广义边界下含双相流水平井钻柱频率特性分析

钻柱在内流作用和旋转因素的影响下容易产生耦合振动,发生疲劳失效。本文基于微分求积法（DQM）对含双相流水平井钻柱耦合动力学特性进行了研究。利用扩展的Hamilton变分原理建立了计入内流、轴向压力及旋转等因素影响的水平井钻柱动力学方程。在振动问题中考虑了广义边界条件,通过改变边界等效弹簧刚度将模型简化为简支、悬臂等简单边界条件模型进行研究。通过分析旋转角速度、轴向压力、液相流速、气体体积分数等因素对模型频率特性的影响,得到了无量纲固有频率随不同参数变化的特征曲线。分析结果表明：不同边界条件下模型的频率特性曲线有很大的差别;气体体积分数对临界流速的影响在悬臂管系统中表现的更为明显;在简支管模型中,随着轴力的增大会产生模态耦合颤振。此外,通过液相流速和旋转角速度的频率云图展示了两种因素对钻柱频率特性的影响。     

振动切削深孔加工初始偏差对孔直线度误差的影响

构建了振动切削深孔加工钻杆在轴向振动、振动切削力和切削液流体力影响下的多跨动力学有限元模型。引入自由模态综合技术,将钻杆线性自由度的特征模态进行缩减,仅保留具有非线性动力特征的模态,从而可有效降低耦合系统自由度数,减小计算量。利用该缩减后的模型,研究了辅助支撑位置和加工深度与孔直线度误差的作用关系,获得了孔直线度随初始偏差量变化的规律,为大跨度振动切削深孔加工机床的精度设计和加工误差分析提供了依据。通过试验与数值计算结果的对比,验证了所提出方法的有效性与准确性。     

考虑结合面和轴向力的主轴系统动力学特性

汽车覆盖件淬硬钢模具由于硬度高,在铣削过程中动态铣削力大,易发生颤振,而主轴系统动力学特性直接影响铣削稳定性。为了准确建立主轴系统动力学模型,考虑主轴系统铣削状态下产生的轴向铣削力和离心力对主轴结合面接触刚度的影响。通过分析得到,轴向铣削力对主轴结合面接触刚度有强化作用,使主轴系统固有频率有微小的增加;而离心力对结合面接触刚度有软化作用,随着主轴转速升高,系统的固有频率减小,尤其高转速时主轴系统的动力学特性偏差较大,对比而言离心力的软化作用多于轴向铣削力的强化作用,故主轴系统在铣削过程中动力学特性相比静止无载状态下仍是软化现象;分析结合面预紧力、刀具参数等因素对主轴系统动力学特性的影响规律,为准确分析主轴系统动力学特性和预测铣削稳定性提供理论参考。     

钻削GH4169高温合金薄壁件钻削力仿真研究

GH4169高温合金的薄壁钻孔与厚壁钻孔相比有特殊性,运用ABAQUS软件进行钻削GH4169高温合金薄壁件的仿真,研究钻削加工过程中钻削参数和工件厚度对钻削力的影响规律及变化特征,分析应力的分布规律。结果表明:钻削初期,横刃的挤压和主切削刃切削长度的增加使钻削力和扭矩增大;稳定钻削阶段,横刃切出后,主切削刃切削长度不变切削直径增加,钻削力和扭矩稳定增加;钻削后期,副切削刃参与切削,主切削刃切削长度减小,轴向钻削力和扭矩减小,但副刃与孔壁的挤压摩擦,曲线波动较大;钻削速度、进给量及工件厚度的增加都会导致轴向钻削力和扭矩的增加;钻削时的最大应力分布在横刃和主切削刃与工件的接触部位。     

Timoshenko beam-based stability and natural frequency analysis for heavy load mechanical spindles

The heavy load mechanical spindle is an important functional component in a 5-axis computer numerical control (CNC) machine tool, which is used to process large and complex free-form surfaces. It is necessary to obtain the natural frequency and analyze the spindle stability for improving the machining precision. In this paper, Timoshenko beam theory is introduced to model the mechanical spindle shaft, where the centrifugal force and gyroscopic effects are considered. Stability of the heavy load mechanical spindle shaft is analyzed, and the buckling load of the spindle shaft is obtained under different rotational speeds. The natural frequency of spindle is investigated in a freedom and restraint state, respectively. Comparing the proposed method with the simplified hollow cylinder and shaft prototype in the freedom state, the results show that they are highly correlated with experimental results. For the restraint state, the axial load, rotational speed, gyroscopic effect, and centrifugal force are discussed, and all of these parameters affect the natural frequency. The proposed modeling approach can be used for spindle design and optimization in a given machining process and can be easily extended to other spindle design.     

