Influence of Three-Dimensional Effects on the Stress Intensity Factors of Compact Tension Specimens
SourceThe stress freezing technique of photoelasticity was utilized to study the stress intensity variation between full thickness and center slices of compact tension specimens for various crack lengths. Specimen geometries covered an a/w range of 0.3 to 0.7 for values of w/B of 2 and 3.5.
Normalized stress intensity factor results for geometries within ASTM Test for Plane-Strain Fracture Toughness of Metallic Materials (E 399-72) specifications (that is, w/B = 2.0, a/w = 0.50) agreed with the ASTM solution to within experimental error. However, for a/w values outside the ASTM range (0.45 to 0.55), experimental results were measurably higher than the ASTM results for w/B = 2.0 and averaged 13 percent higher for all a/w studied at w/B = 3.5. The center slice SIF was found to be 5 to 10 percent higher than the through the thickness average on all tests.