Chapter 40 Implosion of a Tube Within a Closed Tube: Experiments and Computational Simulations Sachin Gupta, James M. LeBlanc, and Arun Shukla Abstract A comprehensive series of experiments were conducted to study the mechanics of an implosion of a tube occurring within a closed tube. The outer tube has an inner diameter of 0.178 m (700), a length of 1.82 m (7200), and a maximum hydrostatic pressure of 10.3 MPa (1,500 psi). The implodable volumes consist of aluminum 6061-T6 cylindrical tubing and were placed concentrically within the outer tube and equidistant from the two ends. The effect of the length to diameter (L/d) ratio on the mechanics of the implosion was investigated by varying the outer diameter of the implodable volume while holding the length constant, 0.304 mm (1200). The L/d ratios of 3, 4, 6, and 8 were utilized. The wall thicknesses of the tubes were chosen so as to obtain approximately constant collapse initiation pressures in all of the experiments. The pressure histories generated by the implosion event were captured by dynamic pressure transducers mounted on the inner surface of the outer tube. Computational models of the implosion experiments are currently being developed using the Dynamic System Mechanics Analysis Simulation (DYSMAS) software package. The computational results will be provided in the presentation. Keywords Implosion • Buckling • Collapse shape • Pressure vessel • Cavitation 40.1 Introduction The objective of this study was to investigate the mechanics of an implosion of cylindrical tubes occurring within a closed outer tube. A cylindrical pressure vessel designed to a 10.3 MPa (1,500 psi) hydrostatic working pressure was used as the outer tube in which aluminum 6061-T6 implodable volumes were collapsed. The pressure waves generated during the implosion experiments were captured by dynamic pressure transducers mounted on the inner wall of the outer tube. Recently there has been an increased interest in the pressure waves generated from the implosion of volumes, particularly when the implodable volume is located near an adjacent structure. When a volume is submerged in the high pressure water environment, the pressure differential can cause structure instability. The loss of structure stability results into the collapse of the structure and during this collapse process, a certain amount of energy is released into the surrounding fluid. This energy is generally equal to the product of critical (collapse) pressure and internal volume of the air inside (PcV). This released energy produces pressure waves in the surrounding environment that can potentially damage the nearby structures. An example of this effect is Super-Kamiokande experiment, where approximately 6,000 photomultiplier tubes were imploded in a chain reaction [1, 2]. In this accident, the implosion of one of the tubes generated pressure waves, which triggered the implosion process in the other tubes. S. Gupta (*) • A. Shukla Dynamics Photomechanics Laboratory, Department of Mechanical, Industrial and Systems Engineering, University of Rhode Island, Kingston, RI 02881, USA e-mail: gupsac@gmail.com J.M. LeBlanc Naval Undersea Warfare Center (Division Newport), Newport, RI 02841, USA B. Song et al. (eds.), Dynamic Behavior of Materials, Volume 1: Proceedings of the 2013 Annual Conference on Experimental and Applied Mechanics, Conference Proceedings of the Society for Experimental Mechanics Series, DOI 10.1007/978-3-319-00771-7_40, #The Society for Experimental Mechanics, Inc. 2014 327
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