Power skiving is a significant gear manufacturing method that offers excellent performance in terms of efficiency and precision. Particularly, cylindrical power skiving tools attract lots of attention and gain powerful competitive since its cylindrical tool shape maintains the cutting edge geometry after rake flank sharpening against traditional conical tools. However, the small clearance between the tooth flank and the slot surface makes them prone to interference. To overcome this drawback, this work developed a concise interference-free design method for cylindrical power skiving tools. Firstly, an eccentricity installation model of power skiving that taking swivel angle of skiving tool as direct variable to control the clearance angle is introduced. The basic forward cutting edge curve design and inverse cutting profile simulation with respect multi-radial infeed are briefly studied by discrete enveloping to satisfy its generality for common gear profile. Further, the interference between cutting teeth flank and the machined slot surface is equivalent to the overcutting of teeth up edge and the negative instantaneous relief angle around cutting edge with respect entire infeed process. At last, a complete design procedure that adopting both enlarging the swivel angle is proposed, where cutting teeth helix angle revising is involved, and its effectiveness is validated by the design results of an internal gear power skiving.
摘要: 为更好地研究天线索网结构对展开态形面精度的影响机理,针对六棱柱模块化天线构型,提出一种六边形索网结构高精度几何设计方法。首先,根据支撑结构特点、工作波段及天线形面方程等参数,开展了天线索网构型设计,建立了形面精度与索长、索段等分数间的参数化模型,并基于机器人学齐次坐标变换理论,建立了考虑悬垂效应的边界节点数学模型;其次,以实际应用工程案例作为比较,对上述模型进行了验证,并在六棱柱单模块样机上对索网结构进行了实物研制,对误差进行了分析与研究;最后,开展了多参数影响分析,研究了展开口径、抛物面方程、网格密度等参数对形面精度的影响规律。研究结果表明:索段实测绝对误差均值约为4.9 mm,相对误差均值约为3.38%,实测值与理论值吻合良好;索网形面误差减小的趋势随着索段密度的增加相对变缓;采用增大反射面焦距、降低天线口径等方式可有效改善索网精度。该研究可为后续索网结构找形分析、形面精度调整及同类天线索网结构的研究等提供借鉴与参考。
摘要: 针对IN718镍基合金和316L不锈钢异质金属连接形成的明显界面导致构件整体强度低的问题,采用激光定向能量沉积(Laser directed energy deposition, LDED)工艺制备了IN718和316L直接连接和梯度连接构件。采用扫描电子显微镜(Scanning electron microscope, SEM)和电子背散射衍射(Electron backscattered diffraction, EBSD)观测了异质金属直接连接和梯度连接构件的界面处微观组织分布。此外,采用数字图像相关法(Digital image correlation, DIC)原位拉伸技术研究了IN718/316L异质金属直接连接和梯度连接构件的整体强度,以及拉伸过程中界面处的应变规律。结果表明, IN718/316L直接连接构件存在明显界面,界面处微观组织分布存在较大差异;从IN718端至316L端,Fe等元素含量明显升高, Ni和Nb等元素含量明显降低。IN718/316L梯度连接构件无明显的连接界面,沿梯度方向,微观组织由胞状晶向柱状树枝晶转变。抗拉强度与直接连接构件相比提高了约28.77%。采用异质金属梯度连接可有效消除异质金属间的明显界面,实现元素分布渐变,明显提升异质金属的抗拉强度。
摘要: 等几何分析能够将几何建模的基函数与结构数值分析的形函数统一,从而得到高精度的结构数值分析结果。面向柔性机构,提出了一种基于等几何拓扑优化的柔性机构设计方法:通过NURBS基函数和Shepard函数构造增强密度分布函数,该函数的高阶连续性可确保优化结构边界的光滑清晰;然后根据密度分布函数建立柔性机构的等几何拓扑优化模型;最后,将该方法应用于柔性机构设计。通过算例结果可知,等几何拓扑优化方法特有的计算原理可提高数值计算的精度和效率,能有效避免由网格依赖、棋盘格现象等产生的边界问题,确保了优化结构均具有较好的光滑性和连续性,验证了提出的方法能有效避免柔性机构的铰链现象。
摘要: 半球谐振子作为半球谐振陀螺仪的核心器件,其加工质量直接影响谐振子的性能参数,进而影响半球谐振陀螺仪的工作精度和使用寿命,因此非常有必要对半球谐振子的性能与其几何参量的映射关系进行研究。本研究以直径为30 mm的熔石英半球谐振子为研究对象,分析其能量损耗的形式、机理,针对谐振子几何参量对其热弹性阻尼的影响进行研究,建立半球谐振子热弹性阻尼能量损耗模型,分析谐振子结构参数、加工误差、表面质量对其能量损耗的影响规律,探究不同几何参量变化对能量损耗的敏感性,结果表明谐振子壳体结构和过渡圆角参数对其热弹性阻尼影响较大,加工误差导致的壁厚不均匀高于半径不均匀对其热弹性阻尼的影响;壳体半径由10 mm增至15 mm,QTED减小幅度为61%,亚表面损伤层厚度从0增至100 μm,QTED减小至其原值的7.5%,研究结果可为半球谐振子专用机床误差分配设计及其高性能制造研究提供参考。
