机床主轴滚动轴承滚道偏心对工件加工精度的影响

文章讨论了机床主轴滚动轴承滚道的几何偏心对工件加工精度的影响.通过理论分析并借助实例证明,外环内滚道的几何偏心一般只影响工件的几何形状精度,而内环外滚道的几何偏心则相反,一般只影响工件加工面相对基准面的相互位置精度.当两者共存,则误差结果叠加.     

高速走丝电火花线切割加工断丝分析及解决办法

针对高速走丝电火花线切割加工过程中经常出现的断丝现象,详细分析了电极丝断丝的六个主要因素：操作使用的因素、贮丝和运丝机构因素、被加工工件因素、高频电源电参数设置因素、加工液因素、电极丝的选择等,并提出了与之对应的预防和解决办法,希望对我们同行业中经常遇到此问题的一些工人和技术人员提供帮助。     

前挤压工件和模具的温度分布有限元分析

在高精密冷成形加工中,工件和模具的温度变化直接影响工件的成形精度.通过对前挤压加工过程机械热力偶合有限元模拟,对材料的流动、由于塑性变形和接触面之间的摩擦所产生的热量、工件和模具中的热传导、工件与模具之间的热交换、在成形期间和其后冷却过程中工件和模具中温度的分布等进行了分析;对工件和模具的机械和热力学性能和诸如冲头的速度、摩擦系数等加工条件对温度在工件和模具中的分布的影响进行了研究.有限元模拟的结果表明,在成形加工中由于热膨胀和冷却的影响,工件和模具中温度的变化将影响工件的成形精度.工件的性能对热的产生和温度分布有决定性的影响;加工条件的变化会影响温度的高低和分布.     

电火花小孔加工电极损耗及形状变化试验研究

对电火花小孔加工进行试验研究,分析电极长度损耗和角损耗的影响因素,得到电极材料、工件材料、加工极性对电极长度损耗和角损耗的影响规律.以模具钢为加工对象进行电火花小孔加工,分析了小孔加工时黄铜电极与石墨电极的形状变化规律.发现电极先发生角损耗,形成球状端面,当进入侧面损耗阶段后,形成锥状电极.试验结果还表明随着加工的进行,工具电极前端面的锥度不断增大,但电极端面圆弧的圆心角基本恒定.     

轨道车辆铝合金车体铆接车底架钻孔工艺研究

为了提高铝合金铆接车体底架钻孔的精度,通过对加工过程中存在的加工缺陷进行分析.分析发现钻孔补偿值的获取方法、工件来料本身、工件的装夹等均会对底架铆接孔的精度产生影响.针对这些影响因素,提出了如优化补偿值获取区域、利用主轴反转去屑、优化加工路径优化、边梁断面微铣削等改进措施和方法结果表明,利用优化后的加工工艺方法进行加工,其加工时间和加工精度相比于优化前分别提高了40 min和0.3 mm左右,在较大程度上提高了加工效率和精度,降低了不良产品的发生率.     

前挤压工件和模具的温度分布有限元分析

在高精密冷成形加工中，工件和模具的温度变化直接影响工件的成形精度，通过对前挤压加工过程机械热力偶合有限元模拟，对材料的流动，由于塑料变形和接触面之间的摩擦所产生的热量，工件和模具中的热传导，工件与模具之间的热交换，在成形期间和其后冷却过程工件和模具中温度的分布等进行了分析，对工件和模具的机械和热力学性能和诸如冲头的速度，摩擦系数等加工条件对温度在工件和模具中的分布的影响进行了研究，有限元模型的结果表明，在成形加工中由于热膨胀和冷却的影响，工件和模具中温度的变化将影响工件的成形精度，工件的性能对热的产生和温度分布有决定性的影响，加工条件的变化会影响温度的高低和分布。     

车削加工物理仿真技术研究

提出获得工件廓形的“三瞬心成形法”,建立多误差作用下车削加工工件精度预测数理模型,可预测实际加工工件表面变化趋势,可显示工件在任一位置的加工精度。     

车削加工物理仿真技术研究

提出获得工件廓形的"三瞬心成形法",建立多误差作用下车削加工工件精度预测数理模型,可预测实际加工工件表面变化趋势,可显示工件在任一位置的加工精度.     

