A Study of Localized Plastic Deformation as Related to Fatigue Mechanisms.
Abstract
This is concerned with a study of the micro- and macromechanics of fatigue crack initiation and crack propagation in an age-hardenable 2048 aluminum alloy, which is the high purity version of 2024 or 2124 aluminum, and their relationship to localized plastic deformation. Special attention was given to the importance of microstructure, including grain size and ageing treatment in cyclic response and low cycle fatigue (LCF) behavior, crack growth along the phenomena of crack tip closure, and on overload retardation effects. Crack closure was studied in detail throughout the course of this research program and its use in describing crack growth was explored. Fracture toughness tests were performed and the results were compared with the KIC value reported in literature. Discussion is also included on the experimental techniques used in this research since they are novel and should have quite general applicability in fracture mechanics theory. The results show that the LCF performance and thus fatigue iniitiation life based on the plastic strain control tests do not show any appreciable differences between different temper materials , but crack closure levels, crack growth rates and overload retardation are well influenced by microstructure. The lowest crack growth related to highest crack tip closure loads and the largest amount of overload retardation are associated with underaged microstructures which are prone to display non-uniform deformation pattern characterized by localized shearing.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1982
- Accession Number
- ADA121806
Entities
People
- Jai-man Baik
- Laurenz Hermann
- Robert J. Asaro
Organizations
- Brown University