Practical Challenges Testing Coupons with Residual Stresses from Cold Expanded Holes / Len Reid, Joy Ransom
- Conference Author:
- Seventh International ASTM/ESIS Symposium on Fatigue and Fracture Mechanics (36th ASTM National Symposium on Fatigue and Fracture Mechanics) (7th : 2007 : Tampa, FL)
- Physical Description:
- 1 online resource (17 pages) : illustrations, figures, tables
- Additional Creators:
- Reid, Len
American Society for Testing and Materials
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- Cold expanding holes in metal components is widely used throughout the aerospace industry to extend fatigue life and damage tolerance. The beneficial residual stresses induced by hole cold expansion arrest or significantly retard the growth of fatigue cracks, and in doing so make fatigue or crack growth life prediction more difficult. Under low stress level/high cycle fatigue testing, residual compressive stresses have been shown to increase the fatigue strength of the material leading to an ¿̐ưinfinite life¿̐ư and consequent ¿̐ưrun-out¿̐ư of test coupons at the test hole or changing the location of failure away from the test hole. While advantageous to aircraft operators, it makes statistical life prediction difficult because the incomplete data have to be censored, leading to a knock-down of the beneficial life attained. Conversely, increasing stress levels toward material yield stress; life improvement factors are more definitive and tend toward unity. This paper reviews the derivation of residual stresses induced by hole cold expansion and discusses benefits to the structure/test coupon and how the residual stress field impacts fatigue life and damage tolerance/durability under cyclic load conditions. Challenges observed when testing coupons that have been processed using hole cold expansion including modification of the crack behavior and its effect on material microstructure, relocation of crack initiation, dynamics of the redistribution of stress and the crack growth mechanism as well as scatter of results, are also discussed with a focus on aluminum materials.
- Dates of Publication and/or Sequential Designation:
- Volume 2009, Issue 1508 (January 2009)
- 9780803169999 (e-ISBN)
- Digital File Characteristics:
- text file PDF
- Bibliography Note:
- Includes bibliographical references 21.
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- Also available online via the World Wide Web. Tables of contents and abstracts freely available; full-text articles available by subscription.
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- Electronic reproduction. W. Conshohocken, Pa. : ASTM International, 2009. Mode of access: World Wide Web. System requirements: Web browser. Access may be restricted to users at subscribing institutions.
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