• Composites Research
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• v.16 no.5
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• pp.21-27
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• 2003

Using the theory of linear piezoelectricity, the dynamic response of a central crack in a functionally graded piezoelectric ceramic under anti-plane shear impact is analyzed. We assume that the properties of the functionally graded piezoelectric material vary continuously along the thickness. By using the Laplace and Fourier transform, the problem is reduced to two pairs of dual integral equations and then into Fredholm integral equations of the second kind. Numerical values on the dynamic stress intensity factors are presented to show the dependence of the gradient of material properties and electric loading.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.2
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• pp.298-309
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• 1990

In this paper, a new method is suggested to analyze impulsive stresses at loading poing of concentrated impact load under certain impact conditions determined by impact velocity, stiffness of plate and mass of impact body, etc. The impulsive stresses are analyzed by using the three dimensional dynamic theory of elasticity so as to analytically clarify the generation phenomenon of cone crack at the impact fracture of fragile materials (to be discussed if the second paper). The Lagrange's plate theory and Hertz's law of contact theory are used for the analysis of impact load, and the approximate equation of impact load is suggested to analyze the impulsive stresses at the impact point to decide the ranage of impact load factor. When impact load factors are over and under 0.263, approximate equations are suggested to be F(t)=Aexp(-Bt)sinCt and F(t)=Aexp(-bt) {1-exp(Ct)} respectively. Also, the inverse Laplace transformation is done by using the F.F.T.(fast fourier transform) algorithm. And in order to clarity the validity of stress analysis method, experiments on strain fluctuation at impact point are performed on a supported square glass plate. Finally, these analytical results are shown to be in close agreement with experimental results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.9
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• pp.805-812
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• 2011

This study investigated the characteristics of heavy-weight floor impact sounds of box-frame type structure using 1:10 scale model. Ten types of floor structures(bare slabs and floating floors) were evaluated in terms of dynamic stiffness and loss factor. Floor vibrations and radiated sounds generated by simulated impact source were also measured. The results showed that the bakelite was appropriate for simulating concrete slab in the 1:10 scale model, and surface velocity and sound pressure level of concrete slab measured from the scale model showed similar tendencies with the results from in-situ in frequency domain. It was also found that dynamic behaviors of layered floor structures in the 1:10 scale model were similar to those in a real scale. Therefore, the use of 1:10 scale model would be useful for evaluating the heavy-weight floor impact sound insulation of layered floor structures when the frequency-dependent dynamic properties of each material are known.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.934-939
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• 2004

The Korea high-speed rail, based on the French design. It also implements new concept to increase the strength of bridge deck by adding an impact factor (dynamic intensity factor) in static load. In order to assure the dynamic stability, SYSTRA and Jeseph Penzien, a professor in CEC (the US) conducted a dynamic stability review on design phase. Analyzing the review results, they developed design criteria for dynamic behavior. This study deal with operating PSC box GIRDER equipped with measurement equipment or measured data of Seoul $\∼$ Taejeon, P.S.C BOX GIRDER bridge and steel comsition bridge equipped with measurement equipment based on structual knowledge about configuration of measuring sensor, response analysis of structure when train runs was performed by using measured data of PSC box girder to directly compare with design criteria. moreover, the dynamic stability with comparison of high-speed rail construction criteria was reviewed and analyzed based on historical records.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.1
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• pp.61-71
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• 2004

The performance evaluation and deflection of 3 spans concrete simplicity slab bridge analyzed by non-destructive and loading test. Compressive strength of slab and pier appeared in the range of each 353∼366 kgf/$cm^2$ and 152∼215 kgf/$cm^2$ in rebound number test. Also, it appeared that concrete quality of slab was good after performance improvement. The average compressive strength of slab by core picking appeared 229 kg/$cm^2$. In reinforcing bar arrangement test of span and member, it appeared that horizontal and vertical reinforcing bar was arranged to fixed interval. The value of calculation deflection that carried structural analysis with deflection analysis wave in static loading test appeared higher than that of experimental deflection and it appeared that hardness of this bridge was good. Maximum impact factor that estimated from deflection by running speed in dynamic loading test appeared by 0.216 in 10 km/hr running speed.

• Journal of the Korean Institute of Gas
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• v.12 no.1
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• pp.1-6
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• 2008

The notched Charpy impact test is one of the most prevalent techniques used to characterize the effect of high impulse loads on polymeric materials. In this study, a method of analysis in nylon plastic materials is suggested to evaluate the critical strain energy release rate for variation of notch angles from the Charpy impact energy measurement. Instrumented Charpy impact tester was used to extract ancillary information concerning fracture parameters in addition to total fracture properties and maximum critical load. The dynamic stress intensity factor of nylon plastic material was calculated for the ASTM Charpy specimen from the obtained maximum critical load. Also, the finite element model was developed to figure out the stress distributions for Charpy specimen with different notch angles subject to 3 point bending load which is equivalent to the load applied in the experiment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.191-195
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• 2003

충격음 저감재의 동탄성계수와 감쇠계수는 차단성능을 평가하는데 있어 중요한 물성치가 된다. 저감재의 동탄성계수는 뜬바닥구조의 고유진동수를 결정짓게 되며, 저감재의 동탄성계수가 높을수록, 즉 고유진동수가 높아짐에 따라 실험실 경량충격음레벨 저감량은 지수함수적으로 감소됨을 실험을 통해 알 수 있다. 또한, 저감재를 포함한 뜬바닥구조를 1자유도 진동계로 가정한 이론값과 실험실 경량충격음레벨 저감량의 결과가 비교적 잘 일치하는 것으로 나타났으며, 이 때 감쇠계수의 영향은 반드시 고려되어야 한다.

• International Journal of Safety
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• v.9 no.2
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• pp.16-21
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• 2010

In this study, the variations of transformed impact factors and load carrying capacity of highway bridges measured from the state of expansion joint are evaluated. the field loading tests were performed on the highway bridge with damaged expansion joint to investigate the variation of the load carrying capacity. From the field loading tests in case that damaged expansion joint exist or do not exist, the static displacements and dynamic displacements were measured, and TIF were calculated, respectively. dynamic test is performed in order to estimate dynamic displacement and TIF according to the level of damage of expansion joint. From the results of TIF, the load carrying capacity of highway bridges with damaged expansion joint were estimated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.10
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• pp.1583-1589
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• 2004

In this paper, A new finite element method for the time domain analysis of the dynamic stress intensity factor of two-dimensional viscoelastic body with a stationary central crack under the transient dynamic load is presented, which is based on the intergrodifferential equations of motion in the isotropic linear viscoelasticity and the Galerkin's method. The vlscoelastic material is assumed to be elastic in dilatation and behaves like a standard linear solid in shear. As a numerical example, the Chen's problem in viscoelastodynamic version is solved for the parametric study about the effect of viscosity and relaxation time on the dynamic stress intensity factor.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.6 s.177
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• pp.1557-1564
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• 2000

When the half infinite crack in the orthotropic material strip with a large anisotropic ratio(E11>>E22) propagates with constant velocity, dynamic stress component $\sigma$y occurre d along the $\chi$ axis is derived by using the Fourier transformation and Wiener-Hopf technique, and the dynamic stress intensity factor is derived. The dynamic stress intensity factor depends on a crack velocity, mechanical properties and specimen hight. The normalized dynamic stress intensity factors approach the maximum values when normalized time(=Cs/a) is about 2. They have the constant values when the normalized time is greater than or equal to about 2, and decrease with increasing a/h(h: specimen hight, a: crack length) and the normalized crack propagation velocity( = c/Cs, Cs: shear wave velocity, c: crack propagation velocity).