Experimental Study on Deformation and Shock Damage of Cylindrical Shell Structures Subjected to Underwater Explosion

2010 ◽  
Vol 224 (11) ◽  
pp. 2505-2514 ◽  
Author(s):  
L-J Li ◽  
W-K Jiang ◽  
Y-H Ai
Keyword(s):  
Cylindrical Shell ◽  
Underwater Explosion ◽  
Experimental Results ◽  
Dynamic Responses ◽  
Shell Structures ◽  
Security Evaluation ◽  
Wave Loading ◽  
Shell Models ◽  
Edge Cracks ◽  
Damage Condition

The security evaluation of some structures shocked by an underwater explosion (UNDEX) frequently plays a key role in some cases, and it is necessary to accurately predict the damage condition of the structure in an UNDEX environment. This study investigates the dynamic linear and non-linear responses and shock damages of two kinds of submerged cylindrical shell models exposed to underwater spherical trinitrotoluene (TNT) charge explosions in a circular lake. Two endplates and a middle plate are mounted on the cylindrical shells to provide support and to create two enclosed spaces. The two kinds of cylindrical shell models with the same geometry characteristics are unfilled and main hull sand-filled. Fifteen different tests are carried out by changing the TNT explosive weights of 1 and 2 kg, standoff distances ranging from 3 to 0.3 m, and two explosion positions. Measured experimental results are compared with each other, and some transformed data are obtained. A detailed discussion on experimental results shows that the dynamic responses and damage modes are much different, and the main hull sand-filled cylindrical shell is more difficult to be damaged by the shock wave loading than the unfilled model. Edge cracks are mainly observed at the instrument hull of the main hull sand-filled model, but surface tearing and cracks are observed on both the main hull and the instrumental hull of the unfilled model, respectively.

Experimental Study on Dynamic Response and Shock Damage of Cylindrical Shell Structures Subjected to Underwater Explosion

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Liang-Jun Li ◽  
Wei-Kang Jiang ◽  
Yan-Hui Ai
Keyword(s):  
Cylindrical Shell ◽  
Underwater Explosion ◽  
Experimental Results ◽  
Dynamic Responses ◽  
Shell Structures ◽  
Shock Wave Loading ◽  
Wave Loading ◽  
Nonlinear Responses ◽  
Shell Models ◽  
Edge Cracks

This study investigates the dynamic linear, nonlinear responses, and shock damage of two kinds of submerged cylindrical shell models exposed to underwater spherical trinitrotoluene (TNT) charge explosions in a circular lake. Two endplates and a middle plate are mounted on the cylindrical shells to provide support and create two enclosed spaces. The two kinds of cylindrical shell models are unfilled and main hull sand-filled, respectively. Fifteen different tests are carried out according to changing the TNT explosive weights of 1 kg and 2 kg, standoff distances ranging from 3 m to 0.3 m, and two explosion positions, and the measured experimental results are compared with each other. Detailed discussions on the experimental results show that the dynamic responses and damage modes are much different, and the main hull sand-filled cylindrical shell is more difficult to be damaged by the shock wave loading than the unfilled model. The edge cracks are mainly observed at the instrument hull of the main hull sand-filled model, but surface tearing and cracks take place both on the main and instrumental hulls of the unfilled model, respectively.

Dynamic Responses of a Cylindrical Shell Subjected to Shock Wave Induced by Underwater Explosion

1997 ◽  
Author(s):  
Zhong Weifang ◽  
Liu Zhongzu
Keyword(s):  
Shock Wave ◽  
Cylindrical Shell ◽  
Underwater Explosion ◽  
Dynamic Responses ◽  
Equilibrium Equations ◽  
Wave Pressure ◽  
Coupled Equations ◽  
Shock Wave Pressure ◽  
Wave Induced ◽  
Interaction Problem

Abstract The dynamic responses of a finite length cylindrical shell submerged in an infinite, inviscid, irrotational, incompressible fluid and subjected to shock waves induced to underwater explosion due to a spherical charge, are investigated in the view of method of modal superposition. Effects of shock wave pressure and hydrodynamic force are considered in shell equilibrium equations. By expanding distribution function of shock wave pressure into Fourier series and using method of Galerkin, the coupled equations of fluid-structure interaction problem are solved numerically. Finally, displacement re sponse of the shell is obtained.

