Life Prediction Methodologies for Aerospace Materials
Abstract
The understanding of the effect of material defects, i.e., inclusions and grain size variances, on tensile and fatigue behavior, specifically initiation, in wrought gamma titanium aluminides was improved. Orientation imaging microscopy (OIM) aided in determining microstructural situations favorable for initiation of fatigue cracks. Finite element models were refined to predict elastic and plastic behavior of fully lamellar microstructures under static loading. An effective ligament model that successfully correlated crack growth rate behaviors parallel to the fibers in fiber titanium-matrix composite (TMC) was developed. Acoustic emission signals were obtained from the specimens during tensile, creep, and fatigue tests to assess damage evolution in a unidirectional TMC. A phenomenological model for the constitutive behavior of the matrix was developed to predict the time-dependent response of a TMC under tensile, creep, and fatigue conditions. Fracture behavior and damage progression in Nextel 720/AS and Nextel 610/AS ceramic matrix composites were studied using middle hole, single edge hole, semicircular double-notched, and double-notched geometries. In addition to the elasticity models of Nextel 720/AS, creep and damage models were developed. Initial room temperature tensile tests on melt infiltrated Sylramic/BN/SiC composite exhibited poor ultimate strength results and provided evidence of oxidized fibers and of large regions of matrix porosity. Fretting fatigue investigations focused on the effects of applied clamping stress, time required for detrimental fretting fatigue damage, and applied shear stress.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2001
- Accession Number
- ADA391400
Entities
People
- A. L. Hutson
- D. J. Buchanan
- G. A. Hartman
- N. E. Ashbaugh
- R. A. Brockman
Organizations
- University of Dayton