多夹钳式板材柔性拉形工艺的数值模拟

多夹钳式柔性拉形工艺可克服传统拉形工艺存在的成形缺陷。研究了多夹钳式柔性拉形机的结构组成,分析了多夹钳式柔性拉形工艺的特点,分别选取S形曲面、马鞍形曲面和球形曲面,并利用有限元分析软件ABAQUS,对多夹钳式板材柔性拉形过程进行数值模拟分析。结果表明:在兼顾工件成形质量与拉形机研发制造难度的前提下,相对较高的夹钳离散化程度可提升S形工件的成形质量;相比于普通铰接方式,夹钳与液压缸之间采用球铰接方式时,马鞍形件有效成形区端部的成形质量更好;通过改善板料与模具之间的润滑条件,使球形件有效成形区板料的拉伸变形更充分,卸载回弹量更小。     

基于可变型面模具的蒙皮件柔性夹钳拉形技术研究

介绍了传统的蒙皮件拉形工艺,提出基于可变型面模具的新型柔性夹钳拉形技术。对自主研发的可变型面模具和柔性夹钳拉形机的成形原理、结构组成和技术优势进行了阐述,论述了蒙皮件柔性拉形的工艺过程,并用所研制的可变型面模具和柔性夹钳拉形机进行了球形件和鞍形件的拉形实验,给出了拉形实验结果,验证了装置的可行性和实用性。     

高柔性多夹钳拉形机的结构设计

介绍了一种高柔性多夹钳拉形机的结构设计,探讨其拉形原理。首先分析目前常见的拉形机结构和拉形方式以及存在的主要问题;再根据不同形状蒙皮类工件的成形需要,分析相应的拉形过程,确定多夹钳拉形机的结构设计。通过合理布置多夹钳拉形机的夹钳,实现了高柔性度的拉形。并通过试验验证,确认拉形效果良好。     

基于并联机构的多夹钳柔性拉形机的设计

针对传统拉形机在成形双曲率蒙皮零件时,易产生不贴模、拉裂或起皱等缺陷,基于并联机构拓扑结构理论设计了一种并联多夹钳柔性拉形机。首先,介绍了并联多夹钳柔性拉形机及其辅助装置的结构,对拉形机并联支撑机构进行结构设计与自由度计算;其次,运用ADAMS软件对并联支撑机构进行运动学仿真,对拉形机的并联输出板的位移变化与速率变化曲线进行分析,验证了并联多夹钳柔性拉形机并联支撑机构的稳定性;最终,通过有限元法分析拉形件在不同拉力下的应变云图,验证了并联拉形机拉形方式的合理性。     

柔性压辊拉形中回弹的数值模拟

拉形是飞机蒙皮件的主要成形方法。柔性压辊拉形是一种新的拉形工艺,将传统的拉形过程中使用夹钳进行拉伸包覆的加载方式,改变为利用柔性压辊垂直下压的加载方式,使板料产生变形。对柔性压辊拉形成形球形件的过程和回弹进行数值模拟,分析加载量、板厚、板料与模具之间的摩擦系数等因素对回弹的影响。研究结果表明,在柔性压辊拉形方式下,成形件应力分布比较均匀,且在成形一定尺寸的球形件时,加载量越小,回弹量越大;板料越薄,回弹量越大;板料与模具之间的摩擦系数越大,回弹量越大。     

夹钳数量对双曲顶件拉伸成形的影响

利用有限元软件ABAQUS,以双曲顶件为研究对象,建立不同夹钳数量下的拉伸成形有限元模型,分析夹钳数量对板料成形效果的影响。结果表明：拉形力相同时,随着夹钳数量的增加,板料的成形性更好。整体夹钳和5个夹钳拉伸成形的板料均未完全贴模,后者的贴模程度优于前者;10个和15个夹钳的拉伸成形板料完全贴模,后者得到的成形件的应变、厚度分布比前者更均匀。在柔性拉伸成形装置上进行双曲顶件成形试验,试验结果与数值模拟结果相吻合,验证了双曲顶件柔性拉伸成形的可行性和数值模拟的准确性。     

蒙皮件可变型面模具柔性拉形工艺的研究

针对传统飞机蒙皮件实体模具拉形工艺费用高的问题,提出一种采用可变型面模具进行蒙皮件柔性拉形的先进方法。介绍了可变型面模具的结构组成,阐述了3种模具调形方式的工作原理与特点,以球形件为研究对象,研究了不同的模具离散模式和基本体冲头尺寸对拉形件局部变形和形状误差的影响规律。研究表明:弹性垫的厚度是基本体冲头方体边长的1.25倍时,既能有效地抑制工件的局部变形,又能保证工件的成形精度;对于厚1 mm、曲率半径为1 500 mm球形件,成形精度要求为0.5 mm以下,选择基本体离散排布矩阵为32×40满足生产要求。     

材料和目标形状对多点拉形成形精度的影响分析

多点拉形是将整体拉形模具离散成多点模具,可以在一套多点拉形模具上实现不同形状零件的拉形,省去了模具的设计、制造等大量的生产成本,实现了蒙皮件的柔性成形。多点拉形主要适于成形小曲率、大变形的蒙皮件,材料和目标曲面形状都是影响多点拉形成形结果的重要因素。通过对3种材料成形不同曲率半径球形件的多点拉形过程进行数值分析,研究材料和成形件目标形状对多点拉形的影响。结果表明,在成形件中心区域的形状误差小于边缘区的形状误差,拉伸方向的形状误差大于垂直拉伸方向的误差,成形件的曲率半径越小,成形件的形状误差越大。     

球形件多钳式柔性拉形的数值模拟

多钳式拉形是一种新型的板材柔性拉形工艺.采用有限元软件建立了球形件拉形的有限元模型,探讨了不同工艺方式和工艺参数对工件拉形质量的影响.结果表明:多钳式拉形有助于板材贴模,拉形件的应变分布均匀,可以提高拉形质量.板材与模具之间的摩擦系数越小,板厚减薄量越小;缩短过渡区,可以避免起皱缺陷,提高材料利用率.通过实验验证了数值模拟结果,模拟结果对多钳式拉形设备的优化设计以及实际板材的塑性加工具有指导价值.     

连续柔性成形纵向与横向曲率的相互影响

为准确预测连续柔性成形曲面的最终形状,对成形过程中纵向和横向曲率的相互影响进行研究,并结合回弹因素,建立了数学方程。对典型的三维曲面——鞍形件进行数值模拟和实验验证,基于数值模拟的结果,采用最小二乘法进行拟合,计算出不同纵向曲率对应方程中的参数值;通过对鞍形件的连续柔性成形实验,验证数学方程的有效性和可靠性。     

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.     

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.     

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.     

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.