International Journal of Nanomanufacturing (32 papers in press)
Optical and electrical properties of Nd-doped ZnO films prepared by sol-gel method
by H.-Y. He, Z. He
Abstract: ZnO films doped with Nd contents of 00.81 at.% were deposited by a chemical solution deposition and characterized by X-ray diffraction, field emission scanning electron microscopy, UV-vis and luminescent spectrophotometry and electrical measurement. The experiments revealed that the films have nanoscale particle size that increased with increasing Nd content. The Nd doping resulted in the obvious variations of transmittance in the UV-visible light range, the band gap and resistivity. Thin film showed an optimal optical and electrical properties at Nd content of 0.42 at.%. The films also showed a strong band gap emission and a very weak emission related to intrinsic defect.
Keywords: ZnO; Nd-doping; sol-gel deposition; transmittance; band gap; luminescence; electrical resistivity.
Study on the analysis of the mechanism of EDM based on Su-Field
by Suchang Ma, Zhanhui Wang, Lingyu Lin
Abstract: EDM is an important means of processing in mold processing industry. In this paper, the Su-Field Analysis Method is applied to study the mechanism of EDM, the application process of Su-Field analysis method to solve the problem of EDM discharge system was established, the microscopic process of EDM dielectric breakdown was described, the Su-Field model of the single pulse discharge four phases, discharge channel formation, breakdown discharge, galvanic corrosion throwing and the deionization between the medium, was established, and finally the complete Su-Field model of single pulse discharge process of EDM was got. In the single-pulse discharge established Su-Field model basis, the factors affecting the processing speed, surface roughness and electrode wear were analyzed, further integration of 76 standard solutions, the plan to solve the problem of instability in the discharge process was got, at the same time, a new way for the research of EDM process was provided.
Keywords: Keywords: TRIZ; Su-Field Analysis; 76 Standard Solutions; EDM mechanism; Discharge system.
A study on the prediction of tool wear in drilling the carbon fiber reinforced plastic
by Shin Hyung-Gon, Kim Sun Bum, Oh Je Ha, Yoo Seung Hyeon
Abstract: Carbon Fiber Reinforced Plastics has a lot of merits such as mechanical characteristic, light weight, and thermal resistance. For using Carbon Fiber Reinforced Plastics, the cutting and drilling process is necessary, and the study of optimal cutting conditions is very necessary, too.
Generally, CFRP needs the processes of lathe turning, drilling, milling, and cutting after molding. However, these processes cause such problems as sudden abrasion of the tools, heavy surface roughness and defective layer by crack and delamination. Therefore, the study to examine the conditions for the high precision products by minimizing these problems is very important.
In this study, a sample was made with a CFRP plate to take a drilling test under a set condition with a high speed steel drill. This dissertation is a study on the optimal drilling conditions of CFRP with various drilling condition. The drilling of these various specimens with different machining condition is performed.
Keywords: : Carbon Fiber Reinforced Plastics (CFRP); Cutting Force; Tool wear; prepreg.
A study on the Displacement Analysis in the Injection Molding for the Camera-phone
by JOOSANG LEE
Abstract: Smartphones are currently the most popular electronic devices with high volume production activities driven by high demand and requirements for rapid turnaround time. The changes of displacement were analyzed according to a variable of the gate size and runner system. The radial type and gate with large size were shown that better results in displacement. While the design and production of lenses, the key component of a camera, still need to be improved, the current technology has run into its limit with regard to trends in size and weight reduction. In this study, an injection molding analysis was performed on plastic lenses that are widely employed for smartphone cameras. Specifically, the displacement of lenses at the time of injection molding was studied by varying the gate size and runner system.
Keywords: plastic aspheric lens; runner system; gate size; displacement analysis.
