Micro-Slotting Residual Stress Measurement Technique for Understanding Fatigue Performance of Open-Hole Ti-6Al-4V Samples


Micro-slotting, a microscale relaxation residual stress measurement technique, has been shown in recent years to be a reliable method for measuring local residual stresses in metallic materials. This study demonstrates the unique application of the micro-slotting residual stress measurement technique for measuring near-edge tangential residual stresses around cold-expanded holes in Ti-6Al-4V plates. Knowledge of the near-edge elastic strains induced by the hole processing, in combination with plastic strain information obtained using electron backscatter diffraction, allowed for interpretation of fatigue life differences and crack growth behavior between the as-drilled and cold-expanded conditions. The similar crack initiation lives of the as-drilled and cold-expanded open-hole coupons were attributed to the similar elastic and plastic strains present at the hole edges. The subsequent crack growth resistance observed for the cold-expanded holes was a result of the large compressive residual stress region induced by cold expansion.


Materials Science and Engineering


This work is a collaborative research effort of Boeing and Missouri S&T and was made possible by Boeing€™s presence on the Missouri S&T campus in Rolla, MO. This project was supported by the Air Force Research Laboratory (AFRL)-managed Metals Affordability Initiative (MAI).

Keywords and Phrases

Cold Expansion; Drilling; Fastener Holes; Fatigue; Micro-Slotting; Residual Stress; Ti-6Al-4V

International Standard Serial Number (ISSN)

1059-9495; 1544-1024

Document Type

Article - Journal

Document Version


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Publication Date

01 Sep 2019