Effects of Stress Ratio and Banded Microstructure on Fatigue Crack Growth Behavior of HRB400 Steel Bar

Abstract

This paper investigates the effects of stress ratio and microstructure on the fatigue crack growth (FCG) behavior of HRB4 steel bars widely used in concrete bridges. A constant stress–controlled FCG test with different stress ratios is performed on compact tension specimens. Test specimens are machined from rebar in two directions, i.e., cracks propagate in the radial and axial directions of the steel bar. The FCG rate versus stress intensity factor range under different stress ratios and different crack orientations are obtained. The morphology of the fracture surface and the FCG path are examined by scanning electron microscope and optical microscopy. Following this, the FCG curves, fracture characteristics, and FCG paths are compared. The experimental results show that the radial and axial crack predominantly present the transgranular and intergranular fracture mode, respectively. The material presents a higher resistance to FCG in radial orientation than that in axial direction.