$$$$ CH_THETA NOTICE CHAT 11/09/12 21:15:26 7124 DATE 11/09/12 Procedure CH_THETA Voir aussi : G_THETA ------------------ THETA TABUTIL = CH_THETA TAB1 ; TAB1.'MAILLAGE' .'FISSURE' .'FRONT_FISSURE' .'COUCHE' .'POINT_1' .'POINT_2' .'POINT_3'.'PCENTRE' .'CHPOINT_TRANSFORMATION' .'OPERATEUR' .'EPAISSEUR' Description: ____________ Called by the G_THETA procedure for calculating the energy release rate G or the C integral by the G_THETA methode, the present procedure defines a chpoint field for 2D and 3D crack problems. For a 3D crack front, the procedure creates as many THETA fields as there are points on the crack front. The THETA chpoint fields constructed are local fields that lie on the nodes of the plane normal to the crack front at the considered point (before working out the mesh, make sure that you will have these planes normal to the crack front). This procedure works only for plane cracks. Input data ---------- SUPTAB = Object (TABLE type) used for defining the options and the calculation. The indices of the TAB1 object are words (to be written in words). Here is their list : 1) COMPULSORY FOR ALL CASES °°°°°°°°°°°°°°°°°°°°°°°°°°° SUPTAB.'MAILLAGE' = It is the structure whole mesh (mesh used in the finite elements analysis) SUPTAB.'FISSURE' = Object of MAILLAGE type giving the two lips of a crack if all the two are constructed, or one lip if another one is not constructed for the reason of of symmetry, for exemple. SUPTAB.'FRONT_FISSURE' = This is the crack tip in 2D or in case of thin shell elements (POINT type), but all the crack front in 3D (MAILLAGE type). SUPTAB.'COUCHE' = It is the number of layers of elements surrounding the crack tip in 2D (or surrounding a point on the crack front in 3D), that support the virtual crack extension. If COUCHE = 0, the THETA field equals 1 only at the crack tip (in 2D), or equals 1 for all points on the crack front (in 3D). In general, more the number of layers of elements is important, more the value calculated by the G_THETA procedure is accurate. But the elements included in the number of layers should not attain mesh's border. 2) OPTIONAL ARGUMENTS FOR CIRCULAR CRACKS IN PLANE CONFIGURATION (2D) °°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°° SUPTAB.'PCENTRE' = center of the circular crack 3) OPTIONAL ARGUMENTS FOR STRAIGHT PIPE (3D) WHERE CRACK PROPAGATION IS A TRANSLATION °°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°° transformation of the pipe into a sheet with cylindrical coordinates system SUPTAB.'POINT_1' = Objet of type POINT. Center of the coordinates system. SUPTAB.'POINT_2' = POINT1 to POINT2 constitutes the positiv direction of Z axis SUPTAB.'POINT_3' = POINT1 POINT2 POINT3 constitute the surface which defines theta angle equal to zero 4) OPTIONAL ARGUMENTS FOR STRAIGHT PIPE (3D) WHERE CRACK PROPAGATION IS NOT A TRANSLATION °°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°° A) Crack in a straight pipe (3D, Rotation) SUPTAB.'POINT_1' = Objet of type POINT SUPTAB.'POINT_2' = Objet of type POINT, goes along with POINT_1 to define the crack rotation axis B) Crack in the elbow of a pipe (3D, rotation + transformation into a sheet) SUPTAB.'POINT_1' = Objet of type POINT SUPTAB.'POINT_2' = Objet of type POINT, goes along with POINT_1 to define the crack rotation axis SUPTAB.'CHPOINT_TRANSFORMATION' = field used for transforming an elbow into a straight pipe by using operator 'PLUS' or 'MOIN'. SUPTAB.'OPERATEUR' = MOT. Its value is 'PLUS' or 'MOIN' to indicate the use of operator PLUS or MOIN for transforming the elbow into a straight pipe. 5) OPTIONAL ARGUMENTS FOR CRACKS MODELIZED BY THIN SHELL ELEMENTS (COQ3,COQ4...) (3D) °°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°°° SUPTAB.'EPAISSEUR' = Objet of type FLOTTANT. This is shell's thickness at the crack tip point Output data : ------------- °°°°°°°°°°°°° index pointed type comments object THETA = Objet of type : - TABLE for a 3D crack front, it is a table indexed by the points of the front containing the CHPOINT containing the THETA field. - CHPOINT for a 2D crack front (3D for thin shell element), containing the THETA field. TABUTIL = Objet of type TABLE containing the vector giving the direction of the THETA field
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