Until now, mechanics do not fully understand the specific features of dynamic processes, assuming that the presence of a time derivative in mathematical model is sufficient for the process to be considered dynamic. Therefore, they often tried to use the data obtained under quasi-static conditions to describe shock-wave processes. Naturally, this led to errors and contradictions and raised questions about what physical processes initiated by shock effects are [1].
In section 10.2, we want to show that the dependence of the shear stress on plastic strain for uniaxial planar loading can not be found using experimental relationships for the simple tension-compression of thin rods (section 10.1) recalculated to semi-space. In section 10.3, based on the solution to the problem of the planar shock-induced waveform propagation obtained in Chapter 7, we derive the stress-strain relationship for continuous loading at the constant strain-rate. Then in section 10.4, we show that it is incorrect to separate stress and strain both into elastic and plastic and into bulk and shear parts in advance. It is possible to determine whether the process is reversible or irreversible only after its end by calculating the resulted integral entropy production. In section 10.5, the surface of the integral entropy production is constructed over the plane of the parameters that bind the typical times of relaxation, delay, and loading duration. The fundamental difference between shock-induced and quasi-static processes is discussed in section 10.7. It was found that long-term deformation of condensed matter is a dissipative process, while a short impact, depending on its intensity, can be either reversible or irreversible (section 5).
Experimental research on shock loading of metals [2-5] that revealed relationships between the quantities describing the shock-induced mass and momentum transport elucidates specific features of material response to the shock loading that characterize dynamic loading unlike quasi-static one. In section 10.7, we show that the elastic precursor can form only under short-duration loading due to the delay of post-shock effects. Prediction of final states and possibilities to control them are discussed.