一种预测金属锻造过程失稳变形的模拟方法

提出一种利用失稳变形区热力参数窗口条件和有限元模拟相结合来预测锻造失稳变形的方法,并以Ti-6.5Al-3.5Mo-1.5Zr-0.3Si 合金为例,将该钛合金的失稳变形区热力参数窗口条件集成到商业化的有限元模拟软件平台中。利用二次开发后的有限元模拟软件平台模拟了该钛合金在热压缩过程中失稳变形区的分布及其变化。模拟预测结果与实验结果吻合较好,说明所提出的失稳变形模拟与预测方法是可行和有效的。     

INFLUENCES OF EDGING ROLL SHAPE ON THE PLASTIC STRAIN DISTRIBUTION OF SLAB DURING MULTI-PASS V-H ROLLING PROCESS

Multi-pass slab vertical-horizontal （V-H） rolling process with variable edging roll shape have been simulated with explicit dynamic finite element method and updating geometric method. The distributions of plastic strain contour in slab daring rolling process with different edging roll and under different rolling stage have been obtained. The results show that there exist two thin strain assembling zones in slab when the flat edging roll is used, and there just exist one strain assembling zone in slab when the edging roll with groove is used. And compared the deformation equality between flat edging roll and edging roll with groove, the lateris better than the former, which supplies the theory prove to the slab deformation distribution during V-H rolling process and is helpful for predicting the slab texture.     

Prediction of void closure in steel slabs by finite element analysis

Closure of a spherical voids in a steel slab under plane-strain deformation was investigated using the rigidplastic finite-element method. Variations in the major and minor axes of a void from finite element analysis of a void model were related to the minimum principal strain and hydrostatic stress from finite element analysis of a non-void model. The correlation curves were obtained and a method using these curves to predict the void closure progress was proposed. The method was successfully applied to deformation processes such as simple compression, forging and rolling. Since hydrostatic stress also influenced void closure, the effective strain by itself was not sufficiently capable of predicting void closure. However, the effective strain was used to predict void closure for a specific process because it reached about 0.7 in compression or forging and about 0.78 during rolling as the void completely closed.     

限定型高压扭转变形分析

利用量纲分析研究限定型高压扭转(HPT)变形的相关因素,在此基础上用有限元分析不同侧边摩擦条件和不同径厚比和不同侧面摩擦约束大小对纯铜试样角位移场的特点,讨论理想高压扭转公式适用的范围。量纲分析揭示,试样上变形与几何位置、径厚比、施加压力、材料弹性参数以及模具侧面的摩擦状况相关。有限元分析结果表明,可用幂函数形式的角位移约束来简化侧面摩擦,当幂指数不小于8时,试样上非HPT变形区域大小趋于稳定;当径厚比不小于5时,试样中心存在一个可用纯扭转变形描述的区域,非理想HPT区域大小不超过试样厚度尺寸;当径厚比不大于2时,试样上不存在理想HPT区域。     

Deformation characteristic of semi-solid ZCuSn10 copper alloy during isothermal compression

The compression tests were carried out by Gleeble-1500 thermo-mechanical simulator with samples of semi-solid ZCuSn10 alloy prepared by strain-induced melt activation(SIMA) process. The original microstructure and the deformation temperature of semi-solid ZCuSn10 alloy are different. The strain is 0.2, and the strain rate is 1 s~(-1) for the compression test. The results show that when the semi-solid ZCuSn10 alloy was prepared by SIMA process, the liquid fraction of semi-solid microstructure increases, and the solid grain is smaller,more uniform and more inclined to be round as the rolling pre-deformation increasing. The results also indicate that the deformation resistance of ZCuSn10 alloy in semi-solid state decreases with the deformation temperature increasing or the solid fraction of original microstructure decreasing. The stress–strain curves of the isothermal compression can be divided into quasi-elastic deformation stage and plastic deformation stage, and there are three deformation zones in the samples after isothermal compression, namely the difficult deformation zone, the large deformation zone and the free deformation zone. In the three deformation zones, the main deformation mechanism is flow of liquid incorporating solid particles(FLS)mechanism, plastic deformation of solid particles(PDS)mechanism and liquid flow(LF) combining with FLS mechanism, respectively.     

Rolling consolidation of metal matrix composites

Transverse rolling of metal matrix composite precursor wires is proposed as a consolidation technique for making sheets. Rolling in the transverse direction to the fiber orientation is analytically shown to be feasible, and longitudinal rolling results in fiber breakage. Plasticity analysis is conducted using Hill's general yield criterion for an isotropic materials and the associated Levy-Miles equations modified for plane strain conditions. The slab method is used to calculate the stresses in the material, and the effects of rolling parameters on the principal stress ratio are investigated.At the microscopic level, an elastic-plastic finite element formulation and a computation procedure are presented. Individual fibers are modeled to determine the stress state around each fiber. The principal stress ratio is suggested as a parameter that determines the tendency for void formation due to debonding and fiber breakage; finite element analysis is used to determine the effects of the principal stress ratio on the fiber-matrix interfacial stresses in the micromechanics model. The analysis determines the deformed mesh, plastic zone propagation and the stresses at the interface as a function of volume fraction and principal stress ratio. Interfacial stresses are assumed to be responsible for debonding during the deformation of metal matrix composites. This assumption and the results of the analysis provide guidelines for defining, the level of the biaxial stress field in the plane transverse to the fibers during rolling that will minimize interfacial fiber-matrix stresses.     

