Experimental verification of dynamic stability of vertical cantilevered columns subjected to a sub-tangential force

The intended aim of the paper is to give the experimental verification of t he effect of non-conservative/follower force on the vibration and stability of cantilevered columns. In place of an ideal tangential force, a sub-tang ential force produced by a real solid rocket motor is considered in this pa per. A solid rocket motor is mounted to a vertical cantilevered column at i ts tip end. Rocket thrust of the motor produces a tangential/non-conservati ve force, while the self-weight of the motor a vertical/conservative force. Thus, the combined action of the rocket thrust and the self-weight of the rocket motor produces a sub-tangential force. It is assumed that a solid ro cket motor is a rigid body. Therefore, a concentrated mass, a rotary inerti a and a size of the rocket motor must be taken into account in vibration an d stability analysis. FEM formulation of the vibration problem under consid eration is conducted to depict the dynamic stability in the total applied f orce and the non-conservativeness parameter plane. Experiments were conduct ed to demonstrate the stabilizing effect of follower forces on the dynamics of vertical columns initially subjected to a conservative force due to the rocket motor's weight. It was assumed that the thrust and the self-weight were constant during the burning time of 4 a. The average thrust was 40 kgf (392 N), while the average dead weight of the motor was 14.2 kgf(139 N). F our test runs were made for sub-critical and critical column initially subj ected to the dead weight of the motor. It was observed that the buckled col umn under the dead weight of the motor could be stabilized dynamically by a pplying the rocket thrust of 40 kgf, when a resultant compressive force of 54.2 kgf (531 N) was applied to the column. (C) 2000 Academic Press.