TABLE OF CONTENTS Dynamic loading was defined in Chap. 3 as any loading during which the parts of the body cannot be considered to be in static equilibrium. It was further pointed out that two kinds of dynamic loading can be distinguished: (1) that in which the body has imposed upon it a particular kind of motion involving known accelerations, and (2) impact, of which sudden loading may be considered a special case. In the following sections, specific cases of each kind of dynamic loading will be considered.
The acceleration a of each particle of mass dm being known, the effective force on each particle is dm a, directed like a. If to each particle a force equal and opposite to the effective force were applied, equilibrium would result. If then such reversed effective forces are assumed to be applied to all the constituent particles of the body, the body may be regarded as being in equilibrium under these forces and the actual forces (loads and reactions) that act upon it, and the resulting stresses can be found exactly as for a body at rest. The reversed effective forces are imaginary forces exerted on the particles but are equal to and directed like the actual reactions the particles exert on whatever gives them their acceleration, i.e., in general, on the rest of the body. Since these reactions are due to the inertia...
