• Title/Summary/Keyword: notch length

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A Study on the Impact Fracture Behavior of Side Plate for G/T 35ton Class FRP Vessel (35톤급 FRP선박 외판자재의 충격파괴거동에 관한 연구)

  • Lee, Jin-Jeong
    • Journal of Korea Ship Safrty Technology Authority
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    • no.7 s.25
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    • pp.64-76
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    • 2008
  • This paper describes the failure mechanism and Charpy impact test of Fiber glass Reinforced Plastic composites which it was actually used for side plate of vessel. There are two examinations. The examination I, the specimens which it given temperature range $-25^{\circ}C$-$50^{\circ}C$ and with different initial notch length did impact test and then it compared impact energy(Uc) and impact fracture toughness(GIC). The examination II, the specimens which it putted into fresh water and sea water for scheduled hours did impact test and it compared impact energy(Uc) and impact fracture toughness(GIC). From examination I, it showed that impact energy(Uc) and impact fracture toughness(GIC) were peak at ambient temperature and decrease as temperature reduced. Fracture toughness(GIC) showed increase as initial notch length reduced. From examination II, impact energy(Uc) and impact fracture toughness(GIC) tended to increase which specimens putted in fresh water compared with sea water and maximum tolerance rate tend to decrease as permeation hours will be long.

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Evaluation of direct tensile strength for ultra-high-performance concrete using machine learning algorithms

  • Sanghee Kim;Woo-Young Lim
    • Computers and Concrete
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    • v.34 no.3
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    • pp.367-378
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    • 2024
  • This study evaluates the direct tensile strength of ultra-high-performance concrete (UHPC) using tests. A total of 45 dogbone-shaped specimens are tested, with the test variables being the fiber volume fraction and notch length. The test results showed that the material properties of UHPC were largely dependent on the fiber volume fraction and compressive strength. When steel fibers with more than 1% fiber volume fraction are mixed in the manufacturing of UHPC, the tensile strength can be more than twice that of plain UHPC. In addition, the incorporation of steel fibers enabled the significant improvement of the initial cracking strength. However, the effect of the notch length on the tensile behavior was insignificant. An assessment of the direct tensile strength is conducted using machine-learning algorithms (ML). For evaluation of the direct tensile strength of UHPC using ML, a total of 98 test data, including 53 data from other research works and 45 data from this experimental program, were collected. In total, 67 data with a 70% confidence interval on a normal distribution curve were selected, with 47 data among 67 used for ML training and 20 data used for ML testing. As a result, the machine-learning algorithm with a steel fiber volume fraction predicted that the tensile strength has an average of 0.98 and the lowest values of regression evaluation metrics among analytical and ML-based models. It is considered that an ML-based model can help to predict a more accurate tensile strength of UHPC.

Elacstic-\Plastic Limit Load Analysis of Notched Specimen by the Finite Element Method (노치 ( Notch )를 가진 試片의 有限要素法에 의한 彈塑性 極限 荷重解析)

  • Lee, Taik-Soon;Kim, Dong-Sub;Hwang, Pyung
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.7 no.4
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    • pp.379-385
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    • 1983
  • Many papers have shown limit loads of v-notched tension specimens in plane stress by the elastic-plastic finite element method. But they are always higher than the theoretical maximum loads. The present approach tries to find the reasons and formulates correction factor applicable to any notch shape using virtual work principle with triangular elements. The corrected limit loads are in good agreement with theoretical upper bound solutions and they are little influenced by mesh size and specimen length, which make the computing time save.

Burst pressure tests of axial part-through-wall steam generator tubes (증기발생기 축방향 부분관통균열 전열관의 파열 압력 시험)

  • Lee, Kuk-Hee;Kim, Hong-Deok;Kang, Yong-Seok;Nam, Min-Woo;Cho, Nam-Cheoul
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.10 no.1
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    • pp.56-63
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    • 2014
  • In this research, burst tests for axial notched steam generator tubes were conducted. To measure the burst pressure of notched tubes, a burst testing system was manufactured. The tests were conducted under internal pressure at room temperature. Part-through-wall and through-wall notches which have various geometries with different depths and lengths were machined by electro-discharged-machined(EDM) method. The burst pressure decreased exponentially with increasing notch length and decreased almost linearly with increasing notch depth. A comparison of the burst pressure with existing burst pressure solutions for cracked tube show that the existing solution agree well with the test results.

Fatigue Properties of Friction Weld According to the Location of Small Artificial Defect (미소인공결함의 위치에 따른 마찰용접부의 피로특성)

  • 이상열;정재강
    • Journal of Welding and Joining
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    • v.19 no.6
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    • pp.608-613
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    • 2001
  • In this study, the rotary bending fatigue test was carried out with two kinds of base metal, martensite stainless steel STR3 and austenite stainless steel STR35 and the dissimilar friction welded material with them. To compare the fatigue fifes according to the notch positions, the small circular defect was worked on the bonded line, 1.0mm and 0.5mm distance form the bonded line. The fatigue limits of the STR3 and STR35 base metal were 429.0MPa and 409.4MPa respectably. In comparison with fatigue life at the same notch positions, the STR35 specimens showed about 190% for base metal, 82% for 1.0mm distance notched specimens higher than that of the STR3. But the fatigue life of the 0.5mm distance notched STR35 specimen showed about 35% lower than that of the STR3 specimen. And the bonded line notched specimen was much lower fatigue life than the other specimens because of separation of the bonded line.

