Study On The Auto-meshing Generation Algorithm Of Hexahedral Elements For Typical Weld Joint Models

With the development of computer technology and numerical analysis methods, numericalsimulation method, like finite element method (FEM), has become one of the most essential processesin solving actual engineering problems. There are several steps taken in committing a numericalanalysis including geometry model construction, discrete mesh generation, computing,post-processing, etc., among which geometry construction and mesh generation is of the firstimportance in acquiring a reasonable result. The quality of a discrete meshing could have a directinfluence with the computing convergence and accuracy, and all this goes to the algorithms of meshgeneration. Meanwhile, FEM models of weld structures demand more with the density and geometricquality of the discrete elements, as the distribution of the heat flow is strongly nonlinear during theprocess of welding. As a result, a study on the automatic generation algorithm of transitionalhexahedral elements is carried out for the meshing application in typical weld structure models.Within this context, a relatively new algorithm of hexahedral mesh generation which is based on themapping of a quadrilateral mesh is addressed along with the developing details of a software packageconcerned with the new algorithm.A comparison of the advantages and disadvantages between hexahedral and tetrahedral elementsin the FEM application for elastic-plastic analysis is carried out, which concludes that the hexahedralmeshes have a better performance in computing accuracy, capacity of anti-deforming, computingconvergence, element amount and degree of remeshing. But, hexahedral mesh generation is muchmore complicated and difficult to be implemented automatically. Owing to the highly nonlinearproperty of the weld heat flow distribution, hexahedral elements are chosen for weld structure models,especially the transitional ones.The hexahedral meshing algorithm addressed is based on quadrilateral mesh mapping method.The weld structure model is first scanned to confirm the cross section along the welding direction, andthen the cross section will be meshed to transitional quadrilateral elements using advancing frontpaving method. The final hexahedral meshed will be obtained by mapping of the meshed cross sectionalong the welding direction. The original algorithms are refined for better geometric adaptability andmeshing quality and efficiency in several ways including refinement algorithms for boundary closingand seaming, element density optimization, quadrilateral element quality optimization, missedtransitional hexahedral elements generation, etc..A software package, WeldMesh Helper, is developed with the concern of model data structures, three-dimensional visualization, output file format, user experience, etc.. With the help of WeldMeshHelper, users can build a ideal geometry model quickly by some defined parameters, obtain allhexahedral discrete elements of high quality by a quick click of some buttons and also get a standardoutput file for further FEM analysis easily. WeldMesh Helper is somewhat easily handling, weldingprofessional and practical.