablation depth increases gradually.The ablation products change from submicron SiO_(2)particles to nanoscale particles and floccule.High LAED promotes SiC decomposition and sublimation,which leads to the increase of C element.The SiC phase forms corrugated shape in recast layer and columnar shape in Heat Affected Zone(HAZ)at 56 J/mm^(2).The cold and heat cycle leads to formation of fishbone crack.For ablation specimen under 30 J/mm^(2),the grinding force can be reduced by a maximum of 39%and brittle damage region is reduced.The material removal and microcrack generated will significantly reduce the hardness and improve machinability,which can promote grinding efficiency.

关键词： RB-SiC Laser Ceramic Composites Grinding

Elliptical vibration cutting of large-size thin-walled curved surface parts of pure iron by using diamond tool with active cutting edge shift

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2023年第6期36卷 402-419页

作者： Zhenhua JIAO renke kang Dongxing DU Jiang GUO Key Laboratory for Precision and Non-traditional Machining of Ministry of Education Dalian University of TechnologyDalian 116024China Institute of Mechanical Manufacturing Technology China Academy of Engineering PhysicsMianyang 621999China

Large-size thin-walled curved surface parts of pure iron are crucial in aerospace,national defense,energy and precision physical experiments.However,the high machining accuracy and surface quality are difficult to achieve due to the serious tool wear and deformation when machining the parts with conventional cutting tools.In this paper,an elliptical vibration cutting(EVC)with active cutting edge shift(ACES)based on a long arbor vibration device is proposed for ultraprecision machining the pure iron parts by using diamond tool.Compared with cutting at a fixed cutting edge,the influence of ACES on the EVC was analyzed.Experiments in EVC of pure iron with ACES were conducted.The evolutions of the surface roughness,surface topography,and chip morphology with tool wear in EVC with ACES are revealed.The reasonable parameters of ultraprecision machining the pure iron parts by EVC with ACES were determined.It shows that the ACES has a slight influence on the machined surface roughness and surface topography.The diamond tool life can be significantly prolonged in EVC of pure iron with ACES than that with a fixed cutting edge,so that high profile accuracy and surface quality could be obtained even at higher nominal cutting speed.A typical thin-walled curved surface pure iron part with diameter φ240 mm,height 122 mm,and wall thickness 2 mm was fabricated by the presented method,and its profile error and surface roughness achieved PV 2.2μm and Ra less than 50 nm,respectively.

关键词： Curved surface Diamond tool Elliptical vibration cutting Pure iron Thin-walled parts

The appearance of cytoplasmic cytochrome C precedes apoptosis during Drosophila salivary gland degradation

在线全文

学校读者我要写书评

暂无评论

Insect Science 2024年第1期31卷 157-172页

作者： Shihui Long Wenxin Cao Yongyu Qiu Ruohan Deng Jiali Liu Lidan Zhang renke Dong Fengxin Liu Sheng Li Haigang Zhao Na Li kang Li Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology Institute of Insect Science and TechnologySchool of Life SciencesSouth China Normal UniversityGuangzhouChina Guangdong Laboratory for Lingnan Modern Agriculture South China Agricultural UniversityGuangzhouChina Guangmeiyuan R&D Center Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied TechnologySouth China Normal UniversityMeizhouGuangdong ProvinceChina School of Food Science and Engineering South China University of TechnologyGuangzhouChina ChemPartner PharmaTech Co. LtdJiangmenGuangdong ProvinceChina

Apoptosis is an important process for organism development that functions to eliminate cell damage,maintain homeostasis,and remove obsolete tissues during morphogenesis.In mammals,apoptosis is accompanied by the release of cytochrome C(Cyt-c)from mitochondria to the cytoplasm.However,whether this process is conserved in the fruit fly,Drosophila melanogaster,remains controversial.In this study,we discovered that during the degradation of Drosophila salivary gland,the transcription of mitochondria apoptosis factors(MAPFs),Cyt-c,and death-associated APAF1-related killer(Dark)encoding genes are all upregulated antecedent to initiator and effector caspases encoding genes.The proteins Cyt-c and the active caspase 3 appear gradually in the cytoplasm during salivary gland degradation.Meanwhile,the Cyt-c protein colocates with mito-GFP,the marker indicating cytoplasmic mitochondria,and the change in mitochondrial membrane potential coincides with the appearance of Cyt-c in the cytoplasm.Moreover,impeding or promoting 20E-induced transcription factor E93 suppresses or enhances the staining of Cyt-c and the active caspase 3 in the cytoplasm of salivary gland,and accordingly decreases or increases the mitochondrial membrane potential,respectively.Our research provides evidence that cytoplasmic Cyt-c appears before apoptosis during Drosophila salivary gland degradation,shedding light on partial conserved mechanism in apoptosis between insects and mammals.

