Cyclic Deformation Behavior and Fatigue Crack Propagation of Low Carbon Steel Prestrained in Tension

The tests were performed on low carbon steel plate. In the tension fatigue tests, two angle values (𝜙=0∘ and 𝜙=45∘, 𝜙 is the angle between the loading and the rolling direction) have been chosen. The influence of strain path change on the subsequent initial work softening rate and the saturation stress has been investigated. Dislocation microstructure was observed by transmission electron microscopy. It was found that the strain amount of preloading in tension has obviously affected the cyclic softening phenomenon and the initial cyclic softening rate. It was observed that the reloading axial stress for 𝜙=45∘ case increased more than that of 𝜙=0∘ case, due to the anisotropism of Q235. In the fatigue crack propagation tests, the experimental results show that with increasing the pretension deformation degree, the fatigue crack growth rate increases, especially at the near threshold section.