AFM Based Imaging Conditions Optimization of Cell Topography
by Ya Li
Abstract: Surface topography of cancer cell is particularly vital since cell frequently changes its shape as interacting with neighbouring cells and extracellular matrix. Atomic force microscope (AFM) has an extraordinary superiority in surface scanning of cells but the scanning consequence depends upon experiment conditions or experience primarily. In our study, a quadratic regression orthogonal rotation combination design was operated to acquire optimal parameters for cell profiling via AFM. By iterative calculation, the optimum AFM scanning of cell can be accomplished at setpoint of 0.61 V, scanning rate of 2.23 Hz and proportional gain of 3.85. Satisfactory surface morphology images of human bronchial epithelium BEAS-2B and pulmonary adenocarcinoma cell A549 were acquired at this calculated scanning condition, in which the details of surface coarse particle and cell junction structure are visible. This emerging insight into cell profiling may encourage the understanding of the underlying mechanism for cellular inner reconstruction during cell migration.
Keywords: Atomic force microscopy; quadratic regression orthogonal rotation design; scanning parameter; cell imaging.
Influence of Clearance Angle on Micro/nano Structure Fabrication in Elliptical Vibration Cutting of Hardened Steel
by Jianguo Zhang, Norikazu Suzuki, Yilong Wang, Eiji Shamoto
Abstract: Surfaces textured by sophisticated micro/nano structures can provide advanced and useful functions and features as compared with simply smooth surfaces. To promote widespread use of the structured surfaces, manufacturing technology of structured surfaces for ultra-precision dies and molds made of hardened steel, is absolutely essential. Conventional diamond cutting is not applicable to machining of steel due to rapid tool wear and surface deterioration. On the other hand, elliptical vibration cutting (EVC) equipped with the ultra-precision amplitude control sculpturing method is considered as a potential candidate for the functional surface fabrication on steel materials. In this method, tool geometry, especially the clearance angle, imposes a limit on the machinable part geometry due to the flank face contact to the target shape in the downhill machining. In order to clarify the influence of flank face contact on the machining accuracy and the tool wear, a series of theoretical and experimental investigations are conducted in this paper. A surface with micro sine-sweep profile is fabricated on hardened steel by applying the proposed amplitude control sculpturing method. It verified that the interference between flank face and fabricated structure causes not only the serious machining accuracy deterioration but also the serious tool damage due to the enhancing of ploughing process.
Keywords: Elliptical vibration cutting; Hardened steel; Amplitude control sculpturing method; Clearance angle.
Study on algorithm of automatic alignment compensation of electron gun in a scanning electron microscope
by SEUNG-JAE KIM, DONG-YOUNG JANG
Abstract: Primary electrons are emitted from the cathode in a scanning electron microscope (SEM). The electron guns cathode diameter is ~60
Keywords: SEM; scanning electron microscope; electron beam; automatic alignment; electron gun alignment; beam imaging; tungsten filament; electron scanning.
Comprehensive Error Modeling and Error Compensation for Complex Optical Free-Form Surface Polishing Platform
by En Zhong Zhang, Ji Zhao, Shijun Ji, Gang Li
Abstract: Four-axis polishing platform plays an important role in machining a complex optical free-form surface and the kinematic error generally determine the accuracy of the optical free-form surface fabricated by this platform. This paper analyzes kinematics of the polishing platform based on the homogeneous coordinate transformation theory and the error of kinematics synthesis model is established. Based on minimum error assumption, transition matrix is obtained from machine tool coordinate system to the cutting tool coordinate system and changing rule of comprehensive error in different position and direction is gained in 2-axis motion worktable. Laser interferometer is used to measure the geometric error of polishing platform, it is found that different feed rate and measured spacing had no significant effect on the positioning error of moving axis and positioning error rather than the straightness and angle error has more significant influence on the accuracy of machine tool. Compensation experiment was conducted based on integrated error model, the x-axis and z-axis positioning error was reduced by 87.37% and 90.32% after compensation and the compensation result is remarkable.
Keywords: Four-axis polishing platform; Comprehensive error; Homogeneous coordinate transformation; Compensation.
A multiscale simulation investigation of dislocation behavior of PCD failure process
by Jinxuan Bai, Qingshun Bai
Abstract: Although polycrystalline diamond (PCD) is ever viewed as brittle materials, it can present strong dislocation activity in certain condition. In this paper, the two-dimensional discrete dislocation plastic (DDP) simulation under fully periodic boundary conditions was employed to study PCD dislocation behavior. Crystal dissipation and entropy theory were introduced into the computational study to reveal dislocation density evolution and disordered sequence during PCD failure process. Our result showed that the developed model can capture the essential features of PCD dislocation evolution behavior and realizes accurate description of PCD failure process. Investigations of plastic dissipation and dislocation structure evolution reveal that the dislocation structure evolution plays a key role in the fracture process.
