冲压件侧壁卷曲的机理及控制

侧壁卷曲现象存在于带法兰零件的弯曲和拉深工序中,其导致的冲压件尺寸和形状偏差会给零件的后续焊接和装配造成困难。该文通过分析零件变形过程及最终应力分布,解释了侧壁卷曲现象的成因。通过有限元模拟,对比压边力和施加方式对侧壁卷曲现象的影响。结果表明,单纯增加压边力不能减少侧壁卷曲,理想情况是分两步施加压边力,行程开始时施加较小的压边力,在行程结束前很小的行程内施加较大的压边力。提出采用浮动拉延筋工艺可获得理想的压边力模型以减小零件的侧壁卷曲。为验证所提出的工艺,制作相应的模具进行带法兰U形件的成形,结果表明,该新型工艺简单易行,能有效减小侧壁卷曲。     

基于数值模拟的盒形件拉深成形变拉深筋技术研究

以盒形件为研究对象,建立了盒形件拉延筋成形的数值模型,分别对盒形件固定拉深筋和变拉深筋成形进行了数值模拟研究,并进行了工程试验的验证,对结果及误差进行了分析,实现了基于拉深筋高度变化的变拉深筋技术。这种方法能有效发挥板料成形性能,提高零件拉深成形质量。     

拉延筋对拼焊板盒形件焊缝移动的影响

拼焊板在拉延时发生焊缝线的偏移。为了有效控制偏移,通常的做法是设置拉延筋。利用Dynaform有限元软件对钢-铝拼焊板盒形件拉深进行了模拟。结果表明,在铝板一侧设置3条开放式拉延筋可以有效控制焊缝发生移动。     

抑制U形件冲压回弹翘曲的拉深筋优化设计

介绍一种抑制U形件侧壁翘曲的拉深筋优化设计方案,包括在压边圈上设置第一拉深筋以及在凸模上设置第二拉深筋。拉深初期,只有第一拉深筋作用,有效控制压边力大小,避免了零件早期开裂风险;拉深后期,第二拉深筋起作用,进一步增大进料阻力,保证塑性变形更充分。结果表明,采用该拉深筋结构成形的U形件翘曲量可控制在0.5 mm以内,比传统拉深筋翘曲量减少80%。     

差厚拼焊板方盒件在充液拉深过程中焊缝移动的研究

基于Dynaform分析软件,就差厚拼焊板充液拉深盒形件的压边力、液体压力及加载方式对焊缝移动的影响进行仿真与研究.结果表明,充液拉深时,薄、厚板两侧的压边力差值大小对盒形件底部的焊缝移动影响不大,而控制预胀形所形成的等效拉深筋高度,可有效地减小底部的焊缝移动量;同时,提高充液工作压力可显著减小侧壁焊缝的移动量.这一研究结果对指导拼焊板充液拉深具有现实的意义.     

盒形件凸缘直边的主应力解析与数值模拟研究

对盒形件凸缘直边法兰区主应力进行了力学分析,研究了其成形中法兰部分的变形情况.运用DYNAFORM软件,对盒形件的成形进行了数值模拟,并用硬度计测定了盒形件法兰区的硬度.结果表明:法兰直边靠近中点的材料比靠近圆角部分的材料厚度大,说明材料塑性变形不够充分；长宽比大的盒形件成形后的零件厚度比较大,材料流动困难,不利于成形；同一高度上,圆角部分硬度明显大于相邻两直边硬度,说明圆角部分材料流动良好而加工硬化现象明显,硬度最大值在凹模圆角入口处附近.盒形件法兰变形的实验与数值模拟结果一致.     

盒形件法兰起皱临界压边力影响规律研究

起皱足盒形件拉深成形中的主要缺陷,而压边力是控制法兰起皱的主要手段.本文采用基于C-B准则的理论解析与数值模拟方法,研究了材料性能和工艺参数对盒形件拉深法兰起皱临界压边力的影响规律.结果表明:材料性能参数中强度系数K、硬化指数n对法兰起皱临界压边力影响较大,而塑性应变比γ对临界压边力几乎没有影 响;临界压边力随拉深行程增加而增大,凹模圆角增大时,临界压边力减小,凸、凹模间隙对临界压边力影响较小.     

正多边形盒零件冲压成形凸缘变形区的应力分布计算

首先给出正多边形盒零件凸缘变形区的应力分布式 ,接着分析了凸缘变形区的应力变化规律 ,并以0Cr18Ni9板材和方盒零件为算例给出了凸缘变形区的应力分布曲线。正多边形盒零件凸缘变形区圆角部分的拉深变形是发生皱曲和破裂之源并向直边部分转移材料 ,使直边部分松弛乃至皱曲。因此 ,对于皱曲通常选择设置压边装置 (压边圈、拉深筋等 )来解决。对于破裂通常选择增大侧壁间圆角半径或多次拉深来解决。正多边形盒零件冲压成形最好采用分区 (分块 )变压边力拉深或分区 (分块 )恒压边力拉深     

变压边力对铝合金板拉深成形性能的影响研究

利用数值模拟软件Dynaform研究了可变压边力对铝合金板拉延性能的影响,包括随时间变化的压边力对圆筒形件成形质量及特征节点应变路径的影响和随位置变化的压边力对盒形件成形质量的影响.研究表明,随时间变化的渐增式和(^)型变压边力(筒形件)以及随位置变化分块布置的压边力(盒形件)可以有效地控制起皱和拉裂的发生.这能提高铝合金板的拉深成形性能,从而获得较好的成形质量.     

可控变压边力的盒形件拉深模具设计

压边结构及压边力对板料拉深成形质量有着重要影响。由于盒形件成形时具有应力分布不均匀、变形分布不均匀以及变形速度不均匀的特点，拉深模具压边结构采用了分区方式，将压边圈分为直边部分和圆角部分，各部分可以协调运动。拉深过程中压边力通过控制系统可以随拉深起皱规律而合理变化，有效地改善法兰区变形的不均匀性，提高盒形件的成形质量。     

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。