基于简化热源的金刚石磨粒高频感应连续钎焊温度场仿真研究

针对高频感应连续钎焊温度场有限元仿真多场耦合计算复杂、效率低的问题,提出一种基于高斯分布的高频感应钎焊简化热源模型代替复杂的耦合计算,该模型的参数与感应器结构尺寸以及加热率密切相关。通过与传统电磁场—温度场耦合模型以及试验结果进行对比发现：相对于电磁场—温度场耦合模型,简化热源模型的网格数量和运算时间分别减少26.4%和44.6%,两者的计算结果误差最大为8.02%,而电磁场—温度场耦合模型获得的温度分布和加热曲线更接近试验测试结果;基于简化热源模型的高频感应连续钎焊温度场仿真结果与试验值之间的误差为10.1%,表明该模型能较好地预测移动感应加热的温度;移动感应钎焊仿真结果显示,扫描速度对工件残余应力的影响比较显著,而钎焊温度对工件残余应力的影响不明显。     

基于有限元的激光定点钎焊温度场研究

利用ANSYS软件对激光定点钎焊过程温度场进行了有限元模拟,在分析过程中采用三维单元,并考虑了材料热物性的非线性特征,建立了有限元模型,得出了钎焊过程中,不同工艺参数下试样表面的温度场分布图,并进行了温度测量和实际钎焊实验。结果表明:有限元分析温度曲线与实测温度曲线比较吻合,钎焊后金刚石与基体实现高强度连接。     

动态束源和电磁参数下高压电子枪聚焦特性

以国产ZD-VEBW系列高压电子枪为研究对象,通过理论分析电子枪轴上电位与束腰和束斑直径之间的映射关系以及带电粒子经过聚焦线圈时的运动轨迹,借助于CST仿真平台,构建了电子枪仿真模型。仿真得到了电子束束斑直径在不同静电聚焦结构参数下的变化规律,依据此规律设计了不同孔径的偏压杯、阳极,构建了电子束焊接试验平台;动态调整阴阳极距离和束源参数,进行了电子束焊接的单参数以及正交试验的研究。结果表明：阴阳极距离的增加会导致束斑直径增加,偏压杯孔径的增加会导致束斑直径的减小,阳极孔径对束斑直径的影响存在最优参数,聚焦电流的增加会导致束斑直径的减小;阴阳极距离取28.40 mm、偏压杯孔径取6.00 mm、阳极孔径取10.00 mm时,能够显著提高试验型号设备同功率下电子束焊缝的深宽比,有效提高国产化ZD-VEBW系列高压电子枪的焊接性能,验证了理论和仿真分析的正确性。     

毛细管板接头真空电子束钎焊工艺

应用自制柔性化电子束钎焊系统对毛细管板接头的钎焊工艺进行了研究，探讨了钎焊工艺参数对钎料扩散深度以及钎脚高度的影响。结果表明：随着电子束输入功率或功率密度的加大，钎料向毛细管壁的扩散深度逐渐增大，钎脚高度的增长趋势显著。在一定范围内，钎料扩散深度及钎脚高度随钎料量及装配间隙的增加而增大。工件表面状态对钎脚高度的影响规律是：铰制过的试板，最有利于钎料铺展，钎脚高度最高，酸洗的试板次之，未经任何处理的试板钎脚高度最低。电子束钎焊的优化工艺参数为：加速电压60kV，束流6．5nA，加热时间37s，钎料质量25mg，聚焦电流654mA，装配间隙0．027mm。     

基亏ANSYS的某摇臂组件电子束焊有限元模拟

利用ANSYS有限元分析软件以及APDL的二次开发,编写了不锈钢材料0Cr15Ni5Cu2Ti的电子束焊的模拟程序。建立了圆周焊缝电子柬焊接的有限元模型,用数值模拟的方法从理论上分析焊接过程、焊缝应力分布和收缩变形。通过研究焊接过程中焊接时序、温度控制等关键问题,摸索出最佳电子束焊接工艺参数。试验表明,该工艺方法获得了较好的焊缝质量。有限元分析方法为焊接工艺参数的选择及优化提供了理论指导和参考,缩短了工艺试验周期,节约了费用。     

Al2O3sf/LY12棒材半固态挤压工艺温度场的有限元模拟与分析

基于瞬态热传导问题有限元法的基本原理，建立了半固态挤压成形过程中瞬态轴对称温度场的有限元模型。结合工艺试验采用的数据，利用有限元软件ANSYS对挤压成形复合材料棒材连续过程的温度场进行了数值模拟，得出了反映该过程温度场分布和变化情况的云图。结合试验研究和模拟结果对其工艺规律进行了深入分析，为进一步设计优化工艺参数提供了理论依据。     

金刚石孔钻连续炉钎焊工艺研究

通过在连续炉钎焊炉中对金刚石进行钎焊试验,并用所制得的金刚石孔钻进行钻削试验,得到了批量生产金刚石孔钻的可行钎焊工艺。利用扫描电镜比较了金刚石磨粒分别在真空钎焊和网带炉钎焊后的不同形貌,建立了孔钻的有限元模型,并模拟计算出孔钻在钎焊炉中的热循环曲线。对比热电偶实测结果,验证了有限元模型的准确性,对比分析了真空钎焊工艺和连续网带炉钎焊工艺的异同及其对孔钻使用寿命的影响。     

激光钎焊的温度场有限元分析

综合考虑了材料的非线性热物性特征以及焊件表面的热对流和热传导的影响后,利用ANSYS10.0软件对激光钎焊CBN在不同激光参数下的温度场进行了有限元分析,得到了激光扫描速度对温度场的影响规律,对钎焊工艺参数的选择具有指导意义.     

