Seminar Series - 2002-2003

Three-Dimensional Effects on Fatigue Crack Closure in the Small-Scale Yielding Regime

Robert H. Dodds, Jr.
M.T. Geoffrey Yeh Chair
Department of Civil & Environmental Engineering
University of Illinois, Urbana, IL 61801, U.S.A.

Date:  Friday, March 7, 2003
Time:  3:30 p.m.
Place:  W183 Nebraska Hall


Plasticity induced closure often influences strongly the behavior of fatigue cracks at engineering scales in metallic materials. Current predictive models generally adopt the effective stress-intensity factor ( ) in a Paris law type relationship to quantify crack growth rates. This work describes a 3-D finite element study of mode I fatigue crack growth in the small-scale yielding (SSY) regime under a constant amplitude cyclic loading with zero T-stress and a ratio . Dimensional analysis suggests, and the computational results confirm, that the normalized remote opening load value, , at each location along the crack front remains unchanged when the peak load ( ), thickness (B) and material flow stress ( ) all vary to maintain a fixed value of . Through parametric computations at various levels, the results illustrate the effects of normalized peak loads on the through-thickness, opening-closing behavior and the effects of , where E denotes material elastic modulus. This new scaling relationship and the computational results provide the needed framework to rationalize and extend existing simplified models of the crack closure process.


Back to 2002-2003 Seminars List