• Title/Summary/Keyword: loading performance

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Construction of Modified Yield Loci with Respect to the Strain Rates using Hill48 Quadratic Yield Function (Hill48 이차 항복식을 이용한 변형률 속도에 따른 수정된 항복곡면의 구성)

  • Lee, Chang-Soo;Bae, Gi-Hyun;Kim, Seok-Bong;Huh, Hoon
    • Transactions of the Korean Society of Automotive Engineers
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    • v.18 no.2
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    • pp.56-60
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    • 2010
  • Since the forming process involves the strain rate effect, a yield function considering the strain rate is indispensible to predict the accurate final blank shape in the forming simulation. One of the most widely used in the forming analysis is the Hill48 quadratic yield function due to its simplicity and low computing cost. In this paper, static and dynamic uni-axial tensile tests according to the loading direction have been carried out in order to measure the yield stress and the r-value. Based on the measured results, the Hill48 yield loci have been constructed, and their performance to describe the plastic anisotropy has been quantitatively evaluated. The Hill48 quadratic yield function has been modified using convex combination in order to achieve accurate approximation of anisotropy at the rolling and transverse direction.

Study on Structural Performance of Two Seam Cold-Formed Square CFT Column to Beam Connections with Internal Diaphragm (2-Seam 냉간성형 각형 CFT 기둥-보 내다이아프램 접합부의 구조성능에 관한 연구)

  • Oh, Heon-Keun;Kim, Sun-Hee;Choi, Young-Hwan;Choi, Sung-Mo
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.3 no.4
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    • pp.27-37
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    • 2012
  • The construction of a moment connection for a rectangular hollow section (RHS) column and a H-shaped beam is difficult because the RHS is a closed section. When a inner diaphragm is used for such a connection, in general, it is installed after cutting the HSS columns, which results in increased construction work. This paper suggests a new fabrication method to overcome such problems: An inner diaphragm is welded to inside a C-shaped section first, and then a column is fabricated by welding two C-shaped sections. This fabrication method is superior to a classic method in terms of constructibility. An experimental and a numerical study using Ansys 9.0 were performed in order to compare the strength of connections with respect to the presence of concrete, the corner shape of diaphragm, and the axis of loading. The experimental results including initial stiffness and ultimate loads are reported and the analytical results including load transfer mechanism, degree of stress concentration, and strain distribution are also reported.

Management of Diabetic Foot Ulcer (당뇨병성 족부 궤양의 치료)

  • Seo, Dong-Kyo;Lee, Ho Seong
    • Journal of Korean Foot and Ankle Society
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    • v.18 no.1
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    • pp.1-7
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    • 2014
  • In patients with diabetic foot, ulceration and amputation are the most serious consequences and can lead to morbidity and disability. Peripheral arterial sclerosis, peripheral neuropathy, and foot deformities are major causes of foot problems. Foot deformities, following autonomic and motor neuropathy, lead to development of over-pressured focal lesions causing the diabetic foot to be easily injured within the shoe while walking. Wound healing in these patients can be difficult due to impaired phagocytic activity, malnutrition, and ischemia. Correction of deformity or shoe modification to relieve the pressure of over-pressured points is necessary for ulcer management. Application of selective dressings that allow a moist environment following complete debridement of the necrotic tissue is mandatory. In the case of a large soft tissue defect, performance of a wound coverage procedure by either a distant flap operation or a skin graft is necessary. Patients with a Charcot joint should be stabilized and consolidated into a plantigrade foot. The bony prominence of a Charcot foot can be corrected by a bumpectomy in order to prevent ulceration. The most effective management of the diabetic foot is ulcer prevention: controlling blood sugar levels and neuropathic pain, smoking cessation, stretching exercises, frequent examination of the foot, and appropriate education regarding footwear.

