Volume 8, Issue 6 (November 1980)
A Wide Range Stress Intensity Factor Expression for the C-Shaped Specimen
A new expression has been developed to calculate the stress intensity factor K for the C-shaped specimen over a wider range of specimen parameters, namely, crack depth to width ratio a/W, load eccentricity X/W, and radii ratio r1/r2, than had previously been available. The rationale for the expression was to use known K solutions for short and deep cracks to develop a nondimensional form of K. This nondimensional form of K approaches the correct limiting values as a/W goes to both zero and one. Numerical K results from previous work were then nondimensionalized to this form and the dependence of K on a/W was determined by multivariable linear regression. The final expression agrees with the numerical K solutions within ±1.0% for 0.45 ≤ a/W ≤ 0.55 for all r1/r2 and X/W of either 0 or 0.5; within ±1.5% for 0.2 ≤ a/W ≤ 1 for all r1/r2 and X/W equal to 0 or 0.5; and within ±3% for 0.2 ≤ a/W ≤ 1 for all r1/r2 and 0 ≤ X/W ≤ 1. The accuracy of this expression will allow expanded use of the C-shaped specimen for crack growth resistance curve determination and fatigue crack growth rate testing.