Keywords: polycrystalline diamond (PCD); discrete dislocation plastic; crystal dissipation; entropy; failure.
Performance of PVDF/ TiO2 Nano-composite Film in the Application of Energy Harvester
by NingLi An
Abstract: The compression mode and shear mode for energy harvesting experimental platform was estabished. The energy collection efficiency of PVDF/ TiO2 nano-composite film in the two mode and nonlinear piezoelectric effect were analyzed. Experimental results show that the energy collection efficiency of the shear mode was higher than the compressed mode. The Piezoelectric constant and piezoelectric coupling coefficient have nonlinear changes under large stress. In this paper, the experimental data establish a relationship electromechanical coupling coefficients and parameters of composite thin film piezoelectric stress.
Keywords: Energy Harvester; Nano-composite Film; PVDF; TiO2.
Ultra-precision cutting of linear micro-groove array for distributed feedback laser devices
by Bing Guo, Xin Yu, Qingliang Zhao, Lei Xu
Abstract: The tunable range and beam linewidth of distributed feedback laser were determined by fabrication quality of the periodic linear micro-groove array on substrate, which grooves are high sloped and ranged sub-micron to few microns. Compared with the common micro-groove arrays (size from tens of microns to sub-millimeter), the ultra-precision cutting of these tiny and high-sloped linear micro-groove arrays is more difficult to realize. In this paper, a series of investigations was proposed for ultra-precision cutting of linear micro-groove array on polymethyl methacrylate (PMMA). Firstly, the different cutting processes included planing and fly-cutting were conducted. The workpiece morphology, surface quality and machining efficiency of these processes were investigated. Then, the fly cutting process were optimized by the calculation of non-free chip zone and the analysis of chip interference by cutting experiments. Finally, a novel tool positioning method based on acoustic emission was presented in order to realize high accuracy control of micro-groove arrays dimensions.
Keywords: Linear micro-groove array; Fly-cutting; Planing; Polymer; Chip flow; Tool positioning;.
Water Dissolution Ultra-precision Polishing of KDP Crystal and Its Precision Cleaning
by Yuchuan Chen, Hang Gao, Xu Wang, Xiaoji Teng
Abstract: KDP crystal is a kind of excellent electro-optic material used in many laser facilities, which is also widely acknowledged to be extremely hard to machine. In this work, we developed a process to finish KDP crystal to a precision and clean engineering specimen. A micro-nano water dissolution principle and its planarization mechanism in the machining process are illustrated, which turns the disadvantaged deliquescence property of KDP crystal into the driving force for ultra-precision polishing of the crystal. Micro emulsion fluid with nano water nuclei can precisely control the material removal and realize the selective polishing, thus forming a super smooth and precise surface. Then a subsequent cleaning process developed specially for this ultra-precision polishing method helps to get rid of the polishing fluid, and finally reduces the residue off the crystal to a clean and tidy surface with 1.964 nm rms roughness for engineering application.
Keywords: KDP crystal; water dissolution mechanism; ultra-precision polishing; precision cleaning; FTIR spectrum.
Modeling and Optimization of cutting parameters on surface roughness in micro-milling Inconel 718 using Response Surface Methodology and Genetic Algorithm
by Xiaohong Lu, Furui Wang, Xinxin Wang, Likun Si
Abstract: In recent years, micro-milling techniques have attracted great attention and interest from academia and industry. Inconel 718 is a nickel-based superalloy with good tensile, fatigue, creep and rupture strength and can find great application in nuclear and aerospace industry. In this paper, the response surface methodology (RSM) was applied to develop the model for predicting surface roughness in micro-milling Inconel 718. The magnitudes of cutting parameters affecting the surface roughness, which were depth of cut, spindle speed, and feed rate, were analyzed by the analysis of variance (ANOVA).The validity of the surface roughness prediction model was proved due to the tiny error between the measured values and the prediction results. Then, genetic algorithm (GA) was used to determine the optimal cutting parameters achieving minimum surface roughness in micro-milling Inconel 718 process. All experiments show that the optimized results agree well with the test ones.
