自由曲面模具磁力研磨的试验研究

基于三杆五自由度并联机床进行了对自由曲面模具磁力研磨的试验研究.实验分析了利用球型磨头对工件磁力研磨时,磁场强度、研磨间隙、磨粒粒度等因素对自由曲面模具表面研磨质量的影响.利用五自由度并联机床不仅可以去除自由曲面模具表面的切削残留痕迹,降低模具的表面粗糙度,还解决了传统手工研磨方式所引起的工件研磨质量不一致的缺陷.拓宽了三杆五自由度并联机床的应用范围.     

电解镜面抛光中的尺寸控制

回转零件镜面抛光时不仅要求达到预期的表面粗糙度,往往也要求控制其尺寸精度．加工原理表明抛光时的实际加工时间与工件直径变化呈线性关系．经过试验,给出了两种加工条件下工件尺寸变化的平均值及其方差,利用这些数据可以计算抛光余量及抛光前工件尺寸偏差,使抛光后工件尺寸达到预定的精度     

磁流变抛光超光滑光学表面

研究了利用初始粘度达到0.5Pa·s、具有相对大范围稳定性的标准磁流变抛光液,并结合设计独特的公自转组合运动永磁抛光轮进行了试验,对抛光过程中的主要参量包括抛光轮与工件之间间隙、抛光轮与工件之间相对运动速度、氧化铈浓度及抛光时间对材料去除特性的影响进行了研究.磁流变抛光对工件(K9玻璃)表面粗糙度提高效果的抛光试验结果证明,该套系统具有良好的抛光特性,抛光28min后工件表面粗糙度由最初的10.98nm收敛到0.6315nm,获得了超光滑量级的抛光表面.     

建筑材料表面红外双向反射分布函数实验分析

为了深入研究建筑物表面红外反射分布特性和散射分布特性,选择建筑外饰面常用的3种典型材料(如花岗岩、铝板和镀膜玻璃),通过自行搭建双向反射分布函数(BRDF)实验台,利用聚四氟乙烯粉压制的标准白板(近似朗伯体)为单一参考试样,分别用0.632 8、1.340 0和3.3900 μn波段3种激光器,在不同的入射角度下,对各...     

无磨料低温抛光件表面分形特性

利用HL Ⅱ型微机控制原子力显微镜(AFM)系统对无磨料低温抛光件表面的轮廓曲线进行了测量。基于分形理论,分析和讨论了不同工艺参数对表面分形维数D和轮廓算术平均偏差Ra的影响。研究结果表明:D与Ra反映了表面质量的不同方面,它们之间有一定的对应关系,但并不是线性的;对于同样的加工方法,硬质合金材料的D值比铝合金材料的D值大;分形维数可以揭示超光滑表面的表层质量。     

Effects of chairside polishing and brushing on surface roughness of acrylic denture base resins

The effects of 3 chairside polishing kits and mechanical brushing on the surface roughness of 3 different acrylic denture base resins were compared. Acrylic denture base resins (auto-polymerizing, heat-polymerizing, injected heat-polymerizing resins) were examined after a tungsten carbide bur, and after chairside polishing using 3 polishing kits and pumice. The specimens were subjected to mechanical brushing using a wear tester to simulate 30 000 strokes of brushing. The surface roughness of the acrylic denture base resin specimens was measured using a contact profilometer. After the test, the random polished acrylic resins were evaluated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Acrylic denture base resins polished using the 3 types of polishing kits had a smoother surface than those finished with the tungsten carbide bur (p<0.05). The surface of the resin polished by a TC cutter exceeded the R _a of 0.2 μm (p<0.05). The auto-polymerizing resin showed a significantly higher surface roughness than the heat-polymerizing resin and injected heat-polymerizing resin (p>0.05). In the case of polishing step wise, there was almost no change in surface roughness after brushing (p>0.05).     

