Effects of stress amplitude ratio on short fatigue crack behaviour under
Fatigue tests with solid round bar specimens were carried out to
investigate the effect of stress amplitude ratio on the axial-torsion
fatigue failure of low carbon steel under a certain equivalent stress.
The processing of surface short cracks initiation and propagation were
recorded by replica technology. It is observed that all the crack
propagation curves based on the criterion of dominant effective short
fatigue crack (DESFC) clearly exhibits a similar oscillations tendency
caused by the microstructure. In addition, the fatigue life, fracture
angle and crack source vary with the value of stress amplitude ratio.
Hence, a short crack model incorporating the effects of stress amplitude
ratio was used to simulate the short crack growth rate, and the model
can directly estimate the biaxial short cracks growth rate under
different stress amplitude ratios according to the experimental data of
uniaxial short cracks. A good agreement is achieved between simulation
results and experimental data.