Influence of Material Viscosity on the Theory of Shaped-Charge Jet Formation

摘要

The USSR has been engaged in viscosity measurements and visco-plastic material modeling for shock loaded materials since 1940. Shaped-charge jet or plate collapse models have been developed which are incompressible, one-dimensional, and viscid. In contrast, the USA employs a different modeling strategy where incompressible, inviscid flow is assumed for the simple one-dimensional jet or plate collapse models, and compressible, inviscid flow is assumed in the advanced axially symmetric hydrocode models. The USA advanced hydrocode models consider elastic-perfectly plastic stress-strain relationships or work hardening models, whereas the USSR models jet or plate collapse, under shock loading conditions, via visco-plastic or rate-dependent models. The USA establishes a jet-no-jet criterion and a jet cohesiveness criterion based on Mach number considerations or impinging angle considerations. Usually the Mach number is based on an ambient bulk speed of sound value. The USSR, with their incompressible, viscid flow model, uses a critical Reynolds number criterion to define the jet-no-jet condition. To use the USSR visco-plastic model, the constant (but unknown) viscosity coefficient must be determined. This parameter has been obtained from experiemental data for various materials under shock loading conditions. The purpose of this report is to present the one dimensional, USSR, viscous for jet or plate collapse and the USSR criterion f or jet formation and jet cohesiveness.