• Structural Engineering and Mechanics
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• 제68권2호
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• pp.203-213
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• 2018

This paper presents a study of geometric nonlinear forced vibration of carbon nano-tubes (CNTs) reinforcement composite plates on nonlinear elastic foundations. The plate is bonded with piezoelectric layers. The von Karman geometric nonlinearity assumptions with classical plate theory are employed to obtain the governing equations. The Galerkin and homotopy perturbation method (HPM) are utilized to investigate the effect of carbon nano-tubes volume fractions, large amplitude vibrations, elastic foundation parameters, piezoelectric applied voltage on frequency ratio and primary resonance. The results indicate that the carbon nano-tube volume fraction, applied voltage and elastic foundation parameters have significant effect on the hardening response of carbon nanotubes reinforced composite (CNTRC) plates.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.814-819
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• 2004

In this paper, a modeling method for the vibration analysis of rotating structures employing multi-reference frames is presented. The geometric stiffening effect that results from centrifugal inertia force is considered. In most previous studies single reference frame has been employed for the analysis. In the present study, a modeling method employing multi-reference frames is presented, and the effects of employing multi-reference frames on the analysis accuracy are investigated through solving numerical examples.

• Journal of Mechanical Science and Technology
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• 제20권5호
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• pp.717-727
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• 2006

The present study experimentally investigated the effect of flow direction and other flow parameters on two-phase flow distribution of refrigerants at a T-junction, and also suggested a prediction model for refrigerant in a T-junction by modifying previous model for air-water flow. R-22, R-134a, and R-410A were used as test refrigerants. As geometric parameters, the direction of the inlet or branch tube and the tube diameter ratio of branch to inlet tube were chosen. The measured data were compared with the values predicted by the models developed for air-water or steam-water mixture in the literature. We propose a modified model for application to the reduced T-junction and vertical tube orientation. Among the geometric parameters, the branch tube direction showed the biggest sensitivity to the mass flow rate ratio for the gas phase, while the inlet quality showed the biggest sensitivity to the mass flow rate ratio among the inlet flow parameters.

• 한국소음진동공학회논문집
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• 제14권10호
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• pp.983-989
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• 2004

In this paper, a modeling method for the vibration analysis of rotating structures employing multi-reference frames is presented. The geometric stiffening effect that results from centrifugal inertia force is considered. In most previous studies single reference frame has been employed for the analysis. In the present study, a modeling method employing multi-reference frames is presented, and the effects of employing multi-reference frames on the analysis accuracy are investigated through solving numerical examples.

• Wind and Structures
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• 제1권3호
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• pp.255-269
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• 1998

Second-order moments of considerable magnitude arise in tall and slender RC chimneys and towers subject to along-wind loading, on account of eccentricities in the distributed self-weight of the tower in the deflected profile. An accurate solution to this problem of geometric nonlinearity is rendered difficult by the uncertainties in estimating the flexural rigidity of the tower, due to variable cracking of concrete and the 'tension stiffening' effect. This paper presents a rigorous procedure for estimating deflections and second-order moments in wind-loaded RC tubular towers. The procedure is essentially based on a generalised formulation of moment-curvature relationships for RC tubular towers, derived from the experimental and theoretical studies reported by Schlaich et al. 1979 and Menon 1994 respectively. The paper also demonstrates the application of the proposed procedure, and highlights those conditions wherein second-order moments become too significant to be overlooked in design.