Inelastic Behavior and Seismic Retrofit of Inverted V Braced Steel Frames (역V형 철골 가새골조의 비탄성거동 및 내진성능향상 방안에 관한 연구)

  • Kim, Nam Hoon;Lee, Cheol Ho
    • Journal of Korean Society of Steel Construction
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    • v.15 no.5 s.66
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    • pp.571-578
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    • 2003
  • An effective seismic retrofit scheme for inverted V braced (or chevron type) steel frames was proposed by studying the redistribution of forces in the post-buckling range. The steel frames with chevron bracing are highly prone to soft story response once the compression brace buckles under earthquake loading. This paper shows that the seismic performance of such frames could be significantly improved by supplying tie bars to redistribute the inelastic deformation demand over the height of the building. A practical design method of the retrofit tie bars was also proposed by considering the sequence of buckling occurrence.

Analysis of the Numerical Simulation Accuracy in the CFRP-Al Alloy SPR Joint Process According to the CFRP Modeling Method (CFRP 모델링 기법에 따른 CFRP-Al합금 SPR 접합공정의 수치해석 정확도 분석)

  • Kim, S.H.;Park, N.;Song, J.H.;Noh, W.;Park, K.Y.;Bae, G.
    • Transactions of Materials Processing
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    • v.29 no.5
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    • pp.265-271
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    • 2020
  • The purpose of this paper is to analyze the numerical simulation accuracy according to the CFRP modeling method in the CFRP-Al alloy SPR (Self-Piercing Rivet) joint process. The mechanical properties of the CFRP, aluminum sheet are precisely obtained from the tensile test according to the loading direction. Additionally, the hardening curve of rivet was calculated from the inverse analysis of the machined rivet-ring compression test. For the CFRP-Al alloy SPR simulation, two kinds of the CFRP modeling methods were established based on the continuum and layer-by-layer approaches. The simulation results showed that the CFRP layer-by-layer modeling method can provide more reliable prediction shape of the fractured sheets and deformed rivet. This simulation technique can be used in evaluating the CFRP-Metal SPR performance and designing the SPR process conditions.

Improved Design in Fishing Operation System for Small Inshore and Coastal Fishing Vessels-I -Design of a Automatic Winch System- (소형 연근해 어선의 조업 시스템 개선에 관한 연구-I -자동 권양 윈치 시스템의 설계-)

  • 이대재
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.36 no.1
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    • pp.12-24
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    • 2000
  • The electro-hydraulic servo winch system built in a automatic tension control equipment was designed with a latent need for an advanced system in fishing operations of the inshore and coastal fishing vessels. In order to keep the constant tension condition of warp under loading, a tension control circuit was added to the servo winch system.The dynamic performance in the open loop behaviour of the designed winch system was investigated and its applicability was tested for various possibilities of load using a load generator especially developed in order to this study.The mechanical characteristics of this system is different from that of a conventional type, that is, the tension, length, line speed and drum revolution can be automatically controlled by the information from various sensors, such as torque, rpm and pressure transducers. from the experiment results, it was verified that the servo winch system has very good output and tracking behaviour for the control input signals in different operating conditions though overshoot of out 8% in the transient characteristics of torque under the load though a overshoot of about 8% in the transient characteristics of torque under the load condition can be observed when the opening of servo valve, adjustable by the input voltage between - 10 V up to 10 V, changed suddenly.Consequently, the improved fishing winch system can be effectively used as the automatic shooting and hauling equipment of low cost for small inshore and coastal fishing vessels which engage in net fishing.

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Composite Beam Element for Nonlinear Seismic Analysis of Steel Frames (강재 골조의 비선형 지진해석을 위한 합성 보 요소)

  • Kim, Kee Dong;Ko, Man Gi;Yi, Gyu Sei;Hwang, Byoung Kuk
    • Journal of Korean Society of Steel Construction
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    • v.14 no.5 s.60
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    • pp.577-591
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    • 2002
  • This study presented a composite beam element for modeling the inelastic behavior of the steel beam, which has composite slabs in steel moment frames that are subjected to earthquake ground motions. The effects of composite slabs on the seismic behavior of steel moment frames were investigated. The element can be considered as a single-component series hinge type model whose predicted analytical results were consistent with the experimental results. Likewise, the element showed a significantly better performance than the bare steel beam elements. The composite model can also predict more accurately the local deformation demands and overall response of structural systems under earthquake loading compared with the bare steel models. Therefore, composite stabs can significantly affect locally and globally predicted responses of steel moment frames.