关键词： active caspase 3 apoptosis Cyt-c Drosophila salivary gland

Recent progress in flexible supporting technology for aerospace thin-walled parts:A review

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2022年第3期35卷 10-26页

作者： Yan BAO Bin WANG Zengxu HE renke kang Jiang GUO Key Laboratory for Precision and Non-traditional Machining Technology of Ministry of Education Dalian University of TechnologyDaliann 116024China

Thin-walled parts are widely used in the aerospace industry owing to their light weight and high specific strength.However,due to the low rigidity of thin-walled parts,elastic deformation and chatter easily occur,which seriously affect the machining accuracy and workpiece surface quality.To solve this problem,several supporting technologies have been reported in recent years.This paper reviews the recent research progress of flexible supporting technologies in the aerospace field by classifying them based on different principles and characteristics.The principle,progress,advantages,and limitations of the technologies are expounded by systematic comparison and summarized.Finally,the challenges and future development trends of flexible supporting technology,which will provide guidelines for further research,are discussed.

关键词： Aerospace Chatter Deformation Flexible support Low rigidity Thin-walled

Comparison of surface integrity for dry and wet drilling of 49Fe-49Co-2V alloy

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2022年第6期35卷 325-338页

作者： Yuan ZHANG Zhigang DONG Yan BAO renke kang Xin HUANG Dongming GUO Key Laboratory for Precision and Non-traditional Machining Technology of the Ministry of Education School of Mechanical EngineeringDalian University of TechnologyDalian 116024China AVIC Xi’an Flight Automatic Control Research Institute Xi’an 710076China

Working performances of the components made out of 49Fe-49Co-2V alloy are closely related to the surface integrity of the drilled holes,which are influenced remarkably by the cooling conditions.The present study focuses on the surface integrity differences between wet and dry drilled 49Fe-49Co-2V alloy holes.The drilled hole surface roughness and topographies,metallurgical and mechanical properties,and the exit characterizations were obtained using optical microscopy(OM),scanning electron microscopy(SEM),electron backscatter diffraction microscopy(EBSD),transmission electron microscopy(TEM),energy dispersive spectroscopy(EDS)and Vickers hardness techniques,etc.The effects of cooling conditions on the surface integrity were concluded and the influence mechanisms were analyzed based on the force and temperature differences in drilling process with different cooling conditions.It is found that the surface roughness and the thickness of refined-grain region of the dry drilled holes are larger than those of wet drilled holes;work hardening induced by wet drilling is more serious than dry drilling;chippings occurred in the exits of the wet drilled holes due to the material brittleness,which could be avoided by dry drilling.The surface integrity differences of wet and dry drilled holes are closely related to the force and temperature differences in drilling process with different cooling conditions.

关键词： 49Fe-49Co-2V alloy Cooling condition Drilling Exit chipping Microstructure Surface integrity Surface quality Work hardening

Subsurface damage pattern and formation mechanism of monocrystalline β-Ga_(2)O_(3) in grinding process

在线全文

学校读者我要写书评

暂无评论

Frontiers of Mechanical Engineering 2022年第2期17卷 117-127页

作者： Xin YANG renke kang Shang GAO Zihe WU Xianglong ZHU Key Laboratory for Precision and Non-Traditional Machining Technology of Ministry of Education Dalian University of TechnologyDalian 116024China

Monocrystalline beta-phase gallium oxide (β-Ga_(2)O_(3)) 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-Ga_(2)O_(3)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-Ga_(2)O_(3). The results in this work are supposed to provide guidance for the damage control of monocrystalline β-Ga_(2)O_(3)grinding process.

