Study on mixed-mode fracture behavior of TC4 titanium alloy

Mixed mode fracture behaviors of TC4 titanium alloy are studied by finite element method, testing and theo-retical analysis systematically. Results show that there exists II-III coupling effect ahead of crack tip for mixed mode crack, based on which three-dimensional stress intensity factors are defined and calculated; The crack under I-II mixed mode loading exhibits a planar propagation state, the deflection angle increases with mode II component increasing; I-II mixed mode fracture of TC4 shows the characterization of brittle fracture mechanism, and brittle fracture criteria are in agreement with test results with some conservative. While the crack under I-III mixed mode loading exhibits a spatial propagation state, the deflection angle firstly increases then decreases with mode III component increasing; It is due to that the fracture mechanism is from brittle to brittle-ductile mixed fracture mode, as mode III component increases. The brittle criterion has a good prediction on I-III mixed mode brittle fracture behavior, with mode III component lower enough. The conclusions in this paper are of great significance to the mixed mode fracture evaluation of TC4 titanium alloys.