A backward extrusion analysis by the rigid–plastic integralless–meshless method

The rigid–plastic integralless–meshless method is applied to the analysis of plane strain backward extrusion. The rigid–plastic integralless–meshless method, based on the moving least squares approximation and the partial differential equations of mechanical equilibrium, is a truly meshless method. In addition, since there is no any integration in the formulation of the rigid–plastic integralless–meshless method, this method is also an integralless method. Compared with the conventional rigid–plastic FEMs, the rigid–plastic integralless–meshless method has some advantages that are briefly no mesh generation, no remeshing and no integration. Compared with BEMs and FBEMs, the rigid–plastic integralless–meshless method is found to have some merits such as sparse matrix, no singularity, no integration and no fundamental solution. Contours of the equivalent strain rate, the equivalent strain, the equivalent stress and the shear stress, etc. of the backward extrusion analysis using the rigid–plastic integralless–meshless method are obtained successfully.     

铝合金化学铣切工艺研究现状

化学铣切是一种无道具,无切削,无应力和无工件之间协调问题的特种加工工艺,可以加工铝、镁、钛、镍、铜、钢铁等多种金属和合金.本文主要介绍了铝合金材料化学铣切溶液的组成、化学洗切速率的控制以及化学铣切后合金性能的影响等内容.     

中厚板铝合金激光-MIG复合双层焊接方法

提出了激光-MIG复合双层焊接中厚板铝合金方法,该方法分两层进行焊接：第一层为打底焊,解决焊接熔深不足的问题;第二层为盖面焊,解决焊缝成形不良的问题.结果表明,在激光器额定功率为4 kW时,采用激光-MIG复合双层焊接方法焊接ZL114A材料的熔深可达10 mm,接头抗拉强度平均值为238 MPa,大于母材抗拉强度的8...     

药皮类型对E308-XX型不锈钢焊条工艺质量的影响

介绍了E308-XX型不锈钢焊条药皮类型、熔滴过渡形态和冶金学过程的特点,探讨药皮类型对焊条工艺质量的影响。结果表明,E308-XX型焊条药皮类型有五种,其所用电源类型、极性以及适用的焊接位置各异。药皮类型15和25焊条具有短路过渡形态,药皮类型16焊条具有短路+渣壁混合过渡形态,药皮类型17和26焊条具有渣壁过渡形态。药皮类型16、17和26焊条,在熔滴过渡区的渗Si反应使熔滴增氧、细化,有利形成渣壁过渡。药皮类型25和26焊条分别克服了15和16焊条的工艺质量问题,但前者不能完全取代后者;药皮类型17焊条的工艺性最好,但对气孔敏感;药皮类型15、25焊条焊缝的综合性能比16、17和26更好。     

走出家教误区

每个蹩脚的父母，所以因为他没有学过教育理论，不知道教育是科学。在整个教育系统中，学校教育是占支配地位，起主导作用的教育。继续教育、在职教育、终身教育、家庭教育，都只是学校教育的延伸、补充和辅佐。家庭教育不可喧宾夺主，应该当好学校教育的好帮手。家教应给孩子想像的天空。想像是创造的翅膀。培养孩子的创造精神是教育的使命。     

不发泡磨钢球砂轮的研制

本文采用了一种新型的结合剂，改进了传统配方，采用不发泡的方法研制出了磨钢球砂轮。这种砂轮的优点是，磨削能力强，磨削效率高，出厂前不需修整。     

薄壁铸钢件用自硬树脂砂应力与铸件裂纹的研究

热裂产生的主要原因之一就是型 (芯 )砂容让性差 ,尤其是用自硬树脂砂生产薄壁铸钢件时 ,这个问题显得特别突出。本文对型 (芯 )砂容让性的概念作了评述 ,在借鉴和改进了用于精确定量评价自硬树脂砂容让性好坏的应力试样的基础上 ,设计了裂纹试样。由浇注、加工、测量的结果得出型 (芯 )砂的容让性的准确值和造成铸件热裂的容让性临界值 ,为改善自硬树脂砂的容让性 ,防止铸件裂纹的形成 ,提供了有力的评定标准。     

