• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.2
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• pp.14-21
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• 2019

In recent years, the use of composite structures has become commonplace in various fields such as aerospace, architecture, and civil engineering. In this study, A method is proposed to find optimal position of bolt hole for fastening of composite structure. In the case of composites, stress distribution is very complicated, and design optimization based on this phenomenon increases difficulty. In selecting the optimum position of the bolt hole, the response surface method(rsm), which is a method of optimization, was applied. A response surface was created based on design points by multiple finite element analyzes. The position of the bolt hole that minimizes the stress when bolting on the response surface was found. The distribution of the stress at the position of the optimal hole was much lower than that of the initial design. Based on the results of this study, it is possible to increase the design safety factor of the structure by appropriately selecting the position of the bolt hole according to various load types when designing the structure and civil structure.

• Advances in nano research
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• v.8 no.3
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• pp.191-202
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• 2020

The article brings the study of nonlocal, surface and the couple stress together to apparent the frequency retaliation of FG nanobeams (Functionally graded). For the examination of frequency retaliation, the article considers the accurate spot of neutral axis. This article aims to enhance the coherence of proposed model to accurately encapsulate the significant effects of the nonlocal stress field, size effects together with material length scale parameters. These considered parameters are assimilated through what are referred to as modified couple stress as well as nonlocal elasticity theories, which encompasses the stiffness-hardening and softening influence on the nanobeams frequency characteristics. Power-law distribution is followed by the functional gradation of the material across the beam width in the considered structure of the article. Following the well-known Hamilton's principle, fundamental basic equations alongside their correlated boundary conditions are solved analytically. Validation of the study is also done with published result. Distinct parameters (such as surface energy, slenderness ratio, as nonlocal material length scale and power-law exponent) influence is depicted graphically following the boundary conditions on non-dimensional FG nanobeams frequency.

• Journal of the Korea Concrete Institute
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• v.13 no.3
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• pp.268-276
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• 2001

A numerical model for the thermal response analysis of concrete structures is suggested. The model includes the stress-strain relationship, constitutive relationship, and multiaxial failure criteria at elevated temperature conditions. Modified Saenz's model was used to describe the stress-strain relationship at high temperatures. Concrete subjected to elevated temperatures undergoes rapid strain increase and dimensional instability. In order to explain those changes in mechanical properties, a constitutive model of concrete subjected to elevated temperature is proposed. The model consists of four strain components; free thermal creep strain, stress-induced (mechanical) strain, thermal creep strain, and transient strain due to moisture effects. The failure model employs modified Drucker-Prager model in order to describe the temperature dependent multiaxial failure criteria. Some numerical analyses are performed and compared with the experimental results to verify the proposed model. According to the comparison, the suggested material model gives reliable analytical results.

• Structural Engineering and Mechanics
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• v.84 no.6
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• pp.799-811
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• 2022

Adhesive bonding has seen rapid development in recent years, with emphasis to composite patch repairing processes of geometric defects in aeronautical structures. However, its use is still limited given its low resistance to climatic conditions and requirement of specialized labor to avoid fabrication induced defects, such as air bubbles, cracks, and cavities. This work aims to numerically analyze, by the finite element method, the failure behavior of a damaged plate, in the form of a bonding defect, and repaired by an adhesively bonded composite patch. The position and size of the defect were studied. The results of the numerical analysis clearly showed that the position of the defect in the adhesive layer has a large effect on the value of J-Integral. The reduction in the value of J-Integral is also related to the composite stacking sequence which, according to the mechanical properties of the ply, provides better load transfer from the plate to the repair piece through the adhesive. In addition, the increase in the applied load significantly affects the value of the J-Integral at the crack tip in the presence of a bonding defect, even for small dimensions, by reducing the load transfer.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.5
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• pp.305-312
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• 2000

This study deals with the dynamic response of a rotor in Switched Reluctance Motor(SRM) caused by the unbalance force such as the unbalanced mass and electromagnetic force. The method to analyze the mechanical response of the rotor supported on the bearing is based on an extension of the 3-dimensional Transfer Matrix Method(TMM) coupled with the electromagnetic force calculated by Maxwell stress tensor. The displacement of the rotor as a function of frequency according to the position of the unbalanced mass is evaluated from the frequency response function (FRF). The rotor behaviour with the electromagnetic force is compared with that without the electromagnetic force. In addition, the resonance speeds and the vibration modes are analyzed and demonstrated in this paper. These results are useful in designing the mechanical rotor and in balancing properly the rotor to reduce vibration and noise.

