硼化锆基超高温陶瓷材料电火花加工特性研究

硼化锆基超高温陶瓷材料被广泛用于对轻质、耐高温有特殊要求的领域,但其高硬度、高脆性等特性使其成为难切削材料,在加工该材料的零件时极易磨损工具,缩短工具寿命,使加工变得非常困难,甚至无法切削。采用电火花加工方法对硼化锆基超高温陶瓷材料的加工特性进行了研究,对影响该材料加工特性的工艺参数(电参数、非电参数)进行了系统实验,得出工艺参数对加工特性的影响规律,获得了较高加工速度、能稳定可靠加工的参数范围,以此来指导实际应用。     

单位生产成本与加工精度的多工序车削优化

切削参数优化对于加工质量、生产效率、加工成本、产品利润具有非常重要的意义.数控加工过程中,单位生产成本和加工精度很大程度上决定了零件加工成本的高低和加工质量的好坏.建立以单位生产成本与加工精度为双目标的多工序车削优化模型进行切削参数优化选择十分必要.多工序车削模型同时充分考虑了粗精的刀具耐用度、切削功率、切削进给力、稳定切削区域、刀具表面切削温度及精车表面粗糙度等实际约束条件.运用高斯变异和多项式变异的NSGA-Ⅱ算法对多工序车削模型进行比较优化计算,优化实例表明多项式变异的NSGA-Ⅱ算法获得了更好的加工精度、单位生产成本的Pareto最优解集以及相应的粗精切削参数.用多项式变异的NSGA-Ⅱ算法得到的优化粗精切削参数进行切削试验,得到与NSGA-Ⅱ算法优化的加工精度、单位生产成本基本相符,为多工序车削切削参数优化提供了实践指导.     

CFRP切削加工中刀具磨损研究进展

从不同类基体材料的未涂层、涂层刀具2个方面,综述了CFRP切削加工用刀具的磨损部位及形式。现有研究均以宏、微观实验观测为主,宏观上,磨损位置以后刀面磨损及切削刃钝化最为常见;微观上表现为纤维硬质点与刀具间摩擦所致的磨粒磨损,随着切削温度、速度的提高,同时伴有粘着、氧化磨损。整体来说,金刚石类刀具耐磨性表现最佳,尤其适用于连续切削加工的场合。高强、高硬纤维高频刮擦作用下的磨粒、疲劳磨损仍是该类刀具磨损的主要威胁。当前所采用的辅助工艺(冷却气体、微量润滑、超声振动等)、涂层材料改性、微结构等方法,在一定程度上改善了摩擦条件,抑制了刀具磨损,但仍难以满足CFRP连续高质高效加工需求。可见,如何从微纳观多尺度方向深入研究金刚石类刀具的磨损机理及抑制策略,是CFRP高质高效加工的亟需。     

电解电火花复合加工深孔试验研究

概述了难加工材料零件打孔的几种主要工艺方法,提出此类材料小孔、深小孔加工的一种新电解电火花复合加工试验方法.在改造的试验装置上,采用复合型电解液在不锈钢、钛合金试件上进行了小孔、深小孔加工试验.分析了生产率、表面粗糙度和加工精度等工艺效果的成因.结果表明,通过合理进行电解液配制和选择电规准等相关工艺参数,试件的材料去除率达14 mm/min,表面粗糙度值Ra ＜7.9 μm.虽然加工精度低于电火花加工精度,仍验证了该方法用于钛合金试件打孔的有效性.     

基于ESPRIT的机车轴承座加工自动编程与实现

在机车大尺寸轴承座零件批量生产中,多存在结构相似、尺寸不同的零件。为缩短加工编程时间,基于轴承座零件的典型特征分类与表征,进行通用的工艺方案设计。采用VB语言在ESPRIT软件中进行二次开发,建立不同特征的自动编程模板,以便快速完成不同尺寸零件的自动编程。在DMG CTX1250车铣复合加工中心上完成一组轴承座零件的加工,验证了自动编程模块的有效性。该方法可有效缩短批量零件编程时间,为智能切削加工提供一种高效的自动编程方法     

门机壳零件加工工艺研究

为提高门机壳零件的加工质量和生产效率,从门机壳零件的加工工艺着手进行研究。在分析零件的特点及加工要求的基础上,对零件的加工工艺及夹具结构进行了详细的设计,针对不同的加工内容选取合适的加工刀具及切削参数,并运用该工艺进行批量化生产。生产结果表明,零件的加工精度、质量稳定性和效率达到预期目标。     

薄壁铝合金高速铣削工艺寻优及模拟仿真

本文详细讨论了薄壁零件的加工技术.首先,以CAXA软件为技术平台,自动生成零件的刀具路径,并进行了模拟仿真加工;针对薄壁零件刚性差、强度弱、加工工艺性差、易发生加工变形和切削振动等情况,决定采用高速加工技术.通过对机床、刀具、工件以及切削参数等进行全面分析,采用了刚度大的高速切削机床,并选择了合适的切削刀具.通过改变工件装夹方式,优化编程策略和合理选用切削用量,实现了薄壁零件的高速干式切削.     

