Dynamic lateral torsional post-buckling of a beam-mass system: Experiments

The phenomenon of static lateral torsional buckling of a beam with a narrow rectangular cross-section is well known. Specifically, a beam is clamped at one of its ends and is subjected to a shear force at its other end which causes deformation in the principal plane with stiffest resistance to bending. Above a critical value of load, a bifurcation occurs and the beam twists and experiences out-of-plane deformation which tends to transfer bending to the plane of weakest resistance. Here, attention is focused on an experimental study of dynamic lateral torsional buckling. In the experiment, a beam is attached to the shaft of a motor at one of its ends and a relatively large mass is attached to its other end. Rotation of the motor causes deflection of the beam in its principal plane of stiffest bending resistance. By increasing the excitation frequency and/or amplitude of oscillation of the motor's shaft, the shear force applied by the mass on the beam's end exceeds a critical value which causes dynamic lateral torsional buckling of the beam. Special techniques have been developed to produce and measure this phenomenon and the data has been presented in a form that can be used for future validation of analytical or numerical models.