• Plant Biotechnology Reports
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• v.3 no.1
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• pp.57-65
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• 2009

Cultured Cupressus lusitanica cells induced by various stresses are thought to produce different complexes of defense chemicals to optimize defense. To compare the induced products of two stimulations, we investigated the emission of monoterpenes, biosynthesis of ${\beta}-thujaplicin$, and accumulation of lignin in mechanically stressed and fungal elicited cultured C. lusitanica cells. Both mechanical stress and fungal elicitor caused emission of qualitatively similar monoterpene blends indicating de novo biosynthesis of these compounds after stimulation, while mechanical stress alone is sufficient to induce fungal elicitor-related monoterpene emission. Sabinene and limonene were the dominant compounds over the time course in both volatile blends. Although the emitted volatile blends were qualitatively similar, the time course and the relative ratios of the constituents of the volatile blends differed with the type of stimulation. While fungal elicited cells produced significant amounts of ${\beta}-thujaplicin$ over the 5-day time course, no ${\beta}-thujaplicin$ was observed in the mechanically stressed cells. The production of ${\beta}-thujaplicin$ was the main dissimilarity of the induced products of these two treatments, suggesting that synthesis of ${\beta}-thujaplicin$ is not a general response to all types of stresses, but is a specific response and serves as a strong toxic compound against already invaded fungus. Significantly higher amounts of lignin accumulations were observed in the fungal elicited and mechanically stressed cells on the 5th day after induction. Based on these results, we suggest the composition of induced products was dependent on the method of stimulation.

• Coupled systems mechanics
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• v.6 no.3
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• pp.287-316
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• 2017

This paper studies the particularities of the forced vibration of the hydro-elastic system consisting of a moving elastic plate, compressible viscous fluid and rigid wall. This study is made by employing the discrete-analytical solution method proposed in the paper by the authors (Akbarov and Panakhli (2015)). It is assumed that in the initial state the fluid flow is caused by the axial movement of the plate and the additional lineally-located time-harmonic forces act on the plate and these forces cause additional flow field in the fluid and a stress-strain state in the plate. The stress-strain state in the plate is described by utilizing the exact equations and relations of the linear elastodynamics. However, the additional fluid flow field is described with linearized Navier-Stokes equations for a compressible viscous fluid. Numerical results related to the influence of the problem parameters on the frequency response of the normal stress acting on the plate fluid interface plane and fluid flow velocity on this plane are presented and discussed. In this discussion, attention is focused on the influence of the initial plate axial moving velocity on these responses. At the same, it is established that as a result of the plate moving a resonance type of phenomenon can take place under forced vibration of the system. Moreover, numerical results regarding the influence of the fluid compressibility on these responses are also presented and discussed.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.246-255
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• 2016

When spring of the suspension is exerted by an external load, a car should be designed to prevent predictable damages and designed for a ride comfort. We used experiments design to design VON-MISES STRESS and K, a constant, of spring of suspension which is installed in a car as a goal level. We analyzed the result from Edison's Elastic - Plastic Analysis SW(CSD_EPLAST) by setting D, d, n as external diameter of coil, internal diameter of coil, the number of total coil respectively. The experiment design let the outcome be as Full-second order by using Box-Behnken which is one of response surface methods. Experimented and analyzed results based on the established experiments design, We found out design parameter which has desired VON-MISES STRESS and the constant K. Additionally, we predicted life time of when the external load was exerted by repeated load by using fatigue equation, and verification of plastic deformation has also been made. Additionally we interpreted a model, which is formed by optimized design parameter, with linear analysis and non-linear analysis, at the same time we also analyzed plastic deformation with the values from the both models. Finally, we predicted fatigue life of optimized model by using fatigue estimation theory and also evaluated a ride comfort with oscillation analysis.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1455-1458
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• 2008

Amorphous silicon (a-Si:H) thin-film transistors (TFTs) are fabricated on flexible organic polymer foil substrates. As-fabricated performance, electrical bias-stability at elevated temperatures, electrical response under mechanical flexing, and prolonged mechanical stability of the TFTs are studied. TFTs made on plastic at ultra low process temperatures of $150^{\circ}C$ show initial electrical performance like TFTs made on glass but large gate-bias stress instability. An abnormal saturation of the instability against operation temperature is observed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.136-138
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• 2005

The responses of nanocrystalline aluminum powder of different grain sizes, was modeled Using, Khan, Huang, and Liang (KHL) viscoplastic model including hi-linear Hall-Petch type, based on experimental measurements. Correlation of strain-rate-dependent stress responses for different grain sizes were in good agreement with the experimental results.