SOME EXPERIMENTAL-OBSERVATIONS OF ANOMALOUS RESPONSE OF FULLY CLAMPED BEAMS

We describe tests made in an attempt to observe anomalous behavior that had been predicted in computations for the elastic-plastic response of fixed pin ended beams to short pulse loading (SYMONDS and YU, ASME J. Appl. Mech., 52, 517-522, 1985). By 'anomalous' here is meant permanent deflections in the direction opposite that of the applied impulse, and abnormal sensitivity to parameters. Direct impact tests were unsuccessful. A simpler test was devised, in which the impact loading was simulated by pulling the specimen to an initial deflection and then releasing it abruptly. Two out of 36 such tests led to permanent deflections in the direction opposite to that of the imposed initial deflection. A further series of tests is described in which the loading reversals of the dynamic tests were simulated by quasi-static loading, accompanied by concurrent energy calculations. These help to understand the more complex dynamic phenomena, and provide approximate criteria for the possible occurrence of anomalous behavior.