AMESim在电动液压转向系统的转向平顺性研究中的应用

为了满足电动液压助力转向(EHPS)系统在转向助力时的平顺性要求,提出无刷直流电动机(BLDCM)调速系统模糊PID控制方法,介绍模糊PID控制策略以及模糊控制器的设计过程并设计模糊PID控制器。利用AMESim/Simulink联合仿真技术建立电动液压转向系统模型,进行对电机目标电流的跟踪响应仿真、电机转速特性仿真和EHPS系统的转向平顺性仿真。仿真结果表明:基于直流电机调速系统模糊PID控制的电机比传统PID控制的电机具有更好静、动态特性,从而使EHPS系统具有更好的转向平顺性。     

转阀结构参数对流量控制式ECHPS系统可变助力特性的影响

电控液压助力转向系统（ECHPS）具有随车速调节的可变助力特性,可以显著改善驾驶员的转向路感。本文对一种典型的流量控制式ECHPS系统进行了分析,建立了该系统的动态仿真模型;推导了转向器中转阀阀口的通流面积与转阀主要结构设计参数之问的函数关系。通过仿真计算,分析了转阀结构参数对流量控制式ECHPS系统可变助力特性的影响规律,并给出了流量控制式ECHPS系统转阀结构参数选择与匹配的基本原则。     

电控液压动力转向系统的研究

电控液压动力转向(ECHPS)系统可解决大中型汽车转向轻便性和灵敏性的矛盾,使驾驶员在汽车低速行驶时获得较大助力,高速行驶时获得较强的路感.本系统可根据车速传感器提供的信号,经处理后输出PWM的占空比来控制数字阀,以达到控制反力室压力的目的.另外,在发动机与动力转向泵之间增加电磁离合器,由ECU根据转向盘转矩信号控制其离合,使动力转向泵在不需要助力时停止工作,降低了能量消耗.试验表明该系统能满足不同车速下获得不同助力特性的要求.     

数字阀在电控液压动力转向系统中的应用研究

电控液压动力转向(ECHPS)系统可解决大中型汽车转向轻便性和灵敏性的矛盾,使驾驶员在汽车高速行驶时获得较强的路感.本文通过研究ECHPS系统的转向特性及工作原理,提出将数字阀应用到该系统中,并由电控系统根据车速传感器提供的信号,经处理后输出PWM的占空比来控制数字阀,以达到控制反力室压力的目的,使驾驶员在不同车速下获得不同的助力特性.     

基于负载敏感技术的液压助力转向系统研究

针对传统液压助力转向系统的压力和流量损失问题,设计了基于负载敏感技术的液压助力转向系统。基于仿真软件AMESim对负载敏感泵和液压助力转向系统进行了建模。仿真结果表明:当在直线行驶工况下,该系统以低压、小流量的待机状态输出;当有转向需求时,系统能根据转阀开启阀度,快速调节泵出口的压力和流量,并且能够满足助力需求。基于负载敏感技术的液压助力转向系统在车辆行驶过程中能减小能量消耗,达到节能的目的。     

平衡式变量叶片泵节能研究

针对实际汽车液压转向系统中转向油泵的输出流量高于实际需求的流量的现象,提出了一种含有浮动块的新型平衡式变量叶片泵,该泵具有速度补偿特性,能降低泵的无功功率消耗.同时建立了汽车液压助力转向系统的数学模型和汽车液压动力转向系统的Matlab Simulink仿真模型,对平衡式变量叶片泵选择不同的参数进行输出功率特性仿真,对输出结果进行对比和分析.仿真结果表明,该泵在不同转速条件下的功率输出平稳,可显著减少汽车尾气排放和噪声,节能效果明显.是一种较有应用前景的新型转向叶片泵.     

电液比例换向阀对汽车转向系统响应特性的影响

主要研究电液比例换向阀的阀芯直径、阀芯质量、弹簧刚度和弹簧预紧力等对汽车线控液压助力转向系统响应特性的影响。利用AMESim仿真软件建立了其液压模型并进行仿真,对比了不同参数对线控液压系统响应性能的具体影响。     

转阀式液压助力转向系统建模与仿真分析

考虑了汽车液压助力转向器中的机械子系统与液压子系统,建立了相应的数学模型并利用Matlab/Simulink控制系统仿真软件建立了汽车液压助力转向系统的仿真模型.仿真分析了活塞有效面积、扭杆刚度和系统供油流量的变化对系统响应的影响情况,结果表明:增加系统供油流量、减小扭杆刚度都会使转向器的助力油压增大,此时齿条的位移将增大从而使稳定时间延长;活塞有效面积的大小几乎不影响助力油压的大小,齿条助力将随活塞有效面积成正比例变化.     

ECHPS旁通流量比例电磁阀开度模糊PID控制

为了使车辆电控液压转向系统（ECHPS）具有良好的随车速可变的助力特性,研究了用于控制ECHPS旁通流量的比例电磁阀的开度控制策略。分析了旁通流量控制式ECHPS的基本原理和比例电磁阀的结构组成,建立了比例电磁阀的动力学模型和控制模型。针对动态多工况ECHPS旁通流量的精确稳定控制要求,提出了模糊PID控制策略,把模糊推理运用于PID参数的整定,以补偿控制系统因非线性和时变性所导致的误差。仿真结果表明：在低、中、高3种车速工况下ECHPS的旁通流量和比例电磁阀开度的响应符合随车速可变助力特性的要求;与常规PID控制相比,所设计的模糊PID控制具有响应速度快、稳态精度好、超调量小的优点,可实现比例电磁阀开度的精确稳定控制。     

FW-6型地下工程服务车全液压转向系统设计与仿真

FW-6地下工程服务车是一种井下用铰接式车辆,其转向系统采用全液压转向形式.简要介绍该车转向液压系统的工作原理;提出该车转向液压系统的组成方案,详细阐述该车液压转向系统的设计计算以及关键液压元件的选型;建立该车全液压转向系统的数学模型,利用SIMULINK工具建立其仿真分析模型,并对其进行动态特性仿真.仿真结果表明FW-6地下工程服务车转向液压系统的设计方案是合理可行的.同时,该仿真模型对铰接车辆转向液压系统的设计也具有重要的参考价值.     

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.     

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.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。