, Papuga PC method
The formula of this method was defined in [Ppg05]:
,
where the material parameters ac and bc are set in dependency on a material type:
Note that the first definition in [Ppg05] (marked as PC criterion) used only the first part of material parameters, which is suitable above all for brittle materials. Its use for other materials led to conservative prediction. The final formula with both definitions of ac and bc was derived only later and was published in [PR07] under this changed name.
The limiting value of 
and the values of ac and bc parameters was set by a double maximization of the left hand side of the formula over all planes with expectation of two simple load cases - pure fully reversed axial loading and fully reversed torsion. See [PR07] for more details. The most comprehensive overview of the Papuga PCr criterion quality can be achieved by comparison of results in the FatLim Database. This method gives the best results from all the methods there.
Nomenclature:
|
Mark |
Unit |
PragTic variable |
Meaning |
|
|
[MPa] |
shear stress amplitude on an examined plane |
|
|
|
[MPa] |
TENS-1, BEND-1 |
fatigue limit in fully reversed axial loading |
|
|
[MPa] |
TENS0, BEND0 |
fatigue limit in repeated axial loading |
|
|
[-] |
ratio of fatigue limits ( |
|
|
|
[MPa] |
amplitude of normal stress on the plane examined |
|
|
|
[MPa] |
mean (average value of maximum and minimum values) normal stress on the plane examined |
|
|
|
[MPa] |
TORS-1 |
fatigue limit in fully reversed torsion |
Methods & Options & Variables of Calculation – Edit
Decomposition
Elasto-plasticity
- No – currently no option implemented
Solution option
- Searched planes <0~BS algorithm, 1~globe analogy, 2~random>
- Number of scanned planes
- Optimize <1~yes, 0~no>
- Only every x-th data-point taken from load history
- Evaluate envelope curve only <1~yes, 0~no>
Solution variable
- Minimum damage – this option is not active for this high-cycle fatigue method
Material parameters
|
E |
[MPa] |
tensile modulus |
|
NU |
[-] |
Poisson’s ratio |
|
TENS0 |
[MPa] |
fatigue limit in repeated tension (or plane bending) |
|
TENS-1 |
[MPa] |
fatigue limit in fully reversed push-pull (or plane bending) |
|
TORS-1 |
[MPa] |
fatigue limit in fully reversed torsion |
Result detail variables
Damage fatigue index is computed, not the damage as a reciprocal value to number of cycles or repetitions
FDD1 NCX x-coordinate of the normal line vector of the critical plane
FDD2 NCY y-coordinate of the normal line vector of the critical plane
FDD3 NCZ z-coordinate of the normal line vector of the critical plane
FDD4 ALFA angle between the normal lines to the critical plane and to the free surface
© PragTic, 2007
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