Local elastic-plastic strain analysis
In: Local methods
Except for a local elastic stress analysis, this is the other common way how to examine low-cycle fatigue. There is an expectation hidden behind, that the local plastified volume of material on some examined industrial component can be very well replaced by a specimen with a cross-section size related to this volume. Such an expectation allows then the material parameters of Basquin-Manson-Coffin (BMC) curve (relating the number of cycles to initiation of some crack and amplitude of strain) obtained from common fatigue specimens to be used even in this finite volume.
The uniaxial methods of computation are wholly based on this assumption. As regards the multiaxial methods, these very often go even beyond this point and expect, that the same material parameters of BMC curve should be valid even on the critical plane, whatsoever it is oriented.
The Manson-Coffin curve corresponds to the plastic part of strain. The local load data, which are confronted with the BMC curve, should thus conform to real elastic-plastic strains (or stresses). Their computation can be prepared in the FE-solver (non-linear transient analysis), or they can be prepared by post-processing of results of a linear FE-analysis (here Glinka and Neuber methods useful for uniaxial computation only).
There are following methods implemented in the present version of PragTic:
- Smith, Watson & Topper method
- Findley method as defined by Socie
All the methods that check the level of loading only towards the fatigue limit are sorted to local elastic stress methods.
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