• Advances in nano research
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• v.7 no.3
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• pp.145-155
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• 2019

In this article, the influence of small scale effects on the free vibration response of curved magneto-electro-elastic functionally graded (MEE-FG) nanobeams has been investigated considering nonlocal elasticity theory. Power-law is used to judge the through thickness material property distribution of MEE nanobeams. The Euler-Bernoulli beam model has been adopted and through Hamilton's principle the Nonlocal governing equations of curved MEE-FG nanobeam are obtained. The analytical solutions are obtained and validated with the results reported in the literature. Several parametric studies are performed to assess the influence of nonlocal parameter, magnetic potential, electric voltage, opening angle, material composition and slenderness ratio on the dynamic behaviour of MEE curved nanobeams. It is believed that the results presented in this article may serve as benchmark results in accurate analysis and design of smart nanostructures.

• Elastomers and Composites
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• v.41 no.1
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• pp.40-48
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• 2006

Mechanical systems with rubber parts have been used widely in industry fields. The evaluation of the physical characteristics of rubber is important in rubber application. Rubber material is useful to machine component for excellent shock absorbing characteristics. The impact characteristics of rubber were examined by experimental and finite element method. The impact test was conducted with a free-drop type impact tester. The ABAQUS/Explicit was used for finite element analysis. In the finite element analysis, elastic modulus of rubber using impact force was used as dynamic modulus, which are measured and predicted with dynamic property test and WLF model. The analysis result was coincided with the experimental results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.172-178
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• 2017

Thermal property is one of the important characteristic in the field of energetic materials. As the energy material is released during decomposition, DSC(Differential Scanning Calorimetry) is frequently used for the thermal analysis. In case of the dynamic DSC measurements, thermal dynamic change like melting is prevented from the thermal property measurements. And due to the predicting kg scale, the conditions of the heat exchange with the environment significantly is changed. In this study, As the method to resolve the problem, we predict the thermal aging property using the AKTS thermokinetic program from DSC measurements which performed isothermal method. Predicting the thermal aging properties from ARC(Accelerating Rate Calorimetry) measurement, we compare two results.

• International Journal of Highway Engineering
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• v.17 no.4
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• pp.53-61
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• 2015

PURPOSES : The objective of this study is to evaluate the SDAR (solvent deasphaltene residue), which is obtained from the solvent deasphalting (SDA) process, as a pavement material. METHODS : The physical properties of the SDAR were evaluated based on its chemical composition, and asphalt mixtures with the SDAR were fabricated and used for the evaluation of mechanical properties. Firstly, the chemical composition of SARA (saturate, aromatic, resin and asphaltene) was analyzed using the TLC-FID (thin-layer chromatography-flame ionization detector). Moreover, the basic material properties of the asphalt binder with the SDAR were evaluated by the penetration test, softening point test, ductility test, and PG (performance grade) grade test. The rheological properties of the asphalt binder with the SDAR were evaluated by the dynamic shear modulus ($G^*$) obtained using the time-temperature superposition (TTS) principle. Secondly, the mechanical properties of the asphalt mixtures with the SDAR were evaluated. The compactibility was evaluated using the gyratory compacter. Moreover, the tensile strength ratio (TSR) was used for evaluating the moisture susceptibility of the asphalt mixtures (i.e., susceptibility to pothole damage). The dynamic modulus $E^*$, which is a fundamental property of the asphalt mixture, obtained at different temperatures and loading cycles, was used to evaluate the mechanical properties of the asphalt mixtures. RESULTS AND CONCLUSION : The SDAR shows stiffer and more brittle behavior than the conventional asphalt binder. As the application of the SDAR directly in the field may cause early failures, such as cracks on pavements, it should be applied with modifiers that can favorably modify the brittleness property of the SDAR. Therefore, if appropriate additives are applied on the SDAR, it can be used as a pavement material because of its low cost and strong resistance to rutting.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.163-168
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• 2006

In a micro-unit of electronic-machine, vibration can be excited by a small impact, and this vibration acts as a fatigue load. To measure the vibration effect on the micro unit, a micro dynamic tester is needed to test a micro specimen. In this paper, it has confirmed a movement of the PZT(piezo actuator) to use a sine signal. And, it has confirmed a fracture of specimens by using a tension-tension input signal in PZT. A metal-material property in the micro scale has been tested to compare with the macro scale. A fatigue test has been conducted by using PZT actuator to give a bending-tension effect.

