3D Evaluation Method of Cutting Surface Topography of Carbon / Phenolic (C/Ph) Composite

3D evaluation method of cutting surface topography for C/Ph composites was established.The cutting surface was measured by Talyscan 150,using 3D non-contact measurement.Through the results of 2D and 3D roughness evaluating for C/Ph composite and Duralumin,the 2D evaluation method of the cutting surface topography of C/Ph composite loses a lot of information,the characteristics of the surface topography of C/Ph composite can be comprehensively and authentically evaluated only by 3D evaluation method.Furtherm...     

3D evaluation method of cutting surface topography of carbon / phenolic (C/Ph) composite

3D evaluation method of cutting surface topography for C/Ph composites was established.The cutting surface was measured by Talyscan 150,using 3D non-contact measurement.Through the results of 2D and 3D roughness evaluating for C/Ph composite and Duralumin,the 2D evaluation method of the cutting surface topography of C/Ph composite loses a lot of information,the characteristics of the surface topography of C/Ph composite can be comprehensively and authentically evaluated only by 3D evaluation method.Furthermore,3D amplitude and spatial parameters were adopted to evaluate the surface.The results show that: the topography of the C/Ph composite is anisotropic,there are more valleys in the machined surface of C/Ph than that of duralumin,and there are not obvious feeding textures for C/Ph,which indicates the machining mechanism is different from the metal.In conclusion,the topography of the C/Ph composite cutting surface is anisotropic;the cutting surface of C/Ph composite needs 3D evaluation method.     

PBT／CNTs复合材料的制备及其导电性能

采用熔融共混法制备聚对苯二甲酸丁二醇酯（PBT）／碳纳米管（CNTs）复合材料,研究了不同分散工艺处理的原生CNTs和不同CNTs质量分数对复合材料表面电阻的影响。利用扫描电镜观察了处理后CNTs的分布状态和PBT／CNTs复合材料的微观形貌。结果表明：球磨分散使CNTs有更好的分散效果并更好地提高了复合材料的导电率;随着CNTs质量分数的不断增加,复合材料的表面电阻呈不断下降的趋势,导电阀值出现在CNTs质量分数约为4％时。     

周铣加工表面形貌仿真新算法

考虑主轴偏心，基于周铣过程中刀具切削刃上任意点与工件相对运动的轨迹方程和周铣过程几何特征，构造出可以求解周铣加工表面上任意一点形貌高度值的三维表面形貌仿真算法，并给出了相应的仿真算例。该算法无需对刀齿进行微段离散，并且不依赖于工件网格划分，加工表面上任意一点形貌高度值的计算次数等于刀具齿数，具有通用性好、运算速度快、结果准确度高的特点。     

SiCp/Al复合材料三维表面粗糙度信息提取方法

为研究SiCp/Al复合材料三维表面粗糙度信息的提取方法,进行高速铣削实验,并利用OLS3000激光共聚焦扫描显微镜对表面微观轮廓进行非接触式测量.采用最小二乘法、高斯滤波法和扩展高斯滤波法针对已加工表面进行三维粗糙度信息的提取,并计算三维粗糙度参数,从受缺陷的影响程度以及稳定性两方面对3种方法的信息提取效果进行对比.结果表明:高斯滤波法和扩展的高斯滤波法对缺陷的敏感程度较高,且提取出的信息稳定性不好;最小二乘法能很好保留缺陷的信息并具有较高的稳定性,更适合对颗粒增强型铝基复合材料进行三维表面粗糙度信息的提取.     

考虑刀杆柔性的铣削过程动力学模型

针对目前数控加工中心整体刚性较好的特点,首先提出一种新的适合于长径比（长度和直径之比）较大的立铣刀铣削过程动力学模型,然后基于力学变分原理建立了该模型的振动微分方程并且给出广义力和位移的边界条件;最后对给定铣削力条件下刀杆的动力响应进行了计算机仿真．为后续的动态铣削过程仿真以及加工表面形貌预测奠定了基础．     

B-样条小波在加速度信号处理分析中的应用

采用傅里叶变换的数字信号处理方法处理航空弹射加速度信号，运用多分辨率信号分解与重构算法进行处理，用小波重构法滤波得到人体响应输出的幅度谱、功率谱比用FIR滤波得到的波形频谱清晰，且谱峰分辨率高，证明了小波变换方法的可行，且效果优于传统方法。     

Adaptive preprocessing algorithms of corneal topography in polar coordinate system

New adaptive preprocessing algorithms based on the polar coordinate system were put forward to get high-precision corneal topography calculation results. Adaptive locating algorithms of concentric circle center were created to accurately capture the circle center of original Placido-based image, expand the image into matrix centered around the circle center, and convert the matrix into the polar coordinate system with the circle center as pole. Adaptive image smoothing treatment was followed and the characteristics of useful circles were extracted via horizontal edge detection, based on useful circles presenting approximate horizontal lines while noise signals presenting vertical lines or different angles. Effective combination of different operators of morphology were designed to remedy data loss caused by noise disturbances, get complete image about circle edge detection to satisfy the requests of precise calculation on follow-up parameters. The experimental data show that the algorithms meet the requirements of practical detection with characteristics of less data loss, higher data accuracy and easier availability.     