Keywords: micro-milling; Inconel 718; surface roughness; response surface methodology; genetic algorithm.
Study on a non-contact polishing method using motion coupling confined etchant layer technique
by Yongzhi Cao, Yuchao Jia, Yongda Yan, Lianhuan Han, Xuesen Zhao, Zhenjiang Hu, Dongping Zhan
Abstract: The confined etchant layer technique (CELT) has been proved not only an effective electrochemical microstructures fabrication method, but also a potential polishing method due to its distance sensitiveness. To verify its polishing capability in motion mode and examine the influence of motion parameters on polishing efficiency and material removal rate, motion coupling confined etchant layer technique (MCCELT) polishing experiments were carried out on n-GaAs wafers by adopting central composite inscribe (CCI) design of response surface methodology. Furthermore, the interactions between motion, electrochemical reaction and substrate deformation were analyzed using multi-physics coupling finite element simulations. Statistical model shows that sample surface roughness decreases with the decreases of working distance (between the electrode and the substrate) and feeding velocity, and indicates it still has potential to reach more smooth results.
Keywords: Polishing; Multi-physics coupling; Electrochemical; GaAs; Response surface methodology.
Experimental investigation on the abrasive wear of AISI 52100 steel
by Zhixiang Chen, Weifeng Yao, Julong Yuan, Zhongdian Cheng, Wei Hang, Tianchen Zhao
Abstract: AISI 52100 steel has been widely used in various types of bearings in machinery equipment due to its excellent mechanical properties and high availability. In final manufacturing process of bearing parts, usually involve lapping and polishing methods on the ultra-precision machining in order to achieve high accuracy of profile and fine surface quality. The essence of this process is abrasive wear of AISI 52100 steel material. Therefore, in order to improve the super finishing process of bearings super finishing, the experiment of abrasive wear of AISI 52100 steel materials was carried out in this paper. The effects of different abrasive diameter and pressure on the material removal amount of AISI 52100 steel were investigated, the abrasive correction coefficient K in Preston formula was computed and obtained. The result shows that, reducing the abrasive diameter can increase the material removal rate and improve surface quality when other factors are maintained constant.
Keywords: AISI 52100 Steel; Abrasive Wear; Material Removal; Correction Coefficient.
A Study of Materials Effects on the Single Cutting in Ultra-precision Raster Milling
by Sujuan Wang, Sandy To, Chen Xin
Abstract: Ultra-precision raster milling (UPRM) rotates a single crystal diamond tool to discontinuously remove materials from the workpiece and can directly produce freeform surfaces with sub-micrometric form accuracy and nanometric surface finishing. This paper presents theoretical and experimental investigations on the workpiece material effect on single cutting profile in UPRM. Experiments are conducted to study the material effect on cutting profile by single cutting four materials including copper, aluminum alloy 6061, brass and aluminum bronze under the same cutting conditions in UPRM. A characterization method is presented in the paper to study the effect of different workpiece material on the cutting profiles in UPRM. The experimental results show that copper alloy makes the smallest effect on the single cutting profile because of the lowest elastic recovery ratio while the material effect of aluminum bronze is the highest due to the highest elastic recovery ratio and the highest hardness .
Keywords: Material elastic recovery. Single Cutting. Ultra-precision raster milling.
Experimental study and prediction on impact scratching of single abrasive for K9 glass
by Chen Li, Feihu Zhang, Xiaoshuang Rao, Bing Leng
Abstract: The orthogonal test L16(43) was designed, and the impact scratching experiment for K9 glass was carried out by using Vickers diamond indenter on the DMG ULTRASONIC 70-5 linear. The three dimensional morphology of the surface for glass was observed by scanning electron microscope(SEM), which was compared with that in the quasi static state. The strain rate of the grinding process was obtained by choosing the contact zone length as the impact contact length, which was the evaluation Index of impact. The relationships between strain rate and the depth of radial crack, strain rate and the depth of transverse crack, strain rate and normal scratching force were first analyzed. The results showed that the depth of radial of crack, the depth of transversal crack and the normal scratching force decreased with the increase of strain rate. The two layer BP neural network was established, which took the strain rate as input variables. The depth of radial crack, the depth of transversal crack and normal scratching force were predicted and the errors were within 10%, which indicated that the prediction results of BP neural network were reliable.
