On the application of load relaxation in characterizing superplastic Al-Li 8090
- FAMU-FSU Coll. of Engineering, Tallahassee, FL (United States)
High strain rate sensitivity is one of the main features of superplastic deformation which accounts for elongation to large strains ({var_epsilon} {ge} 1.5). Strain-rate sensitivity is typically calculated as the slope of the log {sigma} versus log {dot {var_epsilon}} curve where {sigma} is the steady state flow stress and {dot {epsilon}} is the inelastic strain-rate. A variety of mechanical testing methods are used to evaluate strain-rate change test, and load relaxation tests. In this paper, the use of the load relaxation experiment to obtain the stress/strain rate behavior of an Al-Li 8090 superplastic material is investigated and compared to the strain-rate change tests. The strain rate change tests are found to be highly influenced by prior loading conditions and only valid for incrementally increasing tensile loads. Relaxation tests are found to be very effective for all ranges of strain rates. These tests can also be influenced by transient effects which are primarily due to anelasticity. Such transients can be avoided if the specimen is loaded to fully loaded (steady state) region prior to relaxation.
- OSTI ID:
- 349879
- Journal Information:
- Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 4 Vol. 40; ISSN 1359-6462; ISSN SCMAF7
- Country of Publication:
- United States
- Language:
- English
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