冷激合金铸铁凸轮轴负压工艺的试验

消失模工艺是近无余量、精确成型的新工艺,无需取模、无分型面、无砂芯,因而铸件没有飞边、毛刺和拔模斜度,并减少了由于型芯组合而造成的尺寸误差。本文通过负压的方法,阐述了消失模工艺解决凸轮轴产生缺陷的现象,通过实验证明消失模技术可以减少铸造缺陷,特别是减少分型面存在而导致的缺陷,从而得出了负压工艺进行冷激合金铸铁凸轮轴生产是完全可行的。     

一种新的环保型热硬化无机高聚物铸造粘结剂研究

研究了一种新型热硬型无机高聚物铸造粘结剂.砂芯有满意的湿强度,砂芯硬化后强度高,抗吸潮性强,溃散性好.混砂、造型无气味,浇注过程无烟雾.属绿色环保型铸造材料.     

A rotary flexural bearing for micromanufacturing

This study proposes a design methodology for a novel rotary flexural bearing that is based on the motion principles of elastic flexures. The bearing is capable of providing rotational oscillations of one complete revolution and is characterized by potentially high repeatability, smooth motions, no mechanical wear and no lubrication requirements, no gaps or interfaces, zero maintenance, in addition to its compactness. From the structural characteristics and the basic working principles of the flexural bearings, the study provides a design analysis on the various aspects of the bearing, including material selection, stress analysis and calculations (such as nonlinear finite element analysis, static and fatigue strength designs), motion error analysis and error reduction strategy, parametric design, etc.     

基于APDL语言的柔性铰链机构参数化实体建模

柔性铰链机构是一种新型的微位移机构，具有无机械摩擦、无间隙、无热源、运动连续、不需润滑及分辨率高等优点，因而在许多领域得到了广泛应用。为了分析柔性铰链机构的输出位移，采用大型通用有限元分析软件ANSYS进行参数化有限元分析，APDL语言(ANSYS Parameter Design Language)是ANSYS软件提供的参数化程序设计语言，采用该语言可以分别地建立柔性铰链机构的几何实体模型。文章首先介绍了参数化编程语言APDL，再提出了用该语言进行编程实现参数化实体建模的一种方法，最后，以单平行四杆柔性铰链机构为例证明这是一种方便、快速的实体建模方法。     

Cold expansion and reduction of thin-walled PVC tubes using a die

The production of sound thin-walled tubular parts by expansion and reduction using a die is generally limited to metals. Current research work in the field follows the same trend as that of industry and, therefore, there is no accumulated experience, no practical design rules and no information available in the specialized literature concerning the utilization of polyvinyl chloride (PVC) tubes (as well as other polymers). As far as authors are aware no technology validation studies have ever been performed with the objective of employing cold expansion and reduction forming processes for shaping the end of thin-walled PVC tubes.This paper is concerned with the abovementioned lack of knowledge and is a first step towards the understanding of the mechanics of deformation of tube end forming applied to PVC (and polymers, in general). The presentation addresses the influence of major process parameters on the formability limits of the expansion and reduction of thin-walled PVC tubes using a die and proposes an innovative extension of the flow formulation that is capable of modelling cold plastic deformation of pressure-sensitive polymers under a non-associated flow rule.The overall investigation is assessed with experimental data obtained under laboratory-controlled conditions and results show that free expansion and reduction of thin-walled PVC tubes using a die can be successfully utilized for producing custom and specific shapes at the tube ends.     

内外推管同时推件圆柱齿轮注射模设计

为了推出塑件时不产生超差变形,无顶出痕,设计了内、外推管同时推件圆柱齿轮注射模,并介绍了模具结构特点和工作过程。模具采用爪形浇口进料,塑件脱模时受力均匀,比压小,无推痕。     

Critical evaluation and optimization of the thermodynamic properties and phase diagrams of the Al-Mg, Al-Sr, Mg-Sr, and Al-Mg-Sr Systems

