McDiarmid method v.72

This is the first developed form of the McDiarmid method. Its fatigue parameter was especially complicated:

This older version is implemented in the PragTic program in the MD as well as MSSR variant. The MCCM concept is not used for detection of the shear stress amplitude, but the direction, in which the maximum of the left hand side of the criterion is found, is decisive – i.e. the LPM concept is used instead.

The method cannot be recommended for any particular use. Its results in [Ppg05] as well as in [Web99] are very bad, therefore it is not covered in the FatLim Database.

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]		amplitude of normal stress on the plane examined
	[MPa]		mean normal stress (average value of maximum and minimum values) on the plane examined
	[MPa]	SIG_ULT	tensile strength
	[MPa]	TORS-1	fatigue limit in fully reversed torsion

Methods & Options & Variables of Calculation – Edit

Decomposition

- Whole load path

Elasto-plasticity

- No – currently no option implemented

Solution option

- CP criterion <0~MD, 1~MSSR, 2~MMES>

- 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
SIG_ULT	[MPa]	tensile strength
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 LCX x-coordinate of the critical direction on the critical plane

FDD5 LCY y-coordinate of the critical direction on the critical plane

FDD6 LCZ z-coordinate of the critical direction on the critical plane

FDD7 DELTA_C shear stress range

FDD8 M_N mean normal stress

FDD9 DELTA_N normal stress range

FDD10 ALFA angle between the normal lines to the critical plane and to the free surface

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