• Computers and Concrete
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• 제12권4호
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• pp.565-583
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• 2013

Existing numerical models for strain-hardening cement-based composites (SHCC) are short of providing sufficiently accurate solutions to the failure patterns of coupling beams of different designs. The objective of this study is to develop an effective model that is capable of simulating the nonlinear behavior of SHCC coupling beams subjected to cyclic loading. The beam model proposed in this study is a macro-scale plane stress model. The effects of cracks on the macro-scale behavior of SHCC coupling beams are smeared in an anisotropic model. In particular, the influence of the defined crack orientations on the simulation accuracy is explored. Extensive experimental data from coupling beams with different failure patterns are employed to evaluate the validity of the proposed SHCC coupling beam models. The results show that the use of the suggested shear stiffness retention factor for damaged SHCC coupling beams is able to effectively enhance the simulation accuracy, especially for shear-critical SHCC coupling beams. In addition, the definition of crack orientation for damaged coupling beams is found to be a critical factor influencing the simulation accuracy.

• 한국생산제조학회지
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• 제7권2호
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• pp.54-61
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• 1998

This paper examines the crack growth behavior of 7075-T651 aluminum alloy for small tensile overload under high-low block loading condition. The cantilever beam type specimen with a chevron notch is used in this study. The crack growth and closure are investigated by compliance method. The applied initial stress ratios are R=-0.5 R=0.0 and R=0.25 Crack length, effective stress intensity factor range, ratio of effective stress intensity factor range and crack growth rate etc, are inspected with fracture mechanics estimate.

• 대한기계학회논문집
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• 제17권10호
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• pp.2518-2534
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• 1993

Fracture behavior of carbon/epoxy laminates under pin loading is studied experimentally and analytically. Effects of ratios of specimen width to hole diameter and edge distance to hole diameter on bearing strength are investigated. Characteristic length of the laminates obtained using HK model has good agreement with the experimental data. The larger hole size induced, the lower bearing strength is measured under pin loading . The bearing strength and failure mode could be predicted using HK model and Zhangs analytical solution of stress distribution around a pin loaded hole. Chamis' prediction method of bearing strength is also considered to predict failure mode and bearing strength. A modification of Chamis' method is made using the factor of rupturc. The predicted bearing strength by the modified method is reasonably close to the experimental data.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 A
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• pp.312-314
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• 1997

In this paper, Computer Aided Optimum Design Technique for Three-Phase Induction Motors is proposed. In the technique, reference magnetic flux, specific electric loading factor, specific magnetic loading factor(magnetic flux density) and current density are adopted as design parameters, and minimum total cost including material cost and loss power cost is adopted as a objective function which has to satisfy output condition too. As a result of application to the existing motor, it is proved that this technique is very effective in view of gradually increasing energy costs.

• 대한조선학회지
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• 제25권1호
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• pp.21-32
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• 1988

An experimental study was carried out to identify the fatigue fracture behavior of steel for merchant ships. The bending and shear loads were applied simultaneously on the specimens to simulate of real load condition for a ship. The effects of the stress intensity factor under mode I with mode II loading condition on the initiation and the propagation of a crack were investigated, with particular emphasis on mode II. When the $K_{II}$ stress intensity factor in mode II was applied under mode I loading condition, the propagation behavior of a crack is to be affected mainly by the anisotropic characteristic of materials.

• 한국환경과학회지
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• 제15권11호
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• pp.1017-1025
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• 2006

This study was conducted to evaluate characteristic of water duality in coastal sea of Incheon using a multivariate analysis. The analysis data in coastal sea of Incheon was aquired by the NFRDI data which was surveyed from March 1997 to November 2003. Eleven water quality parameters were determined on each survey The results were summarized as follow : Water quality in Incheon coastal sea could be explained up to 64.62% by three factors which were included in loading of fresh water and nutrients by the land(36.98%), seasonal variation(16.19%), and internal metabolism (11.24%). The results of time series analysis by factor score, in case of factor 1, station 1 influenced by Han river was shown to high factor score and station 3 located by outer sea was shown to low factor score. In case of factor 2, station 1 was appeared to high variation and station 3 was appeared to low variation. The result of cluster analysis by station was classified into three group that has different water quality characteristics. Especially, station 1 which affected by Han river and station 4 which affected by sewage treatment plant was appeared to considerable water quality characteristics against other station. In yearly cluster analysis, three group was classified and water quality in 2003 years due to high precipitation was different to another year. It could be suggested from these results that it is important to control discharge of fresh water by Han rivet and sewage treatment plant for water quality management of coastal sea of Incheon.