Keywords: impact scratching; K9 glass; strain rate; depth of crack; BP neural network.
Performance evaluation of coated cemented carbide inserts milling 508III steel
by Li Liu, Yaonan Cheng, Rui Guan, Ming Xu, Tong Wang
Abstract: A large amount of material is removed during the milling of a water chamber head manufactured of high-strength 508Ⅲ steel. The performance and service life of coated cemented carbide inserts have significant influences on processing efficiency and the quality of nuclear power components. This study will conduct single-factor milling experiments of water chamber heads relevant to practical working conditions. Influences of different milling parameters on the insert failure behavior are analyzed based on experimental results and simulation data. The failure mechanism of insert wear and fracture was also discussed. Finally, the influences of coating types and thickness values on the wear behavior of cemented carbide insert while cutting 508Ⅲ steel were investigated. The results of this research can be implemented in the improvement of coated cemented carbide inserts in regards to failure resistance and service life.
Keywords: water chamber head; 508Ⅲ steel; coating; cemented carbide; crater wear.
Non-linear phase error compensation for fringe deflectometry measuring system
by Lili Jiang, Xiaodong Zhang, Fengzhou Fang
Abstract: Fringe deflectometry technique (FDT) plays a more and more important role in specular surface measurement due to its large measurement range in surface slope. However its accuracy is heavily dependent on the quality of the extracted phase data. The gamma effect of Liquid crystal display (LCD) and CCD camera in FDT system introduces significant phase distortion, resulting in a periodical phase error and therefore measurement error. A mathematical model is established to illustrate phase error introduced by Gamma effect, and then an optimal algorithm based on four-time four-step phase-shifting (FFPS) method is proposed to retrieve phase from distorted fringes. Simulation results prove that FFPS phase retrieval method can compensate for the phase error caused by the nonlinearity of the LED and CCD point-by-point, thus it is immune not only to calibration error, but also to the non-unitary of the Gamma effect spatially and temporally. Experimental results are also presented to verify the performance of the proposed method.
Keywords: Fringe deflectometry; phase error compensation; freeform surface.
The Effects of Chemical Components in the Bath Solution on Mechanical Properties of the Electroplated Coating on Diamond Tools
by Qingqiu Chen, Zhongming Cui, Qingshan He, Jingjing Wang, Chuangju Feng
Abstract: The bath compositions are critical to mechanical performance of the coating layer for electroplated diamond tools. In this paper, the effects of different chemical components in bath solution on mechanical properties including tensile strength and hardness of the electroplated coating were investigated by orthogonal experiments. The influences of different chemical components including nickel sulfate, cobalt sulfate and sodium chloride on mechanical properties of the electroplated coating were analyzed. The results showed that the component of nickel sulfate was crucial for mechanical performance of the electroplated coating. Increasing the component of nickel sulfate caused an unstable situation on tensile strength and hardness of the electroplated coating. The maximum value was up to 651 MPa in tensile strength and 39 HRC in hardness when nickel sulfate was at 270 g/L and other components were unchanged. In contrast, it had no effect on tensile strength of the electroplated coating with the increase of the component of cobalt sulfate. However, hardness of the electroplated coating could be improved by increasing the component of cobalt sulfate. The concentration of sodium chloride had no obvious effect on mechanical properties of the electroplated coating layer. The experimental results revealed that the optimized bath compositions were at 270 g/L nickel sulfate, 20 g/L cobalt sulfate, and 10 g/L sodium chloride.
Keywords: bath compositions; electroplated diamond tools; electroplated coating; mechanical properties.
