Testing of 7050-T7451 Aluminum Strain-Life Coupons for a Probabilistic Strain-Life Curve
Abstract
Fleet life tracking is an integral part of NAVAIR s approach to ensuring the airworthiness and operational readiness of U.S. Naval Aviation assets. Historically, life limits for Naval airframe components have been derived by deterministic analyses of stress-life or strain-life fatigue models. To improve fatigue life prediction capabilities for airframe structures, NAVAIR has begun development of a Probabilistic Strain-Life model. As a first step in the development of the Probabilistic Strain-Life method, an extensive testing program was initiated to characterize the scatter in standard ASTM strain-life test coupons for 7050-T7451 aircraft aluminum. Two different coupon geometries are described in the relevant standards: an axially loaded, uniform gage section test coupon and an axially loaded, hourglass gage section coupon. Both coupon types were investigated to determine the differences in fatigue life characteristics between the two. Two different test laboratories were also utilized for testing, to obtain a measure of interlaboratory variation in fatigue results. This investigation shows that the choice of coupon geometry, test procedures, and the test laboratory all have an effect on the statistics of the strain-life test results. From these tests, a probabilistic strain-life curve can be developed to characterize the scatter in material fatigue resistance.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 02, 2006
- Accession Number
- ADA457449
Entities
People
- David T. Rusk
- Paul C. Hoffman
- Robert E. Taylor
Organizations
- Naval Air Warfare Center