基于BP神经网络的波形刃铣刀片模糊综合评判系统

针对波形刃铣刀片耦合场的非稳态特性,基于铣削温度和铣削力试验以及有限元分析,利用BP神经网络LM算法预测了铣刀片温度场和应力场;运用模糊数学理论,根据加工要求和专家分析,用VC++开发了波形刃铣刀片模糊综合评判系统。该系统可对多因素作用下的铣刀片温度场、应力场和耦合场的优劣进行评判,为铣刀片三维复杂槽型的重构提供依据。     

多场耦合下粉末成型固结设备结构设计

为了满足多场耦合下粉末成型固结技术的需求,对多场耦合下粉末成型固结设备进行总体结构设计。该设备耦合了加压、加温、放电和放磁等多个功能,结构简单紧凑,提供多种压制方式供选择,可实现真空环境下的多件连续生产,具有较高的灵活性和生产效率。对设备的关键部件机身进行了结构设计,并用有限元分析方法进行静力分析,得出在不同的工况下机身的变形受力情况,验证了机身结构强度、刚度的合理性。     

磁场环境中几何非线性导电薄板的热弹性耦合振动

基于涡电流热效应引起的温度场初边值问题和非线性热磁弹性力学的基本方程,在计及面内磁体力的前提下,研究几何非线性导电薄板在横向时变磁场及面内恒定磁场共同作用下的热弹性耦合动力响应,并对导电薄板的涡电流、磁力、温度以及挠度随外加磁场的变化情况进行定量模拟.数值结果表明,在考虑面内磁体力和几何非线性效应的情况下,当横向磁场较小时,面内磁体力的作用可以忽略,但必须考虑涡电流的热效应,而当横向磁场增加到一定值时,面内磁体力对变形场造成的影响作用比涡电流热效应的大,此时必须同时考虑面内磁体力和涡电流热效应对多场耦合行为分析所带来的影响.     

双螺杆捏合机螺杆转子多场耦合特性数值模拟

以某新型双螺杆捏合机螺杆转子为研究对象,采用间接耦合以及弱耦合方法实现转子温度场和应力场、流场和应力场的耦合特性的数值模拟。将温度场作为体载荷施加在流固耦合结果上,实现螺杆转子温度场-流场-应力场的多物理场耦合特性数值模拟,以研究不同工况下在流场温度、流体压力和不同扭矩对双螺杆转子的综合应力和综合变形的多场耦合作用机理,并对螺杆转子在各物理场单独作用及耦合作用下的应力和变形情况进行对比分析。研究结果表明:与流场对转子产生的变形与应力相比,热变形是导致转子实际变形的主要因素,螺杆转子热变形的变化趋势与其实际综合变形的变化趋势基本一致,而由温度场导致的转子热应力值较小,远小于转子受到流场以及扭矩产生的应力值。根据分析结果可以确定双螺杆捏合机中对转子强度、刚度起主要影响作用的因素,以及确定转子合理工作间隙。研究结果对转子微观形貌的主动反演设计以及工作间隙的合理选择提供理论依据。     

小方坯连铸电磁搅拌流场和温度场三维耦合数值分析

应用磁流体力学MHD(Magnetohydrodynamics)的基本原理,建立了钢水在洛仑兹力作用下流场和温度场三维耦合分析数学模型.依据错列网格法SIMPLE(Semi-implicit method for pressure linked     