Two-stage quasi-zero-stiffness vibration isolator(TQZS VI)can effectively suppress low-frequency vibrations and quickly attenuate high-frequency vibrations.An electromagnetic shunt damping(ESD)has also been proven to be a feasible way to harvest energy from vibrating structures.By integrating the TQZS VI and the ESD,a novel TQZS VI that realizes dual functions of vibration control and energy harvesting is proposed.Both layers of quasi-zero-stiffness are achieved by a vertical spring connected in parallel with two symmetrical transverse springs,and electromagnetic shunt damping as a viscous dissipative element between the upper and lower layers is provided by an ESD connected to an external resonant resistance-capacitance-inductance(RCI)series circuit.First,the mechanical and mathematical models of the two-stage quasi-zero-stiffness vibration isolator with electromagnetic shunt damping(ESD-TQZS VI)are established.Then,the amplitude-frequency response equation of the ESD-TQZS VI is solved using the harmonic balance method(HBM)and the arc length continuation method.Moreover,the force transmissibility and output power of the ESD-TQZS VI are defined,and the effects of system parameters on vibration isolation and energy harvesting are analyzed.It is found that a sizeable damping ratio is beneficial for attenuating resonance peaks while having a negligible effect on energy harvesting.Significant shunt resistance is not conducive to attenuating resonant peaks and can narrow the isolation frequency band of the system.Finally,the bifurcation and attractor coexistence characteristics of the ESD-TQZS VI system after parameter optimization are revealed.The results indicate that the ESD-TQZS VI can considerably attenuate resonance peaks of low-frequency vibration and achieve vibration energy harvesting at the same time.
摘要: 光元件具有优良的光束扩散性能,被广泛应用于投影、照明及成像系统,抛光可有效去除匀光模具表面刀纹从而提升性能,但现有的抛光方法通常难以在保持微结构面形精度的同时提升表面质量。为解决上述问题,提出了一种用于阵列微结构模具的高性能非接触仿形抛光方法,研究了加工间隙和工具转速对材料去除的影响,分析了模具表面质量及面形变化。最后,通过打光测试表征了不同加工方法与元件性能的关系。结果表明,抛光对匀光元件性能提升作用显著,提出的高性能非接触仿形抛光方法可大幅提高塑件匀光性能。抛光后,模具表面粗糙度由初始的164.2 nm Ra下降至8.1 nm Ra,形状精度误差小于0.8 μm,同时刀纹和毛刺被有效去除。塑件匀光亮度提升了40.4%,匀光均匀度提升了67.1%,塑件匀光性能显著提升。提出的非接触仿形抛光方法可以为高性能光学微结构元件的制造提供技术支撑。
A generation algorithm of periodic high fidelity representative volume element(RVE)model of unidirectional fiber-reinforced polymer(UD-FRP)is introduced.Firstly,based on the random walk algorithm,the fiber morphology is characterized as the Bézier curve,and the tangent direction at each control point is adjusted to follow the multivariable Von-MISES FISCHER function to generate a preliminary soft-core fiber network.Then based on the force-biased algorithm,the corresponding hard-core model is created by adjusting the overlap between fibers to ensure that the fibers in RVE do not twist excessively.In the adjustment process,a three-dimensional near-neighbor list is introduced to significantly improve the algorithm's speed.Finally,the RVE containing fiber waviness is preliminarily calculated for transverse shear,so as to reveal the research value and application field of this method.The results show that the RVE of the required size and fiber waviness can be generated effectively and quickly by this method,the transverse shear strength of UD-FRP can be affected by the fiber configuration with waviness characteristics.The transverse shear strength of UD-FRP increases with the increase of fiber waviness.
