Abstract: The local mechanical properties of TC4 titanium alloy sheet are tested for the specimens with a U-shaped notch on the back of the metallic material by a small punch test device. The commercial software ABAQUS is used to establish the finite element model of the small punch specimen with U-shaped notch. The local mechanical property parameters of TC4 titanium alloy under the three dimensional state of stress with tensile stress are obtained by combining finite element method. Meanwhile, the variation rule of Mises stress and void volume fraction (VVF) are analyzed. The test results show that the equivalent stress on the notch tip of the specimen increases with the constant pressure of the punch, reaching the peak stress of 1 150 MPa, and the VVF at the notch tip also increases to the critical VVF, finally resulting in the fracture failure. On the upper surface of the specimen, the VVF is lower. With the further pressing of the punch, the equivalent stress on the notch tip decreases gradually, while VVF show higher on the notch tip region and the edge region of the punch. When the peak load is reached, the stress triaxiality along path dropped from 2.28 to -0.64. It can be seen from the results that the void volume fraction at the notch root area is higher. And the distribution trend of stress triaxiality and void volume fraction of the path did not show significant change.

Key words: TC4 titanium alloy, small punch test, local mechanical heterogeneity, U-shaped notch, finite element method