• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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• pp.329-338
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• 2006

The resilient mounts of a diesel engine installed onboard a ship should be designed for both static and dynamic loads. If possible, the resonance frequencies of the six rigid body modes of the installation and the flexible modes of the engine support structure should not lie within the engine operation range. In this paper a design criterion is proposed to evaluate an isolation system which involves the summation of dynamic forces transmitted through the resilient mounts and elastic potential energy index stored in the mounts. A case study is also presented in which a diesel engine generator, which had an elastic foundation and was mounted in a 5500 TEU container vessel, was studied both theoretically and experimentally. The theoretical analysis of the test model was performed by using a single mass 6 degree of freedom system. Actual measurements of mechanical vibration of the engine and its foundation onboard were carried out, which showed the importance of including the flexibility of the engine support structure in the mode.

• Bulletin of the Korean Chemical Society
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• v.7 no.4
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• pp.257-262
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• 1986

Thixotropy is a time-dependent shear-thinning phenomenon. We derived a new thixotropic formula which is based on the generalized viscosity formula of Ree and Eyring, $f={\Sigma}\frac{X_i}{{\alpha}_i}sinh^{-1}$ () (Refer to the text concerning the notation.) The following is postulated: (1) thixotropy occurs when small flow units attached to a large flow unit separate from the latter under stress (2) elastic energy(${\omega}$) is stored on the large flow unit during the flow process, and (3) the stored energy contributes to decrease the activation energy for flow. A new thixotropic formula was derived by using these postulations, $f={\frac}{X_0{\beta}_0}{\alpha_0}{\dot{s}}+{\frac}{X_1{\beta}_1}{{\alpha}_1}{\dot{s}}+{\frac}{X_2}{{\alpha_x}}sinh^{-1}$[$({\beta}_0)_2$ exp $(-C_2{\dot{s}}^2/RT){\cdot}{\dot{s}}$] f is the shear stress, and s is the rate of shear. In case of concentrated solutions where the Newtonian flow units have little contribution to the viscosity of the system, the above equation becomes, $f=\frac{X_2}{\alpha_2}sinh^{-1}$[$({\beta}_0)_2$ exp $(-C_2{\dot{s}}^2/RT){\cdot}{\dot{s}}$]. In order to confirm these formulas, we applied to TiO2(anatase and rutile)-water, printing ink and mayonnaise systems. Good agreements between the experiment and theory were observed.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.12
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• pp.1031-1035
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• 2002

The development of the solar and the wind power energy is necessary since the future alternative energies should have no pollution and no limitation. currently power generation system of MW scale has been developed, but it still has a few faults that its operation depends on with the weather condition. In order to solve these existing problems. combined generation system of photovoltaic(400W) and wind power generation system(400W) was suggested. It combines wind power and solar energy to have the supporting effect from each other. However. since the combined generation system cannot always generate stable output with ever-changing weather condition, power compensation device that uses elastic energy of spiral spring was added. In an experiment. when output of system gets lower than 12V(charging voltage), additional power was from the stored rotational energy of spiral spring.

• Coupled systems mechanics
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• v.9 no.4
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• pp.381-396
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• 2020

Analytical investigation of the fracture of inhomogeneous beam with two parallel lengthwise cracks is performed. The thickness of the beam varies continuously along the beam length. The beam is loaded in three-point bending. Two beam configurations with different lengths of the cracks are analyzed. The two cracks are located arbitrary along the thickness of the beam. Solutions to the strain energy release rate are derived assuming that the material has non-linear elastic mechanical behavior. Besides, the beam exhibits continuous material inhomogeneity along its thickness. The balance of the energy is analyzed in order to derive the strain energy release rate. Verifications of the solutions are carried-out by considering the complementary strain energy stored in the beam configurations. The influence of the continuous variation of the thickness along the beam length on the lengthwise fracture behavior is investigated. The dependence of the lengthwise fracture on the lengths of the two parallel cracks is also studied.

• Journal of the Korean Society for Nondestructive Testing
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• v.16 no.2
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• pp.79-85
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• 1996

Prediction of fatigue life and monitoring of fracture process for adhesively bonded CFRP composites joint have been investigated by analysis of acoustic emission signals during the fatigue and tension tests. During fatigue test, generated acoustic emission is related to stored elastic strain energy. By results of monitoring of AE event rate, fatigue process could be divided into two regions, and boundaries of two regions, fatigue cycles of the initiation of fast crack growth, were 70-80% of fatigue life even though the fatigue life were highly scattered from specimen to specimen. The result shows the possibility of predicting catastrophic failure by acoustic emission monitoring.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.6
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• pp.90-97
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• 2010

