Trajectory planning for roboticbelt grinding of turbine blade

In order to improve the quality and efficiency of blade grinding, the robot and belt grinding technologies were applied to blade machining, and the characteristics and working procees of the system were introduced. Through the comparison of multi-axial machining trajectory generation technologies, equal chord deviation fitting method and equal scallop height method were adopted to plan the robot traaectory. Because of their shortcomings in blade grinding, these two methods were improved. In order to evaluate the improved methods and compare efects of manual and robotic proceesing, a test was carried out. The experimental results show that, the blade machined by robot has much beter surface quality than that by hand. The relevant experiment validates the eefectivenees of robotic machining and the improved methods. [ABSTRACT FROM AUTHOR]     

基于ANSYS的某型航空发动机涡轮叶片的振动特性分析

以某型航空发动机的高压涡轮叶片为研究对象,采用Solidworks软件建立其三维实体模型,基于有限元分析软件ANSYS对其进行振动特性分析,得出叶片的振动频率特性和前六阶振动模态特性。仿真结果对涡轮叶片的设计和改进具有一定的指导意义。     

Creep feed grinding induced gradient microstructures in the superficial layer of turbine blade root of single crystal nickel-based superalloy

The service performance of the turbine blade root of an aero-engine depends on the microstructures in its superficial layer. This work investigated the surface deformation structures of turbine blade root of single crystal nickel-based superalloy produced under different creep feed grinding conditions. Gradient microstructures in the superficial layer were clarified and composed of a severely deformed layer (DFL) with nano-sized grains (48–67 nm) at the topmost surface, a DFL with submicron-sized grains (66–158 nm) and micron-sized laminated structures at the subsurface, and a dislocation accumulated layer extending to the bulk material. The formation of such gradient microstructures was found to be related to the graded variations in the plastic strain and strain rate induced in the creep feed grinding process, which were as high as 6.67 and 8.17 × 107 s?1, respectively. In the current study, the evolution of surface gradient microstructures was essentially a transition process from a coarse single crystal to nano-sized grains and, simultaneously, from one orientation of a single crystal to random orientations of polycrystals, during which the dislocation slips dominated the creep feed grinding induced microstructure deformation of single crystal nickel-based superalloy.     

六轴联动叶片型面砂带磨削方法及加工仿真研究

依据砂带接触轮与叶片型面的最佳接触条件,提出了叶片型面六轴联动砂带磨削加工方法,并进行了叶片砂带磨削的刀位点计算;采用VERICUT构建了虚拟数字机床并进行了仿真加工实验,验证了叶片型面砂带磨削加工刀位点以及轨迹计算的正确性.     

叶片机器人砂带磨抛点云匹配算法优化

为解决机器人磨抛路径中工件坐标系难以计算的问题及校正工件装夹误差,将三维点云配准技术应用到叶片机器人砂带磨抛系统中。由三维激光扫描仪扫描工件型面获得工件点云,采用基于主成分分析(PCA)的全局配准算法和改进的迭代最近点(ICP)算法完成了扫描点云和工件模型离散点云间以及不同工件扫描点云间的匹配,以获取工件坐标系和校正工件装夹误差。相关仿真和试验结果表明,优化后的算法在匹配速度与精度上有了长足改进,且加工后产品精度和质量都能满足实际加工要求。     

风力机叶片气动外形设计和三维实体建模研究

针对大型风电机组叶片最佳设计攻角、升力系数呈非线性变化问题,基于叶素-动量理论,通过Wilson设计法,对1.2MW风电机组叶片的气动外进行了设计形.并在此基础上提出了风力机叶片的三维建模方法,即利用点的坐标转换理论来计算叶片各截面翼型的空间实际坐标,然后运用Pro/ENGINEER的三维曲面功能来对叶片进行三维实体建模.     

