ZK60镁合金高压扭转模拟及实验研究

为了研究高压扭转工艺对ZK60镁合金组织及性能的影响,采用有限元法对ZK60镁合金试样高压扭转成形过程进行数值模拟,分析成形过程中等效应力、应变分布及变化趋势。通过压扭设备和专用模具对镁合金试样进行高压扭转实验,采用金相显微镜观察试样的显微组织,利用维氏硬度计测量试样的显微硬度。结果表明:高压扭转能有效细化晶粒,改善材料组织结构;在一定的压力下,随着压扭圈数增加,晶粒得到细化,整体显微硬度有较大的提高;高压扭转后试样的显微硬度沿试样径向呈V型分布,与有限元模拟中试样径向的等效应变分布趋势一致。试样不同区域的等效应力、应变和显微硬度差异较大,边缘处的等效应力、应变最大,显微维氏硬度值最高。     

搅拌摩擦焊接过程的有限元模拟

对摩擦搅拌焊接工艺进行数值仿真，建立了搅拌摩擦焊接的二维数值计算模型，通过数值手段进行焊接参数研究。并研究了焊接工艺过程中焊件材料的流动情况以及在焊接过程中材料的应力和应变情况，且与已有结果进行比较。证实了所建立模型的正确性与可靠性。     

Finite element analysis of the effect of micro-pore defect on linear friction welding of medium carbon steel

Micro-pore is a very common material defect. In the present paper, the temperature fields of medium carbon steel joints with and without micro-pore defect during linear friction welding （LFW） were investigated by using finite element method. The effect of micro-pore defect on the axial shortening of joints during LFW was examined. The x- and y-direction displacements of micro-pore during the LFW process were also studied. In addition, the shape of micro-pore after LFW was observed. The heat conducted from the weld inteace to the specimen interior. The fluctuation range of the temperature curves for the joint with micro-pore is larger than that without micro-pore. Position of micro-pore changes with the change of the friction time. The circular shape of micro-pore becomes oval after welding.     

冷轧平整过程轧制压力分布非线性有限元研究

利用非线性弹塑性有限元法,建立了冷轧平整过程仿真模型。运用该模型对平整轧制多组工况进行模拟,得到了薄带平整时轧制压力分布规律,与经典板带轧制理论中轧制压力具有单一峰值-摩擦峰不同,随着延伸率的改变,轧制压力分布呈现单峰、双峰等多峰分布。分析了张力、摩擦系数的变化对轧制压力分布的影响,模拟结果与实验数据基本一致。基于MSC.Marc软件平台,利用VB6.0开发了平整轧制过程专用有限元仿真软件,实现了冷轧平整过程的快速建模和仿真,结果后处理。     

定宽机定宽过程轧制力有限元分析

为了研究板坯定宽过程中不同变形区内轧制力的变化情况，利用有限元的方法建立了板坯定宽有限元模型，系统地模拟了板坯定宽的全过程，得到轧制力随时间变化的规律，为制定板坯的侧压规程提供了理论依据。     

钢轨端部压力矫直的有限元分析

平直度是衡量钢轨质量的重要指标之一,它直接影响列车的运行速度、安全性及舒适性。本文应用ANSYS软件针对钢轨端部弯曲的压力矫直进行了有限元分析,建立了其载荷-挠度模型,使用该模型可进行矫直行程和矫直载荷的计算。实例计算表明,有限元计算结果真实可靠,与实际吻合,对于现场生产和相应自动矫直设备的开发具有实际指导意义。     

Analysis of stress states in compression stage of high pressure torsion using slab analysis method and finite element method

High pressure torsion (HPT) is useful for achieving substantial grain refinement to ultrafine grained/nanocrystalline states in bulk metallic solids. Most publications that analyzed the HPT process used experimental and numerical simulation approaches, whereas theoretical stress analyses for the HPT process are rare. Because of the key role of compression stage for the deformation of HPT, this paper aims to conduct a theoretical analysis and to establish a practical formula for stress and forming parameters of HPT process using the slab analysis method. Three equations were obtained via equations derivation to describe the normal stress states corresponding to the three zones of plastic deformation for HPT process as stick zone, drag zone and slip zone. As to the compression stage of HPT, the stress distribution results using the finite element method agree well with those using the slab analysis method. There are drag and stick zones on the contact surface of the HPT sample, as verified by the finite element method (FEM) and slab analysis method.     

航空铝合金板材搅拌摩擦连接有限元分析

根据搅拌摩擦连接特点,充分考虑搅拌摩擦连接过程中搅拌针各部位与连接板材之间的摩擦生热及在连接过程中连接板材摩擦系数随温度变化规律,建立了适合搅拌摩擦连接自身特点的动态热元模型,并利用此模型进行了航空铝合金板材搅拌摩擦连接过程的有限元分析模拟.通过模拟结果和试验结果对比验证了所建立的动态热源模型和有限元分析过程是合理的.模拟结果显示搅拌摩擦连接残余拉应力主要集中在连接区,且在连接区中间位置出现最大残余拉应力区,连接区两端及其它部位出现残余压应力.     