功能材料的力、电、磁耦合行为的实验研究

自行研制成功力—电、力—磁耦合加载设备,实现进行多场耦合实验;研究开发出力—电耦合场和力—磁耦合场下的力学量与电磁学量的量测技术,实现测量过程自动化;从而具备了同时对铁电材料施加应力场和电场的技术,对铁磁材料同时施加应力场和磁场的技术。解决了高电压的绝缘、防电弧放电、防电击穿、电荷测量与数据采集等难题,设计一系列有效的实验装置和实验环境。实验研究了耦合场作用下压／铁电材料的本构关系,提出旨在消除内偏场的冲击极化方式;采用三点弯实验,测试了铁电材料的断裂韧度,发现极化方向对断裂韧度的显著影响。将云纹干涉技术应用于力电耦合场作用下裂尖变形场的测量。首次对预制有贯穿裂纹的铁电材料试件进行电疲劳实验,获得了电致疲劳裂纹扩展曲线,发现一些新的电疲劳损伤现象,例如不同载荷作用下裂纹的扩展模式、疲劳裂纹闭合效应、电致裂纹扩展的磨损与击穿等。实验制备并研究0-3联和1-3联铁电复合材料的介电性能、压电性能。制备PZT／MgO纳米复相铁电陶瓷,在保证其压电性能的前提下,改善铁电材料的韧度。有关铁磁材料的实验研究,量测不同力磁耦合载荷作用下纯镍、6号镍、锰锌铁氧体、Terfenol-D等几种铁磁材料的磁滞回线、磁致应变曲线,获得磁导率、磁致伸缩系数、压磁系数、磁弹性系数等。实验研究磁场对Ni52Mn24Ga24单晶与多晶体相变行为的影响。对于三种导磁率的锰锌铁氧体陶瓷,采用在磁场下的三点弯断裂实验和维氏压痕实验,发现外磁场对材料断裂韧度的影响很小。     

热、力、磁耦合作用下大挠度矩形薄板的分岔与混沌特性

针对大挠度三边简支一边自由矩形薄板,研究其在热、力、磁耦合作用下的分岔与混沌运动特性。在板壳与磁弹性力学理论的基础上,导出薄板在耦合场共同作用下的非线性控制方程,利用伽辽金原理得到薄板的非线性热磁弹性耦合振动方程。由次谐轨道Melnikov函数法,求出该动力系统Smale马蹄变换意义下出现混沌运动的阈值条件,并对该系统振动方程进行数值模拟,得到系统随机械载荷、电磁场以及温度场的参数变化的分岔图及相应的位移波形图、相平面轨迹图及庞加莱截面图。由仿真结果可知,在热、力、磁耦合作用下的大挠度矩形薄板系统的振动方程具有明显的非线性,运动特性比较复杂,呈现出非常丰富的混沌与分岔现象。通过变化机械载荷、电磁场和温度场参数,可以控制系统的振动特性。     

基于ABAQUS制动器热流多场耦合建模分析

制动器工作过程中盘片摩擦产生的热流为非轴对称的,二者之间的热流耦合及其他场的耦合作用是影响制动效能的重要因素。基于以上问题,针对盘式制动器建立热传导方程,对盘片之间的摩擦传热和热流耦合现象进行分析。根据盘式制动器的结构特点和所建立的热传导数学模型,基于ABAQUS/Explict搭建其三维瞬态温度/应力场有限元模型,分析正常制动和紧急制动等典型工况下制动盘的温度场和应力场,对多场耦合现象进行分析;分析制动盘打孔后的温度场、热应力场等分布。结果表明:车辆在正常制动和紧急制动时,多场耦合有较大区别;正常制动工况最高温升160℃,紧急制动最高温升622℃;紧急制动工况,场耦合情况严重,温度场在轴向和径向上存在较大的温度梯度,对制动效能有较大影响;打孔不适用所研究的制动器,对场分布产生不利影响,会降低制动效能。所搭建模型和分析结果为实际设计提供参考。     

多场耦合作用下动涡旋盘的变形和应力研究

利用Pro/E建立了涡旋压缩机动涡旋盘的三维实体模型,基于有限元法分别对动涡旋盘在气体力、温度场和惯性力作用下的应力和变形分布情况进行分析,并对气体力、温度场、惯性力耦合作用下动涡旋盘的变形和应力进行了数值计算。结果表明温度场引起的轴向变形较大,惯性力使涡旋齿尾部的变形增加,多场耦合作用下最大变形发生在涡旋齿头,最大应力发生在涡旋齿头的底部和驱动轴承座孔内。     

小方坯连铸电磁搅拌流场和温度场三维耦合数值分析

应用磁流体力学MHD（Magneto hydro dynamics）的基本原理,建立了钢水在洛仑兹力作用下流场和温度场三维耦合分析数学模型。依据错列网格法SIMPLE（Semi-implicit method for pressure linked equation）和有限控制容积法,开发了相应的分析软件。就小方坯电磁搅拌洛仑兹力的分布规律、搅拌范围、拉坯速度以及浇注温度对流场和温度场的影响进行分析。     