Clarification of abrasive jet precision finishing with wheel as restraint mechanisms and experimental verification

According to the critical size ratio for the characteristic particle size to film thickness between grinding wheel and work, the machining mechanisms in abrasive jet precision finishing with grinding wheel as restraint can be categorized into four states, namely, two-body lapping, three-body polishing, abrasive jet machining and fluid hydrodynamic shear stress machining. The critical transition condition of two-body lapping to three-body polishing was analyzed. The single abrasive material removal models of two-body lapping, three-body polishing, abrasive jet finishing and fluid hydrodynamic shear stress machining were proposed. Experiments were performed in the refited plane grinding machine for theoretical modes verification. It was found that experimental results agreed with academic modes and the modes validity was verified.     

钛合金的已加工表面残余应力的数值模拟

为了揭示高速切削对航空钛合金加工表面残余应力的影响，利用三维斜角切削有限元模型对钛合金Ti6Al4V的高速切削加工过程进行了模拟，获得了不同切削速度和不同切削深度下的已加工表面残余应力分布.模拟结果表明：切削速度对已加工表面残余应力具有重要影响，而切削深度对已加工表面残余应力影响较小; 已加工表面层残余应力为拉应力，沿深度方向由拉应力逐渐过渡到压应力; 3个主方向的残余应力值随切削速度的增加而增加，而随切削深度的增加无明显变化; 切削速度和切削深度对残余应力层的厚度影响都很小.     

Prediction method for surface finishing of spiral bevel gear tooth based on least square support vector machine

The predictive model of surface roughness of the spiral bevel gear (SBG) tooth based on the least square support vector machine (LSSVM) was proposed.A nonlinear LSSVM model with radial basis function (RBF) kernel was presented and then the experimental setup of PECF system was established.The Taguchi method was introduced to assess the effect of finishing parameters on the gear tooth surface roughness,and the training data was also obtained through experiments.The comparison between the predicted values and...     

Online application of automatic surface quality inspection system to finishing line of cold rolled strips

An automatic surface quality inspection system installed on a finishing line of cold rolled strips is introduced. The system is able to detect surface defects on cold rolled strips, such as scratches, coil breaks, rusts, roll imprints, and so on. Multiple CCD area scan cameras were equipped to capture images of strip surface simultaneously. Defects were detected through "Dark-field illumination" which is generated by LED illuminators. Parallel computation technique and fast processing algorithms were developed for real-time data processing. The application to the production line shows that the system is able to detect defects effectively.     

钛表面处理对增强钛/瓷结合强度的影响

为了提高钛/瓷结合强度,通过不同方法对钛表面进行处理,研究了钛表面处理后钛/瓷界面组织及结合强度。试验结果表明,烤瓷前进行钛表面喷砂处理,对增强钛/瓷结合强度的影响并不显著,但对抑制钛/瓷界面裂纹的扩展起到积极作用;钛表面预氧化处理能够在钛表面形成一层均匀的氧化膜,使参与界面反应的TiO2增多,反应层增厚,但预氧化温度对钛/瓷结合强度有重要影响;钛表面磁控溅射Zr中间层能够抑制钛表面生成过厚氧化层,而中间层厚度对钛/瓷结合强度也有较大影响。     

超高速摄影中转镜力学特性的数值模拟

从弹性力学基本理论和三维应力应变方程出发,利用有限元结构强度分析原理,结合实验结果及转镜具体结构,建立了转镜镜面变形量、应力分布的计算机仿真原理与方法,并对四面体转镜的计算结果做了实验对比,得出了四面体转镜应力分布、应力最大点和镜面变形的定量数值．     

