20 vol％SiCp/Al复合材料—硬质合金摩擦磨损表面形貌研究

以YG6X硬质合金为对磨材料,借助MMUD-5摩擦磨损试验机研究了载荷、转速和温度对20vol%SiC_p/Al复合材料干滑动摩擦磨损性能的影响,并采用SH-4000M扫描电镜和VHX-2000三维超景深光学显微镜对试样的摩擦磨损带进行观察。结果表明:当载荷小于150N时,表面质量较好,只有轻度涂覆现象;当载荷大于200N时,随着载荷的增加,表面质量越来越差,表面磨损主要为犁沟和剥离;在较低转速下,表面磨损主要是剥离和犁沟;在较高速度下,材料表面因较高的温度产生塑性形变,出现了裂纹和粘着磨损;当温度超过100℃后,磨损表面产生塑性变形,且随着温度升高,表面磨损由犁沟和剥离转变成粘着磨损和颗粒拔出等损伤。     

碳化硅增强颗粒含量和尺寸对铝基复合材料超精密车削表面的影响

用聚晶金刚石刀具(PCD)研究了增强颗粒的含量、尺寸等对SiC颗粒增强铝基复合材料超精密车削表面的影响.结果表明:SiC增强颗粒的去除方式主要有拔出、破碎和切断等,SiC颗粒的含量和平均尺寸越大,其拔出和破碎现象就越多,复合材料获得的加工表面粗糙度值也越大;当SiC颗粒主要以切断方式被去除时,可望获得含有较少坑洞和裂纹等加工缺陷的超精密切削表面.     

虚拟数控车削表面形貌的仿真与表面粗糙度预测

在国内外各种研究工作的基础上,综合考虑影响表面轮廓形成的各种相关因素,提出矢量叠加和参数动态修正两种方法相结合而建立加工表面轮廓的模型,从而解决了全方位、真实预测数控车削表面粗糙度这一技术难题。阐述了应用VC 6.0和OpenGL建立其不规则表面轮廓的关键技术。     

金刚石车削工件表面轮廓的仿真与分析

对振动情况下加工的工件表面的三维形貌进行了仿真 ,并从理论上对工件表面形貌的径向、周向与刀具螺旋轨迹方向的截面轮廓进行了分析。结果表明 :不同的截面轮廓分别载有不同的表面特征信息 ,利用这些特征有助于对刀具与工件间的相对振动进行辨识。采用有关文献中的试验数据对仿真结果进行了验证     

6061铝合金径向超声振动车削的表面完整性研究

为研究径向超声振动参数及切削参数对车削6061铝合金表面残余应力、表面粗糙度以及表面形貌的影响,采用与普通车削进行对比的方法对6061铝合金进行纵向超声振动切削试验。结果表明:与普通车削相比,径向超声振动辅助车削能显著提高零件加工表面的残余压应力;在两种切削方式下,表面残余压应力均随切削速度的增加而增大;在相同切削参数下,随着径向超声振幅的增加,6061铝合金加工表面的残余压应力变大;与普通车削相比,径向超声振动车削使工件表面的粗糙度变大,并且伴随振幅的增加,表面粗糙度呈上升趋势;通过对加工表面的三维形貌进行观测发现,超声振动辅助车削能有效抑制传统车削加工中的积屑瘤和鳞刺等表面缺陷,并显著提高加工表面质量。     

复合材料的切削加工表面质量

从已加工表面几何特性，加工硬化和残余应力几方面探讨了复合材料的切削加工表面质量问题。研究结果表明，复合材料的已加工表面包含大量的加工所致缺陷，增强体的特性和取向分布，刀具条件是决定复合材料已加工表面形貌的主要因素；复合材料已加工表面硬度甚至低于加工材料，而皮下层材料通常发生显著的加工硬化；微观上复合材料切削变形区的应力状态很复杂，实践上，复合材料的已加工表面常残余压应力，或表面加工缺陷使大部分热应力和弹性恢复应力均被释放。     

