• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.350-355
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• 2008

A Rubber mount is widely used for mechanical parts or engineering materials. Especially, it plays an important role in reducing mechanical vibration due to cyclic loading. But, rubber mount is damaged due to the cyclic loading and resonance. Therefore, it is necessary to investigate evaluation of fatigue life considering vibration characteristics for rubber. In this study, a vibration fatigue analysis was performed and based on Power Spectral Density(PSD) and the stress-life curve and a result of frequency response analysis in the finite element method. The measured load history in experiment was transformed to PSD curve. The stress-life curve was obtained by nonlinear static analysis and fatigue test. In addition, frequency response analysis was conducted for mechanical part. In order to evaluate fatigue life of rubber mount, vibration fatigue test was conducted at the constant acceleration-level as well. Fatigue life was determined when the load capacity is reduced to 60% of its initial value. As a result, predicted fatigue life of rubber mount agreed fairly well with the experimental fatigue life.

• Earthquakes and Structures
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• 제16권1호
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• pp.41-54
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• 2019

Reinforced Concrete (RC) shear walls are widely used in Nuclear power plants as effective lateral force resisting elements of the structure and these may experience nonlinear behavior for higher earthquake demand. Short shear walls of aspect ratio less than 1.5 generally experience combined shear flexure interaction. This paper presents the results of the displacement-controlled experiments performed on six RC short shear walls with varying aspect ratios (1, 1.25 and 1.5) for monotonic and reversed quasi-static cyclic loading. Simulation of the shear walls is then carried out by Finite element modeling and also by macro modeling considering the coupled shear and flexure behaviour. The shear response is estimated by softened truss theory using the concrete model given by Vecchio and Collins (1994) with a modification in softening part of the model and flexure response is estimated using moment curvature relationship. The accuracy of modeling is validated by comparing the simulated response with experimental one. Moreover, based on the experimental work a multi-linear hysteretic model is proposed for short shear walls. Finally ultimate load, drift, ductility, stiffness reduction and failure pattern of the shear walls are studied in details and hysteretic energy dissipation along with damage index are evaluated.

• 열처리공학회지
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• 제24권2호
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• pp.92-98
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• 2011

The influence of the cooling condition after solution treatment on the high temperature fatigue resistance of 23Cr-26Ni heat resistant steel was investigated. Two different cooling conditions were applied to the steel after solution treatment at $1200^{\circ}C$ for 3 hours. One specimen was water quenched immediately after the solution treatment. The other one was furnace cooled at a rate of $0.5^{\circ}C/min$ down to $750^{\circ}C$ after the solution treatment. Then, both specimens were aged at $750^{\circ}C$ for 5 hours. Under two different heat treatment conditions, the low cycle fatigue (LCF) test was performed at $600^{\circ}C$ and room temperature (RT). Only cyclic hardening continued from the beginning until fracture at all strain amplitudes during LCF at $600^{\circ}C$. This phenomenon was attributed to the increase in the dislocation density due to cyclic deformation, which resulted in the interaction between the newly created dislocations and precipitates. Cyclic hardening followed by saturation and cyclic softening was observed at RT. Cyclic softening was attributed to the dislocation annihilation rate exceeding the dislocation generation rate. Other probable factor for cyclic softening was some cavities formed around grain boundaries after 20 cycles. WQ and FC have a similar LCF behavior at RT and $600^{\circ}C$ as shown in the cyclic stress response curves.

• Structural Engineering and Mechanics
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• 제14권4호
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• pp.435-454
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• 2002

The paper proposes analytical forms able to represent with very good approximation the constitutive law experimentally deducible by means of uniaxial cyclic compressive tests on material having softening post-peak behaviour in compression and negligible tensile strength. The envelope, unloading and reloading curves characterizing the proposed model adequately approach structural responses corresponding to different levels of nonlinearity and ductility, requiring a not very high number of parameters to be calibrated experimentally. The reliability of the model is shown by comparing the results that it is able to provide with the ones analytically deduced from two reference models (one for concrete, another for masonry) available in the literature, and with experimental results obtained by the authors in the framework of a research in progress.