单线横涡式电子束聚焦线圈聚点束斑试验研究

为了寻找电子束熔粉设备的单线横涡式线圈在不同高度上电子束聚焦电流和束斑直径的标定,结合观察法和铜膜截束法获得了聚焦电流与聚焦距离关系。使用动态偏转扫描的方法在不同的聚焦距离处使用0.2 mm厚的紫铜带截采电子束,最后拟合分析了获得的不同距离下的聚焦电流。结果发现,肉眼观察到的聚焦状态下的束斑并非最佳的聚焦状态;拟合发现随着聚焦距离的变小聚焦电流以幂函数的形式增长。对比不同聚焦距离下的最小束斑大小发现,随着聚焦距离的变小聚焦电流下的束斑直径也变小,但是束斑圆度变差,为本文提出的方法对选区熔粉成形工作距离的选择提供了指导性的依据。     

四毛细管-板结构件扫描电子束钎焊

开发了一个基于虚拟仪器的扫描电子束钎焊系统,采用四叶形扫描轨迹对四毛细管-板结构件进行钎焊,升温速度采用PID控制方法。结果表明:扫描电子束钎焊中最高温度为1 050℃时,钎焊接头质量满足结构技术规范,此情况下钎焊接头平均升温速度为25℃/s,高温停留时间为10 s,温度控制精度为±1℃,避免了薄壁毛细管出现溶蚀、熔穿和堵塞等缺陷。     

A numerical study on parameter control for remelted coating processes

A parametric finite element analysis was carried out to investigate the relation between processing parameters in remelted coating processes (e.g. remelting power, beam diameter, and scanning speed) and thermal behavior of the coating/substrate system such as dilution, melt pool, and heat affected zone. In the simulation, nickel-based alloys and alumina are studied as coatings deposited on AISI 1040 carbon steel substrate. A wide range of processing parameters are investigated. Scanning speed ranges from 5 to 100mm/s. Machining beam radius is taken from 0.5 to 3mm. It is found that the dilution is very sensitive to the re-melting power, scanning speed and machining beam radius. The role of the preheating temperature of the coating/substrate system is also considered. Significant reductions in remelting power of around 20%, 30% and 40% can be seen when the coating/substrate system is preheated at 250, 500 and 750°C, respectively. Numerical results provide useful suggestions for a re-melting process in practice.     

TiC颗粒增强镍基合金激光熔覆工艺仿真

通过有限元分析方法对不同激光功率、扫描速率以及光斑直径下TiC/Inconel 718复合材料制造过程中的热-力学特征进行了研究。通过线性组分公式确定复合材料的热物理性能参数,选用半球高斯热源模拟激光温度载荷,利用生死单元技术实现金属粉末增材过程。采用间接法进行激光熔覆热-力耦合分析,基于温度分析结果转换单元类型进行热应力计算。研究表明个工艺参数与温度、温度变化率及残余应力的变化存在一定的规律,且激光加工功率在225～250 W之间、扫描速度在1.0～1.5 mm/s之间、光斑半径在2.5～3.0 mm之间达存在最佳加工参数,可以达到较好的熔覆效果。     

扫描电子束铝合金表面处理应力场仿真与试验验证

研究扫描电子束铝合金表面处理应力场的分布规律,对了解残余应力的形成机理具有十分重要的理论及实际意义。在热弹塑性理论的基础上建立电子束表面处理应力场的有限元模型,分析高温热力学参数对电子束表面处理应力场的影响;通过仿真与试验验证相结合的方法确定材料的高温热力学参数,得到铝合金电子束表面扫描后的应力分布规律。随着弹性模量和切变模量的增加,ADC12铝合金材料表面的变形量和最大应力均成非线性增加。经电子束表面处理后试样表面扫描带附近为拉应力,而在其他位置为压应力;最大拉应力出现在扫描带的内侧边缘处,外侧边缘次之,而扫描带中间的拉应力最小;最大表面应力为127.6 MPa,变形量为1.8 mm。     

Design and optimization of coil structure based on the uniformity of core temperature field

Coil structure size parameters during electromagnetic induction heating affect the temperature field and heating rate of a carbon fiber-reinforced polymer (CFRP) shell. In this study, a finite element analysis model is established on the basis of a single-screw coil structure, and the influence of coil diameter, length, turns, and position relationship on the temperature field distribution and heating rate of the CFRP shell is studied. According to image entropy theory, the influence of coil structure size parameters on the uniformity of a temperature field distribution is analyzed. Furthermore, the accuracy of the coil structure size parameters with respect to temperature field variation is verified with a CFRP induction heating experiment. This study provides theoretical support and a verification method for the selection, design, and optimization of the coil structure size parameters of CFRP shells during induction heating.

     

Quality control on crimping of large diameter welding pipe

Crimping is used in production of large diameter submerged-arc welding pipes. Many researches are focused on crimping in certain manufacturing mode of welding pipe. The application scopes of research achievements become limited due to lack of uniformity in theoretical analysis. In order to propose a crimping prediction method in order to control forming quality, the theory model of crimping based on elastic-plastic mechanics is established. The main technical parameters are determined by theoretical analysis, including length of crimping, base radius of punch, terminal angle of punch, base radius of die, terminal angle of die and horizontal distance between punch and die. In addition, a method used to evaluate the forming quality is presented, which investigates the bending angle after springback, forming force, straight edge length and equivalent radius of curvature. In order to investigate the effects of technical parameters on forming quality, a two-dimensional finite element model is established by finite element software ABAQUS. The finite element model is verified in that its shapes error is less than 5% by comparable experiments, which shows that their geometric precision meets demand. The crimping characteristics is obtained, such as the distribution of stress and strain and the changes of forming force, and the relation curves of technical parameters on forming quality are given by simulation analysis. The sensitivity analysis indicates that the effects of length of crimping, technical parameters of punch on forming quality are significant. In particular, the data from simulation analysis are regressed by response surface method (RSM) to establish prediction model. The feasible technical parameters are obtained from the prediction model. This method presented provides a new thought used to design technical parameters of crimping forming and makes a basis for improving crimping forming quality.     

扫描电子束表面改性过程温度场的有限元分析

根据热传导理论和扫描电子束焊机的实际工作状态,模拟了扫描电子束表面改性过程的温度分布。采用六面体划分网格和四面体划分网格两种模式,来模拟改性过程的温度变化,并比较了两种模式下的温度分布。结果表明:六面体划分网格和四面体划分网格两种模式下的温度分布基本相似,而采用六面体划分网格的模型的计算效率较高。     

管内可控铰接柔性结构双层接触非线性力学分析

管内可控万向铰接柔性细长结构是超短半径侧钻水平井的特有结构。考虑可控万向铰结构中的机构问题、结构不连续和开槽不完整结构的三体两层接触问题，将空间梁单元、万向铰单元、刚性梁单元和梁梁接触单元相结合，建立了管内可控万向铰接柔性结构双重接触非线性有限元模型及数值计算方法。与有解析解的算例进行比对，计算结果吻合较好。通过对超短半径水平井造斜钻进时的柔性钻具进行力学分析，得到了柔性钻具受力变形状态、载荷传递规律及其与井壁之间的接触力分布规律。     

悬臂梁双压电晶片振子发电性能研究

以双压电晶片振子为研究对象,对悬臂梁式双压电晶片振子在正压电效应下电压输出特性进行了有限元分析与试验研究,给出了压电晶片在悬臂梁上的最佳粘贴位置,并且利用有限元分析软件建立了悬臂梁双压电晶片振子的有限元模型,进行了结构尺寸参数对悬臂梁双压电晶片振子输出电压影响规律的仿真分析;利用压电陶瓷发电能力测试系统进行了试验测试,通过仿真和试验结果对比分析,得出了结构尺寸参数对悬臂梁双压电晶片振子发电的输出电压影响规律。     

Process simulation and optimization of laser tube bending

A 3D thermomechanical finite element analysis model for laser tube bending is developed based on the software MSC/Marc. The processes of single- and multi-scan are analyzed numerically. The gradient and development of the temperature between the laser scanning side and the nonscanning side leads to the changing complexity of the stress and strain. Consequently, the length of the laser scanning side becomes shorter than that of nonscanning side after cooling. The length difference between both sides makes the tube produce the bending angle. The relationship between the number of scans and the bending angle is about in direct ratio. The bending angle induced by the first irradiated time is largest. Meanwhile, the finite element simulation is integrated with the genetic algorithm. Aiming at different process demands, corresponding objective functions are established. Laser power, beam diameter, scanning velocity, and scanning wrap angle are regarded as design variables. Process optimizations of maximum angle bending and fixed angle bending after single laser scan are realized. Groups of optimized process parameters can be obtained according to different optimization objectives. The bending angle can approach to the maximum when the laser power, spot diameter, scanning velocity, and scanning wrap angle are 381.24 W, 3.37 mm, 16.34 mm/s, and 123.1°, respectively. When the laser power, spot diameter and scanning velocity are 426.12 W, 4.9 mm, 14.31 mm/s respectively, a fixed angle bending can be achieved.     

电触头电阻钎焊关键工艺优化研究

利用电触头电阻钎焊有限元分析模型,分别对下电极与铜基体的接触方式及不同焊接电流下铜基体,在容易产生氢脆和软化的高温区域的停留时间进行优化对比,得到中心区域温度高于四周的温度场分布,以利于液态钎料填缝时焊渣及气体的排除,从而提高接头质量,通过优化加热方式降低铜基体所受影响,最终得到更加合理的电触头电阻钎焊工艺。