基于DYNAFORM的汽车横梁模具型面的参数化设计与工艺分析

探讨了汽车覆盖件的成形特点和覆盖件拉伸模型面参数化设计的方法,包括冲压方向、工艺补充面、压料面、拉伸筋等设计。介绍了基于DYNAFORM软件以汽车横梁为例如何实现汽车覆盖件的型面参数化设计,以仿真模拟判断模面的优劣,再根据模拟结果对模面进行快速修改。这种模面设计和分析方法为类似零件成形工艺的制定提供一定了的经验。     

覆盖件拉延模型工艺补充部分的参数化设计

拉延工艺设计是汽车覆盖件冲压工艺设计的重要内容,也是在对该类零件进行成形过程数值模拟时的前序工作,因此一个完整的汽车覆盖件冲压成形数值模拟软件应该包括覆盖件拉延模型设计模块,以便于将通过CAD软件输入的产品模型向适用于CAE分析的拉延模型转化.拉延工艺设计主要包括冲压方向调整、压料面和工艺补充部分的设计以及拉延筋布置等工作.本文分析了拉延件常用工艺补充部分的形状特点,在此基础上介绍了在自主开发的CAE软件系统Sheetform中,以参数化方式进行工艺补充部分的设计,并利用凹模开口线和零件边界线的位置对应关系自动求解工艺补充特征截面线和构造工艺补充组成曲面的算法,研究了曲面生成中所遇到的问题和相应的解决方案.整个设计过程操作简单,自动化程度高,简化了CAE分析中的模具型面设计工作.     

汽车覆盖件成形数值模拟与模具型面设计

以某汽车覆盖件为研究对象,利用板料分析软件Autoform对其进行了冲压方向的确定、压料面和工艺补充面设计、拉延筋设计以及拉延成形过程的数值模拟。通过仿真预测了板料成形过程中拉裂、减薄、起皱等缺陷,并根据模拟结果分析了板料与凸凹模的摩擦、工艺补充面、压边力、拉延筋等因素对缺陷产生的影响,进而调整优化了板料成形工艺参数和模具型面结构,消除了零件成形中的质量缺陷,提高了成形工艺的可靠性,为实际生产中覆盖件冲压工艺确定和模具型面设计提供了参考和依据。     

拉延筋设置对汽车覆盖件成形质量的影响

在汽车覆盖件成形过程中,由于各个部分变形情况复杂、板料流动速度不一致,易出现拉裂,起皱等现象,另外覆盖件还有很高的质量和强度要求.因此需要在凹模周围布置拉延筋来改善覆盖件的成形质量.文章以Dynaform有限元分析软件为平台,对汽车覆盖件的成形过程进行模拟,得到相应的成形极限图.在模拟过程中重点探讨了拉延筋的设置对覆盖件成形质量的影响,获得了满足零件质量要求的拉延筋设置方案.     

汽车前围板拉延成形模面及工艺优化

汽车复杂覆盖件的拉延模面决定了冲压件的成形性、表面质量和尺寸精度,合理设计工艺补充面可以有效改善板料变形的均匀性。基于CAD/CAE协同设计思路,对某新款汽车前围板零件拉延成形过程进行数值模拟,通过对模拟结果的分析,设计合理的拉延成形模面,同时进一步优化成形工艺参数。对模拟结果与实际成形产品进行板料厚度对比分析发现,优化后的模拟结果与实际成形产品的变化趋势相同,验证了模拟精度的可靠性。因此,通过冲压成形数值模拟可以有效预测板料的成形缺陷,极大地缩短产品周期,节约成本。     

数值模拟技术在汽车覆盖件拉延模具设计中的应用

介绍了板料数值模拟软件Auto form的功能、特点.以某汽车覆盖件的拉延模具为例,利用Autoform软件实现汽车覆盖件的模具设计,包括模具压料面、工艺补充面以及拉延筋设计;模拟在给定工艺条件下板料成形的全过程,预测可能出现的缺陷,并根据结果优化结构参数.与传统的模具设计相比,利用数值模拟技术提高了模具设计的质量和效率.     

覆盖件拉延模型CAD系统的实现

汽车覆盖件拉延工艺的设计是覆盖件冲压工艺设计的重要内容,对于模具设计的成败和制造调试的难易程度有着直接的影响,因此在覆盖件冲压成形数值模拟计算中,能否方便、有效地建立合理的拉延模型是影响计算结果好坏的重要因素。文章在分析拉延工艺设计一般原则的基础上,介绍了在自主开发的汽车覆盖件冲压成形数值模拟软件系统Sheetform中,对覆盖件零件模型添加压料面和工艺补充部分,从而得到拉延模型,使之适用于模拟计算的主要算法。     

基于CAD/CAE的汽车覆盖件拉延模设计

对汽车覆盖件拉延模的设计进行了研究。以汽车发动机盖外板为例,在零件数模建立的基础上,借助拉延成形仿真对成形过程中的拉裂、起皱等缺陷进行预测,得到零件的成形极限图和厚度变化图,并依此来判断其成形效果。通过改变结构参数和工艺参数优化拉延成形方案,根据最佳的成形方案进行了拉延模结构设计。最后通过试验对设计结果进行验证,试模结果与仿真分析结果一致,零件的最大变薄率为27.5%,最大变厚率为9.5%,满足成形要求。研究结果表明,基于CAD/CAE的汽车覆盖件拉延模设计方法是可行的,能够缩短产品开发周期,提高设计水平。     

基于FASTAMP的汽车覆盖件拉延模具设计

以专业板料成形模拟软件FASTSTAMP为平台,介绍了汽车覆盖件拉延模具工艺型面设计过程,对其成形过程进行数值模拟,预测成形过程中减薄、拉裂、起皱、成形不充分等缺陷并分析缺陷产生的原因,进而优化成形工艺参数和模具结构.     

辉光离子渗氮技术在汽车拉延模表面强化中的应用

汽车覆盖件拉延模具的成形表面工作条件差，易产生塑性变形和磨损失效，对其成形表面的强度、光洁度、硬度和耐磨性等都有较高的要求。该文以桑塔纳轿车覆盖件拉延模为例，介绍了辉光等离子氮化技术在汽车拉延模大型面表面强化处理方面的应用，分析了该技术应用中的特点，并通过实例说明了该表面技术可有效提高MoCr铸铁材料的表面性能。     

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。