• Structural Engineering and Mechanics
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• 제14권6호
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• pp.649-660
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• 2002

Experimental results are presented from tests conducted on reinforced concrete beam-column joints with lap splices under reversed cyclic loading simulating earthquake action. Response curves are compared for twenty-four specimens designed according to Eurocode 2. The main parameters of the investigation are, the geometry of the reinforcing bar extension, the applied axial load (normalized), the available cover over lap splice region extended as length required from Eurocode 2, as well as the shape and the volumetric percentage of the stirrups confining the lap splice zone. The results are evaluated with regards to the load intensity, the energy absorption capacity and the characteristics of the load deflection curve.

• Structural Engineering and Mechanics
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• 제22권3호
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• pp.311-330
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• 2006

Standard compression tests of steel fiber reinforced concrete (SFRC) cylinders are conducted to formulate compressive stress versus compressive strain relationship of SFRC. Axial pullout tests of SFRC specimens are also conducted to explore its tensile stress strain relationship. Cover concrete spalling and reinforcement buckling models developed originally for normal reinforced concrete are modified to extend their application to SFRC. Thus obtained monotonic material models of concrete and reinforcing bars in SFRC members are combined with unloading/reloading loops used in the cyclic models of concrete and reinforcing bars in normal reinforced concrete. The resulting path-dependent cyclic material models are then incorporated in a finite-element based fiber analysis program. The applicability of these models at member level is verified by simulating cyclic lateral loading tests of SFRC columns under constant axial compression. The analysis using the proposed SFRC models yield results that are much closer to the experimental results than the analytical results obtained using the normal reinforced concrete models are.

• Computers and Concrete
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• 제2권3호
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• pp.215-238
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• 2005

This work is based on a nonlinear finite-element model with proven capacity for yielding realistic predictions of the response of reinforced-concrete structures under static monotonically-increasing loading. In it, the material description relies essentially on the two key properties of triaxiality and brittleness and, thus, is simpler than those of most other material models in use. In this article, the finite-element program is successfully used in investigating the behaviour of a series of RC walls under static cyclic loading. This type of loading offers a more strenuous test of the validity of the proposed program since cracks continuously form and close during each load cycle. Such a test is considered to be essential before attempting to use the program for the analysis of concrete structures under seismic excitation in order to ensure that the solution procedure adopted is numerically stable and can accurately predict the behaviour of RC structures under such earthquake-loading conditions. This is achieved through a comparative study between the numerical predictions obtained presently from the program and available experimental data.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(II)
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• pp.1188-1190
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• 1987

Recently, new fast transform (such as discrete Hartley Transform) have been proposed which are best suited for the computation of real sequence. Two approaches using Fourier or Hartley transform are first compared. This paper is treated real sequence, compared number of addition of cyclic convolution with using the FFT and FHT the convolution technique is defined as a separating system impulse response to the given input and output of the system.

• 한국강구조학회 논문집
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• 제9권1호통권30호
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• pp.95-105
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• 1997

Structures subjected to strong seismic excitation may undergo inelastic deformation cycles. The resulting cumulative fatigue damage process reduces the ability of structures and components to withstand seismic loads. Yet, the present earthquake resistance design methods focus mainly on the maximum displacement ductility, ignoring the effect of the cyclic responses. The damage parameters closely related to the cumulative damage need to be properly reflected on the aseismic design methods. In this study, two cumulative damage assessment methods derived from the plastic fatigue theory are investigated. The one is based on the hysteretic ductility amplitude, and the other is based on the dissipated hysteretic energy. Both methods can consider the maximum ductility and the cyclic behavior of structural response. The validity of two damage methods has been examined for single degree of freedom structures with various natural frequencies against two different earthquake excitations.

• Steel and Composite Structures
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• 제6권2호
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• pp.139-157
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• 2006

In this paper, a cyclic mechanical model is presented to simulate the behaviour of top and seat with web angle beam-to-column connections. The introduced mechanical model is compared with Eurocode 3 Annex J, its extension, and with experimental data. To have a better insight regarding the actual response of the joints, available results of the experiments, carried out on full-scale top and seat angle joints under monotonic and cyclic loading, are first considered. Subsequently, a finite element model of the test setup is developed. The application of the proposed model, its comparisons with the experimental curves and with the Eurocode 3 Annex J and with its modification, clearly show the excellent quality of the model proposed.