张力卷取过程卷筒压力的有限元分析

用有限元方法对张力卷取过程进行了数值模拟 ,分析了卷取过程中带卷内的压力和应力分布情况 ,并对影响卷筒压力的几个主要因素 (张力、摩擦力、带卷外径 )进行了分析 ,得出了卷筒压力和张力、摩擦力、带卷直径之间的关系。根据计算结果 ,得出一适于工程计算的卷筒压力计算公式 ,对实际生产具有一定的参考价值     

组合凹模中内压力作用位置的有限元分析

针对组合凹模早期断裂失效现象,应用有限元法对结构受整体内压状况进行分析,分析结果表明凹模应力较大,后将整体内压改为局部内压,同时改变作用位置,改进后凹模所受最大应力降低40．5％,提高了模具使用寿命。     

高强钢辊弯回弹的有限元分析

随着高强钢越来越多地应用于冷弯型钢,辊弯加工中回弹也就成了辊型设计的难点之一。文章建立了U形型钢辊弯成形回弹的有限元模拟模型,并验证了该模拟建模是可靠的。同时基于该模拟建模方法,探讨了各材料参数及工艺参数对高强钢(屈服强度300MPa~600MPa)辊弯加工产生回弹的影响规律。研究表明,在材料参数中随着屈服强度和强化系数的增加,产生的回弹明显增加;而随着强化指数和厚向异性系数的增加,产生回弹变化不明显;在工艺参数中随着弯曲角增量的增加,产生的回弹减小;随着机架间距增加,产生的回弹增加。     

界面润滑条件对薄壁零件黏性介质压力缩径影响的有限元分析(英文)

利用有限元软件ANSYS/LS-DYNA对薄壁零件黏性介质外压缩径过程中模具与筒坯之间摩擦因数对变形的影响进行有限元分析模拟。结果表明:在缩径过程中筒坯料的变形速度方向与作用在表面的黏性介质的运动方向始终保持一致。模具与筒坯的摩擦因数的临界值是0.12,当小于0.12时,摩擦因数对缩径成形过程的影响较小;当大于0.12时,随着摩擦因数的增大,其对缩径成形过程的影响不断加剧。改善模具与筒坯之间的界面润滑条件有助于缩径成形极限的提高。     

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。     

压力缸体封闭部强度的有限元分析

压力容器封闭部分的结构模式很多，本文仅对采用螺纹连结封闭的结构式用有限元方法进行理论分析并加以验证，进而为压力缸体的设计和使用提供依据。     

Finite element modeling of friction stir welding—thermal and thermomechanical analysis

Friction stir welding (FSW) is a relatively new welding process that may have significant advantages compared to the fusion processes as follow: joining of conventionally non-fusion weldable alloys, reduced distortion and improved mechanical properties of weldable alloys joints due to the pure solid-state joining of metals. In this paper, a three-dimensional model based on finite element analysis is used to study the thermal history and thermomechanical process in the butt-welding of aluminum alloy 6061-T6. The model incorporates the mechanical reaction of the tool and thermomechanical process of the welded material. The heat source incorporated in the model involves the friction between the material and the probe and the shoulder. In order to provide a quantitative framework for understanding the dynamics of the FSW thermomechanical process, the thermal history and the evolution of longitudinal, lateral, and through-thickness stress in the friction stirred weld are simulated numerically. The X-ray diffraction (XRD) technique is used to measure the residual stress of the welded plate, and the measured results are used to validate the efficiency of the proposed model. The relationship between the calculated residual stresses of the weld and the process parameters such as tool traverse speed is presented. It is anticipated that the model can be extended to optimize the FSW process in order to minimize the residual stress of the weld.     

Finite element simulation of material flow in friction stir welding

Abstract

A brief summary of recent finite element simulation results for the friction stir welding process is presented. The focus of the present study is on the characterisation of material flow around the rotating tool pin. Material flow patterns predicted by finite element simulations are found to compare favourably with experimental observations. The simulation results also reveal that material particles tend to pass and move behind the rotating pin from the trailing side, rather than both sides, of the pin. Possible variations in the material flow pattern due to variations in process parameters are discussed.     

变形路径对ECAP变形影响的有限元分析

通过对不同变形路径等径弯曲通道(Equal Channel Angular Pressing,ECAP)变形过程的数值模拟,获得了4种路径8道次ECAP变形的等效应变分布图,分析了挤压试样变形不均匀现象及其形成原因。结果表明,试样尾部与冲头的摩擦、头部未发生明显剪切变形是这两个部位变形程度低的主要原因,造成了ECAP变形的不均匀现象,而这两个部位的不同转移方式,又形成了各种挤压路径的ECAP变形差异。试样中间截面上平均等效应变排序为CBCABA,分别为10.416、10.358、8.669和8.530;试样中间截面等效应变不均匀程度的系数排序为CBCABA,分别为0.090、0.112、0.154和0.467。若追求细化效果应选择路径BC和路径C;如果追求试样材料整体均匀性,可以采用路径A。