服役破损叶片的曲面重构及刀路生成方法

A model reconstruction and CNC tool path generation of broken blades was proposed for the conditions that damage regions locatesd on the leading/trailing edges and on the tips. Measured data points were sorted, adjusted, and then utilized to construct sectional spline curves. The section curve was smoothed based on the theory of minimized energy, a method of aligning the sectional curves according to the curvatures was proposed. A model reconstruction method based on the lofting strategy was presented for the edge broken blades and the tip broken blades. The damaged regions were extracted, based on which the algorithm for generating zigzag tool path and the spiral tool path was given for CNC machining. Preliminary simulation results reveal that the proposed method guarantees the smoothness of the reconstructed surfaces and the approximation to the blade's real size. The feasibility of the proposed tool path generation method was testifiecl.     

应用复合进化算法的叶栅气动优化设计方法的研究

采用结合进化算法和单纯形法的复合进化算法为优化算法,对跨音速轴流压气机叶栅进行气动优化设计。气动性能评价采用Reynolds平均Navier Stokes方程求解技术,采用Baldwin Lomax紊流模型封闭求解的方程。优化设计目标是最大化静压比。设计变量是叶栅型线的Bezier曲线控制点坐标。优化设计结果表明优化设计得到的叶栅具有高静压比和良好的气动性能,同时证明了复合进化算法是一种高效寻优算法。     

[刀具及切削工艺]一种基于几何调控的辊轧叶片前后缘加工曲面自适应重建方法

针对航空发动机压气机辊轧叶片前后缘溢料端数控加工问题,提出了一种基于设计曲面几何调控的前后缘加工曲面自适应重建方法。根据自由变形理论以及曲面能量控制原理,建立了具有变形约束能力的自由曲面几何调控模型;利用该模型建立了基于遗传算法求解的辊轧叶片前后缘加工曲面自适应重建策略。该策略通过微量调整叶片设计曲面几何形状,使其在逼近叶身型面测量数据的同时尽可能维持初始几何形状,最终实现了辊轧叶片前后缘加工曲面的自适应重建。实例验证结果表明：利用该方法获得的辊轧叶片前后缘加工曲面可以在保证叶片形状精度的同时实现其与实际叶身的圆滑转接。     

A novel spiral machining approach for blades modeled with four patches

This paper aims at developing a novel spiral machining technique for four- or five-axis milling of blades. The main contributions are twofold. First, detailed algorithms are presented to model the blade surface with the idea that it can be separated into four patches, i.e., the pressure surface, the suction surface, the leading edge surface, and the trailing edge surface. The G¹ continuity across the boundary of each patch is considered. Second, based on the four patches modeled, the key routine of a new spiral machining method is further addressed in detail. It is carried out by machining the pressure and suction surfaces actually whereas passing by the leading and trailing edges in air cut. Experimental results show that the proposed methods can improve the machining quality and avoid overcut near the leading and trailing edges.     

叶片进排气边光学测量系统的实现

针对航空发动机叶片进排气边的制造精度和一致性较差等问题,搭建了非接触式的叶片进排气边光学测量系统,以实现叶片进排气边的几何尺寸和轮廓形状的快速精确测量。该系统以传统的三坐标测量机框架为平台,采用由两个互成一定角度的新型激光扫描测头构成的专用测头作为前端传感器,并且内置了多种数据后置处理算法。在测量过程中,在每个叶片截面的进排气边处选取5条截线,分别测量这5条截线上的轮廓信息,从而确定叶片进排气边的几何尺寸和加工余量。该系统可以作为叶片加工系统的组成部分,从而将叶片的设计、制造和测量3个环节紧密地联系在一起。最后,应用该系统对某一精锻叶片的3个等高截面上的进排气边进行了多次测量实验,结果验证了所搭建的叶片进排气边光学测量系统的实用性和有效性,而且测量结果的重复性精度能够满足系统的设计要求和叶片进排气边的检测需求。该项研究为叶片进排气边的加工质量提供了一种高效率、高精度和高一致性的评定手段。     

