Optimization experiment on eccentric lapping of cylindrical rollers

Cylindrical rollers are important elements of bearings,and their machining accuracy and consistency affect the bearing quality.Using a GCr15 cylindrical roller ofФ11×12 as the processing object in this study,the effects of loading pressure,abrasive concentration,and speed combination on cylindrical roller machining precision were investigated using the orthogonal experimental design method on a double-side eccentric pendulum lapping and polishing machine.The machining parameters of the lapping stage were optimized,and the lapping optimal process parameters were determined by S/N response analysis and analysis of variance(ANOVA).The results show that when the experiment was optimized using loading pressure of 10 N/roller,abrasive concentrationof 20.0 wt%,and rotational speed combination,the material removal rate(MRR)of cylindrical roller reached 0.0896μm/min;the average roughness of the batch decreased from 0.056μm to 0.027μm,51.8%lower than the original batch average roughness,and the deviation decreased from the initial 0.022μm to 0.014μm;the batch average roundness error decreased from 0.47μm to 0.28μm,40.4%lower than the original batch average roundness error,and the deviation decreased from the initial 0.19μm to 0.038μm;and the batch average diameter variation decreased from 4.5μm to about 3.6μm,20%lower than the original batch average diameter variation.The double-side eccentric lapping of cylinder rollers does not only lead to improvement in the surface quality and shape accuracy of rollers,but also improvement in the batch consistency.

Modeling and Validation of Indentation Depth of Abrasive Grain into Lithium Niobate Wafer by Fixed-Abrasive Lapping

The prediction of indentation depth of abrasive grain in hydrophilic fixed-abrasive(FA)lapping is crucial for controlling material removal rate and surface quality of the work-piece being machined.By applying the theory of contact mechanics,a theoretical model of the indentation depth of abrasive grain was developed and the relationships between indentation depth and properties of contact pairs and abrasive back-off were studied.Also,the average surface roughness(Ra)of lapped wafer was approximately calculated according to the obtained indentation depth.To verify the rationality of the proposed model,a series of lapping experiments on lithium niobate(LN)wafers were carried out,whose average surface roughness Ra was measured by atomic force microscope(AFM).The experimental results were coincided with the theoretical predictions,verifying the rationality of the proposed model.It is concluded that the indentation depth of the fixed abrasive was primarily affected by the applied load,wafer micro hardness and pad Young′s modulus and so on.Moreover,the larger the applied load,the more significant the back-off of the abrasive grain.The model established in this paper is helpful to the design of FA pad and its machining parameters,and the prediction of Ra as well.

Damage mechanisms during lapping and mechanical polishing CdZnTe wafers

CdZnTe wafers were machined by lapping and mechanical polishing processes,and their surface and subsurface damages were investigated.The surface damages are mainly induced by three-body abrasive wear and embedded abrasive wear during lapping process.A new damage type,which is induced by the indentation of embedded abrasives,is found in the subsurface.When a floss pad is used to replace the lapping plate during machining,the surface damage is mainly induced by two-body abrasive and three-body abrasive wear,and the effect of embedded abrasives on the surface is greatly weakened.Moreover,this new damage type nearly disappears on the subsurface.

High Speed Lapping of SiC Ceramic Material with Solid (Fixed) Abrasives

An experimental investigation is carried out to machine SiC ceramic material through the method of high speed plane lapping with solid(fixed) abrasives after the critical condition of brittle-ductile transition is theoretically analyzed. The results show that the material removal mechanism and the surface roughness are chiefly related to the granularity of abrasives for brittle materials such as SiC ceramic. It is easily realized to machine SiC ceramic in the ductile mode using W3.5 grit and a high efficiency, low cost and smooth surface with a surface roughness of R_a 2.4?nm can be achieved.

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

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.

