Cimatron E7.0在模具型腔加工中的应用

通过实例阐述了Cimatron E7．0在模具加工方面的应用,讲解了其加工刀路的设计及其加工过程的模拟。     

基于Pro/E及VB的注射模设计动态演示系统

分析了基于Pro／E Wildfire的注射模设计的基本流程,构建了动态演示系统的功能模型,并以VB6．0为主要开发工具开发了动态演示系统。     

基于HT-12D的分布式测温系统

在介绍HT-12D芯片工作原理的基础上,设计了一套分布式测温系统。通过3根导线,将控制编码部分与多个测温单元连接,实现多点温度测量。温度信号以电流形式传输,提高了系统的抗干扰能力。     

基于逆向工程的明代圈椅模型重构与设计创新

目的 通过数字化模型的重构降低圈椅三维建模的难度,缩短以明代圈椅为原型进行设计创新的周期。方法 基于逆向工程技术、三维激光扫描仪和Imageware反求软件,获取圈椅的三维数字化点云数据,借助Pro/Engineer软件进行结构优化设计,形成圈椅的数字化原型。对圈椅的椅圈、靠背等零部件进行创新设计,通过组合重构的方式形成全新的圈椅形态。结论 借助逆向工程对传统家具进行设计创新不仅有益于明代圈椅的传承,并在减低设计创新成本,缩短设计周期方面也具有重要的意义。     

Effect of mean stress on fatigue properties of 1800 MPa-class spring steels

Fatigue tests were conducted for 1800 MPa-class spring steels at various stress ratios. For comparison, similar fatigue tests were conducted for conventional steels whose tensile strength was lower than 1200 MPa. The spring steels exhibited fish-eye fractures, and the origins of these fractures were oxide, TiN and the matrix itself. In contrast, the conventional steels never exhibited fish-eye fractures. The fatigue strength of these steels decreased monotonously as the stress ratio increased, when the fatigue strength was evaluated in terms of stress amplitude. However, the fatigue strength degradation was less than that expected from a modified-Goodman line, and the best fit line was obtained by connecting the fatigue limit at zero mean stress to true fracture strength instead of tensile strength. This research also reviewed application of a power low to the stress ratio effect evaluation. In these results, the difference between the spring and conventional steels was negligible.     

Effect of size and shape of metal particles to improve hardness and electrical properties of carbon nanotube reinforced copper and copper alloy composites

Utilizing the extra-ordinary properties of carbon nanotube (CNT) in metal matrix composite (MMC) for macroscopic applications is still a big challenge for science and technology. Very few successful attempts have been made for commercial applications due to the difficulties incorporating CNTs in metals with up-scalable processes. CNT reinforced copper and copper alloy (bronze) composites have been fabricated by well-established hot-press sintering method of powder metallurgy. The parameters of CNT–metal powder mixing and hot-press sintering have been optimized and the matrix materials of the mixed powders and composites have been evaluated. However, the effect of shape and size of metal particles as well as selection of carbon nanotubes has significant influence on the mechanical and electrical properties of the composites. The hardness of copper matrix composite has improved up to 47% compared to that of pure copper, while the electrical conductivity of bronze composite has improved up to 20% compared to that of the pure alloy. Thus carbon nanotube can improve the mechanical properties of highly-conductive low-strength copper metals, whereas in low-conductivity high-strength copper alloys the electrical conductivity can be improved.     

Microstructure characterization of CVI-densified carbon/carbon composites with various fiber distributions

Mechanical behavior of multi-phase composites is crucially influenced by volume fractions, orientation distributions and geometries of microconstituents. In the case of carbon–carbon composites manufactured by chemical vapor infiltration, the microconstituents are carbon fibers, pyrolytic carbon matrix, and pores. The local variable thickness of the pyrolytic carbon coating, distribution of the fibers and porosity are the main factors influencing the properties of these materials. Two types of fiber arrangements are considered in this paper: 2D laminated preform and random felt. The materials are characterized by determining their densities and their fiber distribution functions, by establishing types of pyrolytic carbon matrix present in the composites, and by studying the porosity. A technique utilizing X-ray computed tomography for estimation of the orientation distribution of the fibers and pores with arbitrary shapes is developed. A methodology based on the processing of microstructure images with subsequent numerical simulation of the coating growth around the fibers is proposed for estimation of the local thickness of the coating. The obtained information is appropriate for micromechanical modeling and prediction of the overall thermo-mechanical properties of the studied composites.     

一种5.0~9.3 GHz低功耗宽带低噪声放大器设计

针对Wi-Fi 6、Wi-Fi 6E(5 GHz、6 GHz)的低功耗、宽带宽等无线局域网(WLAN)设备需求,基于65 nm CMOS工艺设计了一款两级低功耗宽带低噪声放大器(LNA)。电路第一级采用结合互补共源电路的共源共栅结构,通过电感峰化技术和负反馈技术的运用,提高输入跨导,降低噪声,并拓展带宽和提高增益平坦度。第二级在共漏极缓冲器基础上引入辅助放大结构、电感峰化技术,实现抵消第一级共源管的噪声并拓展带宽。电路采用提出的前向衬底自偏置技术,以降低电路对电源电压的依赖,整体电路实现两路电流复用,从而有效降低了功耗。仿真结果表明,在5~9.3 GHz频带内LNA的S21为17.8±0.1 dB,S11小于-9 dB、S22小于-11.9 dB,噪声系数小于1.34 dB。在0.8 V电压下整体电路功耗为5.3 mW。     

基于Pro/E二次开发的卫星装配设计研究

为解决卫星型号设计的周期长、投入大和效率低的问题,在Pro/E2.0的平台上,开发了卫星型号设计系统,实现了卫星型号设计的快速建模与装配以及卫星的质量特性分析、光压分析、遮挡分析、敏感器视场分析等分析计算功能。以卫星型号设计中的太阳电池翼的装配为例,详细阐述了利用二次开发工具Pro/ToolKIT实现数字化装配设计的程序设计思想。最后通过系统运行实例表明了参数化装配设计的准确性和高效性。