| Large cavity blade is the key part of the ship’s power system,the accuracy and performance requirements are high.In order to eliminate internal stress and improve the performance of metal materials,the large cavity blades obtained by heat treatment are subjected to heat treatment.Because the blade contains a very complex composite profile,and has a unique structure of internal cavity,large curvature and long airfoil,a certain degree of deformation occurs during the heat treatment process,which affects the performance of large cavity blades.Therefore,the digital measurement and evaluation process of large cavity blades before and after heat treatment has important practical significance.This article focuses on largescale cavity blades before and after heat treatment.The research involves several technical contents in digital measurement and evaluation as follows:In terms of digital measurement,analyze the geometric shape characteristics of large cavity blades,compare the characteristics and principles of commonly used digital measurement methods,determine the digital measurement methods of large cavity blades,and adopt a three-dimensional laser scanning measurement method based on the principle of position conversion measurement of multiple reference points.Obtain the measured data of the blade before and after heat treatment.In the aspect of measurement data processing,it mainly studies the point cloud data denoising and reduction methods,according to the characteristics of large cavity blade measurement data,a fast K-Neighborhood search noise point method based on spatial cell method is proposed.By comparing and analyzing the characteristics of common data reduction algorithms,a hybrid method based on curvature sampling method and bounding box method is proposed to simplify the measurement data,and the effectiveness of the method is verified.In terms of model reconstruction,based on the characteristics of the measurement data,a hybrid segmentation method based on the combination of edges and smoothness-based European clustering algorithms was proposed to segment the point cloud data of the heat-treated leaves,the fitting problem of complex surface is transformed into single surface fitting,which reduces the difficulty of surface fitting.The fitting modeling and fairing method of curve and surface are studied,and the 3D digital model of large-scale cavity blade after heat treatment is reconstructed.In the aspect of benchmark matching and evaluation,the least square method is used to evaluate and analyze the accuracy of reconstruction of large-scale cavity blade model after heat treatment;several commonly used benchmark matching algorithms are compared and analyzed,and a method of combining initial matching and accurate matching is proposed,the point cloud data before heat treatment of large-scale cavity blade is matched with the datum of reconstruction model after heat treatment,and the heat treatment deformation of the blade is evaluated by the approximation algorithm.The results of evaluation and analysis provide a reliable basis for the design of heat treatment fixture of large cavity blade.By analyzing and researching the digital measurement and evaluation of large cavity blades before and after heat treatment,the overall deformation trend and local deformation amount of the blades before and after heat treatment are obtained.The results of the research and analysis can be used as the quality control of large cavity blades,the optimization of mold design and the improvement of production efficiency Reference basis has certain practical application value. |