基于网络的虚拟数控铣削系统

描述了一个基于网络的虚拟数控铣削系统.运用3DSMAX和虚拟现实建模语言(VirtualRealityModelingLanguage-VRML)分别建立了虚拟数控铣床模型和三维铣削场景模型.提出并实现了一种适用于VRML语言的工件毛坯的深度元素(dexel)建模方法.运用VRML的外部编程接口(ExternalAuthoringInterface-EAI)实现了JavaApplet和VRML场景之间的交互.在Tomcat服务器平台上开发了一套基于网络的虚拟数控铣削系统,该系统允许用户通过Web浏览器直观地对虚拟数控铣床进行操作.在某一特定的切削条件下,可以获得铣削力以及加工表面形貌等用户感兴趣的数据.据此可对加工工艺参数的合理性进行评估.     

索桁式玻璃幕墙风荷载时程模拟及风振响应

在利用时域分析法研究索桁式玻璃幕墙在脉动风荷载作用下的响应情况时,需要得到其表面脉动风压时程数据.以随高度变化的风速谱（Sim iu谱）为基础,通过自回归线性滤波法,模拟出空间多结点相关脉动风压时程随机序列;由模拟结果计算出的功率谱与目标功率谱吻合良好.将所得时程数据加载在索桁式玻璃幕墙的有限元模型上进行瞬态计算,对位移结果做统计分析,获得适用于结构设计使用的风振系数.     

基于多感知信息的数控铣削过程智能控制

首次提出基于多感知信息的数控铣削过程智能控制方法．首先,使用分频采样技术,从测力仪分别采集代表铣削力和振动的信息．其次,依据铣削力信号,用模糊逻辑控制,通过改变进给速度实现恒力加工;同时由振动信号的功率谱判断有无颤振发生,并在颤振发生时辨识主振频率,计算最优主轴转速,进而达到实时抑制再生颤振的目的,最后提出试验方案,并实际验证所提方法的可行性．     

热压烧结制备CNTs增强镁基复合材料的研究

对CNTs/Mg/AZ91D混合粉末进行机械球磨,采用热压烧结的方法制备CNTs/Mg/AZ91D复合材料。通过XRD,SEM等对复合材料的物相、组织和断口形貌进行分析。结果表明:复合材料以Mg为主相,含少量的Mg17Al12;复合材料的颗粒界面结合紧密,表现为韧性断裂;断口处CNTs呈拔出或桥联形貌,起到桥联强化和传递载荷的作用;当CNTs质量分数为1.0%时,复合材料显微硬度最大达到61.4 HV,相比不含CNTs的基体材料,显微硬度提高了22.6%。     

Characteristics of alumina particles in dispersion-strengthened copper alloys

Two types of alumina dispersion-strengthened copper（ADSC） alloys were fabricated by a novel in-situ reactive synthesis（IRS） and a traditional internal oxidation（IO） process. The features of alumina dispersoids in these ADSC alloys were investigated by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. It is found that nano-sized γ-Al2O3 particles of approximately 10 nm in diameter are homogeneously distributed in the IRS-ADSC composites. Meanwhile, larger-sized, mixed crystal structure alumina with rod-shaped morphology is embedded in the IO-ADSC alloy. The IRS-ADSC composites can obtain better mechanical and physical properties than the IO-ADSC composites; the tensile strength of the IRS-ADSC alloy can reach 570 MPa at room temperature, its electrical conductivity is 85% IACS, and the Rockwell hardness can reach 86 HRB.     

Fabrication of solid-phase-sintered SiC-based composites with short carbon fibers

Solid-phase-sintered Si C-based composites with short carbon fibers（Csf/SSi C） in concentrations ranging from 0 to 10wt% were prepared by pressureless sintering at 2100°C. The phase composition, microstructure, density, and flexural strength of the composites with different Csf contents were investigated. SEM micrographs showed that the Csf distributed in the SSi C matrix homogeneously with some gaps at the fiber/matrix interfaces. The densities of the composites decreased with increasing Csf content. However, the bending strength first increased and then decreased with increasing Csf content, reaching a maximum value of 390 MPa at a Csf content of 5wt%, which was 60 MPa higher than that of SSi C because of the pull-out strengthening mechanism. Notably, Csf was graphitized and damaged during the sintering process because of the high temperature and reaction with boron derived from the sintering additive B4C; this graphitization degraded the fiber strengthening effect.     

