DYNAMIC RESPONSE ANALYSIS OF PRE-TWISTED BEAMS UNDER HARMONIC LOADING

The behavior of a non-prismatic beam under static and dynamic loads depends on the density distribution and geometry of the beam along its length. An essential type is a pre-twisting beam. In the current study, the dynamic response of a pre-twisted beam vibrated freely and forced under a harmonic force was investigated by establishing finite element modeling via ANSYS software. Beam length and twist angle were considered as pre-twist parameters. Beam length varying from 300 mm to 1000 mm and twist angle ranging from 0 to 360° with incremented 45o. Modal analysis and then harmonic response were implemented to calculate the natural frequency, total deflection and equivalent stress, and the damping ratio variation with pre-twisting beam parameters. The model was validated against previous studies, showing perfect agreement. The obtained results show that the first natural frequency increases when the twisting angle rises till (180o °) and then remains constant. Notably, the influence of the beam length on the harmonic response reduces when the twisting angle is greater than 180o. Similarly, the deflection of harmonic response increases when the frequency ratio is approximately unity. Finally, the influence of the length of the beam and twisting angle on the stress appears when the twisting angle is smaller than 180o