GH4169高温合金薄壁钻削加工钻削力的仿真研究

GH4169高温合金薄壁钻孔与常规的高温合金厚壁钻孔相比有其特殊性,应用有限元分析软件对硬质合金钻头钻削镍基高温合金平板薄壁件的动态过程进行建模,总结钻削过程中钻削力的变化特点以及进给量和钻削速度对钻削力的影响。研究结果表明:当钻尖高度大于薄壁件厚度时,根据钻头与薄壁件的相对位置,可将钻削过程分为三个阶段,在不同阶段钻削力变化特点不同;轴向力和扭矩随着钻削速度的增加而增加,但轴向力增加幅度不大;轴向力和扭矩均随着进给量的增大而明显增大;进给量对钻削力和扭矩的影响较钻削速度明显。     

径向柱塞泵轴配流副液动力矩特性研究

为了研发高性能的海水径向柱塞泵, 建立了轴配流副的三维模型, 对配流副的水力学特性进行研究, 分析了液动力矩的产生机理, 进一步建立配流轴液动力矩的物理模型, 运用MATLAB软件模拟仿真液动力矩的变化规律。搭建试验台架, 并采用开通流孔的方式, 减小液压侧向力对试验结果的影响, 在海水介质条件下, 测试了配流轴的液动力矩随转速和配流窗口压差的变化, 验证了配流副的液动力矩模型的准确性。结果表明, 配流副转速较低时, 所受液动力矩的波动较大, 转速较高时, 所受液动力矩较为平稳;全平衡结构配流轴所受液动力矩不随转角变化, 只与配流轴转速和配流窗口的压差有关。     

高温合金振动钻削断屑实验研究及机理分析

对振动钻削理论进行了分析,建立了振动钻削时断屑的数学模型,利用自制的振动钻削实验装置,采用不同的振动钻削参数进行高温合金振动钻削试验,对轴向振动钻削的断屑效果以及轴向钻削力和扭矩进行了研究,分析了各加工参数对加工过程的影响,发现振动钻削力随钻削参数的变化比较平稳,在大进给量或高转速状态下,振动钻削的钻削力比普通钻削力小得多。通过比较振动钻削与普通钻削所得切屑可知:振动钻削有利于断屑,切屑体积小,排屑顺畅。     

斜孔钻削中钻头折断的判据实验研究

斜孔钻削大量存在于现代制造业中,由于其出钻的特殊加工状态,钻模等辅助方法无法使用。钻头在相当长的时间内处于断续切削状态。轴向力和扭矩均以冲击力出现,极易导致钻头的折断。钻头折断时,轴向力和扭矩均发生了徒增。扭矩的剧烈变化,是折断的主要因素。这为进一步控制和预防钻头折断提供了实验依据。     

多泵磁流体动力学角速度传感器的低频拓展设计研究

针对磁流体动力角速度传感器对低频( <1 Hz)信号检测性能差的问题,在原有的角速度传感器的基础上提出了一种 含多磁流体动力泵的角速度传感器。 采用改进传感器机械结构的方法,在流体通道边缘周向上均匀构建多个磁流体动力 泵,并优化了流体泵磁极形状,以提高流体传感环中径向流速分布大小与稳定性,增强低频下科里奥利力效应。 仿真与实验 结果表明设计的多泵结构传感器相比于单泵结构,径向流速分布提高了 20. 28% ,流体泵通道磁场均匀度增加了 38. 36% 。 测试实验中施加补偿电流后,传感器可以实现对低频角速度信号的检测,全通带范围内幅值波动误差小于 0. 5% ,相位差减 小到 0 ~ 10°范围内。     

Dynamic stability of a rotor with shear-flexible shaft under axial loads

The dynamic stability of shear-flexible rotating shaft with a disk under axial forces has been studied by employing the transfer matrix method. The conventional transfer matrix was modified to include both the applied axial force and the shear deformation. The shear effect is considered based on Engesser’s and Haringx’s buckling theories for shear-flexible beam. A computer program was developed to investigate the influence of both the axial force and the shear deformation on the stability and the natural frequencies of general rotor systems. Two rotor system models are considered: the overhung rotor with or without an intermediate support and the simply supported Jeffcott rotor. The effect of shear deformation and the difference between the Engesser and Haringx approaches increase with an intermediate support for an overhung rotor.     