虚拟车削加工尺寸精度预报方法

研究车削加工直径尺寸形成机理,简化工艺系统尺寸链,得出三瞬心法预测工件加工精度的理论模型;在对工艺系统误差检测与辩识的基础上,实现对虚拟车削加工（一次进刀级）工件的精度预报,其结果与实际加工测量误差可控制在１０％以内。     

虚拟车削加工尺寸精度预报方法

研究车削加工直径尺寸形成机理,简化工艺系统尺寸链,得出三瞬心法预测工件加工精度的理论模型;在对工艺系统误差检测与辩识的基础上,实现对虚拟车削加工(一次进刀级)工件的精度预报,其结果与实际加工测量误差可控制在10%以内.     

Some Key Technologies of a New-type CNC Curve Grinding Machine

This paper presented a new-type CNC curve grinding machine, in order to conquer the disadvantages of conventional NC curve grinding machine and improve surface quality, dimensional accuracy and machining efficiency. The new-type grinder adopts some high and new technologies: ① the normal tracing device could make grinding wheel coincide with the normal direction of the machining points in work piece, and improve surface quality and dimensional accuracy; ② the digital image on-line recognition system could monitor machining process and compensate wheel wear in real time; ③ linear motor drive mechanism could realize the exact adjustment of the grinding head digitally and increase the machining efficiency. The math models of normal tracing and circular tolerance zone were presented. The experimental results show that the new-type CNC curve grinding machine equipped with the three devices mentioned above is easy to realize the precision grinding of any complex curve, and improve surface quality, dimensional accuracy and machining efficiency.     

Dynamic Responses of Long-Span Transmission Tower-Line System Subjected to Broken Wires

A macroscopic finite element modeling approach was proposed to calculate the vibration of a tower-line system subjected to broken wires with software ANSYS/LS-DYNA. In the finite element model, not only the nonlinearity of wires and suspension insulators are considered, but also the support towers are included. The incremental and iterative approaches are combined by applying the unbalanced loads incrementally during each iteration cycle. The approach was illustrated with an example of a Hanjiang-River long-span transmission line system subjected to a shield wire and a conductor failure, respectively. The analysis results showed that the proposed dynamic simulation approach can demonstrate the kinetic process of the tower-line system subjected to wire ruptures: The frequencies of line components were lower and densely distributed, but the frequencies of tower components were higher and sparsely distributed. Anyhow, the dynamic effects of wire ruptures on tower-line system could not be ignored in analysis of tower-line system subjected wire failures.     

Optimization of Numerical Control Program and Machining Simulation Based on VERICUT

In the machining process of large-scale complex curved surface, workers will encounter problems such as empty stroke of tool, collision interference, and overcut or undercut of the workpieces. This paper presents a method for generating the optimized tool path, compiling and checking the numerical control(NC) program.Taking the bogie frame as an example, the tool paths of all machining surface are optimized by the dynamic programming algorithm, Creo software is utilized to compile the optimized computerized numerical control(CNC)machining program, and VERICUT software is employed to simulate the machining process, optimize the amount of cutting and inspect the machining quality. The method saves the machining time, guarantees the correctness of NC program, and the overall machining efficiency is improved. The method lays a good theoretical and practical foundation for integration of the similar platform.     

模具制造中的高速切削技术分析

随着国家高新技术产业的快速发展,对模具制造业也提出较高要求,传统的模具制造通常采用先铣削再淬硬,然后电火花加工及后续抛磨,制造工艺复杂、加工效率低、能源消耗高、污染较大。高速切削技术应用在模具制造业中,可以直接通过高速硬切削获得较高的精度及表面质量,高速切削技术制造工艺过程简单、加工效率较高、能源消耗少、污染较小且具有良好的经济效益,因此,适宜在模具加工中广泛推广应用。     

Electrode wear prediction in milling electrical discharge machining based on radial basis function neural network

