THE EFFECTS OF AN AQUEOUS ENVIRONMENT ON THE FATIGUE CRACK PROPAGATION CHARACTERISTICS OF TITANIUM ALLOYS.
Abstract
Fatigue crack propagation was studied in Ti-6Al-4V, Ti-7Al-2Cb-1Ta, Ti-6Al-6V-2Sn-1Cu-0.5Fe, Ti-6Al-3V-1Mo, and Ti-7Al-2.5Mo alloys. These materials possess yield strengths in excess of 100 ksi, combined with favorable levels of fracture toughness, and they are currently under evaluation for application in large welded structures. Where an application involves repetitive loading, a knowledge of fatigue crack propagation characteristics is required for failure-safe design against fracture. Fabrication and non-destructive testing procedures cannot guarantee that cracklike defects, which can grow to a critical size, will not be present in plate-thickness sections containing welded joints. In addition, the role of an aggressive environment, such as salt water, in this failure mechanism is of the utmost importance. Fatigue crack propagation data were taken in both ambient room air and 3.5% salt-water environments. Surface-notched plate bend specimens were cycled in full-reverse (tension-to-compression) sinusoidal loading. The fatigue crack was observed optically, and the crack growth rate was described as an empirical power-law function of the total (elastic-plus-plastic) strain range. Fatigue crack growth rate relationships were first developed in an air environment and then employed as baselines for establishing the effect of the salt-water environment. Comparisons were made among the fatigue crack propagation characteristics of the several titanium alloys and among a broad spectrum of high-strength structural alloys, both ferrous and nonferrous, previously studied. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 18, 1967
- Accession Number
- AD0664208
Entities
People
- E. A. Lange
- Thomas W. Crooker
Organizations
- United States Naval Research Laboratory