| Description |
An investigation of wax-to-wax impact is presented in an attempt to "model" high-speed impact of metal into metal. Wax is chosen as the modelling substance because of its comparatively low sonic velocity and the physics similarity of wax craters to craters formed at the impact of metal into metal. The sonic velocity in wax is determined as a function of temperature; the work reported is made with the wax targets at a temperature of about 75° F, at which the sonic velocity in wax is approximately 0.7 km/sec. A method of accelerating wax pellets by means of laboratory guns is given; also, use is made of the static charge on wax pellets in some of the velocity measurements. The penetration of the impacting. pellet is for and to vary linearly with the cube : root of the pellet mass and the pellet velocity to velocities in excess of twice the sonic velocity in the wax target. The crater area varies directly as the pellet area and the velocity, both below and above the sonic velocity, but there is a marked increase in the constant of proportionality above the sonic velocity. The volume of the crater per unit. energy of the pellet is discussed, and it is found that in wax this characteristic is not independent of velocity. Values of 'Volume per unit energy range over 1.5-4.0 x 10-8 m?/joule, over the velocity range zero to 2 km/see. Experiments are described which throw some light on the mechanisms of cratering , It is observed that a large part of the crater volume is created by deformation of the target material and that only a small part is due to ejection of target material. There is an apparent cavitation in the target material surrounding the crater, probably caused by a shock wave created by the' impact. A comparison of features of wax craters with ne t al, craters indicates validity of the wax model. |