MINITYPE MACHINING SYSTEM FOR DIAMOND LAPPING & POLISHING BY USING BRUSHLESS DIRECT CURRENT MOTOR AS PRECISE SPINDLE

A minitype precise spindle system which can machine precisely and stably in the process of diamond lapping and polishing is designed. In such minitype spindle system, the brushless DC spindle motor is used to drive the lapping finish table, which is built with fluid dynamic bearings. Some measures have been taken to make the lapping system dynamic balance, and a servo controller which can adjust the speed of motor from 1200 r/min to 5400 r/min is designed. Experiments show that the spindle system is reliable and stable for diamond polishing, and the detection results by atomic force microscope（AFM） show that the surfaces of diamond edge＇s Ra is 6.725 nm and whole diamond average Ra is 3.25 nm.

Subsurface Damage of Monocrystalline Germanium Wafers by Fixed and Free Abrasive Lappings

The subsurface damage(SSD)layers of monocrystalline germanium wafers lapped by three different ways were measured and compared by the method of nanoindentation and micro morphology.Three ways such as ice-fixed abrasive,thermosetting fixed abrasive and free abrasive lappings are adopted to lap monocrystalline germanium wafers.The SSD depth was measured by a nanoindenter,and the morphology of SSD layer was observed by an atomic force microscopy(AFM).The results show that the SSD layer of monocrystalline germanium wafer is mainly composed of soft corrosion layer and plastic scratch and crack growth layer.Compared with thermosetting fixed abrasive and free abrasive lappings,the SSD depth lapped with ice-fixed abrasive is shallower.Moreover,the SSD morphology of monocrystalline germanium wafer lapped with ice-fixed abrasive is superior to those of two other processing ways.

EFFECT OF LAP SURFACE PROFILE ON LAPPING EFFICIENCY

To meet the requirements of improving the efficiency in lapping operat ion, the effect of lap surface profile on the efficiency is analyzed theoretical ly and an experimental study is carried out on lapping of Mn Zn ferrite. It is f ound that the profile of lap surface affects significantly the efficiency by mea ns of its capacity to keep loose grains and fixed grains during lapping, and tha t the efficiency can be increased by several times by using a lap with proper surface profile, while the same work surface roughness can be finally obtained.

CVD Micro-diamond Coated Tool Lapping with Sapphire Wafer

Micro-diamond films were prepared on YG6 substrate by hot filament chemical vapor deposition method.An innovative micro-diamond coated tool was used to the lap sapphire wafer.The effect of load,rotating speed,and lapping time on material removal rate(MRR)and surface roughness was investigated.The results showed that the best process parameters were 3N,100r/min and 15 min.The surface quality of sapphire improved significantly after lapping.The coating after lapping adhered well and did not show any peeling.The innovative micro-diamond coated tool was feasible and suitable for the lapping of the single crystal sapphire wafer.

Finite Element Analysis for Grinding and Lapping of Wire-sawn Silicon Wafers

Silicon wafers are the most widely used substrates for semiconductors. The falling price of silicon wafers has created tremendous pressure on silicon wafer manufacturers to develop cost-effective manufacturing processes. A critical issue in wafer production is the waviness induced by wire sawing. If this waviness is not removed, it will affect wafer flatness and semiconductor performance. In practice, both lapping and grinding have been used to flatten wire-sawn wafers. Although grinding is not as effective as lapping in removing waviness, it has many other advantages over lapping (such as higher throughput, fully automatic, and more benign to environment) and has great potential to reduce manufacturing cost of silicon wafers. This paper presents a finite element analysis (FEA) study on grinding and lapping of wire-sawn silicon wafers. An FEA model is first developed to simulate the waviness deformation of wire-sawn wafers in grinding and lapping processes. It is then used to explain how the waviness is removed or reduced by lapping and grinding and why the effectiveness of grinding in removing waviness is different from that of lapping. Furthermore, the model is used to study the effects of various parameters including active-grinding-zone orientation, grinding force, waviness wavelength, and waviness height on the reduction and elimination of waviness. Finally, the results of pilot experiments to verify the model are discussed.