Thermal expansion and mechanical properties of middle reinforcement content SiCp/Al composites fabricated by PM technology

Middle reinforcement content SiCp/Al composites(Vp=30%, 35% and 40%) for precision optical systems applications were fabricated by powder metallurgy technology. The composites were free of porosity and SiC particles distributed uniformly in the composites. The mean linear coefficients of thermal expansion(20-100 ℃) of SiCp/Al composites ranged from 11.6×10-6 to 13.3×10-6 K-1 and decreased with an increase in volume fraction of SiC content. The experimental coeffi cients of thermal expansion agreed well with predicted values based on Kerner's model. The Brinell hardness increased from 116 to 147, and the modulus increased from 99 to 112 GPa for the corresponding composites. The tensile strengths were higher than 320 MPa, but no signifi cant increasing trend between tensile strength and SiC content was observed.     

Mechanical,electrical, and thermal expansion properties of carbon nanotube-based silver and silver-palladium alloy composites

The mechanical, electrical, and thermal expansion properties of carbon nanotube（CNT）-based silver and silver–palladium（10：1, w/w） alloy nanocomposites are reported. To tailor the properties of silver, CNTs were incorporated into a silver matrix by a modified molecular level-mixing process. CNTs interact weakly with silver because of their non-reactive nature and lack of mutual solubility. Therefore, palladium was utilized as an alloying element to improve interfacial adhesion. Comparative microstructural characterizations and property evaluations of the nanocomposites were performed. The structural characterizations revealed that decorated type-CNTs were dispersed, embedded, and anchored into the silver matrix. The experimental results indicated that the modification of the silver and silver–palladium nanocomposite with CNT resulted in increases in the hardness and Young＇s modulus along with concomitant decreases in the electrical conductivity and the coefficient of thermal expansion（CTE）. The hardness and Young＇s modulus of the nanocomposites were increased by 30%？40% whereas the CTE was decreased to 50%-60% of the CTE of silver. The significantly improved CTE and the mechanical properties of the CNT-reinforced silver and silver–palladium nanocomposites are correlated with the intriguing properties of CNTs and with good interfacial adhesion between the CNTs and silver as a result of the fabrication process and the contact action of palladium as an alloying element.     

Microstructure and properties of electronic packaging shell with high silicon carbide aluminum-base composites by semi-solid thixoforming

The electronic packaging shell with high silicon carbide aluminum-base composites was prepared by semi-solid thixoforming technique. The flow characteristic of the Si C particulate was analyzed. The microstructures of different parts of the shell were observed by scanning electron microscopy and optical microscopy, and the thermophysical and mechanical properties of the shell were tested. The results show that there exists the segregation phenomenon between the Si C particulate and the liquid phase during thixoforming, the liquid phase flows from the shell, and the Si C particles accumulate at the bottom of the shell. The volume fraction of Si C decreases gradually from the bottom to the walls. Accordingly, the thermal conductivities of bottom center and walls are 178 and 164 W·m-1·K-1, the coefficients of thermal expansion（CTE） are 8.2×10-6 and 12.6×10-6 K-1, respectively. The flexural strength decreases slightly from 437 to 347 MPa. The microstructures and properties of the shell show gradient distribution.     

Machining studies of die cast aluminum alloy-silicon carbide composites

Metal matrix composites(MMCs)with high specific stiffness,high strength,improved wear resistance,and thermal properties are being increasingly used in advanced structural,aerospace,automotive,electronics,and wear applications.Aluminum alloy-silicon carbide composites were developed using a new combination of the vortex method and the pressure die-casting technique in the present work.Ma-chining studies were conducted on the aluminum alloy-silicon carbide(SiC)composite work pieces using high speed steel(HSS)end-mill tools in a milling machine at different speeds and feeds.The quantitative studies on the machined work piece show that the surface finish is better for higher speeds and lower feeds.The surface roughness of the plain aluminum alloy is better than that of the aluminum alloy-silicon carbide composites.The studies on tool wear show that flank wear increases with speed and feed.The end-mill tool wear is higher on ma-chining the aluminum alloy-silicon carbide composites than on machining the plain aluminum alloy.     

铣削过程中切削功率的数据采集和预处理

介绍了一种具有人工参与的铣削加工离线控制系统；讨论了由主轴电机变频器获取切削功率信号的方法，以及该信号的特点；设计了相应的检测电路和滤波电路，得到控制过程所需的缓变信号，并利用PCL 812PG数据采集卡对信号进行采集和数字信号预处理，大大减少了数据处理的时间，提高了实时性，为控制系统提供了有效的状态信息.     

球头刀多轴铣削表面形貌建模仿真研究

基于铣削加工刀位轨迹,通过建立球头刀多轴铣削过程中切削刃上任意点相对工件运动的轨迹方程,求解铣削加工表面点形貌高度值.研究了进给方式、刀具倾斜方式、倾斜角度与主轴偏心等因素对加工表面形貌及粗糙度的影响.该算法的优点在于勿需对刀齿进行离散,也不需对工件进行三维网格划分,通用性好.仿真结果与实验及文献结果对比表明,算法对工件表面微观几何形貌和粗糙度的预测准确度高,对实际加工中合理选择加工参数具有指导意义.