A simplified theoretical model of the whipping response of a hull girder subjected to underwater explosion considering the damping effect

Nonobstructive particle damping (NOPD) is a novel passive control technology with strong nonlinear-damping. Many scholars put effort into the research on the internal mechanism of NOPD. In contrast, the application of NOPD to engineering has not received much research effort. A theoretical model based on the principle of gas–solid flows, which is employed to evaluate damping effect of NOPD and to predict dynamic response of a machine rack by a co-simulation approach, is established in this paper. In view of the difference between damping effect acting on the lateral and bottom of NOPD holes directly, total damping force is divided into lateral damping force and bottom damping force according to the Janssen theory of stress changed direction. Moreover, NOPD technology is applied to a machine rack for discussing its vibration isolation performance. The results indicate that NOPD technology can suppress the intense vibration, especially between 4000 Hz and 8000 Hz. It is noted that the theoretical model of NOPD can accurately predict the dynamic response of the machine rack with NOPD. The 1/3 Octave vibration energy spectrum indicates that NOPD technics can dissipate the vibration energy of the machine rack at full frequency, especially in 31.5 Hz, and attenuation up to 39.75 dB.

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Damage evaluation of a simplified hull girder subjected to underwater explosion load: A semi-analytical model

Marine Structures ◽

10.1016/j.marstruc.2015.10.005 ◽

2016 ◽

Vol 45 ◽

pp. 43-62 ◽

Cited By ~ 6

Author(s):

Hao Wang ◽

Yuan Sheng Cheng ◽

Jun Liu ◽

Lin Gan

Keyword(s):

Analytical Model ◽

Underwater Explosion ◽

Damage Evaluation ◽

Hull Girder ◽

Explosion Load

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Dynamic response of hull girder subjected to combined underwater explosion and wave induced load

Ocean Engineering ◽

10.1016/j.oceaneng.2021.109436 ◽

2021 ◽

Vol 235 ◽

pp. 109436

Author(s):

Hongchang Zhou ◽

Xiangshao Kong ◽

Yiwen Wang ◽

Cheng Zheng ◽

Zhiyong Pei ◽

...

Keyword(s):

Dynamic Response ◽

Underwater Explosion ◽

Hull Girder ◽

Wave Induced

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Self-induced vibration of bandsaw blades during cutting

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/0954406991522329 ◽

1999 ◽

Vol 213 (4) ◽

pp. 371-380 ◽

Cited By ~ 7

Author(s):

L Le-Ngoc ◽

H McCallion

Keyword(s):

Theoretical Model ◽

Machine Tool ◽

Vibration Characteristics ◽

Squeeze Film ◽

Physical Explanation ◽

Air Gaps ◽

Damping Effect ◽

Squeeze Film Damping ◽

Machine Tool Chatter ◽

New Interpretation

A new interpretation of the washboarding phenomenon found in bandsawing of wood is given in this paper. A theoretical model of the washboarding pattern was derived by considering the motion of the teeth during cutting. The theory of machine tool chatter was adapted to illustrate the mechanism of self-induced vibration in bandsawing and to provide a criterion for its existence. It was found that the whole cutting span of the band should be used to determine the vibration characteristics instead of the previous practice of using the section between the workpiece and the top wheel. It has been found that the frequencies responsible for washboarding are all torsional frequencies and physical explanation for this is suggested by considering the squeeze film damping effect of the air gaps between the blade and the sawn surfaces.

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Preliminary Calculations for Minehunter's Genset Foundations

Transactions on Maritime Science ◽

10.7225/toms.v08.n01.006 ◽

2019 ◽

Vol 8 (1) ◽

pp. 54-61

Author(s):

Andrzej Grządziela ◽

Marcin Kluczyk

Keyword(s):

Underwater Explosion ◽

Classification Rules ◽

Calculation Methods ◽

Foundation Design ◽

Naval Vessel ◽

Technical Data ◽

Damping Effect ◽

Calculation Results ◽

Shock Resistance ◽

Force Calculation

The requirements for the foundations of naval vessel engines are based on classification rules devised by classification societies or/and military standardization rules. A class guideline was published, defining the requirements, acceptance criteria and machinery seating methods. There is also a schedule of basic calculation procedures for cast resin or rubber chocks which facilitates the process of machinery foundation design, preloading force calculation, the establishment of boundary conditions etc. In case of naval vessels, typical procedures do not meet tactical requirements due to potential explosion loads. Since minehunters are mainly deployed at sea, handling active, naval mines, the shock resistance calculation for the entire machinery, including the Genset, is required. The paper presents preliminary MatLab calculation methods which can be used to analyse the type, number and location of rubber or elastomer chocks. The procedure consists of input data such as UNDEX pressure and technical data of the Genset used in the Polish Navy. Calculation results include the analysis of the dynamic interaction between the Genset and the foundation, as well as the damping effect generated by the UNDEX (UNDerwater EXplosion) shock pulse.

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An experimental study on the dynamic response of a hull girder subjected to near field underwater explosion

Marine Structures ◽

10.1016/j.marstruc.2015.07.002 ◽

2015 ◽

Vol 44 ◽

pp. 43-60 ◽

Cited By ~ 6

Author(s):

Zhenhua Zhang ◽

Yuanxin Wang ◽

Haifeng Zhao ◽

Haifeng Qian ◽

Jinlei Mou

Keyword(s):

Experimental Study ◽

Dynamic Response ◽

Near Field ◽

Underwater Explosion ◽

Hull Girder

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A theoretical model for understanding dentists' behavior in treating patients with AIDS

Journal of Dental Education ◽

10.1002/j.0022-0337.1991.55.11.tb02589.x ◽

1991 ◽

Vol 55 (11) ◽

pp. 708-716 ◽

Cited By ~ 1

Author(s):

MS Chen

Keyword(s):

Theoretical Model

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A Model for Analyzing Suicide Prevention

Crisis ◽

10.1027//0227-5910.21.2.80 ◽

2000 ◽

Vol 21 (2) ◽

pp. 80-89 ◽

Cited By ~ 3

Author(s):

Maila Upanne

Keyword(s):

Risk Factors ◽

Theoretical Model ◽

Protective Factors ◽

Suicide Prevention ◽

Suicide Risk ◽

Practical Work ◽

Individual Risk ◽

Self Assessment ◽

Prevention Project ◽

Individual Risk Factors

This study monitored the evolution of psychologists' (n = 31) conceptions of suicide prevention over the 9-year course of the National Suicide Prevention Project in Finland and assessed the feasibility of the theoretical model for analyzing suicide prevention developed in earlier studies [ Upanne, 1999a , b ]. The study was formulated as a retrospective self-assessment where participants compared their earlier descriptions of suicide prevention with their current views. The changes in conceptions were analyzed and interpreted using both the model and the explanations given by the subjects themselves. The analysis proved the model to be a useful framework for revealing the essential features of prevention. The results showed that the freely-formulated ideas on prevention were more comprehensive than those evolved in practical work. Compared to the earlier findings, the conceptions among the group had shifted toward emphasizing a curative approach and the significance of individual risk factors. In particular, greater priority was focused on the acute suicide risk phase as a preventive target. Nonetheless, the overall structure of prevention ideology remained comprehensive and multifactorial, stressing multistage influencing. Promotive aims (protective factors) also remained part of the prevention paradigm. Practical working experiences enhanced the psychologists' sense of the difficulties of suicide prevention as well as their criticism and feeling of powerlessness.

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