• Title/Summary/Keyword: 축응력

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Analysis of Porous Beams Through FEM Simulation (유한요소해석을 통한 다공성 보의 거동 분석)

  • Kim, Hyun-Young;Kim, Jun-Sik
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.33 no.3
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    • pp.201-207
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    • 2020
  • In this study, various types of porous beams were designed and analyzed to examine the relationship between the behavior of a porous beam and certain nonlocal parameters. The nonlocal parameters were defined as functions of the conditions of defects in the porous material. Finite element analysis was conducted on the beams under typical boundary and loading conditions. Beams with stiffeners having the same dimensions as the defects in the porous beams were also analyzed. The deformation tendency of these beams was determined and described in terms of the nonlocal parameters. The deformation of a porous beam was linearly proportional to the square of the diameters of the defects, whereas that of a beam with a stiffener was linearly proportional to the cube of the diameter of the stiffener. Furthermore, for a stiffened beam with axial loading, the results derived from a 3D solid element and those under 2D plane stress conditions were different.

Spinal Stability Evaluation According to the Change in the Spinal Fixation Segment Based on Finite Element Analysis (유한요소해석 기반 척추 고정분절 변화에 따른 척추 안정성 평가)

  • Kim, Cheol-Jeong;Son, Seung Min;Heo, Jin-Young;Lee, Chi-Seung
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.33 no.3
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    • pp.145-152
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    • 2020
  • In this study, we evaluated spinal stability based on the change in the thoracolumbar fixation segment using finite element analysis (FEA). To accomplish this, a finite element (FE) model of a normal thoracolumbar spine (T10-L4), including intervertebral discs (IVD), ligaments, and facet joints, was constructed, and the material properties reported in previous studies were implemented. However, L1 was assumed as the lesion site, and three types of posterior fixation, namely, L1-L2, T12-L2, and T12-L1-L2, were implemented in the thoracolumbar FE model. In addition, the loading conditions for flexion, extension, lateral bending, and axial rotation were adopted. Through the series FEA, the deformation, equivalent stress, range of motion, and moment on the pedicle screws, vertebrae, and IVD were calculated, and the spinal stability was evaluated based on the FEA results.

A Study on the Prediction of the Strength and Axial Strain of High-Strength Concrete Columns Confined by Tie Reinforcement (띠근 보강 고강도 콘크리트 기둥의 강도 및 축변형 특성 산정에 관한 연구)

  • Park, Hoon-Gyu;Jang, Il-Young
    • Magazine of the Korea Concrete Institute
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    • v.11 no.2
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    • pp.197-208
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    • 1999
  • The use of high-strength concrete which permits smaller cross sections, reduced dead loads, and longer spans has been getting more popular in tall buildings. However, there has been little research on behavior of high-strength concrete columns laterally reinforced with square ties and subjected to compressive loading. With the addition of transverse reinforcement which lead to triaxial compressive state, ductility behavior of high-strength column member shall be increased. In this study, rational quality and quantity evaluations were made to investigate the ultimate strength and strain ductility by confinement effect of tie reinforced high-strength concrete columns subject to uniaxial loads. Concrete failure theory at the triaxial compressive state and statistical results based on conventional experimental data were applied for this propose. Up to 185 columns, tested under monotonically increasing concentric loading, were evaluated in terms of strength and strain ductility. Analytical results show that confinement stress, maximum compressive strength, and increase of strain equations were developed with the consideration of concrete strength, yield strength, spacing, volumetric ratio, and configurations of tie reinforcement.

