VSV作动筒跟踪误差分析及减小误差方法的研究

基于对发动机可调静子叶片作动筒跟踪误差的要求,对影响跟踪误差的因素进行了分析,并从影响因素中寻找减小误差的方法。从可调静子叶片作动筒液压控制系统的给定误差和反馈误差分析了影响误差精度的程度;基于可调静子叶片作动筒的原理进行分析,建立了电液位置伺服系统的动态模型,并从动态模型中分析出VSV作动筒所受的负载力为影响跟踪误差的主要因素,提出通过力传感器的数值及其变化速度来补偿位移的方法;通过半物理试验表明所分析的跟踪误差来源的正确性,通过仿真试验验证了位移补偿方法的有效性。     

三坐标测量机动态误差与测球半径补偿误差的研究

分析了影响给定的三坐标测量机动态误差的因素,对动态偏转角误差进行了测量,并推导出由动态偏转误差得到测头处的动态位移误差的计算公式.同时分析了测球半径补偿误差的成因及解决措施.     

基于磁致伸缩传感器的辊压机压下位移监测及误差补偿

考虑到辊压机工作时设备温度变化范围大、外界干扰强烈等特点,研究了基于磁致伸缩传感器的辊压机压下位移监测及误差补偿方法。通过理论分析和实验手段,对磁致伸缩位移传感器的精度影响因素进行研究。分析了磁致伸缩位移传感器的工作原理,结合传感器实际使用经验,确定外界环境干扰主要是使用环境温度的变化以及电磁干扰的影响,并通过理论分析磁致伸缩位移传感器受温度和电磁干扰的机理。使用最小二乘支持向量机补偿模型,针对温度变化和电磁干扰产生的误差进行补偿。实验研究结果表明,磁致伸缩位移传感器测量精度受使用环境温度和电磁干扰影响较大,使用本文研究的补偿模型后,可以减小温度和电磁干扰对传感器精度的影响。     

数控机床丝杠动态误差补偿分析研究

针对机床定位误差补偿研究大多是通过实验反推模型,补偿模型复杂且鲁棒性较差,难以在实际生产中应用。分析了滚珠丝杠副各部分热源的传热机制,提出包含移动热源的一维离散化非稳态热传导模型;随后,分析滚珠丝杠副误差形成机制,建立基于滚珠丝杠副几何螺距误差和热误差的综合补偿模型;最后,设定运行工况进行数值仿真,并通过试验进行验证。试验结果表明,丝杠在运行至20、40 min时的累积定位误差从补偿前的110μm、169μm变为补偿后的8μm、6.7μm。在省去实验的情况下其动态累积误差平均降低了94%,达到了较好的补偿效果。     

基于BP神经网络的磨床力误差补偿方法

为建立磨削加工参数与磨削力导致的力变形误差之间的关系模型,提出基于神经网络的力误差建模和实时补偿方法.建立经遗传算法优化的BP神经网络以表征磨削参数与磨削力的关系;运用有限元方法对零件进行力学分析,建立磨削力与力变形量的关系模型;建立加工参数与切削力误差映射模型,预测误差补偿量,进行实时补偿.实验结果表明:该切削力误差...     

基于摩擦补偿的电液作动器高精度控制

电液作动器因其集成度高、占用空间小,容易组成分布式集中控制系统,在航空航天与工程机械领域飞速发展,但是在低速运行工况下,由于摩擦力以及液压系统的非线性等因素,难以完成高精度轨迹跟踪工作甚至产生低速爬行。为此,从摩擦特性对电液作动器轨迹跟踪精度的影响出发,提出一种前馈补偿+ESO的控制策略,引入LuGre动态摩擦力中的鬃毛平均变形量,建立精确伺服系统状态空间方程,在Simulink平台上搭建摩擦力模型和泵控非对称缸模型,采用正弦位置指令对该解决方案的轨迹跟踪精度进行了仿真验证。结果表明:前馈补偿+ESO的控制策略跟踪误差仅为常规PID控制的1/4,跟踪精度达到0.2 mm。     

融合光纤感知的气动执行器夹持力控制策略研究

为了降低气动执行器夹持力/气压迟滞的影响,提高夹持力跟踪控制精度,提出一种基于Prandtl-Ishlinskii （P-I） 逆模型的前馈补偿结合模糊PID的控制策略。分析气动执行器的夹持力/气压迟滞特性,通过初载曲线法辨识迟滞模型参数,建立P-I逆模型;设计融合FBG力感知的模糊PID控制算法,基于自制的FBG传感器实现夹持力反馈,通过标定实验验证传感器的静态特性。在Simulink中构建前馈补偿和融合FBG力感知的模糊PID相结合的复合控制器,完成与传统PID以及模糊PID控制器的夹持力控制仿真对比。仿真结果显示：前馈补偿可以降低稳态误差,提高控制精度。最后,在气动执行器夹持力控实验平台上开展动态跟踪实验,验证了所设计复合控制器的有效性。     

光栅尺测量精度误差补偿系统研究

文章主要研究影响光栅尺测量精度的因素,探索提高测量精度的途径。通过研究影响光栅尺测量精度的因素分析了其静态误差模型;然后,通过设计可调的光栅尺误差检测平台并结合优化的测量方案对各个测量点进行了大量的误差检测,并分析了各个测量点测量误差的统计特性,再对检测结果进行正态分布检验,获得了较为准确真实的光栅尺测量误差曲线,验证了其静态误差模型;最终在光栅尺数显系统分别采用全程线性补偿及分段线性补偿方法对光栅尺测量误差进行修正。实验结果经第三方计量机构检测表明:经一次全程线性补偿后,在直线光栅尺90mm测量长度内,测量精度由0~19.42μm提高到-3.26~1.32μm,经二次分段线性补偿后,测量精度提高到-1.453~0.9332μm。     

多轴机床几何误差建模与补偿技术的研究

基于多体系统运动学理论,分析了多轴机床的拓扑结构关系及各个运动轴的误差项元素,建立了多轴机床运动空间的几何误差模型。基于Labview开发了误差补偿平台,进行了误差补偿试验。通过对比补偿前后各轴线性定位误差和补偿前后的数控加工代码,验证了所建立的误差模型的正确性,且该补偿方法是可行的。     

数控机床热误差动态灰色优化建模研究

为降低热误差对加工精度的影响,以减少补偿成本、简化数据采集、提高补偿精度为目标,提出采用灰色GM(0,N)模型进行数控机床热误差建模预测;以优化数据配置、改善补偿系统动态品质、提高鲁棒性为目的,建立了GM(0,N)优化模型。采用智能温度传感器和位移传感器采集了MCH63精密卧式加工中心温度数据和主轴3个方向热位移量,并根据采集数据构建热误差模型。试验结果表明:GM(0,N)建模方法简单,数据量少,运算时间短,预测精度较高;优化模型可根据在线输入的新数据不断修正模型本身,其精度高、鲁棒性强、通用性好,适合于在线建模。     

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.