残余应力重分布引起的结构件铣削变形研究

航空铝合金结构件毛坯在成形过程中产生很大的残余应力,使得其在后续机械加工过程中极易发生翘曲变形,这已经成为国防武器快速开发和高效加工的瓶颈.采用有限元数值模拟技术,建立了航空铝合金板材残余应力释放引起加工变形的力学模型,分析了在7050T7451铝合金板材材料去除过程中残余应力释放引起的加工变形规律,并针对7050T7451隔框零件进行铣削加工变形实验研究,并与有限元模拟结果进行比较,验证了数值模拟结果具有较高的精确度.     

残余应力引起的铣削变形有限元分析

应用弹性力学理论推导出了二维连续铣削过程中工件内应力再分布及其引起变形的计算递推公式.解决了有限元建模、初始应力加载、变形评估等仿真关键技术,建立了残余应力引起铣削变形的二维有限元仿真模型.最后对实例进行了仿真计算,分析了残余应力引起的加工变形规律,并用解析法对仿真结果的进行了验证.     

残余应力作用下的航空整体结构件加工变形仿真

铝合金预拉伸板在成型过程中会产生较大的残余应力,在切削过程中毛坯的初始残余应力的释放对整体结构件的宏观变形有重要的影响。在弹塑性力学的基础上,综合运用Hypermesh和ABAQUS建立残余应力单因素作用下的三维铣削仿真加工变形场的有限元模型,利用生死单元技术模拟了材料的去除,分析了铝合金板材材料去除过程中残余应力释放引起的加工变形规律。并且运用Hypermesh提高了有限元前处理的速度,解决了复杂模型的残余应力加载困难与单元去除困难的问题。     

铝合金薄壁件侧壁加工变形有限元分析

在分析现有文献有关铣削加工力学模型的基础上,利用有限元分析软件ANSYS10.0,针对铝合金薄壁板进行铣削力求值及变形分析.对薄壁件加工变形有限元分析过程进行关键技术讨论,为实际切削做出理论性的探索.     

Comprehensive investigation on the residual stress of large screws by whirlwind milling

This study investigated the influence of cutting parameters on the residual stress obtained in whirlwind milling of AISI 52100 steel. Single-factor and Box-Behnken experiments were separately carried out. A prediction model of residual stress was developed on the basis of response surface methodology using experimental data. Results indicated that the cutting depth was the dominant factor, and the interaction between cutting speed and tool number was significant. The developed model could be effectively used to predict surface residual stress within high confidence. The optimum value and cutting condition were validated by confirmation experiments.     

多齿圆周铣削残留面积高度研究

提出了一种非简化的多齿圆周铣削几何运动模型,该模型考虑进给速度对刀齿运动轨迹的影响,发现在多齿圆周铣削中存在残留面积的现象,并推导出计算残留面积高度的公式,公式表明多齿圆周铣削的残留面积高度与刀具齿数、每齿进给量和刀具半径有关;然后以残留面积高度公式为基础,利用Visual C++(MFC)为平台开发出计算和辅助分析残留面积高度的系统;最后采用Matlab仿真软件验证非简化模型的合理性和在多齿圆周铣削中存在残留面积.     

薄壁铝合金结构焊接应力变形数值模拟

实际结构焊接过程的三维数值模拟因为计算量大而往往难以进行。为了采用三维热弹塑性有限元方法对薄 壁铝合金结构的焊接过程进行数值模拟,提出了粘贴单元和混和单元两种网格划分技术相结合的单元划分方案进 行有限元建模,通过薄板对接模型试验验证了此方案的可行性,并研究了不同建模方案对计算效率的影响。将这 种单元划分方案应用到实际薄壁筒体结构焊接过程的数值模拟中,对焊接过程产生的残余应力和变形进行了成功 地预测。结果表明:对于薄壁构件,采用粘贴单元和混合单元相结合的单元划分方案可以在保证一定精度的前提 下,可大大减少有限元网格划分工作量,同时可降低计算规模,提高计算效率。     