非圆表面的车削

非圆表面的加工原理是毛坯绕几何轴线旋转,而刀具以高于毛坯旋转几倍的频率作径向往复运动或摆动运动。此种加工方式不仅直接在车床上加工,而且可在有机械手装置的专用机床上加工,这些专用机床还可加工正弦曲面以及其它成形面。由于非圆表面加工使系统产生较大的交变载荷,所以,只宜在修理或小批量生产的情况下使用。在图1中,车削非圆表面需有两个主运动B_1、B_2和刀具的进给运动S。具有转数n_1的B_1是工件绕其几何轴线2运动,而具有转速n_2的B_2是轴线2绕轴线3运动。B_1和B_2就是围绕着相距为e的平行轴线旋转而     

GH4169高速车削参数对加工表面完整性影响研究

使用PVD-TiAlN涂层硬质合金刀片进行高温合金GH4169的高速车削正交试验,建立了表面完整性特征中表面粗糙度、表面残余应力、显微硬度的经验公式,分析了车削参数对表面完整性各特征量的影响规律,并观测了高速车削加工的表面形貌。结果表明:表面粗糙度随车削速度的增加而减小,随进给量和切削深度的增加而增大,进给量是影响表面粗糙度的最主要因素;随着进给量的增加,表面形貌变差;轴向残余应力表现为压应力,切向残余应力表现为拉应力,减小进给量,降低车削速度可减小车削加工的残余应力,轴向残余应力对进给量最敏感,切向残余应力对切削深度最敏感;显微硬度随车削速度的增大而增加,车削速度是影响显微硬度的主要因素。     

干式车削不同淬硬状态淬硬钢已加工表面粗糙度及三维形貌的试验研究

使用 PCBN 刀具对5种不同淬硬状态(40±1HRC,45±1HRC,50±1HRC,55±1HRC,60±1HRC)Cr12MoV模具钢进行干式硬态车削试验,揭示了切削速度、走刀量、切削深度、工件硬度对已加工表面粗糙度及三维形貌的影响规律及机理.研究结果表明:与车削硬度为40±1HRC、45±1HRC、60±1HR...     

硬质合金刀具车削GCr15轴承钢表面微观形貌试验研究

通过硬质合金刀具车削加工GCr15轴承钢试验,对比了车削表面微观形貌几何模型与实际加工表面,获得了刀尖圆弧半径rε分别为0.4mm与0.8mm的表面微观形貌的差别,分析了已加工表面上细小沟槽形成的原因。     

统一框架下的五种三维表面纹理合成方法及其性能比较

提出一个三维表面纹理合成的总体框架,在此框架下介绍对三维表面纹理进行重光照的表示子框架,并提出表示形式之间的转换方法。在基于图像缝合的二维纹理合成方法基础上,提出并比较了五种三维表面纹理合成方法。     

Study of cutting force and surface roughness in the turning of polytetrafluoroethylene composites with a polycrystalline diamond tool

Despite the importance of the polytetrafluoroethylene (PTFE) composites in many industrial applications, especially for space industry, very little is known about the machinability of these composites. This paper presents an investigation into the turning of PTFE composites using a polycrystalline diamond tool in order to analyze the effect of the cutting parameters and insert radius on the cutting force and surface roughness. A strain gauge based dynamometer for the main cutting force measurement in turning was constructed. The force signals were captured and processed using a strain data acquisition system based on the Sider8 and CATMAN software. Cutting force and surface roughness were measured through longitudinal turning, according to the experimental plan developed based on the Taguchi methodology. The signal-to-noise ratio and the analysis of variance were applied to the experimental data in order to determine the effect of the process variables on the surface roughness and cutting force, and predictive models have been derived.     

Experimental investigations of surface roughness in orthogonal turning of unidirectional glass-fiber reinforced plastic composites

Cutting parameters and the resulting cutting forces have a great effect on the machinability of materials during the turning process. The effects of cutting parameters on machinability have been examined by many researchers and studies on determination of suitable cutting conditions for various materials are still under investigation. In this study, surface roughness of unidirectional glass-fiber reinforced plastic composite was examined on the basis of cutting parameters such as depth of cut, feed rate, tool geometry, and cutting speed. The surface quality was found to relate closely to the feed rate, cutting speed, and cutting tool.     

