Effects of strain rate on the characteristics of PLC deformation bands for AA5083-H116 aluminium alloy

Abstract

An experimental, theoretical and numerical investigation of the Portevin-Le Chatelier (PLC) effect in the aluminium alloy AA5083-H116 is described. Five different tests at different overall strain rates were carried out on smooth flat specimens in order to determine the effects of strain rate on the characteristics of the deformation bands and their propagation. Both digital image correlation and digital infrared thermography were used to capture and characterize the spatio-temporal features of the PLC behavior. Inhomogeneous deformation with various localization bands caused by the PLC effect was observed in all the tests and the formation, evolution and propagation of these deformation bands were visualized, allowing their characteristics to be measured. An elasto-viscoplastic constitutive model, developed for metals exhibiting dynamic strain ageing, is used to represent the material behavior. Linear stability analysis with the adopted constitutive model is shown to give the orientations of the bands, but fails to predict the critical strain at which serrated yielding occurs. Finally, the model is used in three-dimensional numerical simulations of the physical tests using explicit finite element analysis. The numerical results are compared with the experimental observations and the main deviations between tests and simulations are discussed.

Keywords:

• negative strain-rate sensitivity
• dynamic strain ageing
• digital image correlation
• digital infrared thermography
• elasto-viscoplasticity
• finite elements

Acknowledgements

The authors would like to thank Francois Hild and Stephane Roux for discussions concerning digital image correlation and thermography. This work was supported by Ecole Normale Supérieure de Cachan, the Structural Impact Laboratory (SIMLab), Centre for Research-based Innovation (CRI) at the Norwegian University of Science and Technology (NTNU), CNRS through PICS-3052, the French-Norwegian Foundation and the Brazilian Ministry of Education through CAPES.