不同压制工艺对粉末冶金制品性能影响的有限元模拟

利用MSC/MARC有限元分析软件对金属粉末压制过程进行模拟分析.采用基于更新拉格朗日方法的热-力耦合分析不同工艺条件(温度、摩擦条件和压制方式等)对压坯性能的影响规律,同时对压制过程中的力学特征(压制力、脱模力、侧压力和应力分布等)进行分析.结果显示,摩擦条件是影响压坯密度大小及分布的关键因素,通过采用双向压制方法可以有效地改善单向压制压坯密度分布不均、差值较大的现象.温度的提高有利于提高粉末颗粒的塑性变形能力,但效果不明显.另外,由于温度影响润滑剂润滑性能,因此在制定压制工艺时需考虑温度对压坯性能的影响.此外温度的提高、摩擦的降低均有利于降低压制力,提高压坯密度均匀性,改善压坯应力集中现象.     

基于FEM的电磁缩径耦合场数值模拟

对管件电磁缩径的磁场力和动态变形进行了耦合场FEM数值模拟。应用ANSYS计算作用在管件上的瞬态磁场力,然后以该力为边界条件模拟工件高速变形,实现管件变形与磁场力之间的耦合。研究结果表明,作用于工件的磁场力及其径向变形分布不均匀;工件变形可以间接说明磁感应强度和磁场力的分布;工件变形较大时,全耦合模拟结果较半耦合模拟更合理,而变形较小时,二者模拟结果相近。管件变形的模拟值与测量结果吻合较好。     

Cosserat continuum theory to simulate microscopic rotation of magnetic powder in applied magnetic field

Numerical method based on the Cosserat continuum theory is proposed for simulating behavior of a magnetic powder in an applied magnetic field. The Maxwell stress is induced in the magnetic powder. During powder forming process in the magnetic field, the magnetic particles are thus rotated and transferred by both mechanical and magnetic interaction. To simulate such powder behavior, we formulate a finite element equation considering Maxwell stress based on the Cosserat continuum theory of compressible plasticity. The powder behavior with magnetic alignment during compaction in magnetic field is simulated by the proposed method and the effect of couple-stress on the powder behavior is discussed.     

钢铝复合轨/受电靴摩擦热与接触电阻热耦合的温度场有限元模拟研究

基于ANSYS有限元软件建立钢铝复合轨/受电靴在接触电阻热和摩擦热耦合作用下的温度场模型,给出了2种热量耦合的方法,计算了模型的温度场,研究了模型在不同电流、速度和位移条件下的耦合最高温度变化。结果显示:在相同位移和法向压力条件下,耦合的最高温度随电流的增大而增大,随速度的增大而减小;在电流、速度和压力相同的条件下,耦合最高温度随位移的增大成线性增大趋势。     

In situ study of electric field‐induced magnetization in multiferroic BiFeO3 nanowires

In this work, we have studied electric field‐induced magnetization effect of multiferroic BiFeO₃ (BFO) nanowires in situ using magnetic force microscopy (MFM). Changes in magnetic domain contrast have been observed in the MFM phase images under applied electric potential, which indicate local magnetoelectric (ME) coupling in the nanowires. The values of saturation and magnetization at different applied electric fields were evaluated. These results suggest that one‐dimensional multiferroic BFO nanowires are potential candidates for realizing multiferroic devices at nanoscale with unique functionalities. SCANNING 36:224–230, 2014. © 2013 Wiley Periodicals, Inc.     

轴向交变磁场对电场活化烧结工艺温度场影响的数值模拟

提出了在电场活化烧结过程中施加轴向交变磁场与脉冲电场耦合改善烧结体径向温度场以减小其温度差的方法,并对不同大小磁场的作用进行了数值模拟.结果表明:施加轴向交变磁场可使横截面上的最大温度差减少3/4.其原因是交变磁场的感应电流具有集肤效应,可以使试样外部得到更多的热量.试验结果证明了模拟的准确性.     

