Multiaxial Creep of 2618 Aluminum under Proportional Loading Steps.
BROWN UNIV PROVIDENCE R I ENGINEERING MATERIALS RESEARCH LAB
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Creep data of 2618-T61 aluminum alloy under multistep multiaxial proportional loadings at 200 degrees C 392 degrees F are reported. Two viscoplastic flow rules were developed using constant stress creep and strain recovery data. One was based on the accumulated strain strain hardening, and the other on a tensorial state variable kinematic hardening. Data were represented by two models a nonrecoverable viscoplastic model and a viscous-viscoelastic model in which the time-dependent strain was resolved into resolved into recoverable viscoelastic and nonrecoverable components. The modified superposition principles was used to predict the viscoelastic strain component under variable stress states for both models. The experiments showed that the viscous-viscoelastic model with either strain-hardening or kinematic hardening gave very good predictions of the material responses. Strain hardening was best in some step-down stress states. The viscoelastic component accounted for not only the recovery strain but also the transient creep strain upon reloadings and step-up loadings.
- Metallurgy and Metallography