CAD-DIRECTED INSPECTION PLANNING FOR FREEFORM SURFACE USING CONTACT PROBES

A methodology for CAD-directed measurement of freeform surface using a coordinate measuring machine equipped with a touch-trigger probe is presented,mainly including adaptive sampling of measurement points and registration of freeform surface.The proposed sampling method follows four steps: Freeform surface is fitted by bi-cubic B-spline; Curvedness measure of the surface is computed; Given a number of sampling points,an iterative algorithm is constructed for selecting a set of measurement points by employing the curvedness information; The measurement points is regularized for tradeoff between maximizing the measurement accuracy and minimizing the sampling time and cost.The aforesaid algorithm is demonstrated in term of a marine propeller blade.An offset surface registration method is presented to improve alignment accuracy of freeform objects,and Monte Carlo simulation is conducted to verify the effectiveness of the method.     

动静干涉下低压涡轮非定常气动载荷研究

为研究动静干涉下轴向间距和尾缘锯齿结构对低压涡轮叶片非定常气动载荷的控制作用,对高效节能发动机(energy efficient engine,简称E3)低压涡轮最后一级的内部流场进行了数值仿真,研究了不同轴向间距和静叶尾缘锯齿结构两种情况下,下游动叶表面非定常气动载荷的变化规律。研究发现：增大轴向间距可以加强尾迹与主流的掺混,消除气流不均匀性,削弱下游动叶表面的非定常气动载荷;静叶采用尾缘锯齿结构不仅可以加强尾迹与主流的掺混,同时还会改变尾缘处的涡结构,对下游动叶前缘产生破坏性干涉效应,使其最大载荷波动降低约30%,减少静叶尾迹速度亏损75.7 m/s,还能适当提升涡轮的流通能力和时均效率。与采用直尾缘静叶的模型相比,采用锯齿尾缘静叶不仅能大幅度地改善涡轮的转静干涉效应和气动性能,还能在不影响涡轮效率的前提下,将涡轮轴向间距缩短10%。     

基于UG的水轮机叶片的逆向反求

借助三坐标测量机测量叶片原始点数据并在三维CAD软件UGS NX中用进行三维造型的逆向反求工程方法.叶片建模的点数据来自实物叶片的测量资料,包括样板曲线和叶片表面上不规则的测量点云.逆向反求过程为数据采集、数据处理转换、数据导入、创建叶片轮廓曲线、用三维数据创建叶片轴面型线、创建叶片网格曲线、创建叶片外表面曲面、创建叶...     

An intelligent sampling method for inspecting free-form surfaces

The two most important factors in sampling during coordinate verification of a surface are the number of measuring points that accurately represent the surface and the distribution of those points. Three algorithms are developed in this paper for sampling of free-form surfaces at a patch scale (not the entire surface). The three developed algorithms take each patch on the surface as a separate unit and distribute the points within the patch in two steps, namely, sample the most critical points that depend on maximum and minimum Gaussian curvature of each patch and add more points depending on the overall distribution of the most critical points distributed on the surface. In each step of sampling, the maximum difference between the CAD model and the surface created using those sampled points is obtained, and an optimum number of measuring points is determined. This minimizes sampling effort and (non-value-added) measurement time. A comparison is performed between the three proposed algorithms and two well known sampling techniques: the equiparametric approach and the patch-size-based sampling method. The proposed algorithms distribute the points in each patch based on a specific plan. The results show that the developed algorithms help select an efficient number of sampling points.     

