Analysis of Cyclic Mean Stress Relaxation and Strain Ratchetting Behaviour of Aluminium 7050.
Abstract
The cyclic constitutive behaviour of aluminium 7050 under elstoplastic deformation has been investigated in this report. Experiments were performed under strain-controlled and stress-controlled cyclic loading, respectively, with a view to quantify the phenomena of mean stress relaxation and strain ratchetting. To mathematically describe the experimentally observed cyclic stress-strain behaviour, the framework of constitutive theory for rate-independent plasticity has been reviewed and the state-of-art development in the field summarised. A detailed discussion has been presented for a class of constitutive models which uses nonlinear differential equations to describe the kinematic hardening, using a single back stress or multiple back stresses. Using the available steady-state experimental data, the material constants in the model have been identified. A comparison to the experimental results shows that the model can provide very good representation of the material stress-strain behaviour under cyclic loading, in terms of the general shape of hysteresis loops. A numerical procedure for determining the notch-root stress and strain from the applied remote stress or strain has also been developed. The significance of strain ratchetting on the prediction of fatigue crack initiation and growth life has also been discussed. Further study is needed to improve the accuracy of prediction in the rate of stress relaxation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1999
- Accession Number
- ADA367233
Entities
People
- C. H. Wang
- S. Barter
- Wenyi Hu