On the use of the Fictitious Material Concept in estimating the ultimate load of keyhole notched AA6061‐T6 specimens under large tension‐torsion deformations

Abstract

This paper examines the fracture of AA6061‐T6 specimens with ductile behavior having notches with keyhole geometry under combined loading of tension/torsion. The investigation is performed by theoretical and experimental methods. New fracture tests are performed using a loading fixture on the samples made of AA6061‐T6 weakened by keyhole notches with different notch tip radii. For theoretically estimating the onset of fracture in the tested notched specimens, a concept called “Fictitious Material Concept (FMC)” is used to equate the ductile material with a fictitious brittle material. Therefore, use of this concept allows use of the linear elastic brittle fracture criteria for ductile materials. The brittle fracture criteria utilized are the “mean stress (MS)” and “maximum tangential stress (MTS)” criteria. The small difference between the theoretical and experimental results confirms that use of the combination of FMC with the two criteria is successful in predicting failure of the keyhole notched AA6061‐T6 samples.