Numerical Simulation and Experimental Study on an Ejector System for VOC Recovery (VOC 회수를 위한 이젝터 시스템에 관한 수치모사 및 실험적 연구)

  • Kim, Hyun-Dong;Lee, Dong-Yeop;Kim, Yoon-Kee;Jeong, Won-Taek;Ahn, Joo-Ha;Kim, Kyung-Chun
    • Journal of the Korean Society of Visualization
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    • v.9 no.2
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    • pp.54-60
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    • 2011
  • This paper is a basic study on volatile organic compounds(VOC) recovery system in a crude oil carrier. VOC is easily evaporated in cargo tankers during loading and transportation of crude oil, causes serious environmental contamination and a huge economic loss. An ejector system is designed to mix VOC gas into crude oil flow to reduce VOC concentration. Detail two-phase flow inside the ejector is simulated using a commercial CFD code. To verify the numerical prediction, a scale-down experiment is conducted. Instead of crude oil and VOC, water and air are used as the working fluids. Flow characteristics and main parameters are obtained by two-phase flow visualization and PIV measurements. Air volume flow rate induced by the ejector is compared with respect to the volume flow rate of water using experimental and numerical results. Overall performance of the two-phase ejector predicted by the CFD simulation agrees well with that of the experiment.

An Experimental Study on the Reaction Characteristics of Anode offgas Catalytic Combustor for 25kW MCFC Systems (25 kW급 MCFC 배가스 촉매연소기의 실험적 연소특성)

  • Lee, Sang Min;Woo, Hyuntack;Ahn, Kook Young
    • 한국신재생에너지학회:학술대회논문집
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    • 2011.11a
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    • pp.92.1-92.1
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    • 2011
  • Anode off-gas of high temperature fuel cells such as MCFC contains a significant amount of combustible components like hydrogen, carbon monoxide and methane according to fuel utilization ratio of the fuel cell stack. Thus, it is important to fully burn anode off-gas and utilize the generated heat in order to increase system efficiency and reduce emissions as well. In the present study, 25 kW catalytic combustor has been developed for the application to a load-following 300kW MCFC system. Mixing and combustion characteristics have been experimentally investigated with the catalytic combustor. Since the performance of catalytic combustor directly depends on the combustion catalyst, this study has been focused on the experimental investigation on the combustion characteristics of multiple catalysts having different structures and compositions. Results show that the exhaust emissions are highly dependent on the catalyst loading and the ratio of catalytic components. Test results at load-following conditions are also shown in the present study.

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Prequalification of a set of buckling restrained braces: Part I - experimental tests

  • Stratan, Aurel;Zub, Ciprian Ionut;Dubina, Dan
    • Steel and Composite Structures
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    • v.34 no.4
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    • pp.547-559
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    • 2020
  • Buckling restrained braces (BRBs) were developed as an enhanced alternative to conventional braces by restraining their global buckling, thus allowing development of a stable quasi-symmetric hysteretic response. A wider adoption of buckling restrained braced frames is precluded due to proprietary character of most BRBs and the code requirement for experimental qualification. To overcome these problems, BRBs with capacities corresponding to typical steel multi-storey buildings in Romania were developed and experimentally tested in view of prequalification. The first part of this paper presents the results of the experimental program which included sub-assemblage tests on ten full-scale BRBs and uniaxial tests on components materials (steel and concrete). Two different solutions of the core were investigated: milled from a plate and fabricated from a square steel profile. The strength of the buckling restraining mechanism was also investigated. The influence of gravity loading on the unsymmetrical deformations in the two plastic segments of the core was assessed, and the response of the bolted connections was evaluated. The cyclic response of BRBs was evaluated with respect to a set of performance parameters, and recommendations for design were given.