残余应力对航空整体结构件加工变形的影响分析

基于理论计算和有限元模拟,研究了毛坯的初始残余应力对大型整体结构件数控加工变形的影响,对单向 应力作用的矩形截面梁在剥层过程中的变形挠度值进行了求解。结果表明,理论解与有限元计算值是一致的。面 向工程应用,采用ABAQUS有限元软件模拟了残余应力对隔框类整体结构件加工变形的影响,并进行了试验验证。 有限元仿真结果与试验数值非常吻合。最后,根据工件加工变形的有限元模拟结果,提出了提高整体结构件制造 精度的工艺措施。     

Design of a passive damper with tunable stiffness and its application in thin-walled part milling

The optimal parameters of a passive damper (i.e., frequency ratio and damping ratio) for the machining vibration attenuation of thin-walled part are quite affected by the material removal process, and the damper becomes ineffective easily due to its narrow vibration band. A design of passive damper with tunable stiffness is proposed for being adaptive to the varying machining process, and the frequency tuning is carried out by orienting the mass block inside the damper. Modal tests are performed to verify the amplitude reduction of the target mode of the thin-walled part. It shows that the optimal vibration suppression is reached when the orientation is 20° due to a smaller frequency difference between the damper and target mode, and the amplitude of the damped frequency response function is reduced to 1.3 %. Finally, machining tests are carried out, and the machining vibration and surface quality validate the large increase of machining stability. The experimental critical depth of cut under optimal tuning is increased by 1.8-folds compared with the most ineffective tuning, and the machined surface roughness is reduced by more than 80 %.     

铝合金航空薄壁框铣削变形预测研究

铝合金航空薄壁框刚性差,铣削加工过程中极易产生加工变形,影响工件加工精度和生产成本。本文利用有限元方法,模拟分析了铣削力对航空薄壁框类零件加工变形的影响,从控制航空薄壁框铣削加工变形的角度出发,分析了不同框体尺寸航空薄壁框的铣削应力与加工变形情况,得到了加工变形规律。本研究可为预测和控制航空薄壁框类零件的加工变形提供方法和依据,对航空薄壁框类零件的结构设计、缩短研制周期和进一步提高生产率等都具有重要意义。     

薄壁结构件铣削加工动态特性研究

分析了国内外有关薄壁件铣削加工力学模型、动态特性及加工变形的研究现状;在已有文献基础上建立了侧壁铣削加工动力学分析有限元模型,并通过试验对模型进行了验证;以建立的模型为基础,进行了大量有限元模拟分析,并对结果进行了讨论.结果表明,在一定范围内提高转速有利于减小薄壁件加工变形,提高加工精度.     

铣削用量对铝合金已加工表面残余应力的影响

基于单因素试验法,在有限元分析软件DEFORM-3D中模拟了硬质合金刀具铣削7075-T6高强度铝合金的加工过程,获得了不同的铣削用量对已加工表面残余应力的影响规律。结果表明,随着主轴转速、每齿进给量和切削深度的增加,工件表面的残余应力有不同程度地增大;而切削宽度的变化对表面残余应力影响不太显著。研究结果为分析7075铝合金零件后续的加工变形和表面质量奠定了扎实的基础。     

Investigation of the coupled distribution of initial and machining-induced residual stress on the surface of thin-walled parts

Residual stress on the machined surface and the subsurface is known to influence the distortion of thin-walled parts. Therefore, it is essential to predict the distribution of surface residual stress accurately. In this paper, the coupled distribution law of initial residual stress and machining-induced residual stress is investigated. Firstly, a model with initial residual stress is established and incorporated into thermal mechanical coupled finite element model of 2-D cutting. Then, a tensile fixture is designed to impose initial stress into a thin-walled part of Al-6061, and cutting experiments are carried out. The residual stress distribution is measured by X-ray diffraction/electropolishing method. The results of experiments and simulation show that in the plastic deformation zone, the initial residual stress has no significant influence on the distribution of the machining-induced residual stress. In the elastic deformation zone, the stress that linear grows along depth from zero to initial residual stress is superimposed on machining-induced residual stress. The mathematical model of stress coupling distribution on the surface of thin-walled parts is established by numerical method. Finally, it is found that the effect of coupled stress distribution on distortion is more significant with the decrease of thickness (from 3 to 0.5 mm) of the thin-walled parts.     

