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Subsections


X.D Predefined criteria

The predefined criteria source code is located in file ``SRC/Result/predfinedCriteria.cpp''. So far, five criteria are defined. They are presented in section X.D.1.

Note that the user can define its own criteria, and some preparatory work has already been done. Some explanation is given in section X.D.2.


X.D.1 List of the predefined criteria

Only five predefined criteria are available at the moment. They are presented and discussed in the sub-sections that follow. Additional information on what is done in the criterion can be obtained by reading ``SRC/Result/predfinedCriteria.cpp'' source file.


X.D.1.1 ``HoneycombAirbusMoS'' criterion

This criterion is used to calculate honeycomb core margin of safety according to the so-called ``Airbus'' core failure criterion than combines the two components of out-of-plane stress tensor. The margin of safety is calculated according to the following expression:

$\displaystyle {\text{MoS}}=
\cfrac{1}{{\text{FoS}}\sqrt{\left(\cfrac{\tau_L}{\sigma_L}\right)^2
+\left(\cfrac{\tau_W}{\sigma_W}\right)^2}}-1\ ,
$

in which $ \tau_L$ and $ \tau_L$ are the honeycomb longitudinal and transversal shear components of Cauchy stress tensor and $ \sigma_L$ and $ \sigma_W$ the corresponding allowables.

The arguments of the criterion are given in Table X.D.1. The method returns an Array of 8 elements according to Table X.D.2:


.

Table X.D.1: Arguments of the ``HoneycombAirbusMoS'' predefined criterion
Pos. Name Type meaning can be modified?
1 dB DataBase DataBase (or derived) NO
2 fos Real factor of safety NO
3 allL Real shear allowable in L-direction NO
4 allW Real shear allowable in L-direction NO
5 stressRes Result Cauchy Stress Tensor NO


.

Table X.D.2: Outputs of the ``HoneycombAirbusMoS'' predefined criterion
Pos. Name Type meaning
1 ElemId Integer Critical Element ID
2 NodeId Integer Critical Node ID
3 LayerId Integer Critical Layer ID
4 SubLayerId Integer Critical Sub-Layer ID
5 sigLmax Real L OOP shear component of stress tensor at critical location
6 sigWmax Real W OOP shear component of stress tensor at critical location
7 mosMin Real Critical margin of safety
8 mosRes Result All the margins of safety that have been calculated


X.D.1.2 ``HoneycombAirbusSR'' criterion

This criterion is used to calculate honeycomb core margin of safety according to the so-called ``Airbus'' core failure criterion than combines the two components of out-of-plane stress tensor. The margin of safety is calculated according to the following expression:

$\displaystyle {\text{MoS}}=
\cfrac{1}{{\text{FoS}}\sqrt{\left(\cfrac{\tau_L}{\sigma_L}\right)^2
+\left(\cfrac{\tau_W}{\sigma_W}\right)^2}}-1\ ,
$

in which $ \tau_L$ and $ \tau_L$ are the honeycomb longitudinal and transversal shear components of Cauchy stress tensor and $ \sigma_L$ and $ \sigma_W$ the corresponding allowables. Actually, one calculates a strength ratio instead of a margin of safety. The relation between strength ratio, reserve factor and margin of safety is as follows:

$\displaystyle SR=\cfrac{1}{RF}=\cfrac{1}{MoS+1} .
$

This leads to the following expression for the strength ratio:

$\displaystyle {\text{SR}}=
{\text{FoS}}\sqrt{\left(\cfrac{\tau_L}{\sigma_L}\right)^2
+\left(\cfrac{\tau_W}{\sigma_W}\right)^2}\ ,
$

(The display of strength ratios instead of margins of safety allows usually a better identification of critical areas. This is true,for example, when results are saved in GMSH format.)

The arguments of the criterion are given in Table X.D.3. Compared to the ``HoneycombAirbusMoS'' discussed in section X.D.1.1, two new parameters are defined: ``strL'' and ``strW'' String arguments. These arguments, allow to specify the Cauchy Stress Tensor components that should be considered for $ \tau_L$ and $ \tau_W$ respectively. Possible values are ``XZ'', ``ZX'', ``YZ'', ``ZY'', ``XY'' and ``YX''. (This capability has been added to allow the post-processing of stress when the usual convention for honeycomb core material definition have not been followed.