Optimum Combination of Carbon and Glass Fiber Composite to Obtain the Hybrid Effect (하이브리드 효과를 주는 탄소섬유와 유리섬유의 최적 조합비)

  • Song, Hyung-Soo;Min, Chang-Shik
    • Journal of the Korea Concrete Institute
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    • v.23 no.4
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    • pp.405-411
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    • 2011
  • Using combinations of carbon and glass fiber composites normally used for strengthening of concrete structures, the hybrid effect from strengthening concrete structures using the composite is studied. To produce the hybrid effects, the specimens were made with optimum proportions of carbon fibers with glass fibers. Then, direct tensile tests were conducted on the hybrid FRP (fiber reinforced polymer) specimens. Unlike the woven fiber sheet currently used in construction sites, the FRP specimens have to be directly combined with the fibers, which make the work very complicated. Therefore, direct tensile test specimens manufacturing method based on the combination of high-tension carbon fibers and E-type glass fibers was proposed and the effects of hybridization is studied through the direct tensile test. By comparing the ductility index, the modulus of elasticity, and the stress-strain curves of the specimens, the most optimum glass to carbon fiber combination ratio for the hybrid FRP was found to be 9 to 1 with ductile K-type epoxy. The study results are discussed in detail in the paper.

Field Tests of Hydraulic Rock Splitting Technique Using Arrays of Injection Holes with Guide Slots (유도슬롯과 주입공 배열을 이용한 수압암반절개 현장 실험)

  • Park, Jong Oh;Woo, Ik
    • The Journal of Engineering Geology
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    • v.29 no.4
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    • pp.405-415
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    • 2019
  • The cracks induced by hydraulic rock splitting technique are formed in the direction parallel to the free plane, which is perpendicular to the minimum principal stress of the ground, or is affected by the pre-existing microcracks. In this study, the hydraulic rock splitting experiments were conducted in which the guide slot was engraved in the direction parallel to the borehole axis on the biotite granite slope, and the hydraulic pressure was injected through the double packer pressure and interval section. The test results show that the cracks along with the guide slots were induced either by the double packer pressurization or the injection of hydraulic pressure into interval section, some cracks extended across the boreholes. Therefore, the hydraulic rock splitting test is expected to control efficiently the induced cracks if the guide slots are engraved in the direction of splitting and a big flow rate is applied.

Shear Stiffness of Shear connections in Full-Depth Precast Concrete Deck Bridge (프리캐스트 바닥판 교량 전단연결부의 전단강성)

  • Shim, Chang Su;Chung, Chul Hun;Kim, Chul Young;Chang, Sung Pil
    • Journal of Korean Society of Steel Construction
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    • v.10 no.4 s.37
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    • pp.749-758
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    • 1998
  • The evaluation of shear stiffness of shear connection in composite bridges with CIP concrete deck is analysed. Shear stiffness of shear connection in full-depth precast concrete deck bridges is obtained from experiments. 3-dimensional finite element analyses of push-out specimen are carried out to investigate the effects of characteristics of filling material strength in shear connection on shear stiffness and local stress distribution. The load-slip relations obtained from the analyses are compared with those of experiments. The equation of initial shear stiffness of shear connection in precast concrete deck bridge is proposed. Linear analyses are performed to evaluate the effects of the shank diameter of shear connector and the strength of mortar on the characteristics of deterioration and failure load obtained by the failure criterions of each material. The failure loads are estimated and compared with test results.

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Identification on Fatigue Failure of Impeller at Single Stage Feedwater Pumps During Commissioning Operation (단단 주 급수 펌프 임펠러에서 시운전 중 발생한 피로 절손에 관한 규명 연구)

  • Kim, Yeon-Whan;Kim, Kye-Yean;Bae, Chun-Hee;Lee, Young-Shin
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.9
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    • pp.937-942
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    • 2008
  • This paper presents a case history on failures of impeller and shaft due to pressure pulsation at single stage feed water pumps in 700 MW nuclear power plant during commissioning operation. The pumps had been service and had run for approximately $40{\sim}50$ hours. For the most part, the failures of impeller occurred with the presence of a number of fatigue cracks. All cracks were associated with the deleterious surface layer of impeller by visual and metallurgical examination. On-site testing and analytical approach was performed on the systems to diagnose the problem and develop a solution to reduce the effect of exciting sources. A major concern at high-energy centrifugal pump is the pressure pulsation created from trailing edge of the Impeller blade, flow separation and recirculation at centrifugal pumps of partial load. Pressure pulsation due to the interaction generating between impeller and casing coincided with natural frequencies of the impeller and shaft system during 1ow load operation. It was identified that dynamic stress exceeding the fatigue strength of the material at the thin shroud section due to the hydraulic instability at running condition below BEP.