Effect of curvature radius on the residual stress of thin-walled parts in laser direct forming

The International Journal of Advanced Manufacturing Technology - In laser direct forming, part geometry especially the curvature radius has a significant effect on the residual stress of the...     

薄壁零件的高速铣削稳定性研究

薄壁结构零件在加工过程中极易发生变形和切削振动,这对提高加工质量和加工效率十分不利.在考虑刀具和工件两个方向自由度的基础上,分析了薄壁零件的动态铣削模型.针对2A12铝合金薄壁结构零件,利用MIKRON UCPDUR0800 高速加工中心和相关仪器、软件,通过铣削力辨识实验和模态实验,进行了高速铣削薄壁零件的稳定域分析和实验验证.     

钛合金铣削刀具磨损对表面完整性影响研究

为了掌握钛合金TC4铣削过程中刀具磨损对表面完整性的影响规律,通过对不同刀具后刀面磨损量下铣削钛合金工件的表面完整性测试,得出了刀具磨损对表面完整性的影响规律,并对其影响机理进行了分析.结果表明,在刀具处于初期磨损和正常磨损阶段,刀具的挤光效应引起的压应力占主导地位,而在刀具剧烈磨损阶段,加工过程中的热塑性变形引起的拉应力占主导地位;随着刀具后刀面磨损量的增加,刀具正常磨损阶段粗糙度值缓慢增加,剧烈磨损阶段粗糙度值迅速增加;随着刀具后刀面磨损量的增加,已加工表面的显微硬度值和表面层的硬化深度都随之增大.     

基于盘铣加工钛合金表面残余应力的工艺参数优化

为探索低速盘铣钛合金时铣削参数与加工表面残余应力的关系,设计完成了铣削速度、切削深度、进给速度三因素三水平的正交实验。实验结果表明,在所选用切削参数范围内,已加工表面残余应力均表现为压应力,铣削速度的变化对其影响最显著,进给速度次之,切削深度影响最小。提出将支持向量机回归技术应用于工艺参数优化,建立了盘铣加工钛合金表面残余应力的支持向量机模型,并通过实验以及与指数型回归经验模型的对比,验证了该方法的实用性和合理性。     

Effects of tool deflection in the high-speed milling of inclined surfaces

The present paper looks at the dimensional errors resulting from tool deflection in the high-speed milling of hardened steel surfaces. These errors are measured as the difference between the theoretical surface and the high-speed milling machined using ball-end mills. The effect of various factors on this dimensional error is investigated. First, account was taken of the workpiece material and the slope of surfaces; the values chosen were those normally used in injection mould manufacturing. The workpiece materials were of 30 and 50 HRC hardness, with slopes of 15°, 30°, and 45°. In this manner, results may thus be of utility to the mould and die industry. The selected tools were solid ball end mills of sintered tungsten carbide, coated with TiAIN. These were of various diameters and lengths, and accordingly exhibited various degrees of slenderness. A great value for this latter parameter is a restraint on the potential application of the high-speed milling technique. This is the main reason for this work. Tests were carried out using three machining strategies, namely, upward, downward, and z-level (horizontal), as well as with two cutting types, downmilling (also called climb milling) and upmilling (or conventional milling). In all cases the resulting roughness was also measured. Dimensional errors in several flat slope planes were measured, comparing with those obtained by simulation. The results of these tests have been applied to the prediction of error in the high-speed milling of two industrial parts. Knowledge of error magnitude may be useful when NC programs are prepared for the machining of mould complex surfaces, since it may then be attempted to enhance accuracy. Reference is made to various practical problems that were necessary to resolve in order to achieve measurement errors less than 20 μm in a process as complex as that of high-speed milling in three axes machining centres.     

薄壁金属直缝圆焊管残余应力超声检测

为了研究小口径的薄壁金属直缝圆焊管焊接区域残余应力的大小,利用临界折射纵波对焊管焊接区域进行残余应力检测。结合静载拉伸实验标定了焊管的声弹性系数。结果表明,残余应力随着拉伸距离的增加而变大;拉伸距离相同时残余应力随着焊管直径的增大而增大;声弹性系数与焊管直径无关。通过与盲孔法检测实验的对比,结果表明了临界折射纵波检测残余应力是可靠的。