The method returns an Array of 8 elements according to Table X.D.4:


.

Table X.D.3: Arguments of the ``HoneycombAirbusSR'' predefined criterion
Pos. Name Type meaning can be modified?
1 dB DataBase DataBase (or derived) NO
2 fos Real factor of safety NO
3 allL Real shear allowable in L-direction NO
4 allW Real shear allowable in L-direction NO
5 strL String shear allowable in L-direction NO
6 strW String shear allowable in L-direction NO
7 stressRes Result Cauchy Stress Tensor NO


.

Table X.D.4: Outputs of the ``HoneycombAirbusSR'' predefined criterion
Pos. Name Type meaning
1 ElemId Integer Critical Element ID
2 NodeId Integer Critical Node ID
3 LayerId Integer Critical Layer ID
4 SubLayerId Integer Critical Sub-Layer ID
5 sigLmax Real L OOP shear component of stress tensor at critical location
6 sigWmax Real W OOP shear component of stress tensor at critical location
7 srMax Real Critical strength ratio
8 srRes Result All the strength ratios that have been calculated


X.D.1.3 ``VonMisesMoS'' criterion

This criterion is used to calculate Von Mises margin of safety. The margin of safety is calculated according to the following expression:

$\displaystyle {\text{MoS}}=
\cfrac{\sigma_{all}}{{\text{FoS}}\sigma_{VM}}-1\ ,
$

$\displaystyle \sigma_{VM}=\sqrt{\cfrac{(\sigma_{xx}-\sigma_{yy})^2+(\sigma_{yy}...
...ma_{zz}-\sigma_{xx})^2}{2}
+3\sigma_{xy}^2+3\sigma_{xz}^2+3\sigma_{yz}^2}\ .
$

The arguments of the criterion are given in Table X.D.5. The method returns an Array of 7 elements according to Table X.D.6:


.

Table X.D.5: Arguments of the ``VonMisesMoS'' predefined criterion
Pos. Name Type meaning can be modified?
1 dB DataBase DataBase (or derived) NO
2 fos Real factor of safety NO
3 sigAll Real allowable stress NO
4 stressRes Result Cauchy Stress Tensor NO


.

Table X.D.6: Outputs of the ``VonMisesMoS'' predefined criterion
Pos. Name Type meaning
1 ElemId Integer Critical Element ID
2 NodeId Integer Critical Node ID
3 LayerId Integer Critical Layer ID
4 SubLayerId Integer Critical Sub-Layer ID
5 vmMax Real Von Mises equivalent stress tensor at critical location
6 mosMin Real Critical margin of safety
7 mosRes Result All the margins of safety that have been calculated


X.D.1.4 ``VonMisesSR'' criterion

This criterion is used to calculate Von Mises strength ratios. The relation between strength ratio, reserve factor and margin of safety is as follows:

$\displaystyle SR=\cfrac{1}{RF}=\cfrac{1}{MoS+1} .
$

This leads to the following expression for the strength ratio:

$\displaystyle {\text{SR}}=\cfrac{{\text{FoS}}\sigma_{VM}}{\sigma_{all}}\ ,
$

in which

$\displaystyle \sigma_{VM}=\sqrt{\cfrac{(\sigma_{xx}-\sigma_{yy})^2+(\sigma_{yy}...
...ma_{zz}-\sigma_{xx})^2}{2}
+3\sigma_{xy}^2+3\sigma_{xz}^2+3\sigma_{yz}^2}\ .
$

The arguments of the criterion are given in Table X.D.7. The method returns an Array of 7 elements according to Table X.D.8:


.

Table X.D.7: Arguments of the ``VonMisesSR'' predefined criterion
Pos. Name Type meaning can be modified?
1 dB DataBase DataBase (or derived) NO
2 fos Real factor of safety NO
3 sigAll Real allowable stress NO
4 stressRes Result Cauchy Stress Tensor NO


.

