FE Analysis of Ship Structures Under Blast Loads

2008 ◽  
Author(s):  
Satyaranjan Sinha ◽  
D. G. Sarangdhar
Keyword(s):  
Solution Process ◽  
Mechanical Damage ◽  
Underwater Explosion ◽  
Time History ◽  
Complex Loading ◽  
Large Structure ◽  
Empirical Formulas ◽  
Load Calculation ◽  
Underwater Shock ◽  
Shock Simulation

Naval vessels and Submarines structures in their fighting role are susceptible to Underwater shock generated due to explosion of torpedoes, mines, depth charges etc. The damage inflicted by Non-Contact Underwater explosion consists of direct shock wave damage of hull, whipping damage of keel and mechanical damage to onboard equipment and associated systems. Hence in order to design a shock resistant structure or to know the shock withstandibility of the same, it is important to simulate these structures and loads and then subsequently analyze the same to predict the response (as performing experiments would be expensive). The Underwater explosion analysis of large structures like ships could be considered as one of the most complicated numerical analysis. The most important steps of these analyses are, the accurate load calculation and then the solution process. Loads can be calculated using published empirical formulas, which are complicated if calculated for a large structure. Also the application of load time history for large structure is a tedious job. To solve the complications related to load calculation and application, an in-house software named IRUNDEX, was developed, which, not only calculates the complex loading at all panels comprising the ship structure, but could also apply the loads (using ANSYS Macro) within minutes, thus saving considerable percentage of time taken for the analysis. It could be recognized that underwater shock simulation and analysis should form an important criterion to verify the design of any Naval Vessel or structure susceptible to explosions. This present work illustrates the use of the FE Software ANSYS, backed up with the in-house developed software, for Underwater Explosion analysis of structures.

scholarly journals Ship Blast Analysis

2021 ◽  
Vol 9 (VII) ◽  
pp. 1249-1255
Author(s):  
E. Deepak Naidu
Keyword(s):  
Shock Wave ◽  
Numerical Analysis ◽  
Mechanical Damage ◽  
Large Structure ◽  
Empirical Formulas ◽  
Large Structures ◽  
Blast Analysis ◽  
Contact Explosion ◽  
Resistant Structure ◽  
Onboard Equipment

Naval vessels and Submarines structures in their fighting role are susceptible to explosion of torpedoes, mines, TNT etc. The damage inflicted by Contact explosion consists of direct shock wave damage to hull, whipping damage to keel and mechanical damage to onboard equipment and associated systems. The order to design a shock resistant structure, it is important to simulate these structures and loads and then subsequently analyze the same to predict the response (as performing experiments would be expensive). The TNT (Trinitrotoluene) explosion analysis of large structures like ships could be considered as one of the most complicated numerical analysis. Loads can be calculated by using published empirical formulas, which are complicated if calculated the large structure. By using of the FE Software ANSYS, backed up with in the developed software, for Explosion analysis of structures.

The Study on the Dynamic Response of Cylindrical Pressure Hull on the Different Shock Loading Empirical Formula

2015 ◽  
Vol 799-800 ◽  
pp. 604-609 ◽  
Author(s):  
Ching Yu Hsu ◽  
Tso Liang Teng ◽  
Cho Chung Liang ◽  
Hai Anh Nguyen ◽  
Chien Jong Shih
Keyword(s):  
Dynamic Response ◽  
Empirical Formula ◽  
Shock Loading ◽  
Failure Modes ◽  
Underwater Explosion ◽  
The Other ◽  
Empirical Formulas ◽  
Underwater Shock ◽  
Simulation Results ◽  
Better Than

This paper focuses on the comparison between underwater explosion (UNDEX) shock loading empirical formulations. First, the numerical simulations for a cylindrical pressure hull subjected to UNDEX loading were conducted and the results are close to the failure modes shown in experiments of Kwon (1993). Second, the empirical UNDEX loading formula of Cole (1948), Keil (1961) and Shin (1994) used in cylinder subjected to underwater shock loading were compared. The simulation results by using three empirical formulas were compared and Shin’s (or Cole’s) empirical formula was shown to be better than the other empirical formulations when subjected to an UNDEX under the same conditions. The analytical results offer a valuable reference to the research of underwater explosion.

scholarly journals Improved Empirical Identification of the Inverse Model of a Squeeze-Film Damper Bearing Based on a Recurrent Neural Network

