The stresses produced in a thin elastic plate by a transverse impulsive force

Abstract

Abstract A description is givon of tests in which a ½ in. or ⅜ in. diameter weighbar, seated vertically on a thin steel plate, was impacted by a finite mms. The force applied to the plate and the principal stresses produced at the bottom of the plate have been derived from the output of resistance strain gauges. The stress-time curves at the centre of the bottom surface of the plate, obtained at a number of impact velocities, have been compared with stress-time curves derived from theoretical considerations. The agreement between the theoretical and experimental results is found to be exceedingly good. In such tests the plate showed no sign of having yielded even though tho stresses reached were much greater than the static upper yield stress of the steel in the plate. This is attributed to the fact that strain rates of the order of 100 sec−1 were attained in the plate in these tests. The manner in which the disturbance created in this type of test, was propagated radially has been determined from the way the principal stresses, at the bottom of the plate, varied with radius and time. It is found that there was an annular area of compression which propagated radially in advance of a central area of tension. Tests have also been made in order to determine the manner in which a disturbance caused by an impulsive point load propagates radially in a plate. A dural and a steel plate were impacted by a high-tensile steel sphere and the principal stresses produced at the bottom surface of the plates were once again determined from the output of strain gauges. It is found that the disturbances produced in these tests propagated in a similar manner to the way the disturbances propagated in the tests in which the force was applied over a finite area.