Experiments and theoretical analyses have been carried out on constitutive equations of copper powders. The results obtained are as follows.
(1) The stress-density relation of electrolytic copper powders is sensitive even to low strain rates of about 10-2∼10-5/sec in compression at room temperature. The higher the strain rate is, the larger the stress at the same density is.
Moreover, stress relaxation phenomena are affected by the history of loading processes. The compacted powders compressed by rather high strain rates show a larger stress relaxation. The compacted powders of lower density show larger stress relaxation.
(2) When the strain rate is changed in the compression process, the stress-density relation changes rapidly to the new one which coincides with the stress-density relation obtained by the constant strain rate test corresponding to the new strain rate.
(3) The above character of powders can be expressed by the three element elastic visco-plastic model, and the behaviour of powders of various loading history can be calculated by this model. The calculation agrees qualitatively with experiments.