2018 ◽  
Author(s):  
Ghaith Ghanim Al-Ghazal ◽  
Philip Bonello ◽  
Sergio G. Torres Cedillo
Keyword(s):  
Neural Network ◽  
Recurrent Neural Network ◽  
Structural Model ◽  
Solution Process ◽  
Time History ◽  
Inverse Model ◽  
Training Data ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
History Of

Most recently proposed techniques for inverse rotordynamic problems seek to identify the unbalance on a rotor using a known structural model and measurements from externally mounted sensors only. Such non-intrusive techniques are important for balancing rotors that cannot be accessed under operational conditions because of temperature or space restrictions. The presence of nonlinear bearings, like squeeze-film damper (SFD) bearings used in aero-engines, complicates the solution process of the inverse rotordynamic problem. In certain practical aero-engine configurations, the solution process requires a substitute for internal instrumentation to quantify the SFD journal vibration. This can be provided by an inverse model of the SFD bearing which outputs the time history of the relative vibration of the SFD journal relative to its housing, for a given input time history of the SFD force. This paper focuses on the inverse model of the SFD and presents an improved methodology for its identification via a Recurrent Neural Network (RNN) trained using experimental data from a purposely designed rig. The novel application of chirp excitation via two orthogonal shakers considerably improves both the quality of the training data and the efficiency of its generation, relative to an earlier preliminary work. Validation test results show that the RNNs can predict the journal displacement time history with reasonable accuracy. It is therefore expected that such an inverse SFD model would serve as a reliable component in the solution of the wider inverse problem of a rotordynamic system.

scholarly journals Numerical Simulation and Response of Stiffened Plates Subjected to Noncontact Underwater Explosion

2014 ◽  
Vol 2014 ◽  
pp. 1-17 ◽  
Author(s):  
Elsayed Fathallah ◽  
Hui Qi ◽  
Lili Tong ◽  
Mahmoud Helal
Keyword(s):  
Numerical Simulation ◽  
Underwater Explosion ◽  
Design Guidelines ◽  
Nonlinear Finite Element ◽  
Steel Plates ◽  
Stiffened Plates ◽  
Shock Loads ◽  
Floating Structures ◽  
Underwater Shock ◽  
Overall Performance

A numerical simulation has been carried out to examine the response of steel plates with different arrangement of stiffeners and subjected to noncontact underwater explosion (UNDEX) with different shock loads. Numerical analysis of the underwater explosion phenomena is implemented in the nonlinear finite element code ABAQUS/Explicit. The aim of this work is to enhance the dynamic response to resist UNDEX. Special emphasis is focused on the evolution of mid-point displacements. Further investigations have been performed to study the effects of including material damping and the rate-dependant material properties at different shock loads. The results indicate that stiffeners configurations and shock loads affect greatly the overall performance of steel plates and sensitive to the materials data. Also, the numerical results can be used to obtain design guidelines of floating structures to enhance resistance of underwater shock damage, since explosive tests are costly and dangerous.

High Pressure Generation Using Underwater Explosion of a Spiral Explosive in a Conical Vessel

2004 ◽  
Vol 126 (2) ◽  
pp. 258-263
Author(s):  
Toru Hamada ◽  
Shigeru Itoh ◽  
Kenji Murata ◽  
Yukio Kato
Keyword(s):  
Shock Wave ◽  
Characteristic Curve ◽  
Three Dimensional ◽  
Underwater Explosion ◽  
Initial Pressure ◽  
Maximum Pressure ◽  
Underwater Shock Wave ◽  
Expansion Curve ◽  
Underwater Shock ◽  
Manganin Gauge

An explosive configuration was studied so that the underwater shock wave converges at the tip of the explosive, and a three-dimensional spiral configuration was obtained. This spiral configuration need to be analyzed theoretically due to the relation of propagation velocity of underwater shock wave, detonation velocity of the explosive and a configuration of vessel to charge the explosive. In order to study an effect of the convergence, pressure measurement at the spiral center was carried out by using a manganin gauge. Therefore, when SEP was used in this experiment, the maximum pressure value was 17.7 GPa. This maximum pressure value is higher than the pressure value of underwater shock wave generated from the underwater explosion of a straight configuration. Furthermore, this maximum pressure value was higher than C-J pressure of SEP. An initial pressure of underwater shock water shock wave that can obtain from an isentropic expansion curve of SEP and a characteristic curve of water is 5.7 GPa, and C-J pressure of SEP is 15.9 GPa. From the above-mentioned, the effect of spiral convergence could be shown well.

