Effect of Surface Roughness and Notch on Tensile Properties of TC4 Titanium Alloy Based on Three Dimensional Digital Image Correlation Method

The effect of surface roughness (0.745, 1.055, 1.395 μm) and notch radius (0, 0.6, 1.2 mm) on the tensile properties of TC4 titanium alloy at room temperature and the displacement field and strain field in the compaction stage was studied based on three dimensional digital image correlation method. The results show that with the increase of surface roughness, the percentage elongation after fracture of the unnotched sample first decreased and then increased, and the tensile strength increased; the percentage elongation after fracture of the notched sample increased slightly, and the tensile strength increased. With the increase of notch radius, the percentage elongation after fracture decreased significantly and then increased slightly, and the tensile strength increased. With the increase of surface roughness and notch radius, the percentage elongation after fracture reduced, showed a reverse interaction; the tensile strength increased, showed a positive interaction. As for unnotched sample, the deformation in x direction was uneven, the axial elongation in y direction was uniform, and the strain in x direction was high in the middle, and in y direction was concentrated in the necking zone. The contours of the displacement field of notched sample with 1.2 mm notch radius were curved and densely distributed at the gap, and the strain field showed concentric circles. The contours of the displacement field of notched sample with 0.6 mm notch radius were converged diagonally toward the gap, but the distribution was relatively open comparing with that of large-notched sample, and the strain field was irregularly distributed.