提高珩磨工序的质量和效率

本文介绍通过改进珩磨头结构和采用柔性塑料条来提高珩磨工序的质量和效率。     

碳化硅在金刚石工具中的应用

在金刚石工具的金属结合剂中,适当加入碳化硅磨料,可以改变结合剂的膨胀系数和耐磨性等物理机械性能,从而改善金刚石工具过渡层与工作层之间的界面结合有效防止工作层的脱落和变形,本文介绍了在这方面进行的探索以及取得的实用效果。     

珩磨工具用中温钎焊材料的研制

针对目前珩磨条钎焊存在的问题,采用中温钎焊对珩磨工具进行了连接试验,对中温钎焊用钎料的化学成分进行了调整,测试了钎料的熔化温度、钎料对珩磨条的润湿性以及钎焊接头的抗拉强度,并比较了不同钎料钎焊后珩磨工具的变形量.研究表明:中温钎焊工艺变形小,强度较高,是珩磨条连接的可行方式.     

加工渗硼45^#钢及离子氮化1Cr18Ni9Ti不锈钢工件用金刚石和…

本文介绍了用于加工渗硼４５钢及离子氮化１Ｃｒ１８Ｎｉ９Ｔｉ工件内孔的珩磨油石。讨论了金属结合剂特性、磨料种类、粒度、浓度及制造工艺对油石性能的影响，使用表明，本文研制的油石能满足用户要求，并取得了较好的经济效益。     

摩托车发动机气缸及连杆珩磨加工用超硬材料珩磨油石的研制

本文介绍了用于加工摩托车发动机气缸及连杆的超硬材料珩磨油石,讨论了金属结合剂特性,磨粒种类、粒度,浓度,制造工艺时油石性能的影响,经使用表明,本文研制的油石能满足用户要求,并取得了较好的经济效益。     

强力珩磨工艺的试验研究

本文探讨了珩磨工艺参数对珩磨效果的影响规律。试验证实了珩磨过程存在临界压力,大于临界压力的珩磨可认为是强力珩磨。珩磨效率可显著提高,从而可代替半精镗、精镗及滚压加工,简化工艺过程。试验确定了具体条件下珩磨工艺参数的选择。     

国外珩磨机采用的新技术

笔者有幸参加了两次铁道部通过中机公司国际招标部组织的珩磨机国际招标和评标，分别与美、德、英、日等国的珩磨机制造厂（包括美国巴恩斯（PARNES）国际股份公司，美国世纪（CENI：IJltY）机床公司，德国格林（GEHRIN）公司，德国卡地亚（KAI）IA）公司，德国纳格尔（NAGEL）公司，英国琼斯（J＆S）公司，日本千岛（CHISHIMA）工业株式会社，日本东洋（TOYO）现代技术有限公司）的技术专家进行了技术交流，并有幸赴德国卡地亚公司进行珩磨机培训，并接待了五批到我厂安装调试的德方技术人员，对历磨工件孔径树一300tylr…     

钛合金TC11深孔珩磨时油石磨料的选择

深孔珩磨钛合金难度很大.本研究针对TC11的特性,选用不同主磨料和辅磨料,按不同混合比例研制了15种珩磨油石,并用它们对TC11钛合金进行深孔珩磨对比试验.利用动态电阻应变仪、函数记录仪和测扭矩传感器进行了数据跟踪,绘制出了各混合磨料油石珩磨钛合金的磨削比和比磨削能图.结合示图分析,最终确定珩磨TC11的油石材料应选用...     

搅拌摩擦焊用搅拌头研究现状与发展趋势

系统地总结和分析了国外搅拌摩擦焊用搅拌头的研究发展现状,并指出了每种搅拌头的设计思想、作用和优缺点。通过各种搅拌头的比较,指出了可自动变轴肩尺寸且可自动伸缩式搅拌头是最有发展前景的搅拌头技术,该技术解决了搅拌摩擦焊接技术早期应用中所遇到的一系列难题。同时指出了如何获得耐高温、高强度的搅拌头仍然是目前搅拌摩擦焊领域急需解决的难点。     

Calibrated method for ultrasonic on-line monitoring of gradual wear during turning operations

On-line tool condition monitoring is essential for modern machining systems, especially in the case of precision and unmanned machining. Knowledge of the condition and the expected life of the tool are very important inputs for determining the optimal machining parameters. Previous efforts have indicated that ultrasonic gaging methods can be used to directly measure in-process gradual tool wear during turning operations. Good correlation was shown between the level of gradual wear and the ultrasonic signals. However, the correlation was tool dependent. This was mainly attributed to variations in the tool materials and inconsistent coupling of the transducer to the tools. This paper describes a robust method for on-line gradual wear monitoring using normalized ultrasonic signals. A consistent calibration mark, cut in the lower comer of the tool nose, is used to generate a calibration echo. The calibration echo is affected by the same variations as that of the gradual wear and is used to normalize the nose and flank echoes. Experiments under various cutting conditions showed that the gradual wear measurements can be made tool independent by normalizing the measurements with the calibration mark. In addition, the variations in the signals which were previously reported are also eliminated.     

