• Journal of the Korean Society for Precision Engineering
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• v.33 no.10
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• pp.805-811
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• 2016

Prior to installation in a navy ship, shipboard equipment should be qualified by shock test requirements. The multi-function console mounted on the elastic platform of the ship should also withstand given shock loads. In this study, both real shock test methods, as well as numerical computer simulations using the finite element method were used to verify structural durability under shock load conditions. First, we used domestic test facilities to perform possible shock tests, including an impact hammer test, a drop table test and a shaker shock test. Full model tests satisfying the shock response spectrum level were performed. Thereafter, an analytical model of the complex console structure was built by the finite element method. Finally, numerical results were verified by modal test results of the real product and an FEA analysis was also performed with a full model transient response analysis.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.3
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• pp.279-287
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• 2018

This study investigated applicability of the fast running model for damage assessment of underground structures by ground shock. For this reason, the fast running model that consists of two main models such as the ground shock generation and propagation model and the underground structural damage assessment model was developed. The ground shock generation and propagation model was programed using theoretical formula and empirical formula introduced in TM5-855-1(US army manual). The single degree of freedom model of structural components was utilized to predict structural dynamic displacements which are used as index to assess damage level of components. In order to confirm the feasibility of the developed fast running model, underground structural dynamic displacements estimated from the fast running model were compared to displacements obtained from the finite element analysis.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.12 no.3
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• pp.103-113
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• 2013

Shock wave model describes the propagation speed of kinematic waves in traffic flow. It was first presented by Lighthill and Whitham and has been deployed to solve many traffic problems. A recent paper pointed out that there are some traffic situations in which shock waves are not observable in the field, whereas the model predicts the existence of waves. The paper attempted to identify how such a counterintuitive conclusion results from the L-W model, and resolved the problem by deriving a new asymptotical shock wave model. Although the asymptotical model successfully eliminated the paradox of the L-W model, the validation of the new model is confined within the realm of the deceleration flow situation since the model was derived under such constraint. The purpose of this paper is to derive the remaining counter asymptotical shock wave model for acceleration traffic flow. For this, the vehicle trajectories in a time-space diagram modified to accommodate the continuously increased speed at every instant in such a way that the relationship between the spacing from the preceding vehicle and the speed of the following vehicle strictly follows Greenshield's model. To verify the validity of the suggested model, it was initially implemented to a constant flow where no shock wave exists, and the results showed that there exists no imaginary shock wave in a homogeneous flow. Numerical applications of the new model showed that the shock wave speeds of the asymptotical model for the acceleration flow tend to lean far toward the forward direction consistently. This means that the asymptotical models performs in a systematically different way for acceleration and for declaration flows. Since the output difference among the models is so distinct and systematic, further study on identifying which model is more applicable to an empirical site is recommended.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.6
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• pp.63-68
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• 2006

Recent statistical data regarding electric shock accidents have been analyzed to examine the electric shock accidents occurred at the voltage of 22,900[V], In order to demonstrate the mechanism of the 22,900[V] electric shock accident, a number of experiments to simulate electric shock accidents have been performed based on the analysis results. In the experiment, the current flowing through a human body model was measured to quantitatively analyze the hazards of the simulated electric shock accidents in various situations. As a result of the experiment, it was shown that once an electric shock accident occurred the accident proved fatal to the human body, regardless of electric shock situation.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1327-1335
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• 2002

The shock wave process represents an abrupt change in fluid properties, in which finite variations in pressure, temperature, and density occur over the shock thickness which is comparable to the mean free path of the gas molecules involved. This shock wave fluid phenomenon is simulated by using the finite difference lattice Boltzmann method (FDLBM). In this paper, a new model is proposed using the lattice BGK compressible fluid model in FDLBM for the purpose of speeding up the calculation as well as stabilizing the numerical scheme. The numerical results of the proposed model show good agreement with the theoretical predictions.

• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.664-670
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• 2004

Navier-Stokes computation based on a new simplified model is proposed to investigate the interactions of a moving shock wave with multiple vortices arranged in the serial manner. This model problem simulates shock-vortexlet interactions at the shear layer of a compressible vortex often observed in the experiment. Applying the Foppl's idea, we extended the Rankin's model generally used for the description of a single vortex to the multi-vortex version. The acoustic pulses accelerated and decelerated are successively generated and propagated from each shock-vortex interaction, which simply explains the genesis of eccentrically diverging acoustic waves appearing in the experimental photograph.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.12
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• pp.1347-1353
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• 2004

With respect to the researches of the optical flying head(OFH) , the head-gimbal assembly should be analyzed to guarantee the stable fabrication and the characteristics of shock resistance. The suitable design is proved through the Probabilistic analysis of the design parameters and material properties of the model. Probabilistic analysis is a technique that be used to assess the effect of uncertain input parameters and assumptions on your analysis model. Using a probabilistic analysis you can find out how much the results of a finite elements analysis are affected by uncertainties in the model. Another factor is analysis of the dynamic shock analysis. For the mobile application, one of the important requirements is durability under severe environmental condition, especially, resistance to mechanical shock. An important challenge in the disk recording is to improve disk drive robustness in shock environments. If the system comes in contact with outer shock disturbance. the system gets critical damage in head-gimbal assembly or disk. This paper describes probabilistic and dynamic shock analysis of head-gimbal assembly in micro MO drives using OFH slider.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.986-992
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• 2011

In this paper, the characteristics of shock behavior of multi-layered panels under impact were studied. The panels consist of four different lightweight materials including al, al-foam, rubber and FRP in order to enhance their shock energy absorption. A commercial code, Ls-dyna was used to build the numerical model and study shock behavior based on the analysis of shock response spectrum and peak response acceleration. The reliability of the numerical model was estimated by its comparison with the experimental results acquired under the same impact conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.1111-1116
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• 2001

A transient T-F(time-frequency) signal processing technique is applied to a tilt drop and a linear shock test rigs for identification of shock characteristics of hard disk drive (HDD). The T-F technique essentially tracks the shock characteristics of pivot point response as well as head slap and lift-off phenomena. From the T-F analysis result, the shock characteristic in HDD is modeled by the two degree of freedom coupled-dynamic system, which consists of actuator arm and suspension. As shock designing tool, the maximax shock response spectrum is employed for prediction of shock performance. Finally, the shock control technique is tested with newly designed actuator arm and suspension. Experimental head slap test result shows that the shock performance is much higher with the new shockproof designed model than the current model

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.250-253
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• 2005

This paper is investigates the separation shock of payload fairing. Separation test of subscale PLF using half separation device and half PLA is performed. Resulting shock loads at equipment bay and fairing joint are measured. Pyroshock estimation is performed using AUTOSEA Pyroshock Module. Input data to analysis model is obtained from the separation test results of subscale PLF. And model of AUTOSEA is updated comparing results between tests and analysis.. This enables us to validate the AUTOSEA model. Tuned model of subscale PLF and separation device is used to update full scale model, and the shock analysis result of full scale model is estimated in this paper. This paper also discusses the results regarding the difficulty of structural modeling and its numerical implementation in AutoSEA2 Software.