一种机翼型叶片冲击式涡轮设计与试验研究

因某项目要求,原有轴流式螺旋线叶片涡轮已不能满足井下发电机的性能要求。笔者在涡轮机械一元流理论基础上进行机翼型叶片冲击式涡轮设计,用CFD软件对涡轮进行了全三维模型数值模拟和力学性能预测。通过合理调整相关参数满足流道、叶片型线和喉部折转角的检验要求,获得满足要求的井下涡轮机械性能。台架试验表明,试验结果与仿真预测结果一致,满足设计要求。     

超声内圆磨削系统新型振子的仿真和实验研究

基于超声振动内圆磨削系统中由超声换能器、变幅杆及工具构成的振子在设计制造中出现的问题,提出了一种新型整体式振子设计方法.使用有限元分析软件对该新型振子模型进行了模态、谐响应仿真分析研究,并通过阻抗分析仪和激光多普勒测振仪对加工的振子样件进行了测试实验,验证了有限元仿真结果的正确性和新型整体式振子设计方法的可行性.     

Roughness modeling for polishing an aero-engine blade with an abrasive cloth wheel

Journal of Mechanical Science and Technology - Roughness is a crucial factor that determines workpiece quality. In this paper, the time-domain signals of polishing force for polishing an...     

汽轮机叶片并联抛光机系统的研究

汽轮机叶片抛光采用人工抛光方法.基于并联机床的设计理论和发展现状,研究开发一种自动抛光的方法即采用并联机床实现叶片的抛光.在UG环境下完成叶片造型和并联机床的建模和抛光仿真.为今后实现叶片抛光自动化奠定了基础.     

汽轮机叶片数控砂带磨床自动编程系统的开发研究

以VC++为编程语言,应用UG/OPEN API二次开发工具,通过对叶片实体模型分析、磨削轨迹生成、刀位点计算、磨削干涉校验和修正及后置处理等关键技术的研究,最终开发完成一套五轴联动汽轮机叶片数控砂带磨床自动编程原型系统.     

A study on an axial-type 2-D turbine blade shape for reducing the blade profile loss

Losses on the turbine consist of the mechanical loss, tip clearance loss, secondary flow loss and blade profile loss etc.,. More than 60 % of total losses on the turbine is generated by the two latter loss mechanisms. These losses are directly related with the reduction of turbine efficiency. In order to provide a new design methodology for reducing losses and increasing turbine efficiency, a two-dimensional axial-type turbine blade shape is modified by the optimization process with two-dimensional compressible flow analysis codes, which are validated by the experimental results on the VKI turbine blade. A turbine blade profile is selected at the mean radius of turbine rotor using on a heavy duty gas turbine, and optimized at the operating condition. Shape parameters, which are employed to change the blade shape, are applied as design variables in the optimization process. Aerodynamic, mechanical and geometric constraints are imposed to ensure that the optimized profile meets all engineering restrict conditions. The objective function is the pitchwise area averaged total pressure at the 30 % axial chord downstream from the trailing edge. 13 design variables are chosen for blade shape modification. A 10.8 % reduction of total pressure loss on the turbine rotor is achieved by this process, which is same as a more than 1 % total-to-total efficiency increase. The computed results are compared with those using 11 design variables, and show that optimized results depend heavily on the accuracy of blade design.     

Composite adaptive control of belt polishing force for aero-engine blade

The existing methods for blade polishing mainly focus on robot polishing and manual grinding.Due to the difficulty in high-precision control of the polishing force,the blade surface precision is very low in robot polishing,in particular,quality of the inlet and exhaust edges can not satisfy the processing requirements.Manual grinding has low efficiency,high labor intensity and unstable processing quality,moreover,the polished surface is vulnerable to burn,and the surface precision and integrity are difficult to ensure.In order to further improve the profile accuracy and surface quality,a pneumatic flexible polishing force-exerting mechanism is designed and a dual-mode switching composite adaptive control(DSCAC) strategy is proposed,which combines Bang-Bang control and model reference adaptive control based on fuzzy neural network(MRACFNN) together.By the mode decision-making mechanism,Bang-Bang control is used to track the control command signal quickly when the actual polishing force is far away from the target value,and MRACFNN is utilized in smaller error ranges to improve the system robustness and control precision.Based on the mathematical model of the force-exerting mechanism,simulation analysis is implemented on DSCAC.Simulation results show that the output polishing force can better track the given signal.Finally,the blade polishing experiments are carried out on the designed polishing equipment.Experimental results show that DSCAC can effectively mitigate the influence of gas compressibility,valve dead-time effect,valve nonlinear flow,cylinder friction,measurement noise and other interference on the control precision of polishing force,which has high control precision,strong robustness,strong anti-interference ability and other advantages compared with MRACFNN.The proposed research achieves high-precision control of the polishing force,effectively improves the blade machining precision and surface consistency,and significantly reduces the surface roughness.     