Dynamic response of cylindrical shell structures subjected to underwater explosion

2009 ◽  
Vol 36 (8) ◽  
pp. 564-577 ◽  
Author(s):  
C.F. Hung ◽  
B.J. Lin ◽  
J.J. Hwang-Fuu ◽  
P.Y. Hsu
Keyword(s):  
Cylindrical Shell ◽  
Dynamic Response ◽  
Underwater Explosion ◽  
Shell Structures

scholarly journals New Statistical Randomness Tests Based on Length of Runs

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Ali Doğanaksoy ◽  
Fatih Sulak ◽  
Muhiddin Uğuz ◽  
Okan Şeker ◽  
Ziya Akcengiz
Keyword(s):  
Statistical Tests ◽  
Random Sequence ◽  
Cryptographic Protocols ◽  
Experimental Results ◽  
Security Evaluation ◽  
Random Numbers ◽  
Statistical Distributions ◽  
Cryptographic Algorithm ◽  
Encryption Algorithms ◽  
Randomness Tests

Random sequences and random numbers constitute a necessary part of cryptography. Many cryptographic protocols depend on random values. Randomness is measured by statistical tests and hence security evaluation of a cryptographic algorithm deeply depends on statistical randomness tests. In this work we focus on statistical distributions of runs of lengths one, two, and three. Using these distributions we state three new statistical randomness tests. New tests useχ2distribution and, therefore, exact values of probabilities are needed. Probabilities associated runs of lengths one, two, and three are stated. Corresponding probabilities are divided into five subintervals of equal probabilities. Accordingly, three new statistical tests are defined and pseudocodes for these new statistical tests are given. New statistical tests are designed to detect the deviations in the number of runs of various lengths from a random sequence. Together with some other statistical tests, we analyse our tests’ results on outputs of well-known encryption algorithms and on binary expansions ofe,π, and2. Experimental results show the performance and sensitivity of our tests.

Some new results and current challenges in the finite element analysis of shells

Acta Numerica ◽  
2001 ◽  
Vol 10 ◽  
pp. 215-250 ◽  
Author(s):  
Dominique Chapelle
Keyword(s):  
Finite Element ◽  
Shell Theory ◽  
Shell Structures ◽  
Engineering Practice ◽  
Element Analysis ◽  
Shell Elements ◽  
Shell Models ◽  
The Finite Element Analysis ◽  
Shell Finite Element ◽  
Mathematical Analyses

This article, a companion to the article by Philippe G. Ciarlet on the mathematical modelling of shells also in this issue of Acta Numerica, focuses on numerical issues raised by the analysis of shells.Finite element procedures are widely used in engineering practice to analyse the behaviour of shell structures. However, the concept of ‘shell finite element’ is still somewhat fuzzy, as it may correspond to very different ideas and techniques in various actual implementations. In particular, a significant distinction can be made between shell elements that are obtained via the discretization of shell models, and shell elements – such as the general shell elements – derived from 3D formulations using some kinematic assumptions, without the use of any shell theory. Our first objective in this paper is to give a unified perspective of these two families of shell elements. This is expected to be very useful as it paves the way for further thorough mathematical analyses of shell elements. A particularly important motivation for this is the understanding and treatment of the deficiencies associated with the analysis of thin shells (among which is the locking phenomenon). We then survey these deficiencies, in the framework of the asymptotic behaviour of shell models. We conclude the article by giving some detailed guidelines to numerically assess the performance of shell finite elements when faced with these pathological phenomena, which is essential for the design of improved procedures.

Stresses in compact end closures for cylindrical pressure vessels

1969 ◽  
Vol 4 (1) ◽  
pp. 57-64
Author(s):  
R W T Preater
Keyword(s):  
Cylindrical Shell ◽  
Rigid Body ◽  
Optimum Design ◽  
Cross Section ◽  
Experimental Verification ◽  
Pressure Vessels ◽  
Rigid Body Motion ◽  
Experimental Results ◽  
Body Motion ◽  
Annular Ring

Three different assumptions are made for the behaviour of the junction between the cylindrical shell and the end closure. Comparisons of analytical and experimental results show that the inclusion of a ‘rigid’ annular ring beam at the junction of the cylider and the closure best represents the shell behaviour for a ratio of cylinder mean radius to thickness of 3–7, and enables a prediction of an optimum vessel configuration to be made. Experimental verification of this optimum design confirms the predictions. (The special use of the term ‘rigid’ is taken in this context to refer to a ring beam for which deformations of the cross-section are ignored but rigid body motion is permitted.)

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