电液伺服阀前压力脉动的仿真研究

本文运用流体网络理论结合液压伺服系统对电液伺服控制系统进行了分析研究，通过仿真研究伺服阀前的压力脉动情况，分析了蓄能器对衰减压力脉动的效果以及压力脉动对液压系统控制精度的影响。     

基于AMESim/Matlab的电液伺服控制系统的仿真研究

利用AMESim及Matlab软件的各自特点,采用AMESim与Matlab联合仿真的方法对阀前供油管路的压力脉动对电液伺服系统的影响进行了仿真研究．同时对脉动衰减型蓄能器衰减伺服阀前供油管路压力脉动的效果及其对系统控制精度的影响进行了仿真研究。     

喷墨打码机墨路循环系统的压力脉动抑制方法

针对以波纹管蓄能器和隔膜泵为基本元件的喷码机墨路循环系统中存在的压力脉动现象,通过对关键部件隔膜泵(含隔膜、吸入液阀、排出液阀等)与波纹管蓄能器的分析建立墨路循环系统的液压仿真模型,分析了波纹管刚度、阻尼孔孔径等重要参数对脉动吸收效果的影响,获得吸收压力脉动的波纹管的最优参数,通过试验验证了仿真结果,压力脉动抑制的关键在于波纹管的刚度必须与隔膜泵工作压力合理匹配。     

高升率液压脉冲系统机制分析与设计

为模拟航空作动器高压力、高升率工作环境进行脉冲试验,设计了T形波脉冲系统,系统采用压力传感器和电液伺服阀构成闭环控制,通过控制经伺服比例阀流入非对称增压缸低压腔的流量建压。在建立蓄能器、电液伺服阀及增压缸-被试工装件的压力-流量数学模型的基础上,基于AMESim搭建仿真模型,对比分析不同工装件容积、脉冲升率对系统动态性能的影响。仿真结果表明,系统主要由蓄能器提供瞬时流量快速建压,释放能量后,液压泵需要在一个周期内为蓄能器补充0.25 L液压油;为保证压力升率,系统最低流通能力为250 L/min。依据仿真结果选择系统关键元器件搭建脉冲试验台,试验台实现峰值压力42 MPa、升率1 100 MPa/s的T形波,并稳定持续20万次脉冲,验证了仿真分析的正确性。     

基于伺服阀前蓄能器动态特性的轧机压下位置控制的实验研究

为实现轧机的高精度控制,提高产品加工质量,以轧机液压系统中伺服阀前蓄能器为研究对象,分析蓄能器动态特性对压下位置控制系统精度的影响。在实验轧机上,通过在伺服阀前更换不同公称容积蓄能器和改变蓄能器充气压力,定量分析其对液压压下位置控制系统的影响,最终确定该轧机伺服阀前蓄能器的最优参数,形成一套不局限于轧机液压系统的伺服阀前蓄能器的选型方法。     

自适应蓄能器在泵阀联合EHA压力脉动抑制中的应用

针对泵阀联合EHA泵源压力变化引起压力脉动的问题,在分析普通蓄能器吸收压力脉动效果基础上,提出由比例控制阀和普通蓄能器组成自适应蓄能器,通过改变比例阀的开口度来改变蓄能器进口管路的流通面积,从而达到改变蓄能器固有频率的目的并设计了控制器。仿真结果表明,在泵源压力变化时自适应蓄能器较普通蓄能器对压力脉动有更好的吸收效果。     

蓄能器组在变压水泵系统中吸收压力脉动的特性研究

在某些特殊应用领域,水液压系统的输出压力是变化的.针对此情况,提出在水压泵的出水口处安装多个蓄能器以吸收不同输出压力工况下的压力脉动.在建立蓄能器吸收压力脉动理论数学模型的基础上,应用相关的仿真分析软件,讨论不同充气压力组合的蓄能器组在不同输出压力条件下吸收压力脉动的特性,并进行对应的试验分析.该理论仿真和试验结果可为变压系统的减振降噪研究工作提供参考.     

基于AMESim的二级双喷嘴挡板电液伺服阀仿真及故障研究

为分析二级双喷嘴挡板电液伺服阀性能及进行故障研究,利用AMESim平台建立了伺服阀的整体仿真模型,通过进行伺服阀动态性能实验获得阶跃信号作用下伺服阀输出流量瞬态、稳态数据,通过数据对比验证了所建仿真模型的正确性。仿真分析了二级双喷嘴挡板电液伺服阀常见故障对频响特征曲线、流量特性、压力特性等性能的影响,仿真结果使得系统故障分析有据可依,可为伺服阀的故障诊断研究提供依据。     

三级电液伺服阀的故障仿真研究

电液伺服阀性能的优劣对液压设备的控制精度、系统的稳定裕度以及可靠性有很大的影响.而对电液伺服阀故障模拟常采用硬件方式仿真模拟,笔者利用液压仿真软件对电液伺服阀进行仿真研究,通过仿真分析得到发生故障时阀的压力曲线,符合实际要求.     

二次调节加载系统中液压蓄能器的研究

建立了二次调节环境下液压蓄能器的数学模型，通过理论分析和仿真研究了蓄能器对二次调节加载系统中恒压网络系统压力脉动的影响以及蓄能器的匹配方法。提出了在恒压系统中针对不同子系统采用相应规格的蓄能器，并通过在高低压端口分别放置蓄能器的方法来降低系统压力脉动对精确加载的影响。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

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。     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

An Easy Way to Quantify the Adhesion Energy of Nanostructured Cu/X(X=Cr,Ta,Mo,Nb,Zr) Multilayer Films Adherent to Polyimide Substrates

An approach based on film buckling under simple uniaxial tensile testing was utilized in this paper to quantitatively estimate the interfacial energy of the nanostructured multilayer films(NMFs) adherent to flexible substrates. The interfacial energies of polyimide-supported NMFs are determined to be *5.0 J/m2 for Cu/Cr, *4.1 J/m2 for Cu/Ta,*2.8 J/m2 for Cu/Mo, *1.1 J/m2 for Cu/Nb, and *1.2 J/m2 for Cu/Zr NMFs. Furthermore, a linear relationship between the adhesion energy and the interfacial shear strength is clearly demonstrated for the Cu-based NMFs, which is highly indicative of the applicability and reliability of the modified models.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.     

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.