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Many experiments have shown that plastic deformation of metals generates heat, leading to temperature rise of the material. However, little is known about the underlying factors that govern the heat generation, especially in polycrystalline metals involving high-rate plastic deformation. In this work, the work-to-heat conversion during high-rate plastic deformation of polycrystalline coppers with and without nanotwins is studied using molecular dynamics simulations. The results show that within a certain range of imposed deformation, smaller grain size results in higher plastic work-to-heat conversion, due to larger proportion of grain boundaries. For a given grain size of polycrystalline copper with twins, the portion of plastic work converted to heat increases as the twin-boundary spacing decreases within a certain deformation range. However, at large deformation the plastic work-to-heat conversion coefficient should be analyzed specifically for each individual sample due to the transformation of the deformation mechanism (i.e., the change of the energy storage). [ABSTRACT FROM AUTHOR]

A series of dynamic shock compressions of metal films are simulated using molecular dynamics method. Characteristics of mechanical shock load are analyzed theoretically. Thermomechanical responses induced by mechanical shock, including pressure, temperature, volumetric strain, and shear strain, are presented graphically and analyzed from viewpoint of thermomechanical coupling. The results show that the temperature rise caused by volumetric strain (elastic) is reversible, while that caused by shear strain is irreversible. Under the same mechanical shock load, several metal films exhibit significant differences in thermomechanical responses and the potential reasons are analyzed from the differences of thermophysical parameters. [ABSTRACT FROM AUTHOR]