Comparison of fatigue limit strength of Ti-6Al-4V in tension and torsion after real and simulated foreign object damage

Among the major findings, stress relieved specimens were generally found to have higher fatigue strengths than those not relieved, indicating that tensile residual stress fields were produced near the ultimate failure locations during the indenting process. Ballistic impact was found to be more damaging than either quasi-static or pendulum impacts. Finally, stress relieved specimens in several cases showed little or no reduction in fatigue strength, even when local values of kt were substantial, indicating some type of strengthening mechanism developed during indentation.