Effects of Steel Case on Underwater Shock Wave

2011 ◽  
Vol 52-54 ◽  
pp. 943-948
Author(s):  
Ji Li Rong ◽  
Da Lin Xiang ◽  
Jian Li
Keyword(s):  
Shock Wave ◽  
Peak Pressure ◽  
Underwater Explosion ◽  
Steel Shell ◽  
Cylindrical Charge ◽  
Underwater Shock Wave ◽  
Shock Wave Energy ◽  
Lag Effect ◽  
Underwater Shock ◽  
Different Thickness

The effects of steel case confinement for the aluminized explosive on underwater explosion(UNDEX) were experimentally and numerically investigated. The experimental results using 1kg cylindrical charge cased 6mm steel shell, show that steel case enhance the peak pressure, impulse, shock wave energy and decay time relative to the bare charge. The effect of different thickness of steel case was analyzed. With the increase of the case thickness, the shock wave were enhanced first and weaken later, and there is a lag-effect for the peak pressure of shock wave. There is an optimal case thickness which could maximum enhance the peak pressure. According to dimensional analysis, it's found that the ratio of case mass and charge mass( ) is a better dimensionless parameter to estimate UNDEX for a cased charge.

scholarly journals Fundamental Characteristics of Underwater Shock Wave due to Underwater Explosion of High Explosives.

1996 ◽  
Vol 62 (601) ◽  
pp. 3278-3283
Author(s):  
Shigeru ITOH ◽  
You NADAMITSU ◽  
Akio KIRA ◽  
Shiro NAGANO ◽  
Masahiro FUJITA ◽  
...  
Keyword(s):  
Shock Wave ◽  
Underwater Explosion ◽  
High Explosives ◽  
Underwater Shock Wave ◽  
Underwater Shock

Basic Study on the Crushing of Frozen Soil by Shock Loading

2007 ◽  
Author(s):  
Toshiaki Watanabe ◽  
Hironori Maehara ◽  
Masahiko Otsuka ◽  
Shigeru Itoh
Keyword(s):  
Shock Wave ◽  
High Speed ◽  
Shock Loading ◽  
Underwater Explosion ◽  
Frozen Soil ◽  
High Speed Camera ◽  
Underwater Shock Wave ◽  
Basic Study ◽  
Underwater Shock ◽  
A New Technique

The aim of study is to confirm a new technique that can crush the frozen soil and/or ice block using underwater shock wave generated by the underwater explosion of explosive. This technique can lead to the earlier sowing, which can have the larger harvest because the duration of sunshine increases. Especially, in Hokkaido prefecture, Japan, if the sowing is carried out in April, we can expect to have 150% of harvest in the ordinary season. This technique is effective against the cold regions. For example, Korea, China, Mongolia, Russia, Norway, and Sweden, etc. At first, we carried out experiments usung a detonating fuse and ice block. The process of ice breaking was observed by means of a high-speed camera. In order to check about that influence we tried to give an actual frozen soil a shock wave.

Influence of Pressure Vessel Shape on Explosive Forming

2018 ◽  
Author(s):  
Hirofumi Iyama ◽  
Masatoshi Nishi ◽  
Yoshikazu Higa
Keyword(s):  
Shock Wave ◽  
Pressure Vessel ◽  
Underwater Explosion ◽  
Metal Plate ◽  
Reflected Shock Wave ◽  
Underwater Shock Wave ◽  
Reflected Shock ◽  
Final Deformation ◽  
Underwater Shock ◽  
Explosive Forming

The explosive forming is a characteristic forming method. This technique is a metal forming using an underwater shock wave. The underwater shock wave is generated by underwater explosion of the explosive. The metal plate is formed with involving the high strain rate on this technique. In generally, the pressure vessel is used in this method due to the effective utilization of the explosion energy. The underwater shock wave is propagated in water and reflected on inside wall of the pressure vessel. This reflected shock wave is affected on the deformation shape of a metal plate. Therefore, the inside shape of pressure vessel is often changed. In other words, the shape of pressure vessel is changed, the shock pressure distribution on the metal plate and it is possible that final deformation shape of the metal plate is changed. Some numerical simulations and experiments have been carried out to clear the influence of the inside shape of pressure vessel in the explosive forming. This paper is included the results and discussions on the numerical simulation and experiment used those conditions.

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