DP600高强钢零件冲压成形有限元仿真及试验

性能稳定的高强度钢板供应,是保证汽车厂避免冲压成形开裂缺陷,提高生产稳定性的重要环节。该文以使用DP600高强钢的横梁减震器后桥零件为例,采用有限元仿真和网格试验的方法分析变形特征,以及主要力学性能参数对冲压成形的影响,提出了保证零件成形钢板的关键性能指标及控制范围。研究结果表明,横梁减震器外板零件高应变区域的变形方式为平面应变-拉延变形,稳定冲压所需的关键性能参数及控制范围为,屈强比σs/σb≤0.68,材料硬化指数n≥0.15,断裂延伸率δ≥25%。     

材料与工艺参数对侧围外板冲压成形的影响

采用有限元仿真的方法研究板料主要力学性能参数,以及表面摩擦状况对整体式侧围外板类零件冲压成形的影响,以获得整体式侧围外板类零件冲压成形材料关键性能参数的选取准则,并进行试验验证。结果表明：对整体式侧围外板类零件,应该选择材料屈强比σs/σb〈0．5,硬化指数n〉0．22,厚向异性系数r〉2．0,延伸率δ≥45％的板料。     

轿车行李箱盖内板冲压成形分析

采用网格应变分析技术,研究不同材料性能下轿车行李箱盖内板冲压成形过程中应变分布,指出了变形过程中可能存在的危险区域,以及这些区域内材料的变形方式;对比了两种不同材料性能下的成形结果,分析了材料性能对该零件成形的影响;给出了模具调整建议.     

汽车发动机罩内板冲压成形分析

采用网格应变分析技术,研究了发动机罩内板零件冲压加工的应变分布.分析了零件高应变区域材料的变形方式、冲压件壁厚减薄状况,指出了变形的危险区域,分析了材料性能参数对零件成形的影响.给出了现场冲压生产模具调整的建议.     

基于起皱分析的钛合金异形盒件缺陷控制研究

针对钛合金异形盒零件成形起皱问题开展研究，对零件热成形过程中失稳起皱的原理进行分析，结合鼓动产生前后接触压力矢量分布情况得到成形过程中材料流动趋势以及褶皱产生的原因。通过监测零件成形过程中受压侧褶皱折弯角度及零件最大应变情况，发现在合模间隙为6 mm时零件发生失稳变形。对该状态下零件型面进行光顺，设计出零件2道次成形的过渡工装型面，并对工装排布与毛料结构进行优化，最后进行试验验证，成形后的零件贴模间隙为0～0.15 mm。结果表明，改进后的工艺方法将零件变形进行分解，使材料变化均匀，过渡型面消除了成形过程中的褶皱问题，实现了零件的精确成形。     

成形纹缺陷影响因素分析及工艺优化

以侧围外板为代表的难成形零件,对零件表面成形质量要求高,成形后用油石打磨表面后存在成形纹缺陷,影响零件寿命以及涂装质量。应变分析后发现缺陷区域应变量安全裕度远大于10%,在此安全裕度下不会出现严重的减薄而导致表面粗糙。由应变云图可以看出,该区域应变状态为平面应变,平面应变状态下材料晶粒之间对变形比较敏感,晶粒间容易出现变形不协调。通过对材料生产中的热轧温度、卷取温度等工艺参数进行优化改进,改进优化后成形件的材料组织得到了细化,成形件打磨后其材料表面较致密,有效解决了材料的成形纹缺陷。     

预磷化电镀锌钢板性能指标对冲压成形的影响研究

以侧围外板零件为例，在分析复杂零件用材需求、冲压成形特征以及生产过程中零件报废率和材料性能对应性关系的基础上，深入探讨了零件高应变区域的变形特征和预磷化电镀锌钢板基本力学参数对该零件成形的影响。     

薄壁槽钢零件辊弯成形边波产生机理及影响因素

薄壁槽钢零件辊弯成形容易出现边波,影响其成形质量。通过对U型薄壁槽钢零件辊弯成形过程进行正交有限元数值模拟,分析U型薄壁槽钢零件辊弯成形后的应力应变,研究了薄壁槽钢零件辊弯成形边波产生的机理,分析了零件材料的屈服强度σ_s、辊弯成形道次n、零件翼缘高度h和材料厚度t等因素对辊弯成形边波波动量Δy的影响。研究结果表明,边波产生的机理为零件翼缘部位各点产生了纵向应力和不可恢复的纵向塑性应变,且其大小沿翼缘长度方向(纵向)及高度方向均不相等;各因素对边波波动量Δy的影响程度依次为零件翼缘高度h材料厚度t屈服强度σ_s辊弯成形道次n,随屈服强度σs和材料厚度t的增加边波的波动量Δy减小,随零件翼缘高度h的增加边波波动量Δy增大,随辊弯成形道次n增加,波动量Δy先减小后增大。这为合理设计类似薄壁零件的辊弯成形工艺提供了指导。     

轿车行李厢外板拉延成形失效分析

在材料力学性能测试和成形极限分析的基础上,采用网格应变分析技术研究行李厢外板零件冲压过程危险区域的变形方式,结合不同区域的应力特征指出材料和模具两方面的改进方向。     

圆锥形件冲压成形过程中毛坯上各变形区域行为的研究

从曲面类零件中较为典型的圆锥形件的拉深成形研究入手,分析了该类零件在冲压成形过程中板料毛坯的的变形情况。采用网格分析法,实测了板料毛坯上各区域内金属质点的3个应变值,并根据各区域的变形程度将毛坯划分为法兰、凹模圆角、悬空锥壁、凸模圆角及锥底等5个部分;着得分析了毛坯主要变形区域（悬空锥壁部分）的变形特点,归纳了圆锥形零件的变形规律;讨论了成形过程中各变形区域的相互作用、相互关系及各自的变化规律;找到了圆锥形零件冲压成形中板材毛坯上最有可能产生起皱、破坏缺陷的危险质点位置;最后分析了毛坯在成形过程中不同拉深阶段中的变形情况,为以圆锥形零件为代表的曲面类零件的深入研究奠定了基础。     

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。