Research on Energy Consumption and Energy Efficiency of Machine Tools: A Comprehensive Survey
by Lorena Moreira, Weidong Li, Michael Fitzpatrick, Xin Lu
Abstract: The increasing demand for energy, coupled with concerns over pollution and climate change, has led governments to establish policy frameworks to reduce CO2 emissions. Moreover, rises in energy price and increasingly greener customer behaviour are pushing the manufacturing industries to develop more sustainable processes. As a major source of energy consumption in manufacturing systems, machine tools have been the focus of sustainability research communities worldwide. This paper provides a survey of manufacturing industrys sustainability trends and presents a technology-foresight-based methodology for gathering key information on the research development in this topic. Furthermore, a correlation between real world aspects, such as legal, economic and environmental, and the development of research on energy consumption and efficiency of machine tools is provided. The results highlight the leading countries, institutions, authors and subject areas in this field. Research & development shows a high correlation with governmental action, and appears to be of core importance to meet CO2 reduction targets.
Keywords: CNC machining; machine tools; energy; sustainable manufacturing; research foresight.
Axicon profile metrology using contact stylus method
by Huimin Gao, Xiaodong Zhang, Fengzhou Fang
Abstract: Axicon lenses, characterized by their cone shape, have rotational symmetry. The generatrix of axicons is the surface profile going across the apex of the axicon and the cone angle of the axicon can be calculated from the generatrix. Axicons, widely used in optical alignment and Bessel-Gauss beam generation, require high accuracy in surface and cone angle metrology. However, current methods focus on measuring the cone angle with a stylus profiler, a process in which misalignment and displacement are common when measuring the generatrix. A method is proposed that multiple parallel measurement paths near the apex of the axicon will obtain the generatrix with the specific algorithm. In experiments, the axicon with a cone angle of about 90
Keywords: Axicon; Alignment error; Displacement error; Profile metrology; Stylus measurement; Generatrix error.
Experimental research on pulse laser assisted micro turning of ZrO2 ceramic
by Xiuqing Hao, Hao Yan, Jinjin Han, Chenjiao Yao, Ning He
Abstract: ZrO2 ceramic materials have outstanding propertied, like high wear resistance, good corrosion resistance, low thermal conductivity, etc., and has been widely applied in modern industry. However, ZrO2 ceramic is one of the difficult-to-machine materials, which would lead to rapid tool wear and poor surface quality. Micro turning combined with pulse laser, as a new kind of process in machining ZrO2 ceramic, is studied in this paper. And a comparative research between micro turning with and without pulse laser assisted of ZrO2 ceramic has been conducted. The results revealed that under the same machining parameters, both the cutting force and machined surface roughness obtained in pulse laser assisted micro turning was smaller than that in micro turning without pulse laser, and the pulse laser could effectively reduce the tool wear. The work carried out in this paper would be helpful to the further research on the pulse laser assisted micro machining of ZrO2 ceramic.
Keywords: ZrO2 ceramic; pulse laser assisted machining; micro turning.
Simulation of microstructure evolution coupled with fabrication parameters for two-phase ceramic tool materials
by Bin Fang, Chonghai Xu, Guangchun Xiao
Abstract: A computer simulation coupled with fabrication parameters for the sintering process of two-phase ceramic tool materials has been developed using a two-dimensional hexagon lattice model mapped from the realistic microstructure. The relationship between fabrication temperature and microstructure evolution, fabrication pressure and microstructure evolution is proposed， respectively. The mean grain size of simulated microstructures by Monte Carlo Potts model integrated with fabrication temperature and pressure increases with an increase in fabrication temperature and pressure, which is consistent with the experiment results. The microstructure evolution of ceramic tool materials during fabrication is simulated by the new Monte Carlo Potts model with considering technology parameters.
Keywords: Simulation; Hot-pressing sintering; Ceramic matrix composites (CMC); Microstructure; Monte Carlo model.
