Contained Explosion inside a Naval Vessel - Evaluation of the Structural Response
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Helsinki University of Technology |
Diplomityö
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Date
2007
Department
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Lujuusoppi
Mcode
Kul-49
Degree programme
Language
en
Pages
90 + (6)
Series
Abstract
The purpose of this master's thesis is to estimate the effects of an explosion inside a naval vessel. The structural behaviour of the steel structure is evaluated by using finite element method. The explosion load is evaluated with semi-empirical equations. The loading initiates large strains and high strain rates in the solid material. Therefore, elasto-plastic and rate-dependent material model is used in finite element computation. The state of the structure is computed with finite element program ABAQUS/Explicit 6.6. Nonlinear material model and the use of large-strain considerations lead to nonlinear computation procedure in structural dynamic analysis. The structure undergoes significant deformation under the explosion load during the time integration. A simple failure criterion is utilized in order to compute the kinematic state and the deformation of the failing structure. Otherwise, if a failure criterion is not used, the computation procedure encounters problems due to undesirably large-strains in the failing structure. The computational part of the study shows that large-strain considerations and rate-dependent material model are crucial when structural response is evaluated under explosion load. Also, the effect of realistic boundary conditions is illustrated. The bulkheads of the analyzed structure fail when the amount impulse is roughly between 75 and 85 kNs/m2. The failure of the structure progresses more easily once an element has failed in the bulkhead. 50 kilogram TNT explosion causes massive damage to the steel structure. The deck and the longitudinal bulkhead undergo almost complete destruction. The transversal bulkhead sustains the water tightness, still undergoing heavy plastic deformation. The nonlinear dynamic procedure, described in this study, is suitable for any type of structural analysis of a rapid physical event.Description
Supervisor
Tuhkuri, JukkaThesis advisor
Mattsson, JormaKeywords
contained explosion, quasi-static pressure, strain rate, isotropic elastoplasticity, large-strain, nonlinear finite element method, dynamic tensile strength test