Fatigue calculation methods
There are several ways to classify the fatigue calculation methods. The decisive point can be e.g.:
* load effect localization
- nominal methods – the local state of loading is estimated from nominal stress and notch factor; the method is unsuitable for automated computation, because the notch factor is very hard to be correctly set from the FE-data. An interaction with the user's own computations is required.
- local methods – local state of loading is assessed directly from FE-calculation results
* physical meaning of the damage parameter
- stress based methods
- strain based methods
- energy based methods
* constitution of damage parameter
- uniaxial analysis – the damage parameter is constituted from some equivalent value of only load amplitude or range
- multiaxial analysis – the damage parameter consists of more than one load effects (e.g. it is a composition of normal and shear stresses acting on an examined plane)
* expectation, if the load states on different planes can interact
- critical plane methods – final damage in the point examined is related to the damage found on some specific plane. Among all the planes examined, the maximum of the damage parameter is decisive.
- integral methods – final damage is related to an integral of the damage parameter. Among all the planes examined, the average value of the damage parameter is decisive.
* question, how the critical plane is set
- MSSR method (Maximum Shear Stress / Strain Range)– the maximum of the shear stress or strain range is looked for.
- MD method (Maximum Damage) – planes are scanned so that the maximum damage was found.
- CPD method (Critical Plane Deviation) – the critical plane is deviated by some specified angle from some given plane.
* expected lifetime
- high-cycle method – stress based methods used above all for mid- and high-cycle fatigue.
- low-cycle method – methods leading to number of cycles till the crack appears.
© PragTic, 2007
This help file has been generated by the freeware version of HelpNDoc