基于四配流窗口液压泵的液压飞轮蓄能器

为提高普通液压蓄能器的能量密度和检验四配流窗口液压泵样机在能量回收方面的性能,利用AMESim搭建液压飞轮蓄能器和四配流窗口轴向柱塞泵的物理仿真模型,并结合重物举升模型和液压挖掘机动臂升降的特性构建了相关的能量回收液压回路,求得变量泵排量与重物运动速度微分方程。通过重物静态升降工况的参数匹配,进一步分析了液压飞轮蓄能器的能量密度和能量回收效果。仿真结果表明:相同体积下的液压飞轮蓄能器和普通液压蓄能器相比,液压飞轮蓄能器在兼顾能量回收效率的同时提高了89.4%的储能密度;运用所求得的微分方程控制泵的斜盘倾角,减小了负载的抖动。     

基于AMESim液压仿真平台的双联轴向柱塞泵液压系统分析及试验研究北大核心

以挖掘机用九柱塞双联轴向柱塞泵为模型,利用AMESim液压仿真平台对泵的液压系统进行仿真分析,得到液压泵的压力、流量和效率等变量特性。根据双联泵系统特性,搭建双联泵液压系统仿真模型,分析不同负载信号下的上述各项变量特性。通过搭建的试验台进行试验验证,分析测试结果。结合仿真结果,对液压系统作出较完善仿真分析,为该泵的进一步研究提供参考。     

基于模糊PI的电比例排量泵控制研究

针对正流量液压系统的挖掘机,使用电比例排量泵替代液控恒功率泵可以实现泵与发动机更加完美的功率匹配。但电比例排量泵的排量调节控制对算法的准确性、稳定性以及比例电磁阀的快速响应性能提出了很高要求。为满足以上条件,电比例排量泵的控制策略采用了基于BP神经网络的恒功率MAP图计算方法以及模糊逻辑整定PI参数的方法,使得电比例排量泵可以根据发动机转速和液压系统工作压力大小准确计算出变量泵排量并调度PI参数,消除液压系统时变特性与非线性对控制性能的不利影响。根据测试结果,采用模糊PI控制的挖掘机液压系统在控制准确性、稳定性方面都得到了提升。     

基于电液混合储能的电动挖掘机动臂节能驱动系统特性

针对现有电动挖掘机采用多路阀控系统造成的能效低、电池装机容量大但续航时间短的不足，提出一种变转速双泵直驱液压挖掘机动臂系统。根据动臂液压缸面积比配置2个液压泵/马达的排量，实现液压缸流量匹配。采用液压蓄能器与超级电容进行混合储能，实现动臂重力势能的高效回收利用。分析所提系统的工作原理，建立系统多学科联合仿真模型，分析系统运行特性和能量特性。研究结果表明：双泵直驱挖掘机动臂系统具有良好的控制特性，速度运行平稳。与传统多路阀控系统相比，双泵直驱挖掘机动臂系统节能效果显著，蓄能器压力21 MPa和容积180 L时，重力势能回收效率为79.9%,能耗减少64.6%,进一步通过合理选择蓄能器工作压力和容积，双泵直驱动臂系统的节能效果可达到65%以上。     

液压混合动力制动能量再生关键参数研究

通过建立液压混合动力车辆制动系统能量再生部分的数学模型,仿真分析得出汽车滚动阻力、空气阻力、变速机构的能量消耗比例,同时定量分析了蓄能器初始压力、变量泵/马达排量及其工作总效率等关键参数对制动能量再生效率的影响,提出一种排量控制曲线来进一步提高液压混合动力系统的能量再生效率,为液压混合动力系统的设计和控制提供一定的理论基础。     

液压系统自适应模糊PID联合仿真研究

根据液压机械无级变速器传动原理，结合HMCVT试验台架、泵控马达测控系统及HMCVT测控系统，对双向变量泵工作效率进行分析，通过Design Expert10建立多元回归模型,并用响应曲面法分析各因素对双向变量泵的效率的影响。为提高变量泵控定量马达系统的工作效率，通过MATLAB/Simulink和多体动力学软件ITI SimulationX建立模糊控制模型与动力学模型,并进行联合仿真，采用自适应模糊PID控制和普通PID控制2种控制方法对定量马达输出转速和双向变量泵排量比进行比较。结果研究表明：定量马达稳定输出转速时间减少了0.86 s，超调量下降11.4%，排量比稳定输出时间减少0.57 s，超调量下降15.5%。为进一步研究HMCVT效率特性及动态特性提供依据     

HMCVT液压系统自适应模糊PID联合仿真研究

根据液压机械无级变速器传动原理,结合HMCVT试验台架、泵控马达测控系统及HMCVT测控系统,对双向变量泵工作效率进行分析,通过Design Expert10建立多元回归模型,并用响应曲面法分析各因素对双向变量泵的效率的影响。为提高变量泵控定量马达系统的工作效率,通过MATLAB/Simulink和多体动力学软件ITI SimulationX建立模糊控制模型与动力学模型,并进行联合仿真,采用自适应模糊PID控制和普通PID控制2种控制方法对定量马达输出转速和双向变量泵排量比进行比较。结果研究表明:定量马达稳定输出转速时间减少了0.86 s,超调量下降11.4%,排量比稳定输出时间减少0.57 s,超调量下降15.5%。为进一步研究HMCVT效率特性及动态特性提供依据。     

泵控马达系统响应特性和效率特性的研究

建立了泵控马达系统仿真模型,对系统响应特性进行仿真研究和试验验证,结果表明:变量泵排量比由电信号决定,定量马达转速由电信号和泵转速共同决定。建立了静液压系统效率模型,对效率特性进行比较研究和试验验证,结果表明:泵控马达系统在大排量、中压、中高转速范围内具有良好的效率特性。     

基于PLC的挖掘机液压动力系统电控节能方案探索

挖掘机以液压技术的应用为基础,其工作条件恶劣,动作复杂,能量消耗巨大。利用现代计算机技术可以实现对挖掘机液压动力系统的程序控制,将电液比例技术应用于工程机械。以挖掘机中发动机与液压变量泵的功率匹配为解决问题的源头,利用PLC控制器的多兼容性和可靠性,对挖掘机液压动力系统各重要部件进行控制,实时处理各种输入和输出信号,并将信号传至上位计算机。通过PLC处理单元输出的控制信号,控制液压变量泵和发动机等执行机构协同动作,从而使发动机功率曲线一直保持在液压变量泵功率曲线之下。经装机测试,达到了很好的节能降耗效果。     

功率回馈式液压泵耐久性试验系统设计

设计一种基于先导压力设定的自动控制变量液压马达的液压泵功率回馈试验系统。系统的特点为液压马达能够适应性地自动调整其排量,以满足试验系统功率回馈的排量匹配要求。同时通过调节液压马达的起始控制压力,可以控制系统的工作压力,从而保证被试液压泵的测试压力要求。     

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.