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|Title: ||EXTRAPOLATION ALGORITHMS AND OVERLOAD EFFECTS IN HIGH CYCLE FATIGUE|
|Authors: ||Krishnan, Venkat Ramanan|
|Keywords: ||cohesive finite elements, high cycle fatigue crack growth, extrapolation scheme, overload effect|
|Issue Date: ||27-Mar-2008|
|Abstract: ||The cohesive fatigue model of A. Ural and K. D. Papoulia (Modeling of fatigue crack growth with a damage-based cohesive zone model, European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS
2004)) is modified and implemented within the finite element code Abaqus.
The model follows a bi-linear damage-dependent
traction-displacement relation coupled with a damage evolution
equation characterized by three material parameters corresponding
to damage accumulation, crack closure and stress threshold.
High cycle fatigue is computationally intractable with
cycle-by-cycle calculations. To make high cycle fatigue
simulations possible, different extrapolation schemes have been
proposed in the literature, with varying degrees of complexity, to
account for the nonlinearity of the equations. Based on simple
observations, two such schemes are proposed and tested in this
work. A logarithmic scheme is found easy to implement, as well as
capable of extrapolating the accumulation of material damage due
non-constant amplitude fatigue loads. Finite element results are
compared with high cycle fatigue test results for an aluminum
alloy. Close matches between the test data and finite element
simulations are obtained for different loading conditions.
The cohesive model is also used to capture the effect of a single
peak overload, viz. crack retardation, in a ductile 316L steel
alloy under plane stress conditions. The results indicate that a
higher peak load results in higher fatigue crack retardation. The
results also agree with experiments that suggest that strain
hardening, not crack closure, is the leading mechanism for the
|Appears in Collections:||Cornell Theses and Dissertations|
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