In the modern machine tool manufacturing scene, as the milling tool of CNC machine tool, the health of the tool directly affects the processing efficiency and product quality. Effective prognostic and health management of tool is critical. Precise monitoring of tool wear helps to avoid product quality problems caused by tool fault and improve production efficiency. Therefore, this paper constructs a tool fault diagnosis method based on deep learning. In order to effectively fuse the vibration signals features from different directions of machine tool spindle, we apply a variety of Channel Attention (CA) mechanisms to Multiscale Network (MSNet) to construct Multiscale-Channel Attention Network (MS-CA Net), and explore the performance gains of these modules in tool wear classification tasks. Among these modules, the CA blocks include Channel Attention Block (CAB), Squeeze and Excitation Block (SEB), and Efficient Channel Attention Block (ECAB). We use the three proposed networks to classify the tool wear status by identifying the vibration signal of the machine tool spindle. At the same time, in order to verify the performance of the proposed tool fault diagnosis method in the actual milling scene, this paper designs a tool wear test platform to collect sample data that meets actual industrial production scenarios, which uses a three-axis accelerometer to collect tool life cycle vibration signals, and a digital universal tool microscope to measure tool wear values. The experimental results show that, compared with the MSNet method, the tool fault diagnosis accuracy rate of the improved method is increased by 4.47%-7.38%.
Axial piston pumps are the heart of the hydraulic system of aerospace,ocean ships,engineering machinery and other high-end equipment.They deliver transmission blood with stable pressure and flow to the hydraulic system.The reliability and safety of axial piston pumps have direct affects on the performance of the hydraulic system and even the complete machine.Therefore,utilizing intelligent technology to achieve predictive maintenance of axial piston pumps has been a research hotspot in recent years.At the same time,the development of unmanned and intelligent equipment has also emphasized the intelligent technology of axial piston pumps.To explore the development direction of the intelligent technology for axial piston pumps and provide a feasible path for the high-quality development,this study reviews the development history and research status of the intelligent technology of axial piston pumps from four aspects,namely,intelligent condition monitoring,intelligent fault diagnosis,intelligent life prediction and intelligent decision regulation.The existing problems and difficulties of the intelligent technologies for axial piston pumps are explored,the challenges of the existing intelligent technologies are summarized,and the future development trends are forecasted.
电弧增材制造技术可以缩短生产周期,降低成本,实现铝合金的快速成形,但存在结构内部含有较多气孔及晶粒粗大的问题.热丝辅助电弧增材制造(HWAAM)可以有效降低气孔率和细化晶粒,进一步提高电弧增材制造Al-Cu-Mg-Ag合金的性能.采用热丝电弧增材制造技术制备了Al-Cu-Mg-Ag耐热铝合金,利用拉伸试验、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等实验方法,研究了电弧增材制造Al-Cu-Mg-Ag铝合金的气孔缺陷、显微组织和力学性能.结果表明,与冷丝成形合金相比,热丝辅助电弧增材制造Al-Cu-Mg-Ag合金气孔率降低25％,气孔球形度增加,空间分布较为均匀;同时晶粒尺寸降低30％,晶粒形貌趋于等轴晶化.冷丝结构件抗拉强度为218 MPa,屈服强度为134 MPa,延伸率为3.2％,使用热丝电弧增材制造后,力学性能提高,其抗拉强度提升至242 MPa,屈服强度提高至148 MPa,延伸率4.2％.最后,分别采用固溶+时效和人工时效热处理工艺,进一步改善了热丝辅助成形Al-Cu-Mg-Ag合金的力学性能.固溶与时效热处理后抗拉强度达到368 MPa,延伸率下降至0.5％,时效热处理后强度达到297 MPa,延伸率2.1％.