W-Fe-Ni合金车削残余应力正交试验研究

采用极差分析法分析基于正交试验的W-Fe-Ni合金车削试验结果。结果表明:加工表面切向残余应力为拉应力,其主要影响因素是切削深度;轴向残余应力为压应力,其主要影响因素是进给量。并讨论了获得较小车削表面残余应力的合理切削条件。     

3D surface form error evaluation using high definition metrology

This paper presents an approach to evaluate 3D surface form error of machined surface using high definition metrology that can measure millions of data points representing the entire surface. A data preprocessing method was developed to convert the mass data into a height-encoded and position-maintained gray image. With the converted image, a modified gray level co-occurrence matrix method was adopted to extract 3D surface form error characteristics, including entropy, contrast and correlation. Entropy measures the randomness of surface height distribution. Contrast indicates the degree of surface local deviations. Correlation could be used to identify different machining techniques. These characteristics can be used with flatness together to evaluate 3D surface form error of large complex surface.     

Optimisation of surface roughness on turning fibre-reinforced plastics (FRPs) with diamond cutting tools

Fibre-reinforced plastics (FRPs) are used in structural components in various fields of application of mechanical engineering, such as automobile, biomechanics and aerospace industries. Their own properties, particularly the high strength and stiffness and simultaneously low weight, allows the substitution of the metallic materials in many cases. As a result of these properties and potential applications, exist a great necessity to investigate the machining of these composite materials.This paper presents an optimisation study of surface roughness in turning FRPs tubes manufacturing by filament winding and hand lay-up, using polycrystalline diamond cutting tools. A plan of experiments was performed with cutting parameters prefixed in the FRP tubes. The objective was establishing the optimal cutting parameters to obtain a certain surface roughness (R_a and R_t/R_max), corresponding to international dimensional precision (ISO) IT7 and IT8 in the FRP workpieces, using multiple analysis regression (MRA). Additionally, the optimal material removal rates have been obtained.     

Surface quality investigation of turbine blade steels for turning process

The quality of surface or surface finish is the widely used index of product quality and it is also critical in functional behavior of the products like turbine blades, especially when they are in contact with other medium or the materials. This paper presents the surface quality evaluation of turbine blade steels (ST 174PH, ST 12TE and ST T1/13W) for different combination of cutting parameters viz. speed, feed and depth of cut in a CNC turning process. The response surface method (RSM) is devised in design of experiments and 20 experiments per material are conducted in surface quality evaluation and analysis. The results are analyzed using ANOVA and different graphical methods like contour plot and 3D surface graphs. The reasons for the highest surface roughness of ST 174PH material are analyzed using metallurgical perspective. The regression equations for predicting the surface roughness of the materials are formulated in terms of cutting parameters based on experimental results and are verified using confirmatory experiments.     

基于Java3D的不规则曲面纹理贴图的研究

针对Java3D对不规则曲面难以贴图的困难,提出离散化二维纹理图案的方法,对待贴图的不规则曲面进行有限数量的网格细分,然后寻找出离散点与局部三角形面片中各点的对应关系,即点对点的转换,从而完成由二维纹理空间到曲面空间的贴图.     

A new quantitative evaluation for characteristic of surface roughness in turning

With turning as the aim, a method for quantitatively evaluating the stability of cutting phenomena and a machining system from the machined surface profile (primary profile and roughness profile) is proposed, based on the hypothesis that when the ideal cutting is achieved, the form of the cutter should be perfectly copied on the machined surface and the process can be replicated. Therefore, if the form and the position of the cutter (normally known) are estimated, should be possible to quantitatively evaluate the stability of the cutting phenomena, including adhesion and built-up edge, based on the difference between the actual machined surface and the position of the cutter estimated. Moreover, due to the estimated positional accuracy of the adjoining cutting edges, it should be possible to evaluate the stability of the machining system based on the vibration and the accuracy of spindle rotation. In this study, a method for estimating a cutting edge during machining from a surface profile was developed. Furthermore, the proposed method was applied to evaluate three elements: a virtually ideal machining surface with good transferability, a machining surface with poor transferability, wherein feed marks are clear, and a surface with variable transferability and feed marks due to chatter or adhesion. The results indicated that the proposed method can be successfully used to extract these characteristics.     

AutoCAD环境下工程自由曲面的一种三维重建方法

提出一种AutoCAD环境下工程自由曲面的三维重建方法 ,根据投影栅相位法测得的三维离散数据 ,将 3DMESH命令与脚本文件相结合 ,实现自由曲面三维模型的自动重建