化学机械研抛过程流体和磨粒分布特性仿真

为深入理解化学机械抛光过程中的摩擦磨损机理,仿真研究了不同工况对抛光作用的影响规律.建立考虑多相流和离散相的三维CFD模型,研究不同工况下晶片和抛光垫间抛光液的速度和压力分布以及抛光磨粒的分布规律.结果表明:膜厚越小,抛光垫和晶片的转速越大,磨粒的分布密度越小.对流体速度和压力分布规律以及磨粒分布特性进行仿真分析,研究抛光过程中磨粒对晶片表面的动压作用过程.用疲劳断裂能量守恒理论,建立可定量分析各种工况下材料去除率的预测模型,采用Matlab软件对去除率模型进行仿真计算,得到不同工况下碳化硅晶片的去除率曲线.结果表明,抛光垫转速越大,膜厚越小,材料去除率越大,但去除率随着抛光的进行呈现减小的趋势.相比抛光垫转速对去除率的影响,膜厚对去除率的影响较小.     

大口径纹影系统主反射镜装调结构分析与设计

研制纹影测试系统中大口径主球面反射镜的装调结构.利用有限元法,对有效通光口径直径为800 mm的主镜进行应力和面变形分析.采用断裂几率预测法校核玻璃机械强度,通过优化得出反射镜面变形的均方根(rootmean square,RMS),以此为依据,设计出满足系统技术要求的主镜装调结构.     

提高大理石表面光泽度的工艺方法

概述了大理石主要化学成分、莫氏硬度以及生产工艺中抛光液的选择与冷却液的应用,并给出了根据大理石的化学成分及其莫氏硬度采用不同的工序来提高大理石表面光泽度的具体措施及若干测试结果.     

车铣粗糙度预测模型的建立和分析

车铣加工是近些年来发展起来的先进的切削加工技术之一.采用正交试验法,进行一系列的正交车铣铝合金切削实验,研究车铣切削用量与表面粗糙度之间的变化规律.通过正交试验法的方差分析进一步确定了各因素对表面粗糙度的影响大小的主次顺序,铣刀转速(切削速度)和工件转速对表面粗糙度的影响较大.采用回归分析原理,建立了表面粗糙度的预测模型,统计检验结果表明,所建立的表面粗糙度预测模型呈高度显著检验状态,具有很高的可信度.     

自由曲面工件的连续高效塑性成形方法

将塑性成形方式划分为整体成形与局部成形两大类,又将局部成形划分为点成形、线成形与面成形三种类型。比较了不同类型成形方式的优、缺点,并探讨了模具成形与柔性成形、分段成形与连续成形的特点及主要区别。在此基础上,提出了自由曲面工件连续、高效、柔性成形的思路;进而提出了采用可弯曲、可调整柔性辊的多点滚压成形技术;开发出了自由曲面板类件柔性滚压成形装置,并给出了成形实验结果,验证了此构想的可行性与实用性。     

响应面优化产碱性蛋白酶菌株的产酶条件

利用Minitab15数据处理软件用响应面法优化了产碱性蛋白酶菌株I13的产酶条件.运用Plackett-Burman设计筛选出3个对酶活力影响极显著因素,即接种量、酵母粉和培养温度,用最陡爬坡试验逼近最大产酶区域,应用中心组合设计和响应面分析确定产酶的最优组合为:酵母粉10.2 g/L,温度14.68 ℃,接种量5....     

Application of ceramic film as means of lubrication for forming of Ti sheet in a highly localized deformation process

Incremental forming is a novel die-less sheet forming process. There is a need for special means to retain lubricant at the tool/sheet interface during forming. To fulfillthe stated aim, a porous ceramic film was developed on pure Ti substrate, and it was done through an electrochemical depsition process known as plasma electrolytic oxidation. The film with preferred pore size could be realized after several attempts by varying the processing parameters. In order to characterize the film, a variety of tests including rnicrostructure, film-substrate bond strength and tribological properties tests were conducted. On-job performance of the film was also examined by forming Ti components employing a range of forming conditions. It was found that the proposed method of lubrication was effective, and the plasma eletrolytic oxidation process can be employed to fabricate films on pure Ti sheet to provide means of lubrication during incremental forming.