In order to understand the biomaterial like the blood vessel of artery, there is a need to quantify the biomechanical behavior of the vessel. Using computer-controlled experimental system, the experiment can acquire data such as inner pressure, axial load, diameter and axial gauge length without contacting the specimen. Rubber-liked material which is similar to passive artery was selected as pseudo-biomaterial. Deformations are measured for pressure-diameter curves. The data were collected and stored online to be used in the feedback control of experimental protocols. Finally, the illustrative data obtained from the experimental system were presented and the system shows that strain invariants are controlled to understand the nonlinear elastic behavior of biomaterial which is involved with strain energy function.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.151-151
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• 2011

Large amounts of natural gas, mainly methane, in the form of hydrates are stored on continental margins. When gas hydrates are dissociated by any environmental trigger, generation of excess pore pressure due to released free gas may cause sediment deformation and weakening. Hence, damage on offshore structures or submarine landslide can occur by gas hydrate dissociation. Therefore, geotechnical stability of gas hydrate bearing sediments is in need to be securely assessed. However, geotechnical characteristics of gas hydrates bearing sediments including small-strain elastic moduli have been poorly identified. Synthesizing gas hydrate in natural seabed sediment specimen, which is mainly composed of silty-to-clayey soils, has been hardly attempted due to their low permeability. Moreover, it has been known that hydrate loci in pore spaces and heterogeneity of hydrate growth in specimen scale play a critical role in determining physical properties of hydrate bearing sediments. In the presented study, we synthesized gas hydrate containing sediments in an instrumented oedometric cell. Geotechnical and geophysical properties of gas hydrate bearing sediments including compressibility, small-strain elastic moduli, elastic wave, and electrical resistivity are determined by wave-based techniques during loading and unloading processes. Significant changes in volume change, elastic wave, and electrical resistivity have been observed during formation and dissociation of gas hydrate. Experimental results and analyses reveal that geotechnical properties of gas hydrates bearing sediments are highly governed by hydrate saturation, effective stress, void ratio, and soil types as well as morphological feature of hydrate formation in sediments.

• Coupled systems mechanics
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• v.7 no.2
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• pp.211-232
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• 2018

In this work we present an upscaling technique for multi-scale computations based on a stochastic model calibration technique. We consider a coarse-scale continuum material model described in the framework of generalized standard materials. The model parameters are considered uncertain, and are determined in a Bayesian framework for the given fine scale data in a form of stored energy and dissipation potential. The proposed stochastic upscaling approach is independent w.r.t. the choice of models on coarse and fine scales. Simple numerical examples are shown to demonstrate the ability of the proposed approach to calibrate coarse scale elastic and inelastic material parameters.

• Geomechanics and Engineering
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• v.15 no.6
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• pp.1153-1160
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• 2018

Rockbursts, catastrophic events involving the violent release of elastic energy stored in rock features, remain a worldwide challenge for geoengineering. Especially at deep-mining sites, rockbursts can occur in hard, high-stress, brittle rock zones, and the associated risk depends on such factors as mining activity and the stress on surrounding rocks. Rockbursts are often sudden and destructive, but there is still no unified standard for predicting them. Based on previous studies, a new Bayesian multi-index model was introduced to predict and evaluate rockbursts. In this method, the rock strength index, energy release index, and surrounding rock stress are the basic factors. Values from 18 rock samples were obtained, and the potential rockburst risks were evaluated. The rockburst tendencies of the samples were modelled using three existing methods. The results were compared with those obtained by the new Bayesian model, which was observed to predict rockbursts more effectively than the current methods.

• The korean journal of orthodontics
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• v.27 no.6 s.65
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• pp.943-954
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• 1997

Forces needed for orthodontic tooth movement are obtained from various appliances such as orthodontic wires or elastic rubber. Orthodontic elastic rubber is widely used clinically, but permanent deformation and force decay may occur from the environmental changes, time of clinical use and the extent of the stretch, making the Prediction of force being applied difficult. The Present study examined and compared the changes in residual force between three brands of elastomeric chains (Ormco Generation II Power Chains ; brand A, RMO : Energy-Chain ; brand B, Unitek : AlastiK ; brand C) under various environmental conditions, amount of initial force, types of elastomer and the rate of extension. The characteristic physical properies of the elastomeric chains were as follows. 1. In all three brands, the residual force ratio was largest when the chains were stored in air, with no difference between water and saliva. 2. In all three brands, after 24 hours, there was no statistical difference in residual force ratio according to the initial force level. 3. In Brand A and B, the presence of filament had no correlation with the residual force ratio. In Brand C force decay was more severe when the chain contained filament. 4. In each brand, rate of extension had no effect on residual force ratio. 5. Brand B showed relatively higher residual force ratio compared to other brands.