钻孔刀架在数控车削加工中的运用

设计钻孔刀架,可自动完成钻中心孔、钻小孔、扩孔、铰孔、攻丝等多个工序,大大提高了加工精度和效率,实现了普通数控车床上带中小孔类零件的全自动加工。     

基于信噪比的微小孔加工工艺参数的分析方法

加工工艺参数准确合理的分析方法是优化组合电火花微细加工中多目标工艺参数的重要前提和保证。文章利用参数设计中的信噪比方法对电火花微小孔加工过程中的工艺参数进行分析研究，得到电火花微小孔加工过程中关键参数单因子工艺指标的优化分析结果，从而达到对电火花微小孔加工工艺参数进行单因子优化设计的目的，为多目标工艺参数综合优化组合提供重要的数据支持。试验结果表明信噪比分析方法能够较好地解决电火花微细加工中的关键工艺参数优化问题，对加工效率和加工精度有一定的改善和提高。     

影响不锈钢加工的几点因素

文章针对不锈钢材料在切削加工中切削力大、切削温度高、加工硬化严重以及容易粘刀,致使刀具磨损严重,影响生产效率,提高了刀具使用成本且很难获得较好的表面光洁度等特点,论述了通过根据具体零件加工的实际条件来合理选择适合的刀具材料,刃磨合适的刀具几何角度,选择适合的切削用量来解决不锈钢材料的切削问题.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of     

Information for Contributors

The Transactions of Nonferrous Metals Society of China, founded in 1991 and sponsored by The Nonferrous Metals Society of China, is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology, including mineral processing, extraction metallurgy, metallic materials and heat treatments, metal working, physical metallurgy, powder metallurgy, with the emphasis on fundamental science. It is the unique preeminent publication in English for scientists, engineers, under/post-graduates on the field of nonferrous metals industry. This journal is covered by many famous abstract/index systems and databases such as SCI Expanded, Ei Compendex Plus, 1NSPEC, CA, METADEX, AJ and JICST.     

INTRODUCTION TO PATENTS

The invention provides a method of making a mold which can reduce SOx generation rate while preventing decrease in hardening rate in the case of using sulfuric acid for a hardener composition. The method has a mixture step in which fire-resistant particles, a hardener composition and a binder composition are mixed to obtain a composition for a mold. The hardener composition contains sulfuric acid. In the mixture step, sodium carbonate is added. A molar ratio of the sulfuric acid to the sodium carbonate is 0.5 or more and 4.0 or less.     

China Foundry Week 2014

China Foundry Week, hosted by the Foundry Institution of Chinese Mechanical Engineering Society （FICMES） each year, is a large academic event in China. It is one of the ten high-impact activities sponsored by the Chinese Mechanical Engineering Society.     

17th Conference of Hydrodynamic and Electromechanical Control Engineering Call for papers

正1.Contents In order to promote the academic exchanges and technical communication of the research in the field of fluid power transmission and control,fluid control engineering specialized committee of the Chinese Society of Theoretical and Applied Mechanics will hold the 17th Conference of Hydrodynamic and Electromechanical Control Engineering on July 27-29,2014 in Tibet,Lhasa city.     

Formulas of Tension of Continuous Rolling Process

The development of computer controlled continuous rolling process calls for a mathematical expression that can express the inequality condition of "constant flow". Tension is the link of the continuous rolling process. From the condition of dynamic equilibrium, a differential equation of tension is given out. On the basis of the physical rules established from the industrial practice and experimental studies, the law of volume constancy, the linear relation of forward slip and tension, the state equation of continuous rolling, the formula of dynamic tension, and the formula of static tension have been obtained. These formulae reflect the functional relations between tensions, thickness, roll velocity, and time in the continuous rolling process. It is implied that the continuous rolling process is a gradually steady, controllable, and measurable dynamic system. An assumption of predicting the thickness of a steel plate using these tension formulae is also put forward.