The study on the influences of residual stresses on fatigue crack propagation in titanium alloy specimens

Fatigue crack growth is a harmful physical phenomenon in engineering materials that can be intensified by the presence of tensile residual stresses. In the present study, the effect of tensile residual stresses on the fatigue crack growth in single-edge notched bending specimens of Ti-6Al-4V is studied. Mechanical residual stresses were created by applying a 4-point bending process. The residual stresses were evaluated utilizing the hole drilling approach under the ASTM E-837 standard. Fatigue crack propagation was measured by experimental test in specimens with and without initial residual stresses. A finite element analysis was conducted using commercial finite element software to study the plastic zone at the crack tip and fracture mechanic parameters. It was observed that the residual stress field is redistributed after each step of crack propagation. The tensile residual stress in front of the crack tip decreased from near yield strength to approximately 30% of yield strength. The tensile residual stresses near the yield strength in Ti-6Al-4V increased the fatigue crack propagation rate by approximately 50%.