Correlation between the Surface Quality and the Lapping Parameters in Loose Abrasive Lapping

As one of the basic finishing operations,loose abrasive lapping is widely used in the surface finishing on metallic parts,non-metallic components,and engineering ceramics.During lapping,lapping parameters have a great influence on surface quality of machined workpiece.In order to provide an experimental basis for the selection of lapping parameters,effects of some important variables such as abrasive size,lapping load,and lapping speed,on surface roughness and residual surface stress of high speed steel workpiece via loose abrasive lapping were discussed in this paper.The results show that the work surface roughness increases with the increasing of abrasives size or decreasing lapping load,and does not change obviously with the lapping speed.Lapping can cause residual compressive stress in the surface layer of lapped workpiece,and the magnitude of residual surface stress becomes larger with increasing abrasive size,lapping load,and lapping speed.

ANALYSIS ON LAPPING AND POLISHING PRESSURE DISTRIBUTION OF HARD MAGNETIC DISK SUBSTRATE

The contact model of lapping and polishing for magnetic disk substrate is presented. Based on elastic contact theory, pressure distribution for this model are analyzed. Further, the effects of various parameters, such as the material properties of the PVA(polyvinyl acetate),grinding stone, the polishing pad and the base plate, the thickness of the pad or the stone on the pressure distribution have been discussed.

DISCUSSING ON SOLID ABRASIVE LAPPING PATH

Relative motion path between lapping tool and workpiece in plane solid abrasive lapping is dis- cussed and its path model is set up. The paths simulate. by this model are compared with the one got in experiments. The changing relationship of workpiece rotating speed with the main spindle rotating speed and eccentricity is also discussed.

RESEARCH ON AMAGNETIC FIELD IN ELECTROLYTIC LAPPING

Taking electrolytic lapping stainless steel for example, the principle of electrolytic lapping with a magnetic field is described, the movement of charged particles in the magnetic field is analyzed in tems of theory. Using a computer, the motion loci of the charged particles in the magnetic field are simulated. The theory and the experiment show that the magnetic field can accelerate the diffusion and mobility of the charged particles, accelerate the electrochemical reaction and reduce the surface roughness of the work more quickly, which improves the lapping efficiency.

EFFICIENCY IN LAPPING FERRITE

The present work has studied the effect of various parameters on the efficiency when lap-ping Mn-Zn ferrite material with fine diamond grains. The main factors affecting the efficiencywere made clear and the optimum lapping condition was discussed. It was found that the efficiencycan be affected greatly by the parameters in terms of the number of active grains per time. while thesurface roughness finally obtained is generally almost the same for a given grain size.

ECCENTRIC CIRCULAR GROOVE LAPPING TECHNIQUE FOR CERAMIC BALLS

A new ball lapping method i s presented.By using the method , there is a distance be- tween the centre Iine of cireular groove and the rotating axis of lapping plate。 The proper dis-tance can make the lapped probability of each point on ball surfaee as consistent as possible。 This method is especially adapted for lapping high hardness ceramic balls due to its high material re- moval rate。

Nanometer lapping technology at high speed

In floating lapping with solid abrasives, the workpiece is taken as an isolated body. The forces that act on it are analyzed. A differential equation about the forces that act on it is set up, so the forces that act on it and its motion rule are received. Combining it with known lapping tool motion, the relative motion rule between the lapping tool and workpiece is determined too. According to the relative motion, the distribution of abrasives density is designed reasonably, which makes the lapping tool wear uniformly, which, in turn, avoids redressing the lapping tool, saves abra-sives, and increases machining accuracy. Combining it with advantages in high speed lapping with solid abrasives, the low cost, high efficiency nanometer lapping at high speed is realized.