Milling electrical discharge machining (EDM) enables the machining of complex cavities using cylindrical or tubular electrodes. To ensure acceptable machining accuracy the process requires some methods of compensating for electrode wear. Due to the complexity and random nature of the process, existing methods of compensating for such wear usually involve off-line prediction. This paper discusses an innovative model of electrode wear prediction for milling EDM based upon a radial basis function (RBF) network. Data gained from an orthogonal experiment were used to provide training samples for the RBF network. The model established was used to forecast the electrode wear, making it possible to calculate the real-time tool wear in the milling EDM process and, to lay the foundations for dynamic compensation of the electrode wear on-line. This paper demonstrates that by using this model prediction errors can be controlled within 8%.     

桥梁缆索钢丝疲劳性能影响因素试验

为研究桥梁缆索钢丝的疲劳与腐蚀疲劳性能，采用不同强度等级新钢丝、服役7年的斜拉桥拉索钢丝和人工加速腐蚀钢丝开展了缆索钢丝疲劳与腐蚀疲劳试验；根据典型疲劳断口宏观形貌特征，探究了缆索钢丝的疲劳断裂机制；采用威布尔分布函数拟合了缆索钢丝的应力-疲劳寿命曲线，对比了不同钢丝应力-疲劳寿命曲线的差异，揭示了强度等级、应力比、腐蚀损伤和腐蚀疲劳损伤4个关键因素对缆索钢丝抗疲劳性能的影响规律，并建议了相应的疲劳强度曲线。试验结果表明：钢丝未发生腐蚀时抗疲劳性能良好，随着强度等级的提高，缆索钢丝的疲劳强度显著增大，对应的疲劳极限也逐渐上升；缆索钢丝的疲劳强度随应力比的增大而显著减小；腐蚀和腐蚀疲劳损伤均会大幅降低缆索钢丝的疲劳强度，腐蚀疲劳损伤对缆索钢丝剩余疲劳寿命的影响大于单一腐蚀损伤；新钢丝的疲劳裂纹起源于表面划痕或材料不均匀处，对于带腐蚀和腐蚀疲劳损伤的钢丝，蚀坑处存在显著的应力集中，疲劳裂纹源形成于钢丝表面蚀坑处，多源裂纹萌生与裂纹不规则扩展的几率增大；桥梁缆索抗疲劳设计与安全评估时应综合考虑钢丝强度等级、应力比、腐蚀和腐蚀疲劳损伤的影响，试验采用国内桥梁缆索广泛使用的钢丝，得到的疲劳强度可...     

薄壁叶片加工误差分析与预测

薄壁叶片在数控加工中容易变形,影响加工精度,提出了采用柔性变形迭代方法计算叶片铣削过程中的变形量．首先利用正交切削仿真试验确定球头铣刀的铣削力模型,并给出叶片数控加工刀触点计算方法,再将切削力加载到叶片的有限元网格节点上,采用柔性变形迭代方法计算出薄壁叶片的变形量．结果表明,所提出的方法能有效地预测薄壁零件的变形,为叶片加工误差补偿提供了依据．     

Research Progress of Interfacial Chemism of High Efficiency Organic Grinding Fluid for Si3N4 Ceramics

IntroductionGrinding is a most important machiningmethod for Si3N4ceramics. There is much re-searche on the grinding fluid acting as one of keyconditions in grinding, but rare on the applicationin engineering ceramics machining, especially Si3N4ceramics. Utilizing interfacial chemistry reactionmembrane can reduce friction coefficiem, and soft-en surface layer can improve the grinding efficiencyof Si3N4ceramics, which is a bran-new research di-rection. Because that the friction coefficient b…     

基于GPS的大跨度桥梁变形监测与数据处理

针对传统变形监测技术的不足,论述了采用GPS技术进行大跨度桥梁几何变形监测及数据处理的理论与方法,包括变形监测过程中GPS基准点和变形监测点的布置、监测网的组建与优化、观测精度与观测周期的技术要求,以及变形观测完成后数据的粗差剔除和精度评定,在此基础上建立回归统计模型进行桥梁关键点变形分析与预报,从而为大跨度桥梁的安全提供可靠的依据.