义齿CAD/CAM系统中标准牙冠数据库的建立

CAD／CAM技术应用广泛，将其应用于口腔修复学中则是一个全新的课题。文章结合标准牙冠数据库的建库实践，从设计与制造技术层面上阐述了义齿CAD／CAM系统中标准牙冠数据库建立的过程，主要包括：利用三维机械式扫描仪扫描全口牙列28颗标准牙冠模型、利用图形处理软件对获得的数据进行处理、重建牙冠三维曲面模型，并根据国人恒牙统计数据调整模型。从而建立了具有标准解剖形态的牙冠图形数据库(动态)，并可以通过调整模型，使模型在任意方向产生位移，旋转和形变。文章最后指出数据库的建立为后阶段义齿的计算机辅助设计和制造(CAD／CAM)打下了基础。     

基于Visual Basic 开发机床主传动非常规变速系统的设计--重复转速的传动系统(实例之二)

本文介绍利用Visual Basic工具开发金属切削机床主传动非常规变速系统的设计总体结构，功能和方法，以重复转速的传动系统为例，重点介绍转速图的拟定过程，本系统具有界面美观，操作方便，易于理解的特点。     

Effect of ultrasonic power and bonding force on the bonding strength of copper ball bonds

Copper wire, serving as a cost-saving alternative to gold wire, has been used in many high-end thermosonic ball bonding applications. In this paper, the bond shear force, bond shear strength, and the ball bond diameter are adopted to evaluate the bonding quality. It is concluded that the ef/~cient ultrasonic power is needed to soften the ball to form the copper bonds with high bonding strength. However, excessive ultrasonic power would serve as a fatigue loading to weaken the bonding. Excessive or less bonding force would cause cratering in the silicon.     

新型全封闭式棒料剪切模

论述了用在通用冲床上的一种全封闭式棒料剪切模的结构形式、工作过程和活塞伐杆设计要点，并给出了实用的模具结构。该剪切模工作可靠，节约能源。     

Study on the flash butt welding of 400 MPa ultra-fine grain steel

A 400 MPa ultra-fine grain steel possesses high strength and toughness. Due to its fine grain size, the heat affect zone (HAZ) of the weld joint will soften during welding. The weldability of 400 MPa ultra-fine reinforced steel bar of flash butt welding is investigated by using the micro metallographical examination and macro-mechanical-property tests. The joint of flash butt welding has a superior mechanical property. The HAZ in the weld joint does not show apparent softening. There is only a localized softening spot inside the weld seam, which does not affect the property of the whole joint. Therefore, flash butt welding is appropriate for joining the 400 MPa ultra-fine grain reinforced steel bars. The resulting weld joint has excellent mechanical properties.     

Effects of CeF3 on properties of self-shielded flux cored wire

0 IntroductionSelf-shielded flux cored wire is a newly developedwelding material used without gas protection. Use of suchcored wires has grown rapidly in developed countriesbecause of the following advantages: simple use, goodwind resistance ability, lower cost resulted from highproductivity and strong desulfurization ability[1]. Self-shielded flux cored wires are preferred for on-site weldingsuch as ship and barge building, storage tank, bridge,offshore oil platform buildings and so on[2 -3].…     

Si及变质处理对Mg2Si/Mg复合材料的影响

分析了Mg-Si二元合金直接原位形成Mg2Si/Mg复合材料的过程,研究了Si含量以及变质处理对复合材料组织和性能的影响。试验结果表明,随着合金中Si含量的增加,合金的流动性降低,复合材料中原位Mg2Si的数量增多,树枝晶形态更为发达;对优化的Mg-8Si合金,进行混合稀土(MM)和Sb变质处理,可明显改善Mg2Si的形态和分布,但Sb变质的效果要好于MM。合金经质量分数为1.2%的Sb变质处理后,Mg2Si以颗粒状均匀分布在Mg基体中,从而使复合材料具有较好的耐磨性。     

Experiment and simulation study of 3D magnetic field sensing for magnetic flux leakage defect characterisation

Magnetic flux leakage (MFL) testing is widely used to detect and characterise defects in pipelines, rail tracks and other structures. The measurement of the two field components perpendicular to the test surface and parallel to the applied field in MFL systems is well established. However, it is rarely effective when the shapes of the specimens and defects with respect to the applied field are arbitrary. In order to overcome the pitfalls of traditional MFL measurement, measurement of the three-dimensional (3D) magnetic field is proposed. The study is undertaken using extensive finite element analysis (FEA) focussing on the 3D distribution of magnetic fields for defect characterisation and employing a high sensitivity 3-axis magnetic field sensor in experimental study. Several MFL tests were undertaken on steel samples, including a section of rail track. The experimental and FEA test results show that data from not only the x- and z-axes but also y-axis can give comprehensive positional information about defects in terms of shape and orientation, being especially advantageous where the defect is aligned close to parallel to the applied field. The work concludes that 3D magnetic field sensing could be used to improve the defect characterisation capabilities of existing MFL systems, especially where defects have irregular geometries.     

线轴注塑模具设计

针对线轴的工艺特点及在生产中存在的平面翘曲、壁厚不均等问题，给出了实用模具结构。详细介绍了模具各系统及成型零件的设计，论述了模具的工作过程。模具结构紧凑，操作方便，可实现塑件的全自动生产，生产效率高，且成型塑件质量好。     

CB20砖和硅莫砖在我厂回转窑上的应用

浩良河水泥厂1995年6月投产的φ3.95m×560m新型干法回转窑生产线,设计产量2000t/d,经技改后目前产量最高达到2400t/d,运行效益良好。在回转窑节能提产的过程中,窑衬也经过了不断的