THE IMPACT OF HOLE MAKING PROCESSES ON THE FATIGUE LIFE VARIANCE OF THE MACHINED COMPONENTS

ABSTRACT

It is well known that a large variance can be associated with the fatigue life of nominally identical components. It may be intuitively true for some experts in surface integrity that different processes may produce different variances of fatigue life. However, little is known in the literature about the potential level of impact of different manufacturing processes on the variation of fatigue life, thus this study. Holes have been made on Ti 6Al-4V samples and finished by drilling and internal grinding using handbook recommended conditions. Tension fatigue tests of constant amplitude under load control have been conducted subsequently. Statistical analysis of the results showed a very significant impact of the hole making processes on the variance of the fatigue life. This finding proves the importance and urgency for further studying the issue in a scientific way.

Keywords:

• Surface Integrity
• Fatigue Life Variance
• Hole Making
• Drilling
• Internal Grinding

ACKNOWLEDGMENT

This project has been supported by NSF award 9713748-DMI cost-shared by USAF ManTech program, and by NSF award 990169-DMI. The fatigue tests have been conducted in Fatigue and Fracture Lab of the School of Aeronautics and Astronautics at Purdue. Assistance of and discussions with Professor Grandt and Mr. Golden are highly appreciated.

Notes

*SR = (Average fatigue life)/(Fatigue life with the corresponding reliability).