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A Study on Parameters Affected the Fatigue Crack Growth in Steel Structure Members( II ) -The Effect of Surface Residual Stress for Crack Closure- (강구조 부재의 피로균열성장에 미치는 제인자에 관한 연구( II ) -표면잔류응력이 균열닫힘에 미치는 영향-)

  • Choi, Young Jae;Kyung, Kab Soo
    • Journal of Korean Society of Steel Construction
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    • v.8 no.3 s.28
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    • pp.3-11
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    • 1996
  • To investigate the effect of fatigue crack growth due to the surface residual stress, it is measured the residual stress distribution by x-ray diffraction at the crack tip each constant crack growth in the notch specimens, and quantitively assessed the effect of crack closure caused to the distribution of compressive stress at the crack tip from evaluating crack openning stress using the finite element analysis. It is concluded that the degree of the residual stress distribution at the crack tip is decreased with increasing the crack length. From the fact that it is similar to the crack openning stress ratio, it is found that the compressive residual stress distribution and size is related to the crack closure effect and surface residual stress field with propagating crack in the notch specimens depends on the stress intensity factor range at the crack tip.

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Crack Growth Behavior of Tensile Overload for Small Load Amplitude (하중진폭이 작은 인장과대 하중의 균열성장 거동)

  • 유헌일
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.7 no.2
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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.

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Minimization of Torque Ripple for an IPMSM with a Notched Rotor Using the Particle Swarm Optimization Method

  • Shin, Pan Seok;Kim, Ho Youn;Kim, Yong Bae
    • Journal of Electrical Engineering and Technology
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    • v.9 no.5
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    • pp.1577-1581
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    • 2014
  • This paper presents a method to minimize torque ripple of a V-type IPMSM using the PSO (Particle Swarm Optimization) method with FEM. The proposed algorithm includes one objective function and three design variables for a notch on the surface of a rotor. The simulation model of the V-type IPMSM has 3-phases, 8-poles and 48 slots with 2 notches on the one-pole rotor surface. The arc-angle, length and width of the notch are optimized to minimize the torque ripple of the motor. The cogging torque of the model is reduced by 55.6% and the torque ripple is decreased by 15.5 %. Also, the efficiency of the motor is increased by 15.5 %.

Three-Dimensional Virtual Crack Closure Technique Based on Anisoparametric Model for Stress Intensity Factors of Patch Repaired Plates with Cracks at Notches (접착 보강된 노치 균열판의 응력확대계수 산정을 위한 비등매개변수 모델 기반의 3차원 가상균열닫힘법)

  • Ahn, Jae-Seok;Woo, Kwang-Sung
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.32 no.1A
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    • pp.39-48
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    • 2012
  • This study deals with numerical determination of stress intensity factors of adhesively patch-repaired plates with cracks at V-shaped or semicircular notches. The p-convergent anisoparametric model are considered and then three-dimensional virtual crack closure technique is presented using formulations of anisoparametric elements. In assumed displacement fields of an element, strain-displacement relations and three-dimensional constitutive equations are derived with three-dimensional hierarchical shape functions expanded from one-dimensional Lobatto functions. Transfinite mapping technique is used to represent a circular boundary. The present model provides accuracy and simplicity in terms of stress concentration factor, stress distribution, the number of degrees of freedom, and non-dimensional stress intensity factor as compared with previous works in literatures. Stress intensity factors obtained by the three-dimensional virtual crack closure technique are estimated with respect to the variation of width of finite plate, radius of notch root, angular inclination of V-shaped notch, and crack length.

Design of a Half-Circle Shape UWB Antenna (반원 형태의 UWB 안테나 설계)

  • Lee Hyo-Kyoung;Lee Jung-Nam;Jang Hwa-Yeol;Park Jong-Kweon
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.16 no.9 s.100
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    • pp.932-940
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    • 2005
  • In this paper, a planar half-circle shape ultra-wideband(UWB) antenna fed by CPW is designed, fabricated and measured for UWB communications. Within the UWB band(3.1 GHz${\~}$10.6 GHz), 5.15 GHz${\~}$5.825 GHz frequency band is used by IEEE 802.1la WLAN applications. It may be necessary to notch out this band to avoid interference with IEEE 802.1la WLAN. Therefore, we have proposed three kinds of UWB antennas having a notch function, such as a rectangular slot, a hat-shaped slot a circle-shaped slot. The notch frequency of the proposed antenna can be adjusted by controlling the slot length or slot width. From the measured results, the proposed antennas show a good gain flatness except the IEEE 802.1la WLAN frequency band and have a reasonable agreement with simulated results.