基于Galerkin法的车用永磁式缓速器热-磁耦合场分析

车用永磁式缓速器磁场、温度场分析是缓速器性能研究的重要内容。论文研究了永磁式缓速器中的磁场和温度场存在的弱耦合现象。温度的升高会造成转子鼓磁性材料的电导率σ升高,磁导率μ下降。磁场变化引起转子盘中的涡流损耗的变化。涡流损耗作为温度场控制方程的内热源,又影响温度场的变化。论文建立了缓速器转子盘热-磁耦合模型,并运用多层修正迭代Galerkin法和变时间步长法对模型解耦。结果表明:对模型的有限元仿真与试验结果吻合较好。在高温区,耦合值、未耦合值存在较大差异。耦合因素对磁场、温度场的影响不能忽略。     

The coupled effect of magnetic field,electric field,and electrolyte motion on the material removal amount in electrochemical machining

Electrochemical machining (ECM) has a strong advantage in dealing with difficult-to-machine materials and complex shaped parts. In order to improve machining accuracy, some researchers, based on the principle of interactions between the magnetic field and electric field, proposed the magnetic field-assisted ECM technology that is advantageous in improving surface roughness and facilitating material removal amount. Pitifully, little attention has been attached to effects of the coupled magnetic field, electric field, and electrolyte motion on the amount of materials removed. This paper aims to find out how arrangements of magnetic fields and coupled of the three energy (which were magnetic field, electric field, and electrolyte motion) will work on the amount of material removed in ECM. Here established a Navier-Stokes equation and a model of material removal amount in the anode under the electromagnetic field. Physical and mathematical models of the electrolyte’s flow characteristics and material removal amount were constructed through the COMSOL Multiphysics software, and simulations were carried out. An experiment was implemented to test models and the simulations. Simulation results indicated that different arrangements of the magnetic field had delivered different impacts on flow characteristics of the flow field and material removal amount. Experiment results revealed that the material removal amount had increased regardless of arrangements of magnetic fields and that the flow rate of the electrolyte had played a role in this connection. The study involved in this paper showed that the introduction of the magnetic field worked favorably to lift the material removal amount and that arrangements of magnetic fields also had the same effect in this regard. Also, it was found that a growing flow rate of the electrolyte had hindered the increases of the material removal amount.     

径向磁轴承磁路耦合对磁力的影响及其解耦控制策略

由于磁路在磁轴承定子磁极间的耦合,磁力的分布会发生变化,致使理论模型推导的控制电流难以提供准确的回复力。基于Boit-Savart定理建立了磁场分布模型并分析了磁路耦合的影响因素;建立了考虑磁路耦合的磁力等效模型;分析了磁路耦合对磁力误差的影响,并提出了解耦控制策略;进行了电磁场仿真,验证了解耦控制的正确性;通过磁轴承稳态悬浮实验,验证了解耦控制策略的有效性。     

Densification behavior of copper powder during the coupled multi-physics fields-activated microforming

External electric field-activated sintering techniques have been widely investigated and applied for the forming of large-sized components. These techniques are, however, rarely utilized for the manufacture of miniature and microsized components. In this paper, a novel, coupled forming, and sintering method is reported, which has been used for the fabrication of microcomponents, wherein the loose powder is loaded directly into the die, followed by simultaneous electrical forming and electric sintering (named coupled multi-physics-fields activation). In the study, the gears with the module of 0.2 and the pitch diameter of 1.6 mm were formed from copper powder. The coupled multi-fields activations were enabled using a Gleeble-1500D thermal simulation machine. Sintered samples with a relative density of 97.20 % have been fabricated at a sintering temperature of 700 °C, heating rate of 50 °C/s, forming pressure of 100 MPa, while these parameters were applied cyclically. The study showed that the axial reduction of the samples increased rapidly with the increase of temperature during the sintering, while the external pressure was maintained. Based on the experimental observations, it can be concluded that the deformation of the particles resulted in an increase in, and then subsequent disappearance of, the interface areas among the particles, which feature plays a key role in the densification of the copper powder.