The Fatigue Module, new in version 4.3a, is intended for fatigue analysis of structures. The term fatigue is used to describe the phenomenon where a component fails after repeated loadings and unloadings, even though the magnitude of each individual load is smaller than the ultimate stress of the material. The Fatigue Module is an add-on module to the Structural Mechanics Module.
Using the Fatigue interface, you can compute the risk of fatigue cracks occurring in a structure where the stress and strain state during a single load cycle has been computed. One of the following physics interfaces—Solid Mechanics, Thermal Stress, Joule Heating and Thermal Expansion, or Piezoelectric Devices—is used along with the Fatigue interface to accomplish this analysis.
Two basic types of evaluation can be performed:
- Stress-based analysis for high-cycle fatigue (HCF). The result is a usage factor, which tells you how close to the fatigue limit the load cycle is.
- Strain-based analysis for low-cycle fatigue (LCF). The result is a lifetime prediction in terms of the number of cycles to fatigue.
When using the Fatigue Module in combination with the Structural Mechanics Module for fatigue analysis, the procedure begins with a stress analysis, followed by an evaluation against fatigue criteria as a separate results and analysis step. All load cycles are assumed to be equal and it is possible to handle non-proportional loading. Non-proportional loading occurs when the directions of the principal stresses and strains are not constant during the load cycle.