Stress Analysis of the Double‐Torsion Specimen

The double‐torsion specimen was analyzed with a 3‐dimensional elastic finite‐element stress analysis. A crack‐front configuration where the stress intensity is constant over ≅ 1/2 of the specimen thickness was determined. That value of the stress intensity is nearly equal to the “strength‐of‐materials” value. The stress intensity is nearly constant for crack lengths > 0.55 × specimen width ( W ) and ligament lengths > 0.65W.