Constitutive models in WONDY for penetration studies into rock targets
Computer simulation appears to be the easiest way of providing a fairly complete description of the physical problem of earth penetration by projectiles. This simulation is limited by the lack of information on the behavior of geologic targets under dynamic loading and also by the description of the constitutive model for the geologic material. Several constitutive models are presented for possible applications to the rock and rock-like materials. Using material property data for Antelope tuff, the required set of constants for each model was selected and used in predicting, for a penetration event, stress distributions on the penetrator surface and also penetration histories. For each of these three models, the average decelerations lie close to the values computed for coefficients of friction of zero and 0.1. Assuming zero friction, curves of deceleration as a function of penetration depth were calculated for the various models. These curves were higher than the experimental curve for the first meter of penetration. This seems to indicate that the models considered here do not contain all the physical details needed for a more accurate prediction. In studies of friction at high speed, the coefficient of friction has been found to increase qualitatively as an exponential function as the velocity decreases. This might possibly explain the lock-in phenomenon occurring at the end of a penetration event. As part of the present study, parameter variation studies were conducted to determine which material properties would be most significant in earth penetration by projectiles. Material compressibility, cohesive strength and internal friction angle were examined in detail. The internal friction angle was found to be the most important and cohesive strength the least important parameter in contributing to the resistive forces experienced by a projectile during penetration.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 5899445
- Report Number(s):
- SAND-81-0817; ON: DE82003087
- Country of Publication:
- United States
- Language:
- English
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