Plastic deformation — its role in fatigue crack propagation |
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Authors: | P K Mazumdar S Jeelani |
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Affiliation: | (1) School of Engineering and Architecture, Tuskegee University, 36088 Tuskegee, Alabama, USA |
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Abstract: | Recognizing the fact that the effective driving force (ΔK
eff) determines the fatigue crack propagation (FCP) rate and that the shear strain, which is considered to develop due to an
occurrence of crack closure, primarily contributes to the plastic deformation, an effort is made here to elucidate the role
of plastic deformation in FCP by developing a correlation between the ΔK
eff and the applied driving force (ΔK) with shear strain as variable. The effect of the degree of plastic deformation (i.e. shear strain level) on the FCP rates
at higher values of ΔK, where ΔK
eff approaches ΔK, approaching the Paris regime, appears minimal. On the other hand, the disparity between ΔK
eff and ΔK, which apparently increases with shear strain level, persists at lower values of ΔK. This suggests a strong influence of the degree of localized deformation on the FCP rates in the near threshold level. Hence,
an improvement of FCP rates in the near threshold level should follow an effort that promotes the plastic deformation near
the crack tip to a greater degree. This approach could, therefore, form the basis to explain the effect of the grain size,
microstructure, environment,R-ratio and crack size on the near-threshold FCP rates. |
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Keywords: | |
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