三自由度串联式快速刀具伺服刀架的研究

快速刀具伺服金刚石车削被认为是针对光学自由曲加工方法中非常有发展潜力的超精密加工技术。针对目前三自由度快速刀具伺服刀架在X、Y、Z3个方向上存在运动耦合、导致在刀具路径规划困难以及影响刀具使用寿命的问题,提出一种新型三自由度串联式快速刀具伺服刀架,通过将X、Y、Z3个方向的运动串联,避免了X、Y、Z 3个方向运动解耦困难;通过分析三自由度快速刀具伺服刀架应具备的要求,确定柔性铰链截面形状、材料以及尺寸;运用ANSYS对该三自由度串联式快速刀具伺服刀架进行有限元分析,得到X、Y、Z3个方向柔性铰链最大应力均远小于材料的许用应力,前6阶振型共振频率远高于伺服刀架的工作频率。结果表明,该刀架满足实际车削过程中的内应力和共振频率要求。     

基于灰色关联度的深切口椭圆柔性铰链稳健性优化设计

针对深切口椭圆柔性铰链设计结构参数存在不稳定的问题,建立了深切口椭圆柔性铰链的柔度运动模型,基于该模型提出了一种基于灰色关联度的稳健设计新方法。该方法是通过描述深切口椭圆柔性铰链柔度的一个关联度序列,分析铰链的柔度线性关系,利用灰色关联度评估铰链的柔度的关联程度,然后根据方差分析表中的方差波动百分比对每个因子的进行排序,得到一个关联度最大的稳健性因子水平组合。结果表明该方法可以为柔性铰链在可靠性稳健设计方面提供一种新的解决途径。     

基于正交试验与层次分析法的柔顺平行四杆机构稳健优化设计

为了提高柔顺平行四杆机构设计结构稳健性,建立了柔顺平行四杆机构的柔度运动模型,针对该模型提出了一种基于正交试验与层次分析法的综合权重计算方法,以柔顺平行四杆机构柔度稳健设计为响应目标,柔性梁和刚性梁的长度、柔性铰链宽度、机构厚度为设计变量,结果表明综合权重分析方法能够准确判断的影响因素主次顺序,确定最佳参数组合,实现了柔顺平行四杆机构稳健优化设计。     

微驱动电极进给机构的设计

根据微细电火花加工对伺服进给系统的要求,以蠕动式进给机构作为微驱动机构,以实现高精度高频响。详细分析了柔性铰链及压电陶瓷的原理和特点,指出压电陶瓷-柔性铰链机构在微进给中具有高响应频率、高精度和无间隙等优点。在此基础上,将压电陶瓷与整体式柔性铰链相结合,设计出一种能满足微细电火花加工要求的压电驱动蠕动式微进给机构。     

基于聚类分析法和粒子群算法的柔顺定位平台优化设计

3-RRR柔顺并联微动平台多响应优化设计中存在各种因子影响和交互影响的情况,导致柔度不稳定。为解决此难题,将聚类分析法和响应曲面法相结合,提出一种优化该机构柔度稳健性的新的设计方法。通过建立微动平台多方向的铰链柔度运动模型,进行试验设计和聚类分析;引入响应曲面法构建响应曲面模型并且利用粒子群算法寻优求解;通过信噪比指标评判结果,得到满足约束条件的稳健优化设计方案。实例表明：引入的聚类分析方法可以为柔性铰链多目标稳健优化设计提供一种新的解决方法且效果良好。     

泳动微机器人主体机构的设计研究

泳动微机器人模仿鱼类游泳的方式驱动。本文利用柔性铰链和差式杠杆放大原理,设计了泳动微机器人主体机构;为了获得足够的推进力,实现三自由度泳动,必须使微机器人工作在谐振状态,因此本文还计算了微机器人主体机构的固有频率。     

微夹持机构中椭圆弧柔性铰链的模糊优化设计

以增大椭圆弧柔性铰链的偏转角αz为目标,通过模糊优化设计,结合ANSYS仿真,研究微夹持机构中柔性铰链的优化问题.建立柔性铰链的参数优化模型,采用MATLAB对铰链的最小厚度t、长半轴a、短半轴b和力矩Mz进行优化,并通过ANSYS仿真进行检验.结果证明:优化后的柔性铰链偏转角大小与有限元仿真结果的相对误差为5.39％,比较吻合,说明了优化设计方法的正确性.     

精密导向膜片设计与优化

针对微振动模拟器中精密导向机构行程小、精度高的要求,提出了一种具有精密导向作用的柔性膜片。首先,基于柔度矩阵法对柔性膜片的轴向与径向柔度进行建模;其次,基于柔性膜片的结构参数对其轴向和径向柔度进行参数化分析;接着,以高轴向柔度、高轴向/径向柔度比和低应力为目标,建立了优化设计模型,并对其进行优化,优化结果表明轴向柔度优化率为233%,轴向/径向柔度比优化率为172%,最大应力优化率为32%。优化后柔性膜片的各目标性能都得到较大提升;最后,通过有限元分析与实验进行验证。有限元分析与实验结果相对于理论分析的相对误差分别为6.7%和7.8%。理论分析与优化方法为柔性膜片提供了一个简单有效的设计思路。     

基于遗传算法的超声电火花微小孔加工用柔性铰链的数值分析与优化

超声电火花(EDM)复合加工是一种加工微小深孔的先进方法,但是电极在高频振动中会产生扰动,即横向振动,增加所加工孔的圆度误差。基于此,设计了一种双直圆柔性铰链结构,在提升轴向振动幅值的同时,有效抑制了横向振动的幅值,进而提升加工精度。首先,建立了柔性铰链的受力模型,并确定了影响其工作效果的主要参数。然后通过遗传算法对其结构进行优化,确定最佳的柔性铰链结构参数。最后,利用有限元分析对柔性铰链与电极组成的系统进行模态分析,通过对比特征频率、横向振动幅值与轴向振动幅值,验证了经过遗传算法优化后的柔性铰链的固有频率更接近工作频率,并且具有最佳的提高轴向振动、抑制横向振动的作用。     

基于APDL语言的柔性铰链机构参数化实体建模

柔性铰链机构是一种新型的微位移机构，具有无机械摩擦、无间隙、无热源、运动连续、不需润滑及分辨率高等优点，因而在许多领域得到了广泛应用。为了分析柔性铰链机构的输出位移，采用大型通用有限元分析软件ANSYS进行参数化有限元分析，APDL语言(ANSYS Parameter Design Language)是ANSYS软件提供的参数化程序设计语言，采用该语言可以分别地建立柔性铰链机构的几何实体模型。文章首先介绍了参数化编程语言APDL，再提出了用该语言进行编程实现参数化实体建模的一种方法，最后，以单平行四杆柔性铰链机构为例证明这是一种方便、快速的实体建模方法。     

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.