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

Design of ultrasonic elliptical vibration cutting system for tungsten heavy alloy

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Mechanical Engineering 2022年第4期17卷 163-180页

作者： Sen YIN Yan BAO Yanan PAN Zhigang DONG Zhuji JIN renke kang Key Laboratory for Precision and Non-traditional Machining Technology of the Ministry of Education School of Mechanical EngineeringDalian University of TechnologyDalian 116024China

Nanoscale surface roughness of tungsten heavy alloy components is required in the nuclear industry and precision instruments.In this study,a high-performance ultrasonic elliptical vibration cutting(UEVC)system is developed to solve the precision machining problem of tungsten heavy alloy.A new design method of stepped bending vibration horn based on Timoshenko’s theory is first proposed,and its design process is greatly simplified.The arrangement and working principle of piezoelectric transducers on the ultrasonic vibrator using the fifth resonant mode of bending are analyzed to realize the dual-bending vibration modes.A cutting tool is installed at the end of the ultrasonic vibration unit to output the ultrasonic elliptical vibration locus,which is verified by finite element method.The vibration unit can display different three-degree-of-freedom(3-DOF)UEVC characteristics by adjusting the corresponding position of the unit and workpiece.A dual-channel ultrasonic power supply is developed to excite the ultrasonic vibration unit,which makes the UEVC system present the resonant frequency of 41 kHz and the maximum amplitude of 14.2μm.Different microtopography and surface roughness are obtained by the cutting experiments of tungsten heavy alloy hemispherical workpiece with the UEVC system,which validates the proposed design’s technical capability and provides optimization basis for further improving the machining quality of the curved surface components of tungsten heavy alloy.

关键词： tungsten heavy alloy ultrasonic elliptical vibration cutting Timoshenko’s theory resonant mode of bending finite element method

Stress-Induced Deformation of Thin Copper Substrate in Double-Sided Lapping

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2023年第1期36卷 80-89页

作者： Jiang Guo Zengxu He Bo Pan Bin Wang Qian Bai Jinxing Kong renke kang State Key Laboratory of High-Performance Precision Manufacturing Department of Mechanical EngineeringDalian University of TechnologyDalian116024China Institute of Mechanical Manufacturing Technology China Academy of Engineering PhysicsMianyang621999China

Double-sided lapping is an precision machining method capable of obtaining high-precision surface.However,during the lapping process of thin pure copper substrate,the workpiece will be warped due to the influence of residual stress,including the machining stress and initial residual stress,which will deteriorate the flatness of the workpiece and ultimately affect the performance of components.In this study,finite element method(FEM)was adopted to study the effect of residual stress-related on the deformation of pure copper substrate during double-sided lapping.Considering the initial residual stress of the workpiece,the stress caused by the lapping and their distribution characteristics,a prediction model was proposed for simulating workpiece machining deformation in lapping process by measuring the material removal rate of the upper and lower surfaces of the workpiece under the corresponding parameters.The results showed that the primary cause of the warping deformation of the workpiece in the doublesided lapping is the redistribution of initial residual stress caused by uneven material removal on the both surfaces.The finite element simulation results were in good agreement with the experimental results.

关键词： Machining deformation Double-sided lapping Residual stress Finite element simulation

Recent progress of residual stress measurement methods: A review

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2021年第2期34卷 54-78页

作者： Jiang GUO Haiyang FU Bo PAN renke kang Key Laboratory for Precision and Non-traditional Machining of Ministry of Education Dalian University of TechnologyDalian 116024China

Residual stress is one of the main factors affecting the mechanical properties of materials, such as their strength, plasticity and surface integrity. For instance, tensile stress conditions can adversely affect material performance or component life, while compressive stress conditions can improve material fatigue strength. During the processing of integrated aviation structures, machining deformation caused by residual stress has become one of the most prominent manufacturing problems. Therefore, it is very important to measure and evaluate the stress for real applications.This paper reviews the research of residual stress measurement methods over the past five years by classifying them according to the measurement methods appearing in each stage. The existing problems and difficulties of each measurement technology are summarized, and future trends are forecasted. This paper provides a reference for further in-depth study of residual stress measurement technologies.

关键词： Destructive testing Future trends Measurement Nondestructive testing Residual stress