Cutting surface quality analysis in micro ball end-milling of KDP crystal considering size effect and minimum undeformed chip thickness

Potassium dihydrogen phosphate (KH₂PO₄ or KDP) crystal is a typical soft-brittle optical crystal, and the size effect and brittle cutting mode are easy to appear in micro ball end-milling of KDP crystal. In this paper, micro-grooving experiments are conducted to study the size effect and brittle cutting in micro ball end-milling of KDP crystal with different feed rate and depth of cut. The cutting force, machined groove base quality and chip morphology are collected and analyzed carefully. The size effect is discovered by the phenomena of the existence of oscillations and relaxations in cutting force and hyper-proportional increase of specific cutting force, when the ratio of feed per tooth to cutting edge radius f_t/r_e is less than 1. While the brittle cutting mode is detected through the existence of sharp fluctuations in cutting force and cracks on the groove base when the ratio f_t/r_e is larger than 2. From the further comprehensive analysis of cutting force, specific cutting force, machined groove base quality and chip morphology, the cutting parameters with ratios of the maximum undeformed chip thickness in one cutting circle to cutting edge radius h_max/r_e around 0.14, 0.2 and 0.4 are regarded as size effect, optimal and brittle cutting points, respectively. The size effect, ductile cutting and brittle cutting zones are divided by the size effect and brittle cutting boundaries (points). Among the optimal points, the depth of cut of 2 μm with the ratio f_t/r_e of 1 is the optimal cutting parameter for micro ball end-milling of KDP crystal.     

Experimental study on fabrication and evaluation of micro pyramid-structured silicon surface using a V-tip of diamond grinding wheel

A mechanical fabrication of micro pyramid-structured silicon surface is proposed using crossed grooving with a 60° V-tip of diamond grinding wheel. It can obtain high form-accuracy, good surface quality and efficient productivity in contrast to laser machining and etching, and also assure a high aspect ratio in contrast to other mechanical processes. In order to describe its micro-structured topography, a white-light interferometer was employed, and its measured point cloud was matched using an Iterative Closest Point (ICP) algorithm. In micro grinding, a novel CNC mutual-wear truing was first developed to sharpen the wheel V-tip; then, the effects of microscopic wheel topography, silicon crystal-orientation and grinding parameter were investigated on ground micro-topography, truing ratio and material removal ratio; finally, its form-accuracy, pyramid top radius, groove tip radius, surface roughness and aspect ratio were evaluated. It is shown that better microscopic grain protrusion topography on wheel V-tip produces much larger material removal ratio and much better micro-structured topography in micro grinding, but it leads to much less truing ratio in finer GC truing. In micro grinding, silicon crystal-orientation has little effect on micro-structured topography due to diamond crystal-orientations that are randomly distributed on wheel V-tip. Although the micro pyramid-structured form error is only about 3.4 μm, its V-groove bottom and pyramidal top have very large form errors (23.1-47.9 μm) due to the sharpness of wheel V-tip and the frangibility of micro pyramid top. On increasing feed speed, its pyramid top radius decreases and its groove tip radius slightly increases, ultimately leading to an increase in aspect ratio, whereas its surface quality descends. It is concluded that the micro-pyramid arrays may be precisely patterned on silicon surface using a SD600 wheel with crossed tool paths, on-machine V-tip truing and the depth of cut in 1 μm.     

