3. Operands#

The POST_K_BETA operator can be used for axisymmetric or three-dimensional models.

In the figures below we show a diagram of a tank slice with the presence of an elliptical defect (negative and positive offset) or a semi-elliptical defect.

Offset elliptical defect in the base metal

_images/Shape1.gif _images/Cadre2.gif

Offset elliptical defect in the coating

_images/Cadre3.gif

Semi-elliptical defect located under the coating

3.1. Operand MAILLAGE#

Mesh-type concept.

3.2. Operand MATER_REV#

Name of the material-type concept defining the material constituting the coating. Needed to recover:

  • Young’s modulus, for calculating influence coefficients (semi-elliptic defect),

  • Elastic limits, for the plastic correction of stress intensity factors.

3.3. Operand EPAIS_REV#

Coating thickness. Needed for:

  • The calculation of stress intensity factors in the case of the influence coefficients method (semi-elliptical defect)

  • The correction of stress intensity factors by edge factors and for plastic correction.

3.4. Operand MATER_MDB#

Name of the material-type concept that defines the material that makes up the base metal. Necessary to recover the Young’s modulus, for the calculation of the influence coefficients (semi-elliptical defect).

3.5. Operand EPAIS_MDB#

Thickness of the base metal, necessary for the correction of stress intensity factors by the method of coefficients of influence (semi-elliptical defect).

3.6. Keyword FISSURE#

Keyword factor for the geometric characterization of the defect. It can only be used once.

3.6.1. Operand FORM_FISS#

Defect shape:

“ELLIPSE “for an elliptical defect,

“SEMI_ELLIPSE “for a semi-elliptic defect,

3.6.2. Operand DECALAGE#

This operand is only used in the case of a “ELLIPSE” shape defect. From the coating/base metal interface, it makes it possible to offset the crack in the:

  • Coating: DECALAGE negative,

  • Base metal: DECALAGE positive or zero.

3.6.3. Operand PROFONDEUR#

Radial dimension of the defect.

3.6.4. Operand LONGUEUR#

Second dimension of the defect (axial or orthoradial depending on the orientation of the defect).

3.6.5. Operand ORIENTATION#

Characterization of the orientation of the defect:

“CIRC “for a circumferential defect,

“LONGI “for a longitudinal defect.

3.7. Keyword K1D#

Keyword factor for characterizing the thermomechanical transient. The repetition of this keyword is possible.

3.7.1. Operands TABL_MECA_REVet TABL_MECA_MDB#

Shape defect “ELLIPSE” with negative offset:

For this type of defect, the two tables TABL_MECA_REVet TABL_MECA_MDB are mandatory, they provide the transient of the stresses experienced by the tank during the history of the loading, respectively on the coating side (from the point A of the defect to the interface) and on the base metal side (from the interface to the point B of the defect).

Shape defect “ELLIPSE” with positive offset:

For this type of defect, table TABL_MECA_MDB is mandatory, it provides the transient of the stresses experienced by the tank during the history of loading, respectively on the coating side (from point A of the defect) and on the base metal side (at point B of the defect) and on the base metal side (at point B of the defect).

Shape defect “SEMI_ELLIPSE” :

For this type of defect, table TABL_MECA_MDB is mandatory, it provides the transient of the stresses experienced by the tank during the history of the loading, respectively on the coating side (from point A of the defect: interface between the coating and the base metal) and on the base metal side (at point B of the defect).

The common parameters required for these tables are:

  • “INST” [R],

  • “SIXX” [R] (in 3D with “LONGI”),

  • “SIYY” [R] (in 3D with “LONGI” or in 2D with “CIRC”),

  • “SIXY” [R] (in 3D with “LONGI”),

  • “SIZZ” [R] (in 2D with “LONGI” or in 3D with “CIRC”).

The required parameters specific to:

  • TABL_MECA_REVsont:

    • “COOR_X” [R],

    • “COOR_Y” [R]

  • TABL_MECA_MDBsont:

    • “ABSC_CURV” [R]

The reader is invited to consult the documentation for commands POST_RELEVE_T [U4.81.21] and MACR_LIGN_COUPE [U4.81,13] for more information on the meaning of the parameters.

In the case of a form defect “SEMI_ELLIPSE” the macro command MACR_LIGN_COUPE must be used with the keywords TYPE =” SEGMENT “and NB_POINTS =5. The influence coefficient method requires the evaluation of a degree 5 polynomial representing the evolution of the stress normal to the segment representing the crack [R7.02.10]. The macro command MACR_LIGN_COUPE allows the user to define the places where the stress is detected and this is independent of the mesh used during the thermo-mechanical study.

3.7.2. Operand TABL_THER#

Table providing the thermal transient in the tank during the history of loading from tip A to tip B.

The required parameters of this table are:

  • “INST” [R],

  • “ABSC_CURV” [R],

  • “TEMP” [R].

The reader is invited to consult the documentation for commands POST_RELEVE_T [U4.81.21] and MACR_LIGN_COUPE [U4.81.13] for more information on the meaning of the parameters.

3.7.3. Operand INTITULE#

Title to specify the group of nodes in question.

3.8. Operand TITRE#

Title attached to the concept produced by this operand [U4.03.01].