Comparison of Fatigue Enhancing Fastener Systems in Aluminum-Lithium Materials
Abstract
Aluminum alloys represent 70 to 80 percent of an aircraft's structural weight. Improvements to structural materials have been concentrated in the areas of increased stiffness and reduction in density. Aluminum-Lithium alloys offer reduction in density of 8 to 10 percent while matching strength and fracture toughness values of traditionally used alloys. These materials have also shown equivalent or superior fatigue performance and a general resistance to corrosion. Although much work has been performed evaluating tensile properties, crack propagation rates, and fracture toughness, very little has been published looking at the material in a fastened state. One of two prime concerns is stress corrosion cracking caused by an imposed stress from radial interference ( expansion) in the short transverse grain direction. The second area, fatigue performance, is typically characterized using ASTM type smooth or notched fatigue coupons. These investigations while addressing notched conditions do not take into account fatigue enhancement processes or stress distributions resulting from fastener design. The purpose of this effort was to generate comparative data on the performance of selected fatigue rated fastener systems in Al-Li and a base line alloy 2024.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1991
- Accession Number
- ADA241250
Entities
People
- Neal R. Ontko
Organizations
- Wright Laboratory