All available thermodynamic and phase diagram data were critically assessed for all phases in the Al-Mg, Al-Sr, and Mg-Sr systems at 1 bar pressure from room temperature to above the liquidus temperatures. For these systems, all reliable data were simultaneously optimized to obtain a set of model equations for the Gibbs energy of the liquid alloy and all solid phases as functions of composition and temperature. The modified quasi-chemical model was used for the liquid. The Al-Mg-Sr ternary phase diagram was calculated from the optimized thermodynamic properties of the binary systems. Since no reliable ternary data were available, three assumptions were made: no ternary terms were added to the model parameters for the thermodynamic properties of the liquid, no ternary solid solutions are present in the system, and no ternary compound is present in the system. The calculated ternary phase diagram is thus a first approximation, which can be improved by the addition of new experimental data and can be used as a base for the calculation of phase diagrams of multicomponent systems.     

Analysis of a novel phase-shifted soft switch converter

In this paper, on the basis of the phase-shifted controlled zero-voltage-switch (ZVS) fuU-bridge converter with pulse width modulation (PWM), a noel zero-voltage and zero-current switch (ZVZCS) PWM converter using a simple auxiliary circuit was designed. The ZVZCS soft switch is achieved by the resonance among the resisting electromagnetic deflection capacitor, the capacitor of the simple auxiliary network and the leakage inductor of transformer. There are no dissipation devices of the saturation inductor and the auxiliary switch in the converter, meantime the capacitor of the auxiliarycircuit is also used to clamp the voltage of the rectifier, and there is no additional clamped circuit. There is no big circulating current in the converter, all the active and passive devices work on the condition of the low current and voltage stress, and the proposed converter has wide load range and small duty loss.     

电视机面壳高光无痕注射模设计

高光无痕注射成型工艺是一种无喷涂的绿色注射新技术,其注射模结构与普通注射模相比有很大差异。通过对电视机面壳结构的分析,结合高光无痕注射成型工艺的要求,阐述了电视机面壳高光注射模的浇注系统、模温控制系统、推出系统和排气系统的设计方法和设计要点。经大规模生产验证,模具结构设计合理,塑件可获得高光泽表面。     

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 高温合金GH536无缝矩管是一种具有中空截面,周边没有接缝的长条矩形钢管。由于现在还没有高温合金无缝矩管检测方法和检测标准,为了矩管的质量得到有效控制,根据矩管生产加工过程中可能出现的缺陷,结合无损检测方法原理,在矩管半成品时用水浸式超声波检测,成品用涡流检测。并结合金相试验分析,可以得出,此种方法适合高温合金GH536无缝矩管的检测。     

高锰钢和U71Mn钢在加焊接介质焊接时的接头组织

用一种焊接介质,采用等离子弧堆焊结合闪光对焊的方法将ＺＧＭｎ１３钢和Ｕ７１Ｍｎ钢加焊接介质进行焊接。结果发现ＺＧＭｎ１３钢热影响区内无碳化物析出,Ｕ７１Ｍｎ钢热影响区内无马氏体产生。中间介质为单相奥氏体组织,熔合区存在大约１０％的δ铁素体     

Some Aspects of the Influence of Manganese in Austenitic Stainless Steels

The effect of Mn on the pitting corrosion resistance of 18 8 steels is due to its sulphide forming ability, because the sulphides are then present as non-metallic inclusions. As is shown by the authors that reduction of the manganese content of these steels (from normally 1.8% to values around 0.2) gives rise to a considerable improvement of the corrosion behaviour. The pitting potential is then displaced toward considerably higher values while no negative aspect is noted on a weldability and no increase of the ferrite content in the ascast and as-rolled conditions is experienced.     

On accommodation helper mechanism for superplasticity in metal matrix composites

Local stresses at the interfaces are analyzed to make clear the role of the liquid phase in superplasticity for metal matrix composites. The local stress caused by sliding at the interfaces is higher than the applied local stress at the interfaces for the composites whose maximum elongation is attained in a state containing a liquid phase, however, the relationship is the opposite for the composites whose maximum elongation is attained in a solid state containing no liquid phase. Therefore, it is suggested that when the stress concentrations are caused, a liquid phase is needed in order to relax the stress concentrations, however, when no stress concentrations are caused, a liquid phase is not needed for superplasticity. This view was supported by investigation of cavitation.