磨削作为大多数典型零件终加工方法,开展典型零件磨削加工工艺智能决策是满足其高精、高效的重要手段,因此提出基于6R模型的典型零件磨削加工智能工艺决策系统框架。首先,结合实例推理与置信度计算各实例的综合置信因子开展实例优选。然后,建立异质集成学习与粒子群算法优化的预测模型获得最优工艺方案输出。最后,基于Qt 4.8.7和SQLite 3开发典型零件磨削加工工艺决策系统。以磨床砂轮主轴磨削为例,根据企业应用报告,使用工艺智能决策系统的方案加工后,零件表面质量提高73.25%,工艺方案决策时间从近20 h缩短到2～4 h,零件加工处理时间从10 min缩短到5 min,单个产品的加工效率提高25%以上,最高达47%,工艺决策准确率达到98.2%,实现了典型零件的高效、高精度磨削加工。
图数据构建质量直接关系图数据驱动的轴承剩余寿命预测性能。目前传统方法通常利用不同时刻的多传感数据来构建时空图，来表征监测对象性能状态，但如何在单传感监测应用场景下构建表征轴承性能退化状态的图数据并保证其质量仍是一个开放问题。面向单传感监测应用场景，提出一种基于路图注意力网络的轴承剩余寿命预测方法。首先，计算轴承全生命周期时序振动信号的时域统计特征并构造路图，其中，路图中的边用于连接相邻时刻振动信号；在此基础上，设计一种图注意力长短时记忆网络，用于挖掘路图的图特征(节点、边连接)中隐含的时序振动信号特征和时间依赖关系，从而深层次地反映轴承全寿命退化过程。在轴承全寿命公开数据集上开展验证对比试验，结果表明，该路图构造方式明确了边连接的物理意义，并提高了图数据表征性能；所提出的预测方法能有效捕获表征轴承退化状态的图特征以及时间依赖关系，为解决单传感监测应用场景下的轴承性能退化预测问题提供借鉴。
为提高平面磁流变抛光效率,首次提出了一种海尔贝克阵列励磁的平面磁流变抛光方法,并对比研究了不同励磁方式磁流变抛光系统的二维、三维磁场分布、磁性颗粒受力分布特性及其抛光性能,证明了海尔贝克阵列具有优良的励磁性能,可以实现高效平面磁流变抛光.对比试验描述了不同装置励磁下,磁流变抛光模形貌特征、抛光压力与痕迹分布、磁流变抛光性能、表面粗糙度与形貌随时间演变的规律,揭示了海尔贝克阵列励磁实现高效平面磁流变抛光的机理.抛光性能试验结果指出,使用N35牌号的钛铁硼永磁材料制造的海尔贝克阵列抛光K9光学玻璃,去除率可达到1.38 mm3/min,是直线气隙磁轭的4.4倍,是N-S极交替阵列的6.9倍.仅需30 min抛光,即可获得表面粗糙度小于Ra1 nm的超光滑表面.海尔贝克阵列性能优异,配置灵活,大大提高了磁流变抛光的效率,对其他磁流变加工工艺和磁场辅助加工工艺具有借鉴意义.
Online automatic balancing system is one of the important research fields to achieve bionic artificial self-recouery and autonomous health of equipment represented by high-end machine tools and aero-engines because it can be used to suppress unbalanced vibration during the operation of equipment in real time.The developed novel electromagnetic automatic balancing system inherits the advantages of fast balancing speed of existing actuators and signal without dynamic transmission,etc.,and improves the driving efficiency of the actuator working process effectively by combined permanent magnet-electromagnetic drive,and the simulation analysis results show that the method can effectively improve the actuator driving efficiency by more than 20％;Focusing on measurement and control methods for this new balancing system,quantitative optimization of key parameters such as reverse electric potential in the measurement and control circuit are done through simulation analysis.Finally,the validity and reliability of the system are verified through simulation tests on the test bench and field tests on actual machine tools.Field experimental results show that the system can reduce the unbalanced vibration of the machine tool from 6.8 μm to 0.7 μm within 20 seconds,effectively improving the surface quality of the processed workpiece.
