Shock-Compression Paradigms Benign and Catastrophic

We can be qualitatively certain that the fluidlike flow of shock deformation is a consequence of motion of defects. We cannot be quantitatively certain as to the significant, detailed descriptions and consequences of these defects. Indeed, the principal unfinished business of shock-compression science is the scientific description of the defective solid in all its manifestations. 

The defect question delineates solid behavior from liquid behavior. In liquid deformation, there is no fundamental need for an unusual deformation mechanism to explain the observed shock deformation. There may be superficial, macroscopic similarities between the shock deformation of solids and fluids, but the fundamental deformation questions differ in the two cases. Fluids may, in fact, be subjected to intense transient viscous shear stresses that can cause mechanically induced defects, but first-order behaviors do not require defects to provide a fundamental basis for interpretation of mechanical response data. 

The benign shock paradigm is clearly an approximation, but one that has proven very effective. The catastrophic shock paradigm corresponds to the known physical, mechanical, and chemical processes, but its characteristics have proven difficult to quantify. 

In large measure the paradigm within which work is carried out is strongly influenced by the objectives of the work, the background of the investigator, and the particular materials model under study. From a strictly fluid mechanics, hydrodynamic, or continuum framework, defect issues are not overtly at issue. From a strictly mechanical framework, the defective solid 

Because of the importance of characteristic solid properties and defects, an equivalence between shock-compressed liquids and shock-compressed solids cannot be assumed. This book focuses on solids as substances with characteristics distinctively different from liquids. 

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