The role of creep in stress strain curves for copper

A model for plastic deformation in pure copper taking work hardening, dynamic recovery and static recovery into account, has been formulated using basic dislocation mechanisms. The model is intended to be used in finite-element computations of the long term behaviour of structures in Cu-OFP for storage of nuclear waste. The relation between the strain rate and the maximum flow stress in the model has been demonstrated to correspond to strain rate versus stress in creep tests for oxygen free copper alloyed with phosphorus Cu-OFP. A further development of the model can also represent the primary and secondary stage of creep curves. The model is compared to stress strain curves in compression and tension for Cu-OFP. The compression tests were performed at room temperature for strain rates between 5 × 10−5 and 5 × 10−3 s−1. The tests in tension covered the temperature range 20–175 °C for strain rates between 1 × 10−7 and 1 × 10−4 s−1. Consequently, it is demonstrated that the model can represent mechanical test data that have been generated both at constant load and at constant strain rate without the use of any fitting parameters.

► A dislocation based model takes into account both dynamic and static recovery.
► Tests at constant load and at constant strain rate modelled without fitting parameters.
► The model can describe primary and secondary creep of Cu-OFP from 75 to 250 °C.
► The temperature and strain rate dependence of stress strain curves can be modelled.
► Intended for the slow strain rates in canisters for storage of nuclear waste.