Research On Defect Characterization Evaluation And Hole Filling Algorithm Of Aero-Engine Blade Based On Ultrasonic C-Scan

With the rapid development of modern science and industrial technology,nondestructive testing,as an important technical means to improve product quality and ensure the safe operation of service equipment,plays a vital role in the safety assurance system of modern industrial equipment.The defect of the aero-engine blade will lead to significant degradation of mechanical properties and even complete failure of the structure.The research on quantitative evaluation technology of aero-engine blades can find the early failure and potential failure of aero-engine,which is conducive to the accurate estimation of residual life of aircraft,and has important practical significance for ensuring the safe service of aircraft.In this paper,the aero-engine blade is taken as the research object.By exploring the transmission theory of ultrasonic wave in the blade,the propagation law of ultrasonic in blade medium is revealed,combined with three-dimensional point cloud processing technology,computer graphics surface display technology,and digital model processing technology,the relevant technical research of 3D visualization,defect quantitative evaluation and hole filling module based on ultrasonic C-Scan point cloud data is carried out.The main contents are as follows:(1)An algorithm for extracting aero-engine blade defect boundary based on a double decision criterion is proposed.Due to the complex geometry,scattered position distribution,and obvious curvature change of the defect holes in aero-engine blades,it is difficult to extract the boundary feature points completely by using a single criterion.By fusing the criterion of the normal angle of sampling points with the adjacent field power force criterion,the eigenvalue and threshold of sampling points are obtained by the weighted method,which can be used as the criterion for extracting boundary feature points.Experimental results show that the method can effectively improve the accuracy of boundary feature point extraction.(2)An algorithm for defect quantitative evaluation based on ultrasonic C-Scan 3D point cloud is proposed.Aiming at the limitation that the traditional defect detection results of aeroengine blades cannot be displayed directly and analyzed quantitatively,the ultrasonic C-Scan point cloud data is applied to the defect characterization evaluation model.The improved DBSCAN clustering algorithm is combined with Delaunay triangulation and mesh growth algorithm to realize the three-dimensional reconstruction of the regional discrete point cloud.Based on the topological relations of the reconstructed triangular mesh,a quantitative defect evaluation model is established.The feasibility and accuracy of the algorithm are verified by taking a blade with several prefabricated flat bottom holes as an example.(3)A complex hole filling algorithm based on detail feature preservation is proposed.To solve the problems that the conventional hole-filling algorithm cannot recover the geometric feature information of the defect hole and the quality of the new triangle is poor,the complex hole is decomposed into simple sub holes by reconstructing the feature line of the hole area,and the local position of the insertion point is adjusted by combining the normal information with concavity and convexity of the boundary feature points.The experimental results show that the algorithm can effectively restore the surface features of the hole area,make the repaired mesh closer to the original geometric shape of the defect hole,and obtain a better hole repair effect.