High-speed milling of titanium alloys using binderless CBN tools

The performance of conventional tools is poor when used to machine titanium alloys. In this paper, a new tool material, which is binderless cubic boron nitride (BCBN), is used for high-speed milling of a widely used titanium alloy Ti–6Al–4V. The performance and the wear mechanism of the BCBN tool have been investigated when slot milling the titanium alloy in terms of cutting forces, tool life and wear mechanism. This type of tool manifests longer tool life at high cutting speeds. Observations based on the SEM and EDX suggest that adhesion of workpiece and attrition are the main wear mechanisms of the BCBN tool when used in high-speed milling of Ti–6Al–4V.     

A new receptance coupling substructure analysis methodology to improve chatter free cutting conditions prediction

The cutting process stability depends on machine tool dynamics that is strongly influenced by the tool. Receptance coupling substructure analysis (RCSA) can be used to estimate the tool tip dynamic compliance and consequently the chatter free cutting conditions when the machine is equipped with a tool that has not been previously tested. This methodology can be particularly useful on real shop–floors where a lot of different tool–tool holder configurations are generally used. RCSA typically combines experimental dynamic compliance measurements performed on a machine equipped with a selected tool and the finite element (FE) models of both the already tested tool and the new ones. This paper presents a new receptance coupling substructure analysis (RCSA) approach that overcomes the drawbacks in the estimation of the receptances that contain rotational and moment contributes. This indeed often limits the accuracy of the RCSA techniques presented in other scientific works. The proposed formulation allows to better estimate both the matrices of receptances of the spindle–tool holder assembly and the tool–tool holder connection stiffness. Those quantities are used, together with the FE model of the new tool, to predict the unknown tool tip dynamic compliance. Some useful guidelines to implement the proposed RCSA are also defined: they allow to manage the procedure accuracy considering the experimental methodology typically used to measure dynamic compliances. The proposed innovative RCSA is experimentally tested and validated.     

PCBN刀具切削性能和磨损机理研究综述

聚晶立方氮化硼(PCBN)刀具是继聚晶金刚石刀具之后的又一种超硬刀具,以其独特的“以车代磨”、“硬态加工”、“干式切削”等方式被誉为21世纪的绿色环保刀具。PCBN刀具在金属切削方面具有广泛的应用,主要用来加工各种淬硬钢、耐磨铸铁等铁基材料。本文介绍了PCBN刀具成分、几何形状、切削参数等对其切削性能的影响,在此基础上分析了不同材料加工时刀具的主要磨损机理,还简单对比了硬质合金和PCBN刀具切削性能上的差异。      

数控镗刀磨损与破损的声发射监测法

通过分析声发射传感器采集的刀具磨损状态信号,提取出反映刀具磨损状态的特征向量MFCC系数及差分系数,然后利用隐马尔可夫模型进行信号处理,建立了检测镗刀刀具状态的监测系统。实验结果表明:在刀具的正常磨损阶段,该监测系统可以实现刀具大致磨损量的预报;在刀具破损或损坏情况下,能够及时监测和预报刀具损坏状态。这种监测方法可用于实时在线监测,为刀具的磨损监测提供了一条切实可行的途径。     

High Speed Turning of H-13 Tool Steel Using Ceramics and PCBN

H-13 is the toughest tool steel used in machined die casting and forging dies. Due to its extreme hardness and poor thermal conductivity high speed cutting results in high temperature and stresses. This gives rise to surface damage of the workpiece and accelerated tool wear. This study evaluates the performance of different tools including ceramics and PCBN using practical finite element simulations and high speed orthogonal cutting tests. The machinability of H-13 was evaluated by tool wear, surface roughness, and cutting force measurements. From the 2D finite element model for orthogonal cutting, stresses and temperature distributions were predicted and compared for the different tool materials.     

Investigation of the wear mechanism of cubic boron nitride tools used for the machining of compacted graphite iron and grey cast iron

Various experiments were performed to investigate the wear mechanism of cubic boron nitride (cBN) tools used for the machining of compacted graphite iron (CGI). Comparative studies for tools used to machine grey cast iron (CI) were also performed in order to find out why in this case the tool lifetime is significantly higher. Two main effects were found that are responsible for tool wear, namely: (1) oxidation of the tool, and (2) interdiffusion of constituting elements between tool and CGI. These wear mechanisms are more or less the same for the machining of CGI and grey CI. The difference in tool lifetime can be explained by the formation of a MnS layer on the tool surface in the case of grey CI. This layer is missing in the case of CGI. The MnS layer acts as a lubricant and as a diffusion barrier and is the reason for the reduced wear in the case of grey CI.     

Modeling and tool wear in drilling of CFRP

This paper presents the prediction and evaluation of thrust force in drilling of carbon composite material. In order to extend tool life and improve quality of hole drilling, a better understanding of uncoated and coated tool behaviors is required. This paper describes the development of a phenomenological model between the thrust force, the drilling parameters and the tool wear. The experimental results indicate that the feed rate, the cutting speed and the tool wear are the most significant factors affecting the thrust force. The model can then be used for tool-wear monitoring. The model presented here is verified by experimental tests.