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The thermo-mechanical response of single crystal and polycrystalline high purity copper is systematically compared at low and high strain rates. The mechanical response of each type of material is very different in terms of strain hardening, although both are distinctly strain rate sensitive. A simplified interpretation of the Taylor–Quinney coefficient, in which the strain dependence is not considered, shows a clear (almost linear) increase of this factor with the strain rate, while the two types show distinct trends. This factor increases with the strain rate but remains markedly lower than the classical value of 0.9. The stored energy of cold work is found to be relatively independent of the strain rate, with the polycrystal storing more energy than the single crystal. A microstructural study (transmission electron microscopy) of representative specimens of each type at low and high strain rates reveals a basically similar microstructure, despite dissimilar values of energy storage. It is proposed that a higher level of storage of the energy of cold work by polycrystalline copper is due to the presence of grain boundaries in this group.

Rapid advances in additive manufacturing techniques promise that, in the near future, the fabrication of functional cellular structures will be achieved with the desired cellular microstructures tailored to specific applications. It is therefore essential to develop a detailed understanding of the relationship between macroscopic mechanical response and cellular microstructure. The present study reports on the results of a series of computational experiments that explore the effect of topology and microstructural irregularity (or non-periodicity) on deformation modes of cellular structures under both uniaxial and biaxial stress states. A simple quantitative technique based on the partition of elastic strain energy into bending and stretch components is used to identify the distribution of deformation modes at a microstructural level. The relationship between nodal connectivity, morphological regularity and deformation modes is then explored through their influence on biaxial yield surfaces as obtained from finite element analyses.