基于离心泵全流场的流固耦合分析

运用ANSYS workbench软件,选取IS100-65-200型单级单吸离心泵作为研究对象,对离心泵包括叶轮、螺母和轴等转子系统进行单向流固耦合分析。在流固耦合计算中,施加到固体结构的流场载荷不仅有叶轮和蜗壳内部流场,同时还考虑了叶轮前后腔的流场载荷;对转子系统力学分析仅对轴承与轴接触处采用轴向和径向约束较符合实际的约束条件。此外,为了解泵转子系统的固有频率和临界转速等问题,本文还对转子系统进行了模态分析,得到了其固有频率和振型,并将计算得到的临界转速与常规的临界转速计算结果进行了对比分析。     

钻井液与钻柱的耦合纵向振动分析

考虑钻井液与钻柱的泊松耦合,基于管内外钻井液与钻柱间的耦合纵向波动方程组,应用特征矢量法,研究地层切变模量和钻柱泊松比边界对钻柱内纵向应力波和钻井液纵向压力波传输的影响。在此基础上推导钻柱纵向振动的频率方程,引入等效质量分析管内外液动压力下的钻柱固有频率。理论求解表明,钻柱的泊松效应造成应力波与压力波耦合,且管内外不同介质间的波速耦合对压力波的影响明显,而对应力波的影响较弱,故耦合对泥浆脉冲传输的影响远大于钻柱声遥测。钻井液的液动压力增加纵振的惯性质量,导致固有频率与不考虑钻井液相比有较大下降。综合等效粘惯性质量、粘性阻尼系数和钻井液惯性力,建立多因素影响下的钻柱纵向耦合振动模型。     

轴向振动钻削切削力的分析

振动切削是近年来发展起来的一种新型加工技术。文中对振动钻削的特点进行了综述，并引用了超低频振动钻削这一概念，对轴向振动钻孔切削力进行了系统研究，给出了瞬时进给量和瞬时切削力的理论表达式，并对影响切削力的切削速度、振动频率、振幅、进给量和频转比等各参数进行了分析，得出进给量、振幅和频转比对切削力的影响也很大，而切削速度和振动频率对切削力的影响就较小。     

奥氏体不锈钢1Cr18Ni9Ti的钻削试验研究

奥氏体不锈钢1Cr18Ni9Ti属较难加工材料,特别是较小孔钻削。为了得到钻头直径与钻削参数对钻削力和钻削温度的影响规律,故用高速钢标准钻头对1Cr18Ni9Ti与45钢进行了钻削对比试验,并用多元线性回归模型建立了钻削力和钻削温度的经验公式。结果表明:1Cr18Ni9Ti的扭矩和轴向力比45钢大,钻削参数对钻削力影响规律与45钢相同,即钻头直径对钻削力的影响最大,进给量次之,钻削速度最小;1Cr18Ni9Ti的钻削温度比45钢约高1.4倍,钻削速度对钻削温度影响最大,进给量次之,钻头直径最小。     

Estimation of the cutting torque without a speed sensor during CNC turning

In this paper, the cutting torque of a CNC machine tool during machining is monitored through the internet. To estimate the cutting torque precisely, the spindle driving system is divided into two parts: electrical induction motor part and mechanical part. A magnetized current is calculated from the measured three-phase stator currents and used for the total torque estimation generated by a spindle motor. Slip angular velocity is calculated from the magnetized current directly, which gets rid of the necessity of a spindle speed sensor. Since the frictional torque changes according to the cutting torque and the spindle rotational speed, an experiment is adopted to obtain the frictional torque as a function of the cutting torque and the spindle rotation speed. Then the cutting torque can be calculated by solving a 2^nd order difference equation at a given cutting condition. A graphical programming method is used to implement the torque monitoring system developed in this study to the computer and at the same time monitor the torque of the spindle motor in real time through the internet. The cutting torque of the CNC lathe is estimated well within an about 3% error range in average in various cutting conditions.     