Free surface transition and momentum augmentation of liquid flow in Micro/Nano-scale channels with hydrophobic and hydrophilic surfaces

We propose a novel micro/nano-scale nozzle structure, featuring an interfacial line between the hydrophilic and the hydrophobic surfaces for a jetting system, such as an inkjet head or electrospray devices. This research will investigate the impact of the interfacial line on flow instability and momentum augmentation as the liquid meniscus moves across the line. The research methods used in this paper, in respect to micro-and nano-scale channels, are computational fluid dynamics (CFD) and non-equilibrium molecular dynamics (MD), respectively. With the growing interest in micro/nano electromechanical systems (MEMS/NEMS), many studies have been conducted to develop an advanced micro/nanofluidic system. However, until now, there have been few in-depth studies on passive flow control in micro and nano nozzles using the hydrophilic and hydrophobic surface characteristics. In this research, the sequential arrangement of hydrophilic and hydrophobic surfaces in the nozzle is presented along with an investigation into how flow instability and momentum augmentation are going to be applied to an efficient micro/nano jetting system. When a liquid meniscus arrives at the interfacial line between hydrophilic and hydrophobic surfaces, the meniscus shape changes from concave to convex and the fluid motion near the wall stops until the concave shape is fully converted. Because the momentum should be conserved, the lost momentum near the wall transfers to the center region, and therefore the liquid at the center region is accelerated as it crosses the line. If we use this nozzle structure and the augmentation of the momentum near the center, a tiny droplet can be easily generated. This paper was recommended for publication in revised form by Associate Editor Haecheon Choi Doyoung Byun received the B.S., M.S, and Ph.D. degrees in school of mechanical and aerospace engineering from the Korea Advanced Institute of Science and Technology (KAIST), Taejon, Korea, in 1994, 1996, and 2000, respectively. From 2000 to 2002, he was in the Korea Institute of Science and Technology Evaluation and Planning as a Senior Researcher. In 2003, he joined the faculty of the School of Mechanical and Aerospace Engineering, Konkuk University, Seoul, Korea. His current research topics are development of electrohydrodynamic inkjet head, microfluidic devices, and biomimetic robot systems. His research interests include microfluidics, MEMS, and biomimetics.     

再制造工程技术及其研究新进展

以中国国家自然科学基金资助项目“再制造基础理论与关键技术”和“机电产品可持续设计与复合再制造的基础研究”,国家科技支撑计划项目“汽车零部件再制造关键技术与应用”、“汽车发动机和轮胎再制造过程质量控制与评价技术研究”所获得的系列科学研究成果为基础,结合装甲兵工程学院装备再制造技术国防科技重点实验室(NKLR)的系列科研成果,构建中国特色再制造工程体系框架,提出再制造工程的科学发展方向。 讨论再制造工程的实现可行性与价值。认为,再制造工程实现的前提是产品设计寿命冗余,方法是重新赋予报废零件新的寿命,价值是最大限度地保留并释放废旧产品蕴含的附加值,核心是避免重复的资源损耗、能量消耗和环境污染,优势是再制造产品性能优于原始制造产品性能,前途是敏锐地吸纳最新科学技术成果。     

Low/distortion on exterior surface of auto body and its correction method

Surface low/distortion is one of the most challenging surface deflections that have a great effect on the exterior appearance of automobiles.Most studies on surface distortion/deflection have focused o...     

复合材料车削表面2D分析和3D分析的对比研究

这里对碳/碳复合材料车削圆柱表面进行了二维轮廓分析和三维形貌分析的对比研究,分析计算表明三维形貌分析方法更能够真实的反映复合材料的表面质量。     

Deformation analysis of micro/nano indentation and diamond grinding on optical glasses

The previous research of precision grinding optical glasses with electrolytic in process dressing (ELID) technology mainly concentrated on the action of ELID and machining parameters when grinding,whic...     

Characterization of surface defects in fast tool servo machining of microlens array using a pattern recognition and analysis method

Microlens array (MLA) is a type of structured freeform surfaces which are widely used in advanced optical products. Fast tool servo (FTS) machining provides an indispensible solution for machining MLA with superior surface quality than traditional fabrication process for MLA. However, there are a lot of challenges in the characterization of the surface defects in FTS machining of MLA. This paper presents a pattern recognition and analysis method (PRAM) for the characterization of surface defects in FTS machining of MLA. The PRAM makes use of the Gabor filters to extract the features from the MLA. These features are used to train a Support Vector Machine (SVM) classifier for defects detection and analysis. To verify the method, a series of experiments have been conducted and the results show that the PRAM produces good accuracy of defects detection using different features and different classifiers. The successful development of PRAM throws some light on further study of surface characterization of other types of structure freeform surfaces.     