薄板坯连铸结晶器内钢液凝固行为的研究

针对薄板坯连铸漏斗型结晶器内凝固过程,采用热弹塑性有限元法,考虑铸坯与铜板的接触状态,建立了热力耦合模型。模拟分析了铸坯经过结晶器过程中坯壳内的温度场和应力场,得到了凝固坯壳形成过程的传热和变形规律。模拟结果表明：铸坯角部温度高于宽面和窄面中心温度并出现两个平台期;两个弧线段交界区域出现应力峰值,是铸坯裂纹敏感区。该结果为漏斗型结晶器形状的设计、结晶器锥度的优化以及提高连铸坯质量提供理论依据和技术基础。     

Prediction of influence parameters on the hot rolling process using finite element method and neural network

In the present investigation, a hot rolling process of AA5083 aluminum alloy is simulated using the finite element method. The temperature distribution in the roll and the slab, the stress, strain and strain rate fields, are extracted throughout a steady-state analysis of the process. The main hypotheses adopted in the formulation are: the thermo-viscoplastic behavior of the material expressed by Perzyna constitutive equation and rolling under plane-deformation conditions. The main variables that characterize the rolling process, such as the geometry of the slab, load, rolling speed, percentage of thickness reduction, initial thickness of the slab and friction coefficient, have been expressed in a parametric form giving a good flexibility to the model. The convergence of the results has been evaluated using experimental and theoretical data available in the literature. Since the FE simulation of the process is a time-consuming procedure, an artificial neural network (ANN) has been designed based on the back propagation method. The outputs of the FE simulation of the problem are used for training the network and then, the network is employed for prediction of the behavior of the slab during the hot rolling process.     

Deep drawing of 6A16 aluminum alloy for automobile body with various blank-holder forces

Based on the ABAQUS/explicit finite element method,the deep drawing of 6A16 alloy pre-aged and then storaged at room temperature for 1 week with various blank-holder forces(10,14,18 kN) was studied.The distribution and variation of stress and strain in deformation zones were investigated to drive the forming property and process of the alloy.Besides,the simulation result was verified combined with the deep drawing experiments.The results show that the stress and strain of the deformation zone have an incremental trend with the blank-holder force increasing while the deformation degree and grain size within a certain deformation zone have an obvious increase and an enlargement,respectively.After the deep drawing,the hardness of products also increases with the enhancement of blank-holder force.The blank-holder force of 18 kN is certified as the preferential one by the analysis of microstructure and simulation results.     

Simulation of stress concentration in Mg alloys using the crystal plasticity finite element method

A crystal plasticity finite element method (CPFEM), considering both crystallographic slip and deformation twinning, was developed to simulate the spatial stress concentration in AZ31 Mg alloys during in-plane compression. A predominant twin reorientation (PTR) model was successfully implemented to capture grain reorientation due to deformation twinning in twin-dominated deformation. By using the direct mapping technique for electron backscatter diffraction (EBSD) data, CPFEM can capture the heterogeneity of stress concentration at the grain boundaries in AZ31 Mg alloys during in-plane compression. The model demonstrated that deformation twinning enhances the local stress concentration at the grain boundaries between untwinned and twinned grains.     

铅黄铜C3771截止阀成形工艺优化研究

模拟铅黄铜C3771锻压和挤压工艺截止阀成形过程,得到锻压和挤压的工艺参数对铅黄铜C3771变形区的应变分布、等效应力分布和冲压载荷的影响规律.结果显示,从载荷分布分析,挤压工艺所用设备较锻压工艺设备的寿命长;.从等效应变来看,挤压模存在应力集中现象;锻压工艺成形时全局流体速率矢量分布较为均为,而挤压工艺成形时的全局流体速率分布不均匀,法兰部位和气门嘴部位的全局流体速率要大于其余部位,气门嘴部位型腔不易充填.     

圆形工件等通道转角挤压应变分布和塑性变形区的三维有限元分析

利用三维有限元方法模拟了圆形工件的等通道转角挤压过程,分析了工件上应变分布情况,其与理论值和二维模拟的结果符合较好.通过对稳定变形阶段塑性变形区的分析,探讨了应变分布不均匀的原因,所得结果有利于理解工件变形过程和优化工艺设计.     

