THEORY OF HIGH SPEED IMPACT
Summary rept. 3 Nov 1960-2 Nov 1961
GENERAL ELECTRIC CO PHILADELPHIA PA MISSILE AND SPACE DIV
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Results of hypervelocity impact tests were gathered and the composite data are presented. The extrapolated results to higher velocities differ with the theoretical prediction from the perfect fluid model. A visco-plastic model for hypervelocity impact is formulated. This is accomplished by introducing a viscosity factor mu sub o and a yield stress tau sub a into the perfect fluid equations. The equations governing the visco-plastic model are studied. Certain dimensionless parameters are found which determine the relative importance of the inertial, viscous and plastic effects during the various stages of the hypervelocity cratering process. To exhibit quantitatively the importance of including the viscous and plastic effects, a one-dimensional impact model was studied. The values of mu sub o and tau sub a are varied since definitive data are available for neither parameter in the hypervelocity range. Two distinct finite difference schemes were developed for performing the required calculations. The results are related to the qualitative model of crater formations that evolved from experimental studies in which the actual cratering process was monitored. The viscous and strength effects strongly affect the cavitation process which is the essential mechanism of crater formation.