• 한국기계가공학회지
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• 제20권5호
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• pp.111-120
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• 2021

A tractor is an agricultural machine that performs farm work, such as cultivation, soil preparation, loading, bailing, and transporting, through attached working implements. Farm work must be carried out on time per the growing season of crops. As a result, the reliability of a tractor's transmission is vital. Ideally, the transmission's design should reflect the actual load during agricultural work; however, configuring such a measurement system is time- and cost-intensive. The design and analysis of a transmission are, therefore, mainly performed by empirical methods. In this study, a tractor with a measurement system was used to measure the actual working load in the field. Its hydro-mechanical transmission was then analyzed using the measured load. It was found that the velocity factor, load distribution factor, lubrication factor, roughness factor, relative notch sensitivity factor, and life factor affect the gear strength of the transmission. Also, loading conditions have a significant influence on the reliability of the transmission. It is believed that transmission reliability can be enhanced by analyzing the actual load on the transmission, as performed in this study.

• 농촌계획
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• 제7권1호
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• pp.27-36
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• 2001

Estimation of current and future loading from watershed is necessary for the sound management of water quality of an estuary lake. Pollution sources of point and non-point source pollution were surveyed and Identified for the Koheung watershed. Unit factor method was used to estimate potential pollutant load from the watershed of current conditions. Flow rate and water qualify of base flow and storm-runoff were monitored in the main streams of the watershed. Estimation of runoff pollutant loading from the watershed into the lake in current conditions was conducted by GWLF model after calibration using observed data. Prospective pollutant loading from the reclaimed paddy fields under cultivation conditions was estimated using the modified CREAMS model. As a result, changes of pollutant loading into estuary lake according to non-cultivation and cultivation conditions of reclaimed tidal land were estimated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1045-1050
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• 2003

In this study, to investigate the effects of omitting low-amplitude cycles from a flight-simulation loading, crack growth tests are conducted on 2124-T851 aluminum alloy specimens. Three test spectra are generated by omitting small load ranges as counted by the rain-flow count method. The crack growth test results are compared with the data obtained from the flight-simulation loading. The experimental results show that omission of the load ranges below 5% of the maximum load does not significantly affect crack growth behavior, because these are below the initial stress intensity factor range. However, in the case of omitting the load ranges below 15% of the maximum load, crack growth rates decrease, and therefore crack growth curve deviates from the crack growth data under the flight-simulation loading. To optimize the load range that can be omitted, crack growth curves are simulated by the stochastic crack growth model. The prediction shows that the omission level can be extended to 8% of the maximum load and test time can be reduced by 59%.

• Structural Engineering and Mechanics
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• 제55권2호
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• pp.435-459
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• 2015

Parametric resonance of shear deformable composite skew plates subjected to non-uniform (parabolic) and linearly varying periodic edge loading is studied for different boundary conditions. The skew plate structural model is based on higher order shear deformation theory (HSDT), which accurately predicts the numerical results for thick skew plate. The total energy functional is derived for the skew plates from total potential energy and kinetic energy of the plate. The strain energy which is the part of total potential energy contains membrane energy, bending energy, additional bending energy due to additional change in curvature and shear energy due to shear deformation, respectively. The total energy functional is solved using Rayleigh-Ritz method in conjunction with boundary characteristics orthonormal polynomials (BCOPs) functions. The orthonormal polynomials are generated for unit square domain using Gram-Schmidt orthogonalization process. Bolotin method is followed to obtain the boundaries of parametric resonance region with higher order approximation. These boundaries are traced by the periodic solution of Mathieu-Hill equations with period T and 2T. Effect of various parameters like skew angle, span-to-thickness ratio, aspect ratio, boundary conditions, static load factor on parametric resonance of skew plate have been investigated. The investigation also includes influence of different types of linearly varying loading and parabolically varying bi-axial loading.