Numerical Simulation Of Underwater Explosion And Its Effect On Structures Based On Commerical Softwares

Underwater explosion and its effect on structures including flat plate, cylindrical shell and torpedo shell were studied in this dissertation by using commercial software AUTODYN, ABAQUS and LS-DYNA. The main work includes: (1) Numerical simulation of underwater explosion process, (2) The re-exploitation of ABAQUS based on Taylor's plate theory and the first-order doubly asymptotic approximation and its application, (3) Numerical study of dynamic response of cylindrical shell subjected to deep water blast wave, (4) The modification of the simulation method of LS-DYNA to calculate far-field underwater shock wave, (5) The elementary analysis of the terminal effect of torpedo-damaging by underwater shock waves, (6)Numerical simulation of the dynamic response of torpedo shell structure subjected to near-field and far-field underwater shock waves.Chapter 1: The research content in this dissertation, as well as the research method and background, were concisely presented, and the evolvement of relative research, as well as the software of numerical simulation and the method to validate the calculation results, were given.Chapter 2: Underwater explosion shock wave and bubble pulse were simulated by using the hydrocode AUTODYN. By comparing calculation results with empirical formulas, theoretical formulas and experimental results, one can conclude that AUTODYN can simulate much of the important physics of underwater explosion, and the suggestion for the engineering application of AUTODYN was given.Chapter 3: Based on Taylor's plate theory and the first-order doubly asymptotic approximation (DAA₁) without considering low-frequency response, a simple and practical method has been presented to simulate the high-frequency dynamic plastic response of basic structure including flat plate and cylindrical shell subjected to underwater explosion shock waves without modeling the fluid field. Commercial finite element code, ABAQUS, was used to conduct this simulation. In order to validate this method, two examples including a fixed flat plate and a free cylindrical shell, all subjected to underwater explosion shock waves, were simulated by the method, and the simulation results are in good agreement with experiment results.Chapter 4: Numerical investigation was carried out on a cylindrical shell subjected to underwater explosion shock waves in deep water by using both static state analysis and dynamic analysis via ABAQUS software package. The influence of the depth of the cylindrical shell lies, orientation of the explosion and prestress were identified, and the breakage of the cylindrical shell in deepwater was also studied.Chapter 5: The elementary analysis of the terminal effect of torpedo-damaging by underwater shock waves was presented, and a simple model to analyze this problem was given. Then the main factors to influence the terminal effect were identified, and an idea was given to direct the following numerical study. Aim at the problem that the peak pressure of shock waves induced by far-field underwater explosion are smaller than actual magnitude when using LS-DYNA to simulate underwater explosion, a equivalent mass method which had been validated was presented to solve it. After this, the dynamic response of a lightweight torpedo shell structure subjected to shock waves induced by far-field underwater explosion was simulated by LS-DYNA, and influence of the torpedo insides and shock environment of the torpedo shell structure were studied. The damage mechanism of torpedo shell subjected to underwater explosion shock waves was simulated by using LS-DYNA. The damage mechanism of the torpedo shell, as well as shock environment and vulnerability of the different torpedo cabin shell, were investigated.Chapter 6: The main conclusions and suggestions for the following investigation are given.