砂型3D打印机X轴运动机构设计

目前砂型3D打印技术主要用于结构复杂零件的一次成型,生产过程灵活,基本不受零件结构、工装夹具的限制。砂型3D打印属于喷墨3D打印,原理上采用逐层打印方式,铺粉器铺设一层粉末（加有固化剂的铸造用砂）,打印头喷射一层粘结剂（树脂）。打印头扫描方向一般定义为X轴、铺粉器铺粉方向定义为Y轴。X轴的运动机构以及打印头自身的喷墨精度对3D打印砂芯的表面质量及尺寸精度影响很大。本文从3D打印机X轴运动系统整体方案设计、零部件选型设计、X轴横梁框架有限元分析等方面进行3D打印机X轴运动机构的理论研究与分析,为3D打印机X轴运动机构的设计提供理论参考。     

双驱动双滑轨复合折边机构运动仿真

模具包边机构在包边成形中反复运动。为减小汽车覆盖件外缘包边尺寸精度误差,提高表面质量,本文利用CAD软件对双驱动双滑轨复合折边机构进行三维建模,通过UG/Motion运动分析模块对其进行运动模拟,分析其机构运动状态,为机构设计提供参考。     

压力机杆系尺寸误差对滑块位置精度的影响

压力机杆系尺寸误差是影响滑块位置精度的重要因素。在理论分析了六连杆压力机杆系尺寸误差对滑块位置精度影响的基础上,开发了压力机杆系尺寸误差对滑块位置精度影响分析软件,可准确计算出杆系各尺寸误差变化引起的滑块下死点位置误差变化值,为六连杆压力机杆系设计提供了参考和依据。     

液压成形大尺寸环形零件的锁模技术

针对某大尺寸环形特征零件的液压成形工艺开发中的锁模问题展开研究。采用数值仿真方法对压力机锁模和螺栓机械锁模两种方式进行了对比分析。由于当零件外形尺寸过大时,很难选取到锁模压力和工作台面尺寸均适合的压力机,而仿真结果表明,当工作台面尺寸小于待加工零件模具投影面积时,即使压力机的锁模力足够大,仍然无法保证成形后零件的尺寸精度。而采用螺栓机械锁模方式,通过对螺栓的直径和数量分别进行合理优化,可最终实现足够的锁模压力且模具各部位的受力均匀。然后,开发了基于螺栓机械锁模方式的大型液压成形模具,并进行了实验验证。结果证实了螺栓机械锁模方式安全可靠,并且对于液压成形大尺寸且小批量零件的效果优异,成形后零件的尺寸精度能够满足设计要求。     

基于ADAMS的曲轴纵放双点压力机传动系统仿真分析与精度研究

为提高曲轴纵放双点压力机滑块下死点处的冲压精度,对零部件加工尺寸误差和装配误差引起的滑块两侧倾斜以及工作时滑块两侧受力状况的研究是非常有必要的。本文首先从双点压力机运动机构中影响压力机精度的理论分析入手,创建了数学模型,再借助ADAMS软件分别对滑块倾斜和受力不均进行了仿真分析,非常直观地给出了各因素影响关系曲线,为双点压力机冲压精度设计和补偿调试提供了可靠的理论依据。     

大型精密六轴联动电火花加工机床精度误差模型研究

针对牛头式大型精密六轴联动电火花加工机床的结构特点,分析了机床运动平移、旋转、热影响和电极损耗等因素产生的误差,运用多体动力学系统理论建立了六轴联动电火花加工机床的综合误差数学模型,为机床主机精度设计进一步做误差分配和多轴联动加工精度预测提供理论依据,也为满足机床的精度要求提供了有效保证,还为以后对机床进行误差实时补偿提供了重要参考。     

FDM精准成型温度FEA分析与试验研究

针对熔融沉积3D打印的相变成型原理在空间中X、Y、Z轴各方向的成型精度尺寸误差,运用ANSYS进行有限元仿真分析,获取典型打印材料PLA的优势流变性温度200℃、210℃、220℃、230℃。设计正交试验得到了外表面尺寸精度、垂直高度尺寸精度、内凹部位尺寸精度分别在230℃、220℃、200℃时最佳;打印参数综合精准成型度较高的最优组合为：打印温度210℃、打印速度40mm/s、分层厚度0.1mm、热床温度60℃。     

三轴机床微细异型电极加工与尺寸误差分析

采用直线插补与圆弧插补算法,在三轴卧式微细电火花机床上加工出圆锥台、四棱台以及带有圆弧曲面的微细异型电极,并对加工结果尺寸误差及导致误差产生的原因进行了全面分析。结果表明,微细异型电极的尺寸误差均在2%以内,而放电间隙的随机性、机床运动精度、尺寸测量精度等均是导致误差形成的原因。     

仿蜻蜓空间扑翼机构设计与分析

为了设计仿蜻蜓扑翼飞行器,对现有曲柄摇杆机构进行改进,提出了一种基于单曲柄轴的仿蜻蜓双翅翼空间扑翼机构。采用理论分析和数值仿真相结合的方法,研究了该扑翼机构的运动学特性。采用ADAMS对设计的仿蜻蜓扑翼机构进行仿真分析,结果表明所设计的扑翼机构可有效实现两侧运动完全对称,并且机构运动流畅平稳,机构扑动幅值达到了仿蜻蜓扑翼飞行器设计要求,且满足前后翼扑动角相位相差90°。     

摆杆式导叶调节机构的设计与研究

为促进变几何涡轮在航空发动机中的广泛应用,提高变几何涡轮的工作效率,设计了一种用于变几何涡轮的摆杆式导叶调节机构。采用Adams软件对导叶调节机构进行了运动学仿真研究,仿真结果验证了调节机构设计的可行性,通过仿真发现这样的导叶调节机构至少需采用3个作动筒同时驱动才能保证涡轮调节的精度要求。在Adams中对机构进行了参数化建模,利用参数化模型分析了尺寸误差和间隙对导叶转动精度的影响,并且以前十次仿真为例计算了调节机构导叶角度重复位置精度的可靠度。研究结果表明设计的导叶调节机构结构合理、可靠性高。     

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。