Diffusion as a model of formation and development of surface topography

Changes of surface topography in tribological systems are due to inelastic processes as plastic deformation, detaching of wear particles and their reintegration into the surfaces. Due to these processes, the material particles are transported either along a surface or from one tribological partner to the other. Both processes are due to random interactions between surface asperities and are stochastic processes. The stochastic mass transfer between the surfaces is interpreted and described in the paper as a random deposition, the transport along a surface as a `diffusion' processes with some effective diffusion coefficient. We consider the development of the surface topography due to the described two kinds of random processes. There exist some stationary (in statistical sense) random surface topography with a power spectrum (spectral density) typical for many real frictional surfaces. The parameters of the model can either be obtained from comparison with measured topography or extracted from simulations at a lower space scale. The proposed mass transport model further allows to determine the wear rate in the system.     

X PS － EDS 联用技术分析金电极表面焊接不良的原因

金电极焊接不良,影响产品质量,焊接不良产生的原因通常与表面存在污染物有关。本实验采用能谱仪（EDS）结合X－射线光电子能谱仪（XPS）对样品表面成分进行分析。分析结果表明,样品由Au、C、O、N等元素组成,而表面污染物中含有F元素,F1s的结合能为688.5ev ,而C1s的结合能在291.7ev处有拟合峰,表明表面存在C F2污染,C F2污染是金电极焊接不牢的原因。     

Kinematic simulation of the uncut chip thickness and surface finish using a reduced set of 3D grinding wheel measurements

This paper combined experimentally-measured grinding wheel topography data taken around the entire circumference of the grinding wheel with a kinematic simulation of the grinding process. Several new methods were developed in order to create the resulting high-fidelity and computationally-efficient simulation. First a novel peak-removal technique was developed and applied to effectively remove erroneous peaks in the raw wheel topography data. Next a method was found to determine only the active cutting points on the wheel model by considering the kinematics of the grinding process. This new approach was able to reduce the simulation time from over twelve hours to about four seconds without losing any information about the cutting edge–workpiece interaction. The resulting predicted workpiece surface was then experimentally validated by carrying out a grinding experiment using the same grinding wheel used to develop the grinding wheel computer model and then measuring the resulting workpiece surface profile. Good agreement between simulated and experimental workpiece profiles was observed. Finally, the validated simulator was used to develop a kinematically-exact method to calculate the maximum uncut chip thickness and the simulation results were investigated for different depths of cut, wheel speeds and workpiece feeds.     

Antimicrobial effect,frictional resistance,and surface roughness of stainless steel orthodontic brackets coated with nanofilms of silver and titanium oxide: a preliminary study

Nano‐silver and nano‐titanium oxide films can be coated over brackets in order to reduce bacterial aggregation and friction. However, their antimicrobial efficacy, surface roughness, and frictional resistance are not assessed before. Fifty‐five stainless‐steel brackets were divided into 5 groups of 11 brackets each: uncoated brackets, brackets coated with 60 µm silver, 100 µm silver, 60 µm titanium, and 100 µm titanium. Coating was performed using physical vapor deposition method. For friction test, three brackets from each group were randomly selected and tested. For scanning electron microscopy and atomic‐force microscopy assessments, one and one brackets were selected from each group. For antibacterial assessment, six brackets were selected from each group. Of them, three were immediately subjected to direct contact with S. mutans. Colonies were counted 3, 6, 24, and 48 h of contact. The other three were stored in water for 3 months. Then were subjected to a similar direct contact test. Results pertaining to both subgroups were combined. Groups were compared statistically. Mean (SD) friction values of the groups 'control, silver‐60, silver‐100, titanium‐60, and titanium‐100' were 0.55 ± 0.14, 0.77 ± 0.08, 0.82 ± 0.11, 1.52 ± 0.24, and 1.57 ± 0.41 N, respectively (p = .0004, Kruskal–Wallis). Titanium frictions were significantly greater than control (p < .05), but silver groups were not (p > .05, Dunn). In the uncoated group, colony count increased exponentially within 48 h. The coated groups showed significant reductions in colony count (p < .05, two‐way‐repeated‐measures ANOVA). In conclusions, all four explained coatings reduce surface roughness and bacterial growth. Nano‐titanium films are not suitable for friction reduction. Nano‐silver results were not conclusive and need future larger studies.     

