# *************************************************************************** # * Copyright (c) 2021 Bernd Hahnebach * # * * # * This file is part of the FreeCAD CAx development system. * # * * # * This program is free software; you can redistribute it and/or modify * # * it under the terms of the GNU Lesser General Public License (LGPL) * # * as published by the Free Software Foundation; either version 2 of * # * the License, or (at your option) any later version. * # * for detail see the LICENCE text file. * # * * # * This program is distributed in the hope that it will be useful, * # * but WITHOUT ANY WARRANTY; without even the implied warranty of * # * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * # * GNU Library General Public License for more details. * # * * # * You should have received a copy of the GNU Library General Public * # * License along with this program; if not, write to the Free Software * # * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 * # * USA * # * * # *************************************************************************** __title__ = "Mesh export for Nastran mesh file format" __author__ = "Bernd Hahnebach" __url__ = "https://www.freecad.org" ## @package exportPyNastranMesh # \ingroup FEM # \brief FreeCAD pyNastran Mesh writer for FEM workbench import FreeCAD # we need to import FreeCAD before the non FreeCAD library because of the print try: from pyNastran.bdf.bdf import BDF except Exception: FreeCAD.Console.PrintError( "Module pyNastran not found. Writing Mystran solver input will not be work.\n" ) from FreeCAD import Console from femmesh import meshtools # ************************************************************************************************ # ********* generic FreeCAD export methods ******************************************************* # names are fix given from FreeCAD, these methods are called from FreeCAD # they are set in FEM modules Init.py def export( objectslist, filename ): "called when freecad exports a file" if len(objectslist) != 1: Console.PrintError("This exporter can only export one object.\n") return obj = objectslist[0] if not obj.isDerivedFrom("Fem::FemMeshObject"): Console.PrintError("No FEM mesh object selected.\n") return write(obj.FemMesh, filename) # ************************************************************************************************ # ********* module specific methods ************************************************************** # writer: # - a method directly writes a FemMesh to the mesh file # - a method generates the pyNastran code # ********* writer ******************************************************************************* def write( fem_mesh, filename ): """directly write a FemMesh to a pyNastran mesh file format fem_mesh: a FemMesh""" if not fem_mesh.isDerivedFrom("Fem::FemMesh"): Console.PrintError("Not a FemMesh was given as parameter.\n") return femnodes_mesh = fem_mesh.Nodes femelement_table = meshtools.get_femelement_table(fem_mesh) export_element_type = get_export_element_type(fem_mesh, femelement_table) model = BDF() mesh_pynas_code = get_pynastran_mesh(femnodes_mesh, femelement_table, export_element_type) mesh_pynas_code += missing_code_pnynasmesh # pynas file basefilename = filename[:len(filename) - 4] # TODO basename is more failsafe pynasf = open(basefilename + ".py", "w") pynasf.write("# written by FreeCAD\n\n\n") pynasf.write("from pyNastran.bdf.bdf import BDF\n") pynasf.write("model = BDF()\n\n\n") pynasf.write(mesh_pynas_code) pynasf.write( "model.write_bdf('{}', enddata=True)\n" .format(basefilename + "_pyNas.bdf") ) pynasf.close() # execute pyNastran code to add grid to the model # print(model) # print(model.get_bdf_stats()) exec(mesh_pynas_code) # print(model) # print(model.get_bdf_stats()) # write Nastran mesh file model.write_bdf(filename, enddata=True) # TODO FIXME "BEGIN BULK" is missing def get_pynastran_mesh( femnodes_mesh, femelement_table, export_element_type, ): if export_element_type is None: Console.PrintError("Error: wrong export_element_type.\n") return # nodes pynas_nodes = "# grid cards, geometric mesh points\n" for node in femnodes_mesh: vec = femnodes_mesh[node] pynas_nodes += "model.add_grid({}, [{}, {}, {}])\n".format(node, vec.x, vec.y, vec.z) # print(pynas_nodes) # elements # Nastran seams to have the same node order as SMESH (FreeCAD) has # thus just write the nodes at once pynas_elements = "# elements cards\n" for element in femelement_table: nodes = femelement_table[element] # print(element) # eleid # print(n) # tuple of nodes if export_element_type == "cbar": pynas_elements += ( "model.add_{ele_keyword}({eid}, {pid}, {nodes}, " "{orientation_vec}, {gnull})\n" .format( ele_keyword=export_element_type, eid=element, pid=1, nodes=nodes, orientation_vec="x=[0.0, 0.0, 1.0]", gnull="g0=None" ) ) else: if export_element_type == "ctetra4": ele_keyword = "ctetra" # N1, N3, N2, N4 the_nodes = [nodes[0], nodes[2], nodes[1], nodes[3]] elif export_element_type == "ctetra10": ele_keyword = "ctetra" # N1, N3, N2, N4, N7, N6, N5, N8, N10, N9 the_nodes = [ nodes[0], nodes[2], nodes[1], nodes[3], nodes[6], nodes[5], nodes[4], nodes[7], nodes[9], nodes[8], ] else: ele_keyword = export_element_type the_nodes = nodes pynas_elements += ( "model.add_{ele_keyword}({eid}, {pid}, {nodes})\n" .format(ele_keyword=ele_keyword, eid=element, pid=1, nodes=the_nodes) ) # print(pynas_elements) mesh_pynas_code = "{}\n\n{}\n\n".format(pynas_nodes, pynas_elements) return mesh_pynas_code # Helper def get_export_element_type( femmesh, femelement_table=None ): return nastran_ele_types[meshtools.get_femmesh_eletype(femmesh, femelement_table)] nastran_ele_types = { "tetra4": "ctetra4", "tetra10": "ctetra10", "hexa8": None, "hexa20": None, "tria3": "ctria3", "tria6": None, "quad4": "cquad4", "quad8": None, "seg2": "cbar", "seg3": None, "None": None, } missing_code_pnynasmesh = """ model.sol = 101 # is this needed? # case control from pyNastran.bdf.bdf import CaseControlDeck cc = CaseControlDeck([ #"ECHO = NONE", "TITLE = pyNastran for generating solverinput for for Mystran", #"SUBCASE 1", ]) model.case_control_deck = cc\n\n """