某大型液压装备的液压冲击装置的设计及试验北大核心CSCD

针对大型液压装备在工作过程中的液压冲击会对设备产生巨大的危害等问题,设计了某大型液压装备的液压冲击装置,对该装置的功能、指标要求进行了介绍,对典型元件进行了计算与选型,并对液压冲击进行了计算,完成了其电气控制系统、测控系统和基于HMI的人机交互系统的设计。以卸荷冲击压力测试工位为例进行了两组试验,试验表明:当系统压力为3 MPa时,开口度为50%时的流量冲击较开口度为100%时大15%左右;当系统压力为5 MPa时却相反,开口度为50%时的流量冲击较开口度为100%时小30%左右。设计的大型液压装备的液压冲击装置实现了对液压冲击的性能参数的分析和测试,这对大型液压装备的液压冲击功能分析、减少液压冲击对设备的影响有着重要的意义。     

架柱式钻机全液压自动控制装置的研究

为适应高瓦斯环境坑道施工的需要,现有架柱式液压回转钻机基本采用全液压系统、人工控制技术,严格要求操作人员在钻机进给油缸系统的操作施工中,要时刻注意钻机立柱顶紧装置液压系统的压力表值变化,当其压力低于一定值时,务必人工给顶紧装置液压系统进行充压操作。利用螺纹插装阀等常用液压元件,研究出了一种能实现架柱式钻机顶紧油缸系统充压及其进给油缸系统工作两种状态全液压自动切换控制的装置,彻底解决了必须人工对架柱式钻机顶紧装置充补压的问题,简化了钻机操作的同时,通过顶紧系统充压与进给系统工作两者间的液压互锁,也极大地提升了整个钻机工作时的安全可靠性。     

挖掘机动臂势能回收系统蓄能器压力设计及试验

为降低液压挖掘机整机能耗,提出一种以蓄能器为储能装置的液压挖掘机动臂闭式回路势能回收系统。以80k N级液压挖掘机为研究对象,基于系统工作原理,建立了能量回收系统电动机-泵/马达轴系力矩平衡模型,分析了蓄能器平均工作压力与负载压力的关系。结果表明:电动机-泵/马达轴系在电动机无功率输出工况力矩平衡时,液压蓄能器工作压力平均值约为动臂负载压力的2倍。并结合半载工况挖掘机动臂下降试验,确定8吨级液压挖掘机蓄能器最小和最大工作压力分别为16.04 MPa和19.56 MPa。     

雾化气体淬火压力边界条件计算及实验研究

雾化气体淬火时试件外表面所受的压力是计算其应力场的重要边界条件,也是影响试件淬火后变形和开裂的因素之一。本文应用计算流体动力学CFD的方法建立雾化气体淬火的三维非稳态模型。基于边界条件实验结果,对工件在不同进口速度工况下淬火过程中的压力场和试件的压力边界进行了数值模拟,并将试件上表面的压力模拟结果与边界条件实验结果进行了对比分析。结果表明,试件外表面的压力数值模拟计算与实验结果较吻合。     

恒载变速工况下液压马达瞬时转速波动与系统效率关联性实验研究

为了研究恒载、变速工况下液压马达瞬时转速波动与液压系统效率之间的变化关系,采用实验验证的方法,在变转速液压实验台中通过在LabVIEW软件中改变电机转速、设定恒定的磁粉制动器加载电压模拟工况,采集、分析恒定载荷条件下液压马达转速斜坡、正弦、阶跃变化时液压马达转速波动、液压系统效率、压力的变化曲线。实验结果表明:液压马达瞬时转速波动与液压系统效率具有关联性,转速越高,液压马达转速波动越小,液压系统效率越高;反之,变化情况相反。转速的变化会引起系统压力小幅度的变化,变化趋势与转速、系统效率相同,与转速波动相反。此研究为液压系统在恒定的负载工况条件下选择合适的液压马达转速范围、减小转速波动、提高液压系统效率提供了参考和借鉴。     