Optimisation of spin coating parameters for the preparation of ZnO thin films by Grey-Taguchi method
by A. Vivek, Akshay Chavan, Shivaraj B. Wali, H.N. Narasimha Murthy, M. Krishna, B.S. Sathyanarayana
Abstract: This work studies the influence of spin coating process parameters on grain size and surface roughness of zinc oxide (ZnO) thin films by sol gel using Taguchi method. ZnO thin films were prepared using zinc acetate dehydrate (ZAD), methanol and diethanolamine (DEA) as the starting material, solvent and stabilising agent respectively. The coating parameters such as precursor concentration of ZAD (0.5, 0.6 and 0.7 M), spin speed (1,500, 2,500 and 3,500 rpm) and annealing temperature (300,400 and 500 °c) was selected and the influence of these parameters on grain size and surface roughness was studied using X-ray diffraction (XRD) and atomic force microscopy (AFM). ANOVA results showed that annealing temperature had 53% effect on grain size and chuck rotation speed had 40% effect on the surface roughness of the film. Using Grey relation technique the optimised parameters was found to be 0.5 M, 2,500 rpm and 400°C. The grain size decreased from 18.054 nm to 16.97 nm and roughness of film decreased from 230.47 nm to 223.5 nm.
Keywords: sol gel chemistry; zinc oxide; grain size; surface roughness; ANOVA.
Optimal design and simulation of the stepped beam of a large-scale ultra-precision optical aspheric machine
by Lin Sun, Shuming Yang, Pu Zhao, Jianjun Ding, Xingyuan Long, Zhuangde Jiang
Abstract: We have designed a precision machine for the manufacture of large-scale optical aspheric mirrors. The beam is one key component of the machine and it has a feature of three steps with the length of 3,100 mm. The technique driven at the centre of gravity has been used in the beam design. This feature makes a contribution to optimise force distribution, increase stiffness and reduce deformation so as to realise high accuracy.
Keywords: optimal design; finite element method; stepped beam.
Design and development of microneedle array-based electrode for bio-potential measurement
by N. Balashanmugam, K. Naveen, Prasad Krishna, G.C. Mohan Kumar
Abstract: Conventional wet electrodes used in bio-potential measurement like EEG, ECG, etc., require the need for conductivity gel application on skin to wet the surface so that more contact area exist between skin and electrode resulting in better signal acquisition. Wet electrodes have certain drawbacks like the gel tends to underperform within one to two hours after application due to reasons like body heat. To overcome this drawbacks, dry electrodes are being developed which can be classified into two types; one penetrating skin and the other not. Both this type of electrodes has the advantages and limitations. The major drawback of filament type non-penetrating dry electrodes is that if the interest is in acquiring signals during motion, these electrodes tend to move relative to the skin resulting in noisy signal where as the microneedle can overcome this drawback by being continuously in contact with skin in all circumstances. In present work we have used micromachining technique to fabricate PMMA microneedle array. The study involves design of microneedle array, fabrication and mechanical testing of microneedles for skin insertion. It was found that for skin insertion upto 150 μm microneedles 7.5 N load was required and microneedles were structurally stable at this load.
Keywords: microneedle; micromachining; micromilling; bio-potential; EEG; PMMA.
Fabrication of helical micro pins by electrochemical machining
by Lih-Wu Hourng, Cha-Guo Liu, Zhi-Wen Fen
Abstract: Helical tools have been proven to enhance the circulation of electrolyte between electrodes in electrochemical micro-drilling. However, the fabrication of micro helical tools is difficult by traditional machining methods. The aim of the present article is to fabricate a helical tungsten micro pin by electrochemical machining. Experimental results show that a helical pin can only be fabricated in the limiting current conditions, and the length of threaded region is proportional to the anode rotating rate. Under the conditions of applied voltage equal to 2.6 V, machining time of two minutes, and the anode rotating rate of 4,000 rpm, an optimal micro helical electrode with thread depth around 17 micro-metre can be obtained. The mechanism for the formation of helical groove is well explained.
Keywords: electrochemical machining; ECM; micro-drilling; helical tool.