油气两相动压密封自振稳定性流固热耦合分析

考虑热与变形对油气两相动压密封自振稳定性的影响,建立基于油气两相动压密封自振稳定性数学模型,采用流固热耦合有限元方法,研究油气比、转速、压差和O形圈阻尼等参数对油气两相动压密封受干扰后的轴向、角向自振稳定性能的影响。结果表明:转速较低时轴向自振稳定性较好而角向自振稳定性较差,转速高时两者相反,O形圈阻尼较低时轴向自振稳定性较差而角向自振稳定性较好,O形圈阻尼高时两者相反,因此在极端转速和取极端O形圈阻尼的情况下轴向或角向临界频率较小,不利于油气两相动压密封自振稳定;压差越大轴向临界频率越大,轴向自振稳定性越好,但角向临界频率越小,角向自振稳定性越差;随着两相介质油气比的增大,轴向临界频率减小而轴向临界质量增大,油气比在0.1～0.15时临界频率、质量以及转动惯量较大,密封综合自振稳定性能较好。     

钛合金旋转超声辅助钻削的钻削力和切屑研究

针对难加工材料钛合金在采用普通麻花钻传统钻削过程中存在钻削力和扭矩较大使得钻孔困难,刀具使用寿命低,连续长切屑易缠绕刀具、划伤孔加工表面、增大刀具-切屑-工件孔壁之间的摩擦以及排屑差引起堵屑和卡刀具的问题,引入一种新刃型刀具（即八面钻）,并结合超声振动钻削技术,进行了钛合金旋转超声辅助钻削试验。分析了旋转超声辅助钻削和普通钻削中切屑形成原理,采用文中所设计的旋转超声振动钻削主轴结合BV100立式加工中心平台、测力系统和非接触激光测量系统进行了无冷却条件下基于八面钻的钛合金旋转超声辅助钻削和普通钻削试验以及钻削力、扭矩和切屑形态的研究。试验结果表明：相比于普通钻削,超声钻削明显降低钻削力和扭矩分别为19.07%~20.09%和31.66%~34.3%,明显增强了钻头横刃和主切削刃的切削能力,获得了良好的断屑和排屑效果,提高了切削过程的稳定性,能够极大改善钛合金钻孔过程钻削困难、刀具使用寿命低和孔加工质量差的问题。     

Stability region of floating intermediate support in a shaft system with multiple universal joints

A floating intermediate support is designed to reduce kinematic and dynamic fluctuations caused by the change of joint angles in a shaft system with multiple universal joints. The dynamic equation of the shaft system is derived via the principle of virtual work, which suggests the angular displacement of the input shaft is the only independent variable. A drive shaft system used in an articulated dump truck is taken as an example to analyze the sensitivities of shaft speed and input torque of the system about structural parameters and system variables, which proves the effectiveness of floating support to attenuate the kinematic and dynamic fluctuations of the shaft system. The stability region of floating support aimed at shaft speed and input torque of the system keeping relatively stable is obtained by setting proper upper limits of objectives, and the analysis results are verified by dynamic simulation in MapleSim platform, which is helpful to decide proper stiffness and damping or determine an optimum control strategy for floating angle of support in design.     

Dynamic response of rotating flexible cantilever pipe conveying fluid with tip mass

In this study the vibration system is consisted of a rotating cantilever pipe conveying fluid and a tip mass. The equation of motion is derived by using the Lagrange's equation. Also, the equation of motion is derived applying a modeling method that employs hybrid deformation variables. The influences of the rotating angular velocity and the velocity of fluid flow on the dynamic behavior of a cantilever pipe are studied by the numerical method. The effects of a tip mass on the dynamic behavior of a rotating cantilever pipe are also studied. The influences of a tip mass, the velocity of fluid, the angular velocity of a cantilever pipe and the coupling of these factors on the dynamic behavior of a cantilever pipe are analytically clarified. The natural frequencies of a cantilever pipe conveying fluid are proportional to the angular velocity of the pipe and a tip mass in both axial direction and lateral direction.