Dynamic Buckling of Submerged Tubes due to Impulsive External Pressure

Abstract

An annular geometry is used to experimentally study fluid-structure interaction and dynamic buckling of tubes submerged in water and subjected to axially-propagating pressure waves. Wave propagation, vibration, and buckling of the specimen tubes are characterized using pressure and strain measurements. Emphasis is placed on pressures near or slightly exceeding the buckling threshold, where buckling deformation is excited but remains elastic or only slightly plastic due to the short duration of the pressure pulse. Measured wave speeds and non-axisymmetric vibration frequencies are in good agreement with predictions from simple fluid-structure interaction models. Near the buckling threshold, the amplitude of non-axisymmetric deformation is observed to grow rapidly with small increases in pressure until plastic deformation occurs, which results in a substantial loss of strength of the tube. Systematic mode 2 variations in wall thickness are found to control the buckle orientation, since the major axis of mode 2 buckles is always aligned with the location where the tube wall is thinnest.