作为深海载人装备结构的优选材料，TC4ELI（Extra-low-interstitial低间隙元素）钛合金的抗疲劳裂纹扩展性能至关重要。对TC4ELI的疲劳裂纹扩展行为进行系统测试与原位观测，同时选取传统TC4钛合金进行对比试验。结果显示，与TC4相比，TC4ELI具有更高的疲劳裂纹扩展寿命；同时，原位观察发现，TC4ELI的疲劳裂纹扩展存在明显偏折现象，导致裂纹路径比TC4更为曲折。进一步，综合利用微观表征手段对TC4ELI疲劳断口、材料组份、裂纹路径区域微结构进行系统的分析。在此基础上，利用有限元模拟计算裂纹扩展驱动力随偏折角度的变化规律，并分析裂纹偏折对TC4ELI疲劳扩展寿命的影响机理。研究对TC4ELI深海装备结构的损伤容限设计提供了参考。
风机叶片在制造、服役和维修阶段的无损检测非常重要。叶片长期在高强度的风力载荷下工作，制造过程产生的任何微小缺陷将在服役中扩大，进一步威胁到风机的正常运行。因而，风机叶片的无损检测一直是工业界与学术界探索的难题。根据叶片视觉检测方法结合无人机技术应用、相关数据包括图像处理方法以及缺陷评判方法的智能程度等方面对前人以及作者所在课题组的前期工作进行综述、总结、分析与对比。目前，可见光视觉检测与红外热成像检测等以视觉为基础的检测手段满足了风机叶片在役运维时非接触、高效、低成本、安全等需求。视觉检测与无人机巡检技术相结合能最大程度的保证人员安全，同时克服了望远镜检测视野受限的难题。然而该检测手段在风机叶片巡检中目前尚存在缺陷定量难、内部缺陷识别率低等方面的不足。通过分析对比可见光检测与热成像检测技术，认为结合智能算法的无人机搭载双光融合检测手段未来有望于解决风机叶片检测中存在的不足。
主动径向技术是进一步提高轨道车辆曲线通过性能、彻底解决直线运行稳定性和曲线通过之间矛盾的有效途径,而实现轨道线路曲率准确、高效的探测是其中的重要环节.为了提高轨道线路曲率探测的精度和实时性,首先提出了一种基于转向架姿态轨迹的曲率探测系统(Bogie attitude trajectory based curvature detection system,BATCDS),该系统由布置于转向架上的速度传感器、角速度传感器、倾角传感器以及算法单元组成,布局简单且易于实现.此后,提出了与上述系统相匹配的曲率探测算法,该算法利用转向架偏航角速度ω和车速v获取转向架在二维水平面上的运行轨迹,并据此初步估计线路曲率;利用转向架侧滚角α和车速v获取转向架的侧滚姿态轨迹,进而估计转向架侧滚角;综合转向架上述各项姿态信息,利用轨道线路固有几何规律融合计算线路曲率.最后,建立了 BATCDS的联合仿真模型,仿真计算的结果表明,该系统在有效滤除原始信号中的高频噪声的基础上,仍能维持较高的实时性;仿真工况下,相较传统的低通滤波而言曲率探测结果的精度和实时性得到显著改善,相对误差率均降低至传统方法的50％以下,最大降幅可达65％.
离合器转矩精确控制直接决定了双离合器自动变速器控制性能,离合器转矩主要受到离合器老化、温升变化等导致摩擦因数变化的影响.针对双离合器自动变速器离合器摩擦因数变化后起步控制适应性差的问题,融合基于模型的控制与数据驱动控制的特点,提出一种摩擦因数自适应的起步过程智能控制方法.首先建立双离合器自动变速器系统动力学模型,基于伪谱法优化起步过程离合器参考转速;然后制定起步过程转速闭环自适应控制策略,利用BP神经网络在线调用离合器参考转速;设计起步过程自适应滑模控制器,采用径向基神经网络估计离合器转矩,实现离合器转速闭环控制;最后通过仿真和实车测试验证所提方法.结果表明,所提方法在变意图、未知摩擦因数变化规律且存在扰动下均具有良好的起步性能,相较于不依赖机理模型的控制器具有更高的自适应能力和鲁棒性,实现了离合器摩擦因数自适应的整车起步智能控制.
混合动力汽车可以通过模式切换获得良好的燃油经济性,但发动机和驱动电机高效工作区间的转速差异会降低耦合驱动效率,发动机启动瞬态冲击也会破坏整车纵向行驶平顺性.为解决上述问题,开展一种可实现发动机与驱动电机高效工作区域重叠的增速离合器的创新设计,并基于其进行发动机启动平顺性控制研究.首先,设计增速离合器三维实体结构,介绍其功能特点;接着,建立增速离合器齿轮传动机理模型、执行机构驱动电机模型和制动系统模型;然后,设计基于滑模速度控制和单神经元力控制的执行机构双闭环控制器;再后,使用遗传算法对力曲线进行寻优,确定最优接合速度与最终结合力;最后,开发增速离合器原理样机并对提出的发动机平顺启动控制方法进行快速原型试验验证.研究结果表明,所设计的增速离合器除了可以提升发动机与驱动电机的耦合工作效率外,基于其进行发动机启动控制还可以有效减少冲击度、滑摩功和扭矩超调量,从而大幅提升发动机启动时车辆的纵向行驶平顺性.
