抄録
The purpose of the present investigation was to measure quantitatively the efficiency of a shield plate in resisting penetration by a rifle bullet. A simple, mechanical, and accurate method for determining the velocity of the bullet was devised, by which the velocity of the bullet after passing through test plates of different thickness was measured.
By this means the residual velocity vers. plate thickness curve for different metals was obtained.
This curve which is called the "characteristic curve" of the shielding efficiency of a metal was obtained for different metals and alloys. The curve not only dives the residual velocity of a bullet after passing throgh a shield plate of a given thickness, but also the thickness of the metal plate which is just sufficient to stop the impinging bullet, on the "penetration distance". The best material found as the result of the present investigation is a special steel, the penetration distance of which is 4·5mm. for a bullet 9 grams in mass and a velocity 790 meters per second.
The penetration distance of laminated plates, and of two plates of equal tbickness separated from each other by a distance was also measured. The same quantity for wood, sand and glass, of different kinds was also measured.