超声激励下单颗磨粒断续切削边界研究

对超声激励复合式振动磨削加工进行单颗磨粒三维运动轨迹的建模与仿真,分析了超声激励下单颗磨粒断续切削存在的边界条件.研究结果表明,各种超声振动磨削模式下,单颗磨粒三维空间轨迹未出现断续冲击切削.通过磨削试验和观察对比试件加工表面的SEM,分析得出轴向超声振动激励所带来的单行程单颗磨粒空间正弦轨迹和单行程相邻磨粒轨迹干涉是超声磨削在切削效率和加工质量上提高的根本原因.     

Molecular dynamics modeling of a single diamond abrasive grain in grinding

In this paper the nano-metric simulation of grinding of copper with diamond abrasive grains, using the molecular dynamics (MD) method, is considered. An MD model of nano-scale grinding, where a single diamond abrasive grain performs cutting of a copper workpiece, is presented. The Morse potential function is used to simulate the interactions between the atoms involved in the procedure. In the proposed model, the abrasive grain follows a curved path with decreasing depth of cut within the workpiece to simulate the actual material removal process. Three different initial depths of cut, namely 4 ?, 8 ? and 12 ?, are tested, and the influence of the depth of cut on chip formation, cutting forces and workpiece temperatures are thoroughly investigated. The simulation results indicate that with the increase of the initial depth of cut, average cutting forces also increase and therefore the temperatures on the machined surface and within the workpiece increase as well. Furthermore, the effects of the different values of the simulation variables on the chip formation mechanism are studied and discussed. With the appropriate modifications, the proposed model can be used for the simulation of various nano-machining processes and operations, in which continuum mechanics cannot be applied or experimental techniques are subjected to limitations.     

Abrasive wear of a single CBN grain in ultrasonic-assisted high-speed grinding

Research into the single grain cutting mechanism is important for understanding complex grinding mechanisms. Based on the characteristics of ultrasonic vibration, the motion equation of the grain is established, and the generated trajectory is theoretically analyzed. By adopting the method of combining high-speed grinding technology with ultrasonic vibration, abrasive wear forms of single cubic boron nitride (CBN) grains under common and ultrasonic conditions are studied. Further studies are conducted on the influence of the grain itself and the main grinding parameters on abrasive wear. Research shows that the main forms of abrasive wear during ultrasonic-assisted grinding are shearing wear and removing wear. However, common grinding leads to micro-crushing wear and a small amount of abrasion wear; the different forms of wear correspond to different grinding force signals. The greater the initial grain protrusion height, the greater is the abrasion of the protrusion; for the same grain protrusion height, the abrasive wear due to ultrasonic-assisted grinding is larger than that due to common grinding. As the grinding depth increases, the abrasive wear of both processing modes increases; however, in the case of ultrasonic machining, the abrasive wear increases slowly and is larger than that under common grinding. This study provides a certain decision basis for real-time monitoring of the ultrasonic-assisted high-speed grinding process. Additionally, it provides guidance and reference for the manufacture and selection of the grinding wheel and for the selection of reasonable processing parameters.     

兆瓦级风力发电机组叶片设计

研究兆瓦级风力发电机叶片翼型建模的方法,应用UG、Matlab建立叶片实体模型,并对叶片的翼型设计提出优化的方法。