Structural Analysis of Underwater Detonations

Sammanfattning: The knowledge how an object withstand an underwater detonation is critical within the defense industry. This is mostly done today with physicals test which are both time consuming and connected with high costs. The aim of this thesis is to provide recommendations and guidelines on how to model and analyze a structural response of underwater detonations. This investigation are focused on firstly investigate several theoretical simulation methods and thereafter develop a model of the chosen method.  The simulation method was decided to be the Multi-Material Arbitrary Lagrangian Euler(MMALE) using the software LS-Dyna. To receive a model with functionality to simulate an explosion a method of six steps is developed to increase the complexity. The final step is to be able to analyze a structural response of an object.  The validation phase contained several convergence studies of the two Equations of states and a varying element size compared to analytical equations. The plan was to perform a validation test but because of travel restrictions due to the Covid-19 situation an alternative validation method was used. This method involved two external reports with specified measurement data.  The aim to develop a model is reached as the model performs well against the cylinder in the validation phase, however the element size is the most important parameter in an accurate model. The developed model shows good agreement regarding the structural response of an object when compared to well defined and reported experiments.