On the saturated impulse for a circular hollow beam under pressure pulse loading

The saturated impulse phenomenon, which may occur in a hollow beam with a circular cross-section, is examined when a rectangular pressure pulse loading is applied uniformly on the upper surface of the beam. A simplified 2DoF model of the dynamic response of a relatively long circular hollow section beam is developed to explore the role of the local and global deformations build up simultaneously during the beam response. In order to simplify the analytical formulation, the elastic deformations of the hollow beam are neglected, and a rigidplastic method of analysis is applied. Finite element simulations using an elastic, perfectly plastic material model are carried out to verify the proposed analytical model and to reveal the influence of the elasticity on the beam response. The limit of the pressure pulse loading, beyond which saturated impulse is not defined for a hollow beam, is obtained numerically. The responses of hollow beams with lengths between 800 and 1200 mm, radius of 40 mm and several wall thicknesses are analysed. It is observed that the proposed 2DoF model can predict satisfactory the local and global saturated deflections while the saturated pressure pulse duration is underestimated due to the disregard of the stored elastic energy in the beam. It is suggested that the analytically predicted saturated impulse can be used as a lower bound estimate for the saturated impulse for a given beam geometry.

Automated summary

The study examines the saturated impulse phenomenon in a circular hollow beam under rectangular pressure pulse loading, developing a simplified 2DoF model to analyze the effects of local and global deformations on the beam response. Elastic deformations of the hollow beam are neglected in the analytical formulation, and a rigid-plastic analysis method is used along with finite element simulations to verify the model and investigate the influence of elasticity on the beam response. The study suggests that the analytically predicted saturated impulse can serve as a lower bound estimate for a given beam geometry's saturated impulse, while also highlighting the underestimated saturated pressure pulse duration due to the disregard of stored elastic energy in the beam.