主驱动密封系统试验台液压系统研究

试验台模拟了盾构机主驱动密封的工作环境,为解决现有的实验装置无法实现使密封圈在左右两腔不同压力点的工作状态,对试验台液压控制系统进行研究。介绍其液压系统的原理组成及其加载装置和动力装置。动力装置通过调节变量泵的排量改变液压马达的转速,以及控制电磁换向阀实现正反转;加载装置通过比例减压阀对油缸输出压力,使波纹管压缩,经由高压液压软管总成对实验容器左右两腔分别加压。并通过AMESIM对以比例减压阀为核心的闭环控制系统进行仿真分析。最终结果表明该控制系统可以满足实验要求。     

平稳工况下液压马达瞬时转速波动与液压系统效率关联性实验研究

为研究平稳工况下液压马达瞬时转速波动与液压系统效率之间的变化关系,采用实验验证的方法,在变转速液压实验台中,通过在LabVIEW软件中改变电机转速、设定恒定的磁粉制动器加载电压模拟工况,采集并分析恒速变载与恒载变速平稳工况条件下液压马达瞬时转速波动与系统效率的变化曲线。实验结果表明:液压马达瞬时转速波动与液压系统效率具有关联性,转速越高,液压马达转速波动越小,液压系统效率越高,反之变化情况相反;在恒载变速的平稳工况条件下,随着电机转速的增加,液压马达转速波动减小,液压系统效率增加,在低转速时效率增加明显,高转速时效率增加减缓;在恒速变载的平稳工况条件下,随着压力的增加,液压马达转速波动增大,液压系统效率减小。研究结果为变转速液压系统在平稳工况下选择合适的电机转速和负载范围、减小液压马达瞬时转速波动、提高系统效率提供了参考。     

管路对液压断带保护装置控制系统特性的影响

全断面液压断带保护装置是以液压控制系统为核心的断带抓捕装置。针对断带保护装置需要快速平稳抓捕的特性,通过优化液压控制系统的管路参数来提高整个保护装置的性能,在理论分析管路对液压特性影响的基础上,利用AMESim仿真软件进行了仿真分析,并通过断带抓捕实验验证。结果表明:管径对抓捕时间和压力峰值的影响较大,油管的长度对液压系统整体的影响较小,当管径为32 mm时系统具有最高的整体效能。     

阀配流乳化液泵新型流量调节策略及其特性分析

针对传统变频流量调节方法用于远距离供液响应滞后问题,提出一种应用于阀配流柱塞泵的快速流量调节方法,即采用比例阀短接泵的吸液阀,通过调节该装置开闭程度和时间来实现泵的排量调节。以BRW500/31.5乳化液泵为研究对象,基于AMESim仿真平台搭建乳化液泵的流量调节模型,从综采工作面液压支架供液系统出发,建立ZY6000/18.5/38型支架液压系统仿真模型,研究不同调节策略对液压支架动作的影响。研究表明：所提出的泵站流量调节方法是可行的,当泵站供液量从300 L/min增加到400 L/min时,其调节时间可减少0.9 s;同时,同等供液流量条件下,短接吸液阀的数量越多流量脉动与压力冲击越小。     

φ10锆—4合金管低周液压下轴向表面裂纹扩展的研究

探索用柔度法测定小口径锆—4合金管低周疲劳裂纹的等效扩展量。已建立了液压疲劳实验装置,采用COD规监控裂纹向深度的扩展运动,记录低周疲劳裂纹的传播过程。实验证实,通过柔度标定曲线可以间接地预测在低周液压下表面裂纹沿深度的扩属量,并由此估算出裂纹扩展速率。实验指出,低周液压下的断裂特征与循环次数有关,随循环次数的增多,逐渐由爆破过渡到泄漏。     

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.     

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.     

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.     

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.