肥胖指标对痰湿型多囊卵巢综合征患者代谢综合征的诊断价值分析

目的不同肥胖指标与痰湿型多囊卵巢综合征患者代谢综合征的相关性。方法回顾360例痰湿型多囊卵巢综合征(Polycystic ovary syndrome,PCOS)患者,根据是否符合代谢综合征(metabolic syndrome,MS)诊断标准,将研究对象分为非MS组216例、MS组144例;比较组内性激素水平及临床特征差异,评估各肥胖指标对痰湿型PCOS患者合并MS的预测价值。结果MS组患者性激素LH、SHBG、P、DHEAS、LH/FSH低于非MS组(P<0.05);MS组BH、BW、WC、HC、BMI、WHR、BRI、ABSI、CI、BAI、AVI、LAP、VAI均高于非MS组(P<0.05);采用受试者工作曲线评估肥胖指标在诊断痰湿型PCOS合并MS时均有预测价值(P<0.05)。结论不同肥胖指标对痰湿型PCOS患者合并MS具有较好的预测价值,其中LAP、VAI、AVI对痰湿型PCOS患者合并MS的预测价值最佳。

Strengthening strategy for high-performance friction stir lap welded joints based on 5083 Al alloy

During aircraft,ship,and automobile manufacturing,lap structures are frequently produced among Al alloy skins,wall panels,and stiffeners.The occurrence of welding defects severely decreases mechanical properties during friction stir lap welding(FSLW).This study focuses on investigating the effects of rotation rate,multipass welding,and cooling methods on lap defect formation,microstructural evolution,and mechanical properties.Hook defects were eliminated by decreasing welding speed,applying two-pass FLSW with a small welding tool,and introducing additional water cooling,thus leading to a remarkable increase in effective sheet thickness and lap width.This above strategy yielded defect-free joints with an ultrafine-grained microstructure and increased tensile shear force from 298 to 551 N/mm.The fracture behavior of FSLW joints was systematically studied,and a fracture factor of lap joints was proposed to predict their fracture mode.By reducing the rotation rate,using two-pass welding,and employing additional water cooling strategies,an enlarged,strengthened,and defect-free lap zone with refined ultrafine grains was achieved with a quality comparable to that of lap welds based on 7xxx Al alloys.Importantly,this study provides a valuable FSLW method for eliminating hook defects and improving joint performance.

TGF-β潜态相关肽及其截短体抑制TGF-β1诱导的LX-2细胞纤维化研究

目的转化生长因子β(transforming growth factor-β,TGF-β)潜态相关肽(latent assotiated peptide,LAP)及其截短体抑制TGF-β1诱导的LX-2细胞纤维化研究。方法LAP全长命名为LAP-F,LAP截短体命名为LAP-B。用TGF-β1对LX-2处理进行纤维化模型的建立。分组后分别加入LAP-F和LAP-B多肽。control组:在正常情况下进行培养;TGF-β组:加入终浓度10 ng/mL的TGF-β1;TGF-β+LAP-F组:造模后加入终浓度60μg/mL的LAP-F;TGF-β+LAP-B组:造模后加入终浓度60μg/mL的LAP-B多肽。通过Western blot进行纤维化指标FN和α-SMA的蛋白水平检测。细胞免疫荧光实验检测细胞中FN和α-SMA的蛋白水平。结果Western blot结果显示,与control组细胞相比,TGF-β组细胞中纤维化相关蛋白FN的蛋白表达水平明显升高(P<0.001),纤维化相关蛋白α-SMA的蛋白表达也明显升高(P<0.01)。与TGF-β组相比,TGF-β+LAP-B组细胞中FN的蛋白表达明显降低(P<0.01),α-SMA的蛋白表达也明显降低(P<0.01)。与TGF-β组相比,TGF-β+LAP-F组细胞中FN的蛋白表达水平明显降低(P<0.01),α-SMA的蛋白表达水平明显降低(P<0.01)。与TGF-β组相比,TGF-β+LAP-F组细胞中FN和α-SMA蛋白荧光强度更低。免疫荧光的结果显示与control组细胞相比,TGF-β组细胞中FN和α-SMA的蛋白荧光强度更高,这意味着纤维化相关蛋白表达增多。与TGF-β组相比,TGF-β+LAP-B组细胞中FN和α-SMA蛋白荧光强度更低。与TGF-β组相比,TGF-β+LAP-F组细胞中FN和α-SMA蛋白荧光强度更低。结论LAP-F和LAP-B两种多肽都具有抗LX-2细胞纤维化能力,为后续研究提供基础。