基于有限元法纵向内筋薄壁筒反向滚珠旋压分析

作为一种连续局部塑性成形工艺,反向滚珠旋压被应用于成形带有纵向内筋的薄壁筒形件。以刚塑性有限元法为基础,采用商业有限元软件DEFORM-3DV6.0,分析了不同变形区的应变状态。并且采用DEFORM-3DV6.0的点追踪技术,研究了金属的流动规律,为纵向内筋薄壁筒形件反向滚珠旋压成形奠定了坚实的理论基础。     

扩展组合模连续铸挤铝管材的挤压力分析(英文)

为了确定管材扩展组合模连续铸挤过程的变形力,将金属扩展组合模的模腔划分为导流区、扩展区、分流区、焊合区和定径区,分析各区金属的受力状态;用切块法建立各区应力计算公式。将金属连续铸挤型腔划分为液相区与半固态区、固态初始夹紧区和固态夹紧区,建立管材连续铸挤挤压力计算公式。在自行设计的连续铸挤机上进行铝管扩展组合模连续铸挤实验并测量其挤压力,获得的径向挤压力实验结果与理论计算结果吻合。     

平板轧制咬入阶段非稳定变形的有限元模拟

采用显式动力学弹塑性有限元方法 ,对平板轧制过程中咬入阶段的非稳定变形进行了数值模拟。轧辊采用刚性辊 ,轧件为弹塑性材料 ,其它工艺参数均采用与实验相同的实际数据。通过模拟 ,得出平板轧制咬入阶段非稳定变形的整体视图 ,并进一步分析了压下率对非稳定变形的影响     

A comparative study of slab deformation under heavy width reduction by sizing press and vertical rolling using FE analysis

A detailed comparison between the quality of slabs formed by sizing press and vertical rolling mill is presented. ABAQUS/explicit commercial finite element software with elasto-viscoplastic constitutive model for material is used to study the geometric characteristics and deformation pattern during width reduction in these processes. Finite element models developed for both sizing press and vertical rolling processes are validated by comparing their results with experimental data available in literature. Parametric studies are performed using validated finite element models for sizing press mill to determine the effect of input process parameters such as initial slab width and thickness, width reduction and transfer pitch on the process outputs such as dogbone formation, head and end fishtail profiles, width necking at the leading end of the slab and slab edge quality. Similarly, developed finite element models for vertical rolling are used to investigate the effects of different input parameters on the slab deformation after passing through a vertical rolling stand with the aim of comparing the two width reduction processes. According to the results, benefits and drawbacks of each width reduction method are discussed. The enhancing effect of subsequent horizontal rolling after sizing press and vertical rolling processes on the final slab thickness is also presented.     

回流焊冷却过程中PBGA焊点力学行为分析

以热弹塑性理论为基础,建立球栅阵列PBGA焊点在回流焊工艺中焊接应力的有限元模型,利用ANSYS的热结构耦合功能,采用生死单元法对Sn-Ag-Cu焊点回流焊的冷却过程进行数值模拟分析.焊点冷却结晶后的初始阶段,等效应力随温度的降低快速增加,当焊点的温度逐渐降低至室温时,等效应力为最大.结果表明,在回流焊接工艺中,PBGA焊点的裂纹极可能发生在焊料冷却结晶后的初始阶段,在焊点高应力集中区首先开裂,并在应力的作用下沿界面逐渐扩展.对焊料凝固初期冷却速率的控制是减少焊接裂纹产生的有效方法.     

激光冲击悬臂薄板变形的理论分析和实验研究

目的激光喷丸技术是一种利用激光诱导等离子体冲击波产生的力学效应来改善材料的机械性能的表面强化技术,但是在激光喷丸过程中,由于高压冲击波的作用会使薄壁件发生宏观变形,造成零件失效,为了控制激光冲击板料宏观变形过程,因此有必要对激光冲击下板料的力学变形特性进行研究。方法通过对激光冲击载荷作用下悬臂板变形过程的理论分析,建立了板料在激光冲击下的受力变形模型,对激光作用下板料的变形量公式进行了理论推导计算,研究了板料变形量与板料厚度、激光能量等之间的相互关系,并通过单点冲击与多点搭接冲击实验和有限元分析相结合的方式验证了理论公式的准确性。结果依据所建立的板料变形理论计算得到的理论值、实验值和有限元分析结果都较为接近,其中板料变形量对厚度的变化十分敏感,在设定条件下,当板材厚度大于3 mm时,板材变形很小,几乎不产生明显的变形。结论板料变形量随着激光能量和光斑数量的增大而增大,板材的厚度对变形量的影响很大,是设计激光喷丸参数时必须考虑的要素。     

Inconel718合金楔横轧成形热力耦合模拟

应用三维刚塑性有限元Deform-3D软件对Inconel718合金的楔横轧成形进行了热力耦合数值模拟,获得了轧制过程中轧件心部温度场、应力-应变场分布规律。模拟结果表明,轧件心部在靠近起楔点位置处温度、变形速率均出现整体最大值,并且应力状态也最为复杂,因此该处最容易出现心部缺陷。     

楔横轧变形过程中轧件内部金属流动的规律

应用DEFORM-3D有限元数值模拟软件,以楔横轧理论为基础,通过对楔横轧变形过程进行三维数值模拟研究,得到了反映轧件内部变形规律的速度场和位移场,以及轧件内部应力应变状态,并研究了不同变形量下轧件内部各主应力应变状态及主应力方向的特征及变化规律,深入地分析了生产中轧件端部产生凹心和变形区前沿的局部隆起现象。