Variation of Axial Tension-Compression Fatigue Characteristics by UNSM on Ti-6Al-4V (Ti-6Al-4V재의 UNSM처리에 의한 축인장압축피로특성변화)

  • Suh, Chang-Min;Cho, Sung-Am;Pyoun, Young-Sik;Suh, Min-Soo
    • Journal of Ocean Engineering and Technology
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    • v.25 no.6
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    • pp.42-48
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    • 2011
  • The present study makes three original contributions to nanoskinned Ti-6Al-4V materials. The nanoskins were fabricated on Ti-6Al-4V material using various surface treatments: deep rolling (DR), laser shot peening (LSP), and ultrasonic nanocrystal surface modification (UNSM). These surface treatments are newly developed techniques and are becoming more popular in industrial fields. A fatigue strength comparison at up to 106 cycles was conducted on these nanoskinned Ti-6Al-4V materials. Fatigue tests were carried out using MTS under axial loading tension-compression fatigue (R = -1, RT, 5 Hz, sinusoidal wave). The analysis of the crack initiation patterns in the nanoskinned Ti-6Al-4V materials found an interior originating crack pattern and surface originating crack type. Microscopic observation was mainly used to investigate the fatigue fractured sites. These surface modification techniques have been widely adopted, primarily because of the robust grade of their mechanical properties. These are mainly the result of the formation of a large-scale, deep, and useful compressive residual stress, the formation of nanocrystals by the severe plastic deformation (SPD) at the subsurface layer, and the increase in surface hardness.

Additional Axial Stress of CWR Track on the Bridge according to the Variation of Design Vehicle Load (설계차량하중 변화에 따른 교량상 장대레일 궤도의 부가축응력)

  • Yun, Kyung-Min;Jeon, Byeong-Heun;Choi, Shin-Hyung;Lim, Nam-Hyou
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.1
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    • pp.807-813
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    • 2015
  • The CWR(Continuous Welded Rail) on a bridge shows complex structural behavior compared to those on the roadbed. The influence factors on the track-bridge interaction are the variation of temperature and vehicle load. The analysis methods for track-bridge interaction, material property, modeling method, loads and combination method are indicated in the domestic railway design principle, KR C-08080. The vehicle load in KR C-08080 was changed in 2014. In this study, to evaluate the effect of the changed vehicle load on the track-bridge interaction, the track-bridge interaction analyses were performed for 22 bridges by using finite element method.

Joint Module with Joint Torque Sensor Having Disk-type Coupling for Torque Error Reduction (토크 오차 감소를 위한 디스크형 커플링을 갖는 토크센서가 내장된 로봇 관절모듈)

  • Min, Jae-Kyung;Kim, Hwi-Su;Song, Jae-Bok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.2
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    • pp.133-138
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    • 2016
  • Force control and collision detection for a robot are usually conducted using a 6-axis force/torque sensor mounted at the end-effector. However, this scheme suffers from high-cost and the inability to detect collisions at the robot body. As an alternative, joint torque sensors embedded in each joint were used, which also suffered from various errors in torque measurement. To resolve this problem, a robot joint module with an improved joint torque sensor is proposed in this study. In the proposed torque sensor, a cross-roller bearing and disk-type coupling are added to prevent the moment load from adversely affecting the measurement of the joint torque under consideration. This joint design also aims to reduce the stress induced during the assembly process of the sensor. The performance of the proposed joint torque sensor was verified through various experiments.