气动技术的发展及在新领域中的应用

从SMC研发的新产品，可以了解到气动技术正朝着节能、环保、机电一体化等方向发展。半导体／微电子制造业、生物工程、医药等已成为气动技术全新的应用领域。     

Improvement in dynamic characteristics of surface grinding machines with a horizontal spindle and a reciprocating work-table by means of a new type of dynamic damper

A number of types of dynamic damper for surface grinding machines with a horizontal spindle and a reciprocating work-table are developed and their effectiveness is investigated experimentally. In all cases, the amplitudes of the tuning-fork mode vibrations of the machines were reduced to about one-fifth of the values in the original states, and chatter marks due to these vibrations have been suppressed completely. In particular, a multi-degrees-of-freedom two-directional type dynamic damper has excellent adaptability to the variation in the dynamic characteristics of the surface grinding machines during machining operations and is also effective in suppressing the horizontal vibration of the wheel-head.     

The composition of lubricant-derived surface layers formed in a lubricated cam/tappet contact II. Effects of adding overbased detergent and dispersant to a simple ZDTP solution

The surface films formed by a set of oils of related additive chemistry, but with differing detergent and dispersant contents, have been chemically characterized using a combination of surface analysis techniques. The films were formed in a cam/tappet friction apparatus with a direct acting bucket tappet geometry. In the absence of overbased detergent, the amorphous films were composed essentially of inorganic zinc phosphates formed by the ZDTP anti-wear additive, and evidence of higher molecular weight phosphates (e.g. metaphosphates) was found. Adding overbased detergent and dispersant resulted in partial replacement of zinc by the detergent metal and loss of the higher molecular weight phosphates in favour of ortho- and pyro-phosphates.     

Review of non-destructive measuring methods for the assessment of surface integrity: a survey of new measuring methods for coatings, layered structures and processed surfaces

Even though the near-surface areas of precisely manufactured parts represent only a few percent of the workpiece’s material volume, they influence its functional behaviour, quality and lifetime significantly. Therefore, sensors and measuring principles able to detect material changes, damage and process influences in the near-edge zone are of increasing importance. However, they have to meet industrial purposes concerning accuracy, measuring time, robustness and costs. In addition, they should work non-destructively and should offer the capability for integration in a production line.     

Surface roughness and the use of a peak to background ratio in the X-ray microanalysis of bio-organic bulk specimens

The use of a net peak intensity and of a peak to background (P/B)-ratio of sulphur and chlorine is examined in the X-ray microanalysis of a 2·4% w/w S bulk standard in Spurr's epoxy resin. In calculating the P/B-ratio, the background intensity is calculated for the same energy region as for the net peak. Analyses were carried out on the flat top of the standard and on the slope running down from the top on the side not facing the X-ray detector. The results obtained for the peak to local background ratios from the top and the slope yielded a relatively small mean deviation (11%) while net peak intensities ultimately were reduced to 7% or less of the initial value for the flat top. This indicated that a peak to local background ratio is to be preferred in the quantitative analysis of bulk specimens which have poorly defined local tilt and takeoff angles. A second advantage is the inherent correction for beam current fluctuations.