基于正交距离回归齿面的齿轮误差评定

为了通过测量齿面拓扑轮廓来获取特征线误差,提出了一种基于正交距离回归齿面的误差计算方法。对该方法涉及的实际齿面与理论齿面匹配算法、拓扑轮廓误差的计算与分解及齿面特征线误差的评定算法进行了研究。首先,通过坐标测量方法获取的齿面拓扑数据,建立包含回归齿面参数的非线性方程。然后,求解非线性方程得到回归齿面参数的最优近似解,从而得到与实际齿面匹配的理论齿面,拓扑测量点相对理论齿面的正交距离即为齿面拓扑误差。最后,基于齿轮误差多自由度理论,对实际齿面进行局部自由度及全局自由度回归,进一步分解出齿面的齿廓误差和螺旋线误差。以一标准圆柱直齿轮的齿面拓扑测量点数据为例进行了误差计算,结果显示:计算的结果与直接进行特征线测量的结果差值小于0.5μm,表明提出的基于正交距离回归齿面进行齿轮误差评定的方法是有效的,可以应用于坐标类仪器检测齿轮误差。     

一种基于标定点拟合的铁路桥梁线性裂缝长度测量方法

针对走向不规则的铁路桥梁线性裂缝骨架,采用单一光滑处理的拟合算法很难精确表达裂缝轮廓特征。提出一种多项式曲线拟合方法,以裂缝轮廓标定点为边界点进行分段,然后再进行叠加来产生一条连续的轮廓曲线,进而实现裂缝长度的测量。通过对比不同形状的线性裂缝测量实验表明:所提算法不仅能有效消除裂缝骨架提取过程中产生的锯齿问题,而且该拟合曲线能够真实表达被测表面的轮廓特征,拟合相对偏差不超过0.15,测量精度达到98.05%,为铁路桥梁裂缝长度测量提供了一种新的测量方法。     

叶片后缘加厚对轴流风机性能的影响

为解决NACA65系列翼型叶片后缘轮廓线内切圆半径收敛至0引起的铸造工艺问题,采用三次多项式函数生成叶片后缘厚度函数,精确调整叶片后缘末端厚度.基于Ansys软件对不同叶片后缘厚度的风机进行流体仿真,并分析其气动性能与静力结构特性.结果表明叶片后缘增厚使得叶片附面层分离损失增加,尾迹与叶栅主流区的掺混损失增大.叶片载荷...     

硅片边缘化学机械抛光的微小去除量测量

针对硅片化学机械抛光工艺的材料去除量非常微小并难以测量的问题,本文介绍一种采用表面粗糙度测量仪,对硅片边缘化学机械抛光的材料去除量进行一种简易、快速的测量方法,且该方法同时还可准确地测量硅片边缘抛光表面粗糙度值。检测结果表明,本方法较好地解决了硅片边缘化学机械抛光表面检测问题。     

基于三坐标测量机双参数向自适应测量自由曲面

提出一种基于三坐标测量机的双参数向自适应测量自由曲面方法。CMM手动测量被测曲面边界点后,连接点生成可测区域,由可测区域自动拓扑生成几条均布初始扫描线以及每条扫描线的均匀初始点,对于U向的各条扫描线,CMM在自动测完初始点后,不断拟合已测点为B样条曲线,由曲线末端曲率自适应预测下一测点并指导CMM自动测量。测完初始扫描线后拟合已测点云为B样条曲面,由曲面V向边界最大曲率自适应确定下一扫描线位置,并进行该条扫描线U向自适应测量,重复这一过程直至曲面测量完毕。测点可随被测曲面自身曲率变化特性而疏密分布,曲率变化大的重要特征区域分布密集,曲率变化小的非重要区域分布稀疏,既保证了重要特征点不会遗漏又避免了数据冗余。理论曲线曲面自适应测量实验结果表明该方法测量精度可达微米级,实例零件应用验证了该方法的可行性。     

齿轮特征线统一模型及在齿轮三维误差评定中的应用

表征渐开螺旋齿轮的特征线有多种,广为熟知的是几何意义明确的渐开线和螺旋线。其实齿面上还有法向啮合齿形、接触线等工程价值突出的其他特征线。但特征线增多带来了两个问题,一是复杂的特征线方程彼此不关联,数学上缺乏统一性;二是除了渐开线和螺旋线,其他特征线没有测量手段,缺乏可测性。据渐开线齿轮传动的特点,将齿面特征线映射到啮合平面里,发现齿面上各条特征线在啮合平面里都有各自对应的二维直线,以此建立直线模型统一表达了齿面各种特征线;基于齿轮三维误差测量数据和特征线统一模型,提出了各种特征线偏差的提取方法,应用于测量实践,通过与通用齿轮仪器测量的渐开线偏差和螺旋线偏差作比对,证明了特征线统一模型及特征线偏差提取方法的有效性和实用性,解决了齿面复杂特征线的可测性问题。同时,齿轮特征线统一模型在齿轮工艺误差溯源、传动性能预报等方面也有重要应用价值。     

