Reconstruction And Measurement Method Of Propellant Shell And Grain Surface

As an important part of various gun-type ammunition,propellant provides energy for the launch of the ammunition,and is an important support and foundation of the weapon and equipment system.A new type of tubular propellant made of translucent FRP material is assembled and combined by grain and shell,and its material is generally manufactured by hot drawing and stretching forming process.Therefore,its surface is prone to mutation,making the outer surface of the grain of the propellant and the inner hole of the shell deformed,which brings difficulties to the assembly of the propellant.At present,manufacturers are still using caliper gauges to measure the propellant shell and grain.Therefore,a measurement method is needed to measure the geometric dimensions and surface conditions of the inner hole of the propellant case and the outer surface of the grain,and a suitable assembly method can be given according to the measurement to make it safe and smoothly assembled together.The research of this thesis has significant application value and theoretical significance to the assembly production of propellant grain.The CMM is used for acquiring point cloud data in the form of measurement of the propellant shell and grain,to do an in-depth study of data acquisition and processing as well as the 3D reconstruction of the surface,and then to do an analysis of the assembly ways of the reconstructed surface.The main work done in this thesis is as follows.（1）Point cloud data measurement of the outer surface of the grain and the inner hole of the shell;on the basis of the characteristics of the object studied in this thesis,the advantages and disadvantages of the main measurement methods used today are dissected.The contact measurement method is selected for acquire point cloud data for the inner bore of the emitter shell and the outer surface of the grain.The measurement paths are planned,the main sampling methods and sampling densities are explained,and finally the combination of equal arc length and circular arc adaptive method and the combination of uniformity and curvature is chosen to obtain the point cloud data of the outer surface of the grain and the inner hole of the shell.（2）Data processing;discusses the judgment of noise points in the point cloud data,as well as the common point cloud denoising and streamlining methods,studies the triangular mesh segmentation and its principles,and finally denoising and streamlining the acquired point cloud data by Geomagic,which provides the basis for the follow-up work.（3）Surface reconstruction and assembly analysis;The surface reconstruction software used in this study is introduced to outline the surface reconstruction process for the inner hole of the emitter shell and the outer surface of the grain.The specific process is: firstly,the obtained point cloud data is pre-processed,and the point cloud of the cross-section obtained by Imageware software is fitted to the curve model by the least squares method,and then the curve is fitted to the surface,and the surface reconstruction of the inner hole of the shell and the outer surface of the pillar is carried out in the way of point-line and surface.The reconstructed surface is then measured and analyzed,and finally,the assembly ways is analyzed and the total process is analyzed for errors.In this thesis,the measurement method of extracting the point cloud from the inner hole of the propellant shell and the outer surface of the grain through surface reconstruction by CMM is more representative than other methods for its measurement to make guidance for its safe and smooth assembly,and realizes the 3D surface construction of the protruding deformed surface.