蜂窝芯类复合材料零件数字化测量方法研究

发布时间：2018-04-18 00:32

本文选题：蜂窝芯测量 + 外形轮廓测量　；参考：《西南交通大学》2017年硕士论文

【摘要】：随着航空制造技术的日益发展,现代飞机正朝着高性能、高减重、以及低成本的方向发展。蜂窝芯结构是现代飞机上采用的一种新型填充复合材料,具有重量轻、稳定性好、强度高特点。但蜂窝芯结构较为复杂,类似蜜蜂巢穴呈空心六方晶格,有规则的排列。蜂窝芯类零件上下表面是密集排列的孔,侧面为切割后不完整的蜂窝孔壁。壁厚占蜂窝芯外形轮廓的总表面积比例较小,且壁厚较薄。结构特殊性给该类零件加工质量测量带了来较大困难。针对这情况,分析了现阶段较为典型的数字化测量技术,针对蜂窝芯结构的外形轮廓和孔特征分别提出较优的测量方案,并将两种不同的测量数据进行了融合研究,主要工作内容如下:1.针对蜂窝芯外形轮廓测量,提出了一种基于三维光学扫描的测量方案。首先在蜂窝芯表面紧密贴合一覆盖层,以覆盖层的外形轮廓间接反映蜂窝芯的外形轮廓。采用三维光学扫描采集覆盖层外形点云数据,通过计算点云的法矢,然后在法矢方向偏置覆盖层厚度,从而获得蜂窝芯的外形轮廓数据。最后通过实例验证了测量方法的可行性。在计算点云数据法矢的过程中,采用计算点云k邻域,以k邻域建立微切平面得到法矢的方法,文中改进了点云k邻域的搜索算法,提高了点云数据法矢的计算速度。2.提出了一种基于三坐标测量机的蜂窝芯孔特征测量方法。首先计算孔截面内包含孔壁最小测量范围,然后利用测针在此范围内采样测量,不断逼近零件孔壁获得近似孔壁点,通过近似孔壁点拟合获得精确的孔心坐标。根据三坐标测量机测针参数、蜂窝芯参数以及孔特征理论数据对测量过程的极限误差进行了分析。3.三维光学扫描数据与三坐标测量数据的精确融合。在测量过程中引入靶标球,用三坐标测量机和光学扫描仪分别对靶标球进行测量,根据不同测量数据中的球心位置计算得到数据的变换矩阵,实现数据的融合。在计算三维光学测量数据的靶标球心过程中,按照球体特性先对球体数据进行初步提取,然后引入了 RANSAC算法,精确提取球体数据,提高了球心的计算精度。研究成果表明:有效的解决了蜂窝芯外形轮廓及孔特征的测量难题,提高了测量效率和测量精度,并实现了不同测量数据的精确融合。
[Abstract]:With the development of aeronautical manufacturing technology, modern aircraft are developing towards high performance, high weight loss and low cost.Honeycomb core structure is a new type of filled composite material used in modern aircraft, which has the characteristics of light weight, good stability and high strength.But honeycomb core structure is more complex, similar to honeybee nest with hollow hexagonal lattice, regular arrangement.The upper and lower surface of honeycomb core parts are densely arranged holes, and the side is incomplete honeycomb hole wall after cutting.The ratio of wall thickness to the total surface area of honeycomb core profile is small, and the wall thickness is thin.The structural particularity makes it difficult to measure the machining quality of this kind of parts.In view of this situation, this paper analyzes the typical digital measurement technology at the present stage, puts forward better measuring schemes for the outline and hole characteristics of honeycomb core structure, and studies the fusion of two kinds of measurement data.The main work is as follows: 1.A measurement scheme based on three-dimensional optical scanning is proposed for the profile measurement of honeycomb core.Firstly, a covering layer is tightly attached to the honeycomb core surface, and the contour of the honeycomb core is indirectly reflected by the outline of the cover layer.The contour data of honeycomb core are obtained by calculating the normal vector of the point cloud and biasing the thickness of the cover layer in the normal vector direction.Finally, the feasibility of the measurement method is verified by an example.In the process of calculating the normal vector of point cloud data, the method of computing point cloud k neighborhood and establishing a micro-tangent plane by k neighborhood is used to obtain the normal vector. In this paper, the search algorithm of point cloud k neighborhood is improved, and the computing speed of normal vector of point cloud data is improved.In this paper, a method for measuring the characteristics of honeycomb core holes based on CMM is proposed.First, the minimum measurement range of the hole wall is calculated in the section of the hole, and then the sample measurement is made by using the needle in this range, and the approximate hole wall point is obtained by continuously approaching the hole wall of the part, and the exact coordinates of the hole center are obtained by fitting the approximate hole wall point.The limit error of the measuring process is analyzed according to the needle parameters, honeycomb core parameters and the theoretical data of hole characteristics of CMM.Accurate fusion of 3D optical scanning data and 3D measurement data.The target ball is introduced into the measurement process, and the target sphere is measured by CMM and optical scanner respectively. The transformation matrix of the data is calculated according to the position of the ball center in different measurement data, and the data fusion is realized.In the process of calculating the spherical center of 3D optical measurement data, the spherical data is extracted preliminarily according to the characteristics of the sphere, and then the RANSAC algorithm is introduced to accurately extract the spherical data, which improves the accuracy of the calculation of the spherical center.The research results show that: the problem of measuring the contour and hole characteristics of honeycomb core is solved effectively, the measuring efficiency and precision are improved, and the accurate fusion of different measurement data is realized.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33

【参考文献】