A new approach for lofted B-spline surface interpolation to serial contours

This paper addresses the problem of B-spline surface interpolation to serial contours, where the number of points varies from contour to contour. A traditional approach to the problem creates a set of B-spline curves via B-spline curve interpolation to each contour, makes them compatible via degree elevation and knot insertion and performs B-spline surface lofting to get a B-spline surface that interpolates them. The approach tends to result in an astonishing number of control points in the lofted B-spline surface. This situation arises mainly from the inevitable process of progressively merging different knot vectors to make the B-spline curves compatible. This paper presents a new approach for fixing this problem. The approach includes a novel process of obtaining a set of compatible B-spline curves from the given contours. The process is based on universal parameterisation [1, 2], allowing the knots to be selected freely but leading to a more stable linear system for B-spline curve interpolation. Since the number of control points in each compatible B-spline curve is equal to the highest number of contour points, the proposed approach can realise efficient data reduction and provide a compact representation of a lofted B-spline surface while keeping the desired surface shape. Some experimental results demonstrate its usefulness and quality.     

超声检测中复杂曲面数字化方法研究

提出了利用超声波检测探头实现自由曲面的路径受控仿形测量方法。针对数据压缩处理引起的各截面曲线上数据点数的不同，提出了一种蒙皮B样条曲面插值方法，该方法在保持插值精度的情况下，减少了曲面重构所需的控制顶点。应用表明，算法计算效率较高。     

基于自适应采样的曲面加工误差 在机测量方法

基于模具在机测量的自适应采样结果,提出一种新的获取自由曲面加工误差的方法。该方法首先基于自适应采样获取加工曲面上少量测点的坐标数据,利用NURBS曲面重构来拟合加工曲面;然后基于广义牛顿法计算重构的实际曲面和理论曲面的法向距离,获得自由曲面的加工误差,并对实验加工的模具模型曲面的轮廓度误差进行分析。实验结果表明,基于自适应采样的加工曲面重构方法能够在机测量且有效地获得自由曲面加工误差。     

The selection of radius correction method in the case of coordinate measurements applicable for turbine blades

The objective of the research presented in the paper is the selection of suitable probe radius correction method in the case of coordinate measurements which can be applied for turbine blades. The investigations are based on theoretical analysis of geometric data and on further computer simulation of measurements and data processing. In the paper two methods for computing coordinates of corrected measured points are verified. Those so-called local methods of probe radius correction are based on Bézier curves. They are dedicated first of all to coordinate measurements of free-form surfaces which are characterized by big values of curvature, e.g. those surrounding the leading and trailing edges of a turbine blade. Numerical simulations are done for several models of the cross-sections of turbine blades with diversified magnitudes of radii of curvature. There are considered both manufacturing deviations and coordinate measurement uncertainty of each examined profile of a turbine blade. Numerical investigations based on the developed analytical models show the advantage of the algorithm which uses the second degree Bézier curves in probe radius correction. Moreover, in the paper there is explained the implementation of the developed algorithms for probe radius correction into the standard CMM software which amplifies the usability of the algorithms.     

自由曲面测量若干关键问题的研究

结合国内外研究现状 ,对自由曲面测量中曲面CAD模型已知时测点的自适应分布、测量路径优化、自由曲面形状误差评定和 CAD模型未知时的测量规划和测点数据处理等几个关键问题的实现方法进行了分析研究 ,并对测点的自适应分布做了仿真研究 ,证明了其有效性