Table X.D.8: Outputs of the ``VonMisesSR'' predefined criterion
Pos. Name Type meaning
1 ElemId Integer Critical Element ID
2 NodeId Integer Critical Node ID
3 LayerId Integer Critical Layer ID
4 SubLayerId Integer Critical Sub-Layer ID
5 vmMax Real Von Mises equivalent stress tensor at critical location
6 srMax Real Critical strength ratio
7 srRes Result All the strength ratios that have been calculated


X.D.1.5 ``SGI_SR'' criterion

This criterion is used to calculate with a single call three connection failure criteria: sliding, gapping and insert. The calculation is done by calculating strength ratios. The relation between strength ratio, reserve factor and margin of safety is as follows:

$\displaystyle SR=\cfrac{1}{RF}=\cfrac{1}{MoS+1} .
$

In this case, three strength ratios are calculated: In these expressions, various scalar values related to the connection force and moment vectors are calculated:

$\displaystyle F_{\text{axial}}=\mbox{\boldmath$F$}\cdot\mbox{\boldmath$d$}\ ,
$

$\displaystyle F_{\text{shear}}=\sqrt{\mbox{\boldmath$F$}\cdot\mbox{\boldmath$F$}-F_{\text{axial}}^2}\ ,
$

$\displaystyle M_{\text{torsion}}=\mbox{\boldmath$M$}\cdot\mbox{\boldmath$d$}\ ,
$

$\displaystyle M_{\text{bending}}=\sqrt{\mbox{\boldmath$M$}\cdot\mbox{\boldmath$M$}-M_{\text{torsion}}^2}\ .
$

The arguments of the criterion are given in Table X.D.9:

The method returns an Array of 15 elements (5 elements for each criterion):


.

Table X.D.9: Arguments of the ``SGI_SR'' predefined criterion
Pos. Name Type meaning can be modified?
1 dB DataBase DataBase (or derived) NO
2 extractionMethod String Forces and Moments extraction method NO
3 fRes Result Vectorial Forces YES
4 mRes Result Vectorial Moments YES
5 csId String/Integer Reference coordinate system NO
6 vx Real X component of connection axis vector NO
7 vy Real Y component of connection axis vector NO
8 vz Real Z component of connection axis vector NO
9 FoSs Real Sliding criterion safety factor NO
10 FoSg Real Gapping criterion safety factor NO
11 FoSi Real Insert criterion safety factor NO
12 Pmin Real Bolt minimum pretension for sliding or gapping NO
13 Cf Real Friction coefficient for sliding criterion NO
14 Lg Real Prying length for gapping criterion NO
15 PSS Real Insert tensile allowable NO
16 QSS Real Insert shear allowable NO


.

Table X.D.10: Outputs of the ``SGI_SR'' predefined criterion
Pos. Name Type meaning
1 ssrMax Real/Boolean Maximum Strength Ratio (for sliding)
2 ENId Integer/Boolean Critical Element/Node ID (for sliding)
3 sfAxialMax Real/Boolean Axial force in critical connection (for sliding)
4 sfShearMax Real/Boolean Shear force in critical connection (for sliding)
5 ssrRes Result/Boolean All the strength ratios (for sliding)
6 gsrMax Real/Boolean Maximum Strength Ratio (for gapping)
7 ENId Integer/Boolean Critical Element/Node ID (for gapping)
8 gfAxialMax Real/Boolean Axial force in critical connection (for gapping)
9 gmBendingMax Real/Boolean Bending moment in critical connection (for gapping)
10 gsrRes Result/Boolean All the strength ratios (for gapping)
11 isrMax Real/Boolean Maximum Strength Ratio (for inserts)
12 ENId Integer/Boolean Critical Element/Node ID (for inserts)
13 ifAxialMax Real/Boolean Axial force in critical connection (for inserts)
14 ifShearMax Real/Boolean Shear force in critical connection (for inserts)
15 isrRes Result/Boolean All the strength ratios (for inserts)


X.D.2 User predefined criteria

The use that wishes to define his own criteria can do it by inserting code in ``SRC/Result/predfinedCriteria.cpp'' source file and re-compiling the library. Three areas are to be modified:


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Next: X.E FeResPost ruby extension Up: X. Appendices Previous: X.C Results characteristics   Contents   Index
FeResPost User Manual Version 4.4.0 (2017/08/27)