Dang Van is a fatigue limit criterion used to predict the endurance limit under complex, multiaxial loading situations. The output from the analysis is expressed as a safety factor and not a fatigue life. It uses specific material parameters calculated from tensile and torsion tests. Manufacturing effects can also be accounted for by using equivalent plastic strain in the unloaded component.
Dang Van Safety Factor calculation
The Dang Van method is designed to provide a safety factor calculation for multiaxially loaded components in the endurance regime (large number of cycles to failure). The theoretical basis can be summarized as follows:
- Fatigue crack initiation normally occurs due to repeated plasticity on shear planes in individual grains.
- The most important factor as to whether a crack will propagate past the first grain and go on to cause fatigue failure is therefore the microscopic shear stress in critical grains.
- The ability of a shear crack to propagate is modified by the hydrostatic stress (which can increase damage by opening existing cracks).
- The state of stress in a grain where repeated plasticity is occurring will be affected by a process of shakedown.