Research On The Key Technologies Of CAD\CAE Integration In The Application Of Dual Interpolation Boundary Face Method

An important topic in the computational field of engineering analysis and scientific computation is to establish a natural link between CAD and CAE.However,the problems associated with the intrinsic drawbacks of the traditional numerical simulation systems are still kept unresolved,such as non-uniform geometric representation of the CAD and CAE models,data loss caused by conversion between CAE and CAD systems and low degree of automatic CAE analysis during frequent interaction between disparate systems,etc.One of the remarkable features in future engineering design is that a truly seamless interaction between CAD and CAE is an attractive computational technique to achieve integration,intelligent and automation of the key technologies of numerical simulation.Numerical simulation is an indispensable tool in engineering design and optimization,which has already been widely applied in many different fields involving auto-making and ship-building,aircraft manufacturing,medical and health,biological technology and new energy resources,etc.The main process of numerical analysis involves several steps,i.e.,geometry modeling,mesh generation,numerical computation and post-process results.And for complex simulation,the pre-process can still be a bottleneck,which depends delicately on the level of professional knowledge and experience of engineering practice.Thus,it is of crucial importance to achieve the integration of CAD and CAE and improve the accuracy of calculation based on an effective and reliable pre-processing algorithm.To overcome the above intrinsic drawbacks,the Dual Interpolation Boundary Face Method(Di BFM)has been proposed,which is an efficient solution method to the Boundary Integral Equation(BIE)and makes direct use of the B-rep data of a solid that available in all CAD packages.The thesis makes a systematic and comprehensive study of automatic geometric model repair,mesh generation and volume element subdivision in the Di BFM implementation.The main research work of this paper is as follows:(1)In order to establish a truly seamless interaction between CAD and CAE,a CAD/CAE integration system has been developed,called the Complete Solid Analysis Software for Engineering Structures.The CAE analyses in the effective simulation tool are implemented directly on the CAD model of an engineering product rather than an elaborately built discretized model,which is different from the real product geometrically and topologically.(2)A dual interpolation boundary face method(Di BFM)is presented for solving three-dimensional potential problems.The Di BFM implementation is based on a new type of elements,called the dual interpolation elements,in which the nodes are classified into virtual nodes and source nodes.The Di BFM is an alternative implementation of the Boundary Face Method(BFM)and inherits all the merits of BFM,which is proposed to unify the continuous and discontinuous elements,improve the accuracy of the interpolation calculation and alleviate the heavy task of mesh generation.The Di BFM is flexible and convenient to handle more complicated,real world structures without any geometric simplification in a fully automated manner.(3)An automatic topology recovery method using T-Spline is presented to reconstruct curves/surfaces by virtual operations for handling unwanted geometric features and facilitating mesh generation without modifying the original input CAD model.It is flexible and convenient to identificate and handle unwanted geometric features in solid modeling automatically,such as short edges,small faces,degenerate edges,degenerate faces,fragmentary boundary edges,sharp features,etc.All operations and further CAE analysis can be set up directly on the CAD model,thus automatic simulation is possible and geometric simplification is avoided.The geometric model repair algorithm can relieve the burden of mesh generation and promote CAE analysis to some extent.(4)An improved rapid calculation algorithm for solving intersections of line and NURBS curve/surface using interval arithmetic with affine transform is presented.Compared with the Newton iteration method,it is not necessary to give a initial iteration value throughout the iterative process.Compared with conventional interval iterative algorithm,the novel algorithm is superlinearly convergent which can greatly reduce number of unnecessary iterations and relax requirements for initial interval simultaneously.And the algorithm with affine transform promotes the performance of interval arithmetic for solving the conservatism of conventional interval arithmetic to some extent.For rapid intersection of line and the complicated solid,the thesis systemically investigates the rapid intersection of line and triangle panels or the Axis-Aligned Bounding Box(AABB).(5)An adaptive unstructured mesh generation based on an improved grid-based method is presented.One of the attractive key innovations of the Di BFM is the alleviation of heavy task of mesh generation.Discontinuous grids used in Di BFM can provide more convenience for mesh generation without considering the hanging points for its simplicity in dealing with complex geometries.The improved grid-based method is based on conventional binary-tree subdivision and geometry-adaptive technique to generate high-quality mesh generation.The refinement field is integrated according to the mesh size,surface curvatures,thickness distribution and other geometry features.Even there are some hanging points in the initial refinement structure,it is worth mentioning that any operations are not required to ensure the conformity of the generated mesh.In order to match the straddling element mesh to the geometric boundary,a set of boundary matching templates are proposed.The matching procedures are conducted by projecting the exterior points of straddling element mesh along the specified direction to the geometric vertices,edges and faces of solid model in sequence.Inevitably,there are still some poor-quality or irregular element meshes in the process of mesh generation.To improve the quality of the ultimate mesh generation,an optimization approach is proposed by using Laplacian smoothing technique and volume element decomposition.The ultimate mesh generation is mainly composed of hexahedral element mesh as a whole and a few pentahedral,tetrahedral and pyramid element mesh for auxiliary around the geometric boundary.(6)An adaptive and efficient volume element subdivision method using binary tree for evaluation of singular domain integrals and nearly singular domain integrals with continuous or discontinuous kernel in BEM has been presented.The automatic volume element subdivision technique is called the Binary-Tree Subdivision Method(BTSM),which is applicable to arbitrary shape volume elements with arbitrary locations of the source point and can guarantee successful high-quality patch generation under any circumstances.The patches in the neighborhood of the source point are smaller than the distant ones,in which the integration points are set denser around the source point,and are sparsely distributed away from it.Thus,extensive unnecessary integration points can be avoided,the computational efficiency of domain integration is increased significantly by the BTSM.With the distinct feature that a single binary-tree data structure can efficiently handle volume element subdivision,it is flexible and convenient for the BTSM to be implemented in the formulation of the boundary integral equation which contains volume integrals.