Study of the Influence of Metallurgical Factors on Fatigue and Fracture of Aerospace Structural Materials
Abstract
This report summarizes the results of a study involving: (1) experimental characterization and analytical modeling of fatigue crack tip micromechanics in aerospace structural (aluminum and titanium) alloys; and (2) identifying and modeling key factors controlling subcritical crack growth and unstable fracture in single crystal nickel-base superalloys. The first section summarizes studies in which mesured crack tip parameters and microstructural characterization are incorporated into a recently developed crack tip geometric model which interrelat4es microstructure with fatigue crack growth. The model is used with 7075-T651 Al, 7091 P/M Al, and Ti-6Al-4V to predict crack growth increments (striation spacings), which are then compared with experimental measurements for the Al alloys. Additional crack tip characterization was performed on an experimental high temperature aluminum alloy (HTAL). By using a recently developed SEM high temperature cycling stage, crack tip yielding and extension was characterized at 315 C, which showed that the interfaces of certain microstuctural elements unique to the HTAL alloy were detrimental to its resistance to elevated temperature fatigue crack growth. The second section describes results of ambient temperature crack growth tests of single crystal Mar-M200. Tests were carried out as functions of stress intensity range, normal stress to shear stress ratio, and crystallographic orientation, and their efect on mode of cracking and crack growth characteristics was established. Additional keywords: Crack tip plasticity; Crack growth modeling; Crystallographic orientation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1985
- Accession Number
- ADA153913
Entities
People
- David L. Davidson
- Gerald R. Leverant
- James Lankford
- Kwai S. Chan
Organizations
- Southwest Research Institute