Processing characteristics of ultrathin SrTiO3 ceramic substrates
by Jisheng Pan, Guoming Li, Qiusheng Yan, Xiaowei Zhang
Abstract: To solve the fracture problem of ultrathin, soft-brittle and large warp SrTiO3 ceramic substrates, a new anti-broken two-sided lapping method was proposed. With this new method, the materials at the convex peak of the substrate surface which thinnest thickness is only 0.19 mm but warp up to 0.6 mm were removed firstly. Then more and more materials were removed and a flat SrTiO3 substrate without broken was obtained ultimately. The main material removal method of SrTiO3 substrate was the fracture of the crystallites rolled by abrasive, while some crystallites were pulled out. As the material was removed, the substrate surface became higher density. Using 1.5 μm Al2O3 slurry, a surface with Ra 0.0285 μm was obtained by using this method. An ultra-smooth surface with Ra 0.0038 m was achieved by cluster magnetorheological polishing, the grain boundary and coarse grain structure on the surface could be seen clearly.
Keywords: SrTiO3 substrate; anti-broken lapping; cluster MR-effect; surface roughness; material removal.
Influence of hydrogen on surface integrity and phase transformation of laser peened 316L stainless steel
by Jianzhong Zhou, Yang Zheng, Shu Huang, Jie Sheng, Wensheng Tan
Abstract: To investigate the influence of hydrogen atoms on the surface integrity and the phase transformation of type 316L stainless steel after laser peening, specimens of laser peened 316L austenitic stainless steel were cathodic hydrogen charged. The surface residual stress of samples subjected to laser peening, the metallurgical structures and the microhardness were studied. The result shows that compressive residual stress is induced by laser peening. The compressive residual stress is 35.55 MPa, 46 MPa and 72 MPa, respectively, when the laser energy is 2 J, 5 J and 8 J. Meanwhile, laser peening refines the grain size, and the surface microhardness reveals that laser peening suppress the increase of microhardness caused by hydrogen atoms. Compared with unimpacted specimens, the amount of hydrogen attacked holes on impacted samples is decreased. The X-ray diffraction reveals that hydrogen charging is responsible for the martensite formed on the surface and the laser peening suppress the formation of martensite.
Keywords: laser peening; 316L stainless steel; hydrogen embrittlement; surface residual stress; surface integrity; metallographic structure; surface microhardness; phase transformation; nanotechnology.
Scratching of SiC ceramics at two dimensional pre-stressing
by Gaofeng Zhang, Yijiang Zeng, Wenbo Zhang
Abstract: A stress field model was built to study the effects of pre-stressing value, normal and tangential load on the three principal stresses and maximum shear stress when the silicon carbide (SiC) ceramics were scratched under two dimensional pre-stressing, and the scratching tests of SiC ceramic were conducted by using a Rockwell diamond indenter at different pre-stress values and normal loads. Scratching induced damage was assessed and characterised via destructive inspection techniques and progressive lapping techniques combined with the digital microscope. Acoustic emission (AE) technology was also used for the online monitoring of the damage. The results showed that, for a given scratching load, the amplitude of AE signals was reduced as the pre-stress values increasing, and surface/subsurface damage of SiC ceramics induced by two dimensional pre-stress scratching was less than that by conventional scratching. So one can believe that the two dimensional pre-stress method can contribute to decreasing the machining damage of brittle materials.
Keywords: scratching; SiC ceramics; two dimensional pre-stress; surface/subsurface damage.
Study on the technological method of ultra-precision grinding for parabolic mirror of monocrystalline silicon
by Yujie Niu, Yifan Dai
Abstract: Curved optics of monocrystalline silicon plays an important role in high power laser system and its form accuracy and subsurface damage (SSD) have a significant impact on the performance of the laser system. In order to improve grinding accuracy and control the depth of SSD, the ultra-precision grinding (UPG) process of Si is studied. Firstly, the grinding theory is introduced and the relationships among the depth of cutting, the depth of subsurface cracks and the load of single particle are analysed. Then the influence of different process parameters on the surface quality of Si was investigated by some process experiments. Based on the result of process experiments, the processing of a 195 mm-diameter parabolic mirror of Si was carried out. The results show that the form accuracy of peak-valley value is promoted up to 3.77 μm from 21.4 μm and Rms value of the roughness is improved up to 0.11 μm from 0.625 μm.
Keywords: monocrystalline silicon; Si; aspheric; ultra-precision grinding; UPG; subsurface damage; SSD.