| In the process of ship construction,the development of hull plate with complex curvature and the accuracy of roll line calculation play an important role in the forming quality and the workload of subsequent process.Considering the characteristics of line-heating process and thickness of ship hull plate,the geometric development algorithm is improved.Using the idea of finite element,the surface is segmented into strips based on base line,and then the strips are separately expanded and spliced.In view of the characteristics of large thickness of ship hull plate,the develop surface is shifted from the profile surface to the neutral layer before development;in view of the characteristics of line-heating process,the overlapping parts between the strips are eliminated and the gap part is reserved during the splicing of the strips,so that the expansion area is increased to compensate for the shrinkage of line-heating process.In order to realize the automatic development of ship hull plate,a software is developed based on CATIA platform.And the development accuracy of the software is tested and verified by compared with the results of TRIBON software.The main work is as follows:(1)The CATIA software is redeveloped by VBA of CATIA to realize the automatic extraction of surface information data.Users can automatically acquire the edge data,surface data and rib data in CATIA model by customizing the number of rows and columns in the three-dimensional data points extracted from the input surface.(2)B-spline surface is used to reconstruct the quadrilateral surface,so as to realize data interpolation and meshing.For a triangular surface,one of its endpoints can be seen as a "degenerate" edge;for a pentagon,two of its edges are merged into one edge.(3)The ship hull plate is developed with the idea of finite element method.Firstly,the surface is separated into several strips;secondly,the strips are united and expanded by using triangle plane instead of surface;finally,the strips are joined together to form an expansion grid graph,which is the basis for drawing the expansion graph.Considering that the hull plate is usually of large thickness,the expansion surface is shifted from the profile surface to the neutral layer before deployment,and the compensation for shrinkage of hydrothermal bending plate is mainly realized by eliminating overlap between the plates in the process of splicing.The algorithm includes six steps: B-spline surface fitting,neutral layer migration,baseline extraction,slab surface partition,slab expansion and slab splicing.(4)The extraction method of rolling line is studied.The two edges with the largest curvature of the outer plate edge are used as the starting edge of the rolling line to obtain the rolling line.Finally,using the idea of conformal mapping,the shape error and angle error of the mapping are reduced by finding the mapping points four times.(5)Using C# language of Visual Studio platform in 2012,the developing console application program is developed.Three methods are used to analyze the accuracy of the deployment results: the first method is to use the surface with mathematical analytic formula(regular surface);the second method is to use the actual hull plate surface(irregular surface)to compare the deployment results with the TRIBON deployment results;and the third method is to use the real ship to carry out the production test.The first and last segments of 63 plates are used to develop,and the difference of each edge between the results with the TRIBON software is calculated.The results show that the error of all test plates is between 1.0 mm and 1.8 mm,and the maximum error is not more than 2 mm,which can meet the actual production requirements. |
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