Transverse Impact on Fluid-Filled Cylindrical Tubes

Abstract

An analytical and experimental study was conducted regarding the effects produced by transverse impact of spherical steel projectiles on circular elastic tubes either empty or else containing stationary or flowing fluids. Similar tests were also executed on acrylic (PMMA) tubes that exhibit viscoelastic behavior. Transients were generated by pneumatically propelled 12.7 mm (1/2 in.) and 4.8 mm (3/16 in.) diameter projectiles striking the midpoint of two types of 3 m long 2024-T3 aluminum tubes with an outer diameter of 25.4 mm and wall thicknesses of 2.41 and 1.25 mm, respectively, and PMMA tubes with outer diameters of 34.93 and 31.75 mm and wall thicknesses of 3.17 and 1.58 mm, respectively. The targets were ballistically suspended by means of strings, and filled either with distilled water or a high-density capacitor fluid, Fluorinert. Most of the tests were performed with stationary liquids when the tube ends were stoppered; in some of the experiments, laminar flow in the hollow cylinders was produced by means of a blood pump. The initial and final projectile velocities were measured by means of a set of two multiple coils wound around an acrylic tube through which the striker passed; the impact force was determined from a sandwiched quartz crystal arrangement placed ahead of the contact point on the targets. Axial and hoop strain histories were ascertained by means of foil strain gages mounted at two stations on the outer hollow cylinder surface. Antisymmetric strain records were compared with the predictions of a modified Timoshenko-beam model; good agreement was noted between these results, particularly for the case of thick-walled tubes.