ANALYTICAL THEORY OF CAVITATION TIME EFFECT ON ELSTOPLASTIC RESPONSE OF CIRCULAR UNDERWATER PLATE SUBJECTED TO EXPLOSIVE LOADING

Original Research Paper Received 18 June 2015 Accepted 19 August 2015 Available Online 11 October 2015 In this paper, the elastoplastic response of copper, steel and aluminum circular plates with clamped boundary conditions subjected to underwater explosion loading is investigated. Cavitation is phenomenon that can be occurred forplatesin the process of underwater explosive forming. The total pressure of the explosion becomes zero at the cavitation time, so that the governing equations of motion time will be different before and after the cavitation. As result, in terms of analysis and design, the cavitation time is significant in studying the behavior of circular plate at underwater explosive loading. By applying the energy method and based on Hamilton principle and variation methodthe equations of motion of an underwatercircular plate subjected to explosive loading are derived. Then, in order to obtain the forced response of the circular plate, the exact free vibration solution is derived to calculate the mode shapes. Then, the velocity and generated stress of plate during cavitation time are calculated and compared with the yield stress plates. Using this method, one can distinguish the occurance of cavitation with in the elastic or plastic regimes.By recognizing the time of cavitation in the range of elastic or plastic, the displacement and velocity field of plate are determined in duration of explosive loading. Results show that the cavitation time is on the order of microsecond. Depending on amount of charge mass and stand-off, the cavitation time may be occurred in elastic or plastic regime.