• 대한산업공학회지
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• 제17권2호
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• pp.75-86
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• 1991

This paper presents a methodology to enable the tolerances on mating parts of an assembly to be specified and be compatible to the precision of an assembly robot so as to achieve maximum system performance. The measure of performance is defined as the Probability of Successful Assembly (PSA). A typical loose fastener assembly, usually called peg-in-a-hole is investigated. The Geometric Tolerancing System is adopted to represent position tolerances of mating parts. Two models are presented by considering modifiers on a position tolerance, Regardless of Feature Size (RFS) and Maximum Material Condition (MMC). Using these models, it is analyzed how the Standard Limits and Fits recommended by ANSI influence the performance of an assembly robot. For this analysis, the Standard Limits and Fits are transformed to the representation scheme of the Geometric Tolerancing System. Due to low PSAs when the Standard Limits and Fits are taken into account, the effect of chamfers around a hole is also analyzed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.834-839
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• 2004

In this paper, modeling methods for the structural dynamic analysis employing single reference frame are presented and their modal and transient analysis results are compared. The geometric stiffening effects often occur when structures undergo large overall motion. These effects were considered in several structural previous modeling methods but the role of reference frame has never been scrutinized. In this study, modeling methods employing single reference frame are presented, and their numerical results are compared. The results show that discrepancy between the two modeling methods increases as the eccentricity of the structural system and the magnitude of the large overall motion increase.

• 한국유체기계학회 논문집
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• 제14권3호
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• pp.45-49
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• 2011

This paper describes the numerical analysis of effect of geometric variation on the straight-bladed vertical axis wind turbine. Geometry variation is performed with pockets on the blades. The results presented in this numerical analysis show the general flow pattern of near the bladed, and azimuth angle variation on stating torque value. It is shown that the pockets makes torque higher about 80%.

• 대한토목학회논문집
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• 제32권6A호
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• pp.327-336
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• 2012

본 논문은 완성계 강사장교의 기하학적 특성이 극한 거동에 미치는 영향을 분석한다. 사장교는 구조형식의 특성에 따라 매우 효율적인 구조체로 알려져 있지만, 이러한 구조 특성에 따라 구조물의 극한 거동에 영향을 미치는 다양한 비선형성과 함께 복잡한 구조거동을 보인다. 본 연구에서는 거더 및 주탑의 단면 크기, 케이블 배치 형식 및 케이블 단면적 변화에 따른 완성계 강사장교의 극한 거동에 대해 다룬다. 선행연구를 통해 도출된 극한거동에 지배적인 활하중에 대해 각 인자의 변화에 대한 매개변수연구를 수행하였다. 활하중에 대한 완성계 사장교의 합리적인 해석을 위해 초기형상해석-활하중해석을 거치는 2단계 해석법을 통해 극한 해석을 수행하였다. 해석에 고려된 사장교 모델은 총 920.0 m의 지간장을 갖는 강사장교이고 케이블 배치각도에 따른 거동분석을 위해 방사형 사장교와 팬 형 사장교 모델을 이용하였다. 본 해석 연구를 통해 각 기하학적 특성 인자 변화에 따른 완성계 강사장교의 극한거동 변화 특성을 도출하였다.

• Steel and Composite Structures
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• 제29권5호
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• pp.647-657
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• 2018

Geometric imperfections may be created during the production process or setting borders of single-layer graphene sheets (SLGSs). Vacancy defects are an instance of geometric imperfection, so investigating the effect of these vacancies on the mechanical properties of single-layer graphene is extremely important. Since very few studies have been conducted on the structure of imperfect graphene (with the vacancy defect) as an anisotropic structure, further study of this defective structure seems imperative. Due to the vacancy defects and for the proper assessment of mechanical properties, the graphene structure should be considered anisotropic in certain states. The present study investigates the effects of site and size of vacancy defects on the mechanical properties of graphene as an anisotropic structure using the lekhnitskii interaction coefficients and Molecular Dynamic approach. The effect of temperature on the severity of the SLGS becoming anisotropic is also investigated in this study. The results reveal that the amount of temperature has a big effect on the severity of the structure getting anisotropic even for a graphene without any defects. The effect of aspect ratio, temperature and also size and site of vacancy defects on the material properties of the graphene are studied in this research work. According to the present study, using material properties of flawless graphene for imperfect structure can lead to inaccurate results.