Accession Number:

ADA409601

Title:

Corrosion-Induced Fatigue Measurements on 2024 and 7075 Aluminum Using Photon-Induced Positron Annihilation (PIPA)

Descriptive Note:

Phase 1 Final rept. 1 Apr-1 Nov 2002

Corporate Author:

POSITRON SYSTEMS INC BOISE ID

Personal Author(s):

Report Date:

2002-12-01

Pagination or Media Count:

43.0

Abstract:

Corrosion-related fatigue damage in aerospace platforms is a significant problem for military aircraft, which, in many cases, are over 20 years old and have projected lifetimes up to 40 years. Specific problems include multilayer corrosion damage in aircraft lap slices that result in cracking at fastener holes and rapid crack growth. A new nondestructive examination technique, photon-induced positron annihilation PIPA, has demonstrated the capability to detect and quantify various types of atomic lattice structure damage, including fatigue, creep, and other mechanisms. The purpose of this project is to evaluate the PIPA technology to assess the effects of relatively low levels of corrosion on early fatigue damage, and to provide an approach for incorporating data of this type into developing confidence levels for CBM reliability models. Specimens of 2024-T3 and 7075-T6 aluminum were subjected to salt spray corrosion for periods up to 96 hours and then subjected to fatigue testing to determine the effects of the corrosion on the fatigue response for these types of aluminum, which have different corrosion characteristics. PIPA results from this study indicate that corrosion-related fatigue damage is detectable at relatively low fatigue levels 10 of failure and that damage to the inside surface of the aluminum specimens is also detectable.

Subject Categories:

  • Metallurgy and Metallography
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE