Investigation of Stress-Strain History Modeling at Stress Risers
Abstract
An experimental and analytical study of the stress and strain history at stress risers was conducted to assess the effects on cracking in aluminum alloy structures. This report covers Phase I of a two-phase program. The program includes cyclic characterization of the 7075-T651 material used, initial residual stress studies, complex sequence testing of super-scale and notched coupons, and analytical modeling of experimental results. Cyclic and time- dependent creep and/or relaxation were evaluated by measuring strain at the stress riser. Thirty different test sequences were run and strain data recorded for analytical modeling. These test sequences included combinations of overloads, underloads, periods between overloads, and hold periods at sustained load. Creep and/or stress relaxation occurs at the stress riser during periods of sustained compression loading. This creep and relaxation is very complex and is a function of both notch stress and notch strain. The elastic-plastic stress and strain field definition is important to both the crack initiation and crack propagation phases of the damage process. Test sequences with sustained load periods reduced specimen life by eighty percent for some loading sequences.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1977
- Accession Number
- ADA042688
Entities
People
- G. J. Gilbert
- James R. Carroll
- R. F. Wilkinson