• Structural Engineering and Mechanics
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• v.44 no.6
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• pp.801-814
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• 2012

The strain rate effects on the interaction between a Mode I matrix crack and an inclined elliptic matrix-inclusion interface under dynamic tensile loadings were investigated numerically, and the results are in agreement with previous experimental data. It is found, for a given material system, that there are the first and the second critical strain rates, by which three kinds of the subsequent crack growth patterns can be classified in turn with the increasing strain rate, namely, the crack deflection, the double crack mode and the perpendicular crack penetration. Moreover, such a crack deflection/penetration behavior is found to be dependent on the relative interfacial strength, the inclined angle and the inclusion size. In addition, it is shown that the so-called strain rate effect on the dynamic strength of granule composites can be induced directly from the structural dynamic response of materials, not be entirely an intrinsic material property.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.12
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• pp.1401-1409
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• 2009

All the forces in the real world act dynamically on structures. Design and analysis should be performed based on the dynamic loads for the safety of structures. Dynamic (transient or vibrational) responses have many peaks in the time domain. Topology optimization, which gives an excellent conceptual design, mainly has been performed with static loads. In topology optimization, the number of design variables is quite large and considering the peaks is fairly costly. Topology optimization in the frequency domain has been performed to consider the dynamic effects; however, it is not sufficient to fully include the dynamic characteristics. In this research, linear dynamic response topology optimization is performed in the time domain. First, the necessity of topology optimization to directly consider the dynamic loads is verified by identifying the relationship between the natural frequency of a structure and the excitation frequency. When the natural frequency of a structure is low, the dynamic characteristics (inertia effect) should be considered. The equivalent static loads (ESLs) method is proposed for linear dynamic response topology optimization. ESLs are made to generate the same response field as that from dynamic loads at each time step of dynamic response analysis. The method was originally developed for size and shape optimizations. The original method is expanded to topology optimization under dynamic loads. At each time step of dynamic analysis, ESLs are calculated and ESLs are used as the external loads in static response topology optimization. The results of topology optimization are used to update the design variables (density of finite elements) and the updated design variables are used in dynamic analysis in a cyclic manner until the convergence criteria are satisfied. The updating rules and convergence criteria in the ESLs method are newly proposed for linear dynamic response topology optimization. The proposed updating rules are the artificial material method and the element elimination method. The artificial material method updates the material property for dynamic analysis at the next cycle using the results of topology optimization. The element elimination method is proposed to remove the element which has low density when static topology optimization is finished. These proposed methods are applied to some examples. The results are discussed in comparison with conventional linear static response topology optimization.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.12 s.117
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• pp.1192-1200
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• 2006

Viscoelastic damping materials are widely used to reduce noise and vibration because of its low cost and easy implementation, for examples, on the body structure of passenger cars, air planes, electric appliances and ships. To design the damped structures, the material property such as elastic modulus and loss factor is essential information. The four-parameter fractional derivative model well describes the dynamic characteristics of the viscoelastic damping materials with respect to both frequency and temperature. However, the identification procedure of the four-parameter is very time-consuming one. In this study a new identification procedure of the four-parameters is proposed by using an FE model and a gradient-based numerical search algorithm. The identification procedure goes two sequential steps to make measured frequency response functions(FRF) coincident with simulated FRFs: the first one is a peak alignment step and the second one is an amplitude adjustment step. A numerical example shows that the proposed method is useful in identifying the viscoelastic material parameters of fractional derivative model.

• Journal of the Korean housing association
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• v.17 no.3
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• pp.61-69
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• 2006

Vertical vibrations on the slab of buildings are affected by types of vibration sources, transfer paths, and the material property and the size of members. Among these parameters, the vibration sources and the transfer path can not be controlled, but the property and the size of members can be controlled in the phase of design the members. In this study, the vibration responses according to the property and size of members were obtained by using a prediction program based on dynamic-stiffness matrix. Three parameters which are not usually considered as major factors for architecral planning were selected fur these analyses. They are the strength of materials, the thickness of wall and the thickness of slab. The ground vibration source located near a building was used as vibration input data in the analyses. This study has its originality on presenting appropriate property and size of structural members in order to reduce vertical vibration of slab in shear-wall structures. Analysing the results from the vibration estimation program according to the variations of parameters, the appropriate ratio among the sizes of structural members were proposed. From these results, the vibration level on the slab which is not constructed yet would be predicted and the vibration peak level can be reduced or shifted into the desirable frequency range. Therefore, the vertical vibration could be controlled in the phase of designing buildings.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.257-262
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• 1995

In this study, after concrete cylinders were made on the condition of varying water-to -cement ratio, and cured 80 days compressive strength and splitting tensile strength were performed and moduls of elasticy is obtained. The fracture energy was obtained by acting three point bending on the 80cm in length. This test involved static loading test and dynamic loading test. In this work, the new interrelation of the material constants was obtained clearly and the property of the mixture was inspected, including the relation between the fracture energy and all kind of the material constants.