Three-Dimensional Characteristic Analysis of Mixed Mode Crack Based on a Mixed Mode Triaxial Stress Constraint Tz

A mixed-mode triaxial stress constraint T-z is introduced. The three-dimensional mixed-mode fracture theories based on linear elastic fracture mechanics and T-z am established. The plastic zone and stress triaxiality R-sigma under three-dimensional mixed mode fields are studied. It is shown that the plastic zone is a function of loading angle Phi, angular direction theta and T-z The plastic zone size decreases with increasing T-z but the direction of its minimum does not change with T-z. The stress triaxiality R-sigma increases with increasing T-z. Under the same loading mixity the direction of R-sigma max changes with T-z. Under given T-z, the value R-sigma max does not change when T-z=0, and decreases with the loading mixity except pure mode II loading condition.