Tribological evaluation of surface modified H13 tool steel in warm forming of Ti–6Al–4V titanium alloy sheet

The H13 hot-working tool steel is widely used as die material in the warm forming of Ti–6Al–4V titanium alloy sheet. However, under the heating condition, severe friction and lubricating conditions between the H13 tools and Ti–6Al–4V titanium alloy sheet would cause difficulty in guaranteeing forming quality. Surface modification may be used to control the level of friction force, reduce the friction wear and extend the service life of dies. In this paper, four surface modification methods(chromium plating, TiAlN coating, surface polishing and nitriding treatment)were applied to the H13 surfaces. Taking the coefficient of friction(CoF) and the wear degree as evaluation indicators, the high-temperature tribological behavior of the surface modified H13 steel was experimentally investigated under different tribological conditions. The results of this study indicate that the tribological properties of the TiAlN coating under dry friction condition are better than the others for a wide range of temperature(from room temperature to 500 C), while there is little difference of tribological properties between different surface modifications under graphite lubricated condition, and the variation law of CoF with temperature under graphite lubricated is opposite to that under the dry friction.     

超塑成型/扩散连接钛合金气动面表面沟槽对其强刚度的影响分析

超塑成形/扩散连接是一种先进的钛合金制造技术,采用该技术,4层结构的钛合金产品表面存在沟槽问题,对某气动面表面沟槽的成因和对强刚度的影响进行了浅析,评估了表面沟槽对该产品强刚度的影响水平.     

整体中空夹层复合材料经向弯曲刚度的预测

提出了预测整体中空夹层复合材料经向弯曲刚度的理论方法。根据织物结构特点,运用夹层梁理论推导出纯弯曲时面板承担的弯矩占总弯矩的比例,在此基础上建立了材料宏观弯曲刚度和面板弯曲刚度的关系式,从而通过计算面板刚度以及相应结构参数预测了材料经向弯曲刚度,并研究了不同织造参数下弯曲刚度的变化。通过与实验值和理论预测值的对比,验证了理论预测方法的正确性。     

多点成形技术的研究进展及应用现状

多点成形将柔性制造和计算机技术结合为一体;基于离散思想,将实体模具离散为一系列规则排列的基本体单元,通过计算机控制各基本体单元高度,构造出成形面,实现板材的三维曲面成形。多点成形技术因其具有的独特优势,已经成为现代制造领域的重要研究方向。     

特种加工精密制造——本刊总编辑刘柱对话北京市电加工研究所所长杨大勇先生

北京市电加工研究所专业从事精密数控电加工机床制造和精密运动控制技术开发,是一个集科研、开发、生产于一体的高新技术企业。凭借完全掌握产品的核心技术和优质的产品服务过程     

无需退刀 直达深度——瓦尔特在EMO上展示XD70钻头XD70 of Walter

瓦尔特将在欧洲国际机床展览会(EMO)这个世界领先的金属加工展览会上向广大观众首次介绍极深钻头XD70。为了制造出这款全球钻深独一无二的钻头,这个来自Tübingen的刀具专家开发了一套全新生产工艺。XD70无需退刀就能在     

板料两道次拉深成形数值模拟方法研究

数值模拟在钣金多道次拉深成形工艺、模具的优化设计和提高模具的研发能力方面具有重大意义。目前研究者已经提出了多道次拉深数值模拟的一般步骤,但是仍有许多待解决的问题。综合考虑了影响数值模拟准确性的两个重要因素,介绍了多道次拉深数值模拟的简化步骤。结果表明：用此方法,成功有效完成了两道次拉深工艺的数值模拟。     

整体叶盘叶型电解加工流场设计及实验简

 电解加工（ECM）是航空发动机整体叶盘制造的主要技术之一,其电解液流场稳定性是影响电解加工精度和表面质量的核心因素。本文在分析原有的二维流场基础上,针对流体在不同流道截面下的流场状态,提出了一种三维复合电解液流场模式,即三股电解液分别从毛坯进气边、叶盆叶根、叶背叶根流入,由排气边交汇流出。采用有限元法对三维复合流场及两类二维流场开展仿真分析,分析结果表明三维复合流场改善了流道突变区域流场状态,有效抑制了二维流场的流场缺陷,有助于提高流场稳定性。对加工区液体流态进行了判断,其结果显示三维复合流场可以满足电解加工要求。开展了3种流场模式的加工速度比较实验,三维复合流场达到的进给速度最高,较二维流场可显著提升加工效率。采用三维复合流场开展了多叶片扇段加工,获得了较好的重复精度与表面质量。     

Adaptive sliding mode control of the A-axis used for blisk manufacturing

As a key assembly in the 5-axis CNC machine tools, positioning precision of the A-axis directly affects the machining accuracy and surface quality of the parts. First of all, mechanical structure and control system of the A-axis are designed. Then, considering the influence of nonlin- ear friction, backlash, unmodeled dynamics, uncertain cutting force and other external disturbance on the control precision of the A-axis, an adaptive sliding mode control （ASMC） based on extended state observer （ESO） is proposed. ESO is employed to estimate the state variables of the unknown system and an adaptive law is adopted to compensate for the input dead-zone caused by friction, backlash and other nonlinear characteristics. Finally, stability of the closed-loop system is guaran- teed by the Lyapunov theory. Positioning experiments illustrate the perfect estimation of ESO and the stronger anti-interference and robustness of ASMC, which can improve the control precision of the A-axis by about 40 times. Processing experiments show that the ASMC can reduce the waviness, averaKe error and roughness of the nrocessed surface by 35.63%, 31.31% and 30.35%, respectively.     

带止裂筋整体翼梁结构的破损安全分析与试验

为了研究带止裂筋整体翼梁结构的裂纹扩展特性,采用ANSYS有限元软件对裂纹尖端应力强度因子进行数值计算,对缩比试验件进行疲劳裂纹扩展试验,当裂纹扩展到止裂筋前时进行剩余强度试验。结果表明:在梁缘条和蒙皮断裂情况下,止裂筋能够降低梁腹板上的应力强度因子幅值,对裂纹扩展起到拟制作用,其能够承担较大的静载荷从而实现破损安全设计,但是用止裂筋阻止疲劳裂纹扩展的效果并不显著;与梁弯曲产生的正应力相比,腹板上的剪应力不足以驱动Ⅱ型裂纹扩展。