• Title/Summary/Keyword: Residual Strengths

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Fatigue Life Evaluation Model of Welded Joints With Residual Stress (잔류응력을 고려한 용접 이음부의 피로수명 평가 모델)

  • Goo, Byeong-Choon;Yang, Sung-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.9
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    • pp.1328-1336
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    • 2004
  • According to our fatigue tests carried out at 20 Hz, R=0.1 on transversely butt-welded joints, fatigue strengths of as-welded specimens, that is, specimens having residual stress are higher than those of annealed specimens in short life range, but vice verse in long life range. This behavior seems to be concerned mainly with residual stress relaxation by applied loading. After analyzing the welding process, we conducted finite element analysis to quantify the degree of residual stress relaxation. By taking into account residual stress relaxation, modified Goodman diagram, and nominal stress, we evaluated the fatigue life of the welded joint from the S-N curve for the parent material. The estimated results are in a good agreement with the experimental results.

Fatigue Life Evaluation of Welded Joints With Residual Stress (잔류응력을 고려한 용접 이음부의 피로수명 평가 모델)

  • Goo, B.C.;Yang, S.Y.
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.108-113
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    • 2004
  • According to our fatigue tests carried out at 20 Hz, R=0.1 on transversely butt~welded joints, fatigue strengths of as-welded specimens, that is, specimens having residual stress are higher than those of annealed specimens in short life range, but vice verse in long life range. This behavior seems to be concerned mainly with residual stress relaxation by applied loading. After analyzing the welding process, we conducted finite element analysis to quantify the degree of residual stress relaxation. By taking into account residual stress relaxation, modified Goodman diagram, and nominal stress, we evaluated the fatigue life of the welded joint from the S-N curve for the parent material. The estimated results are in a good agreement with the experimental results.

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The Characteristics of Shear Strength on Weathered Residual Soils for the Effect of Soaking and Disturbance (수침 및 교란 효과에 따른 풍화잔적토의 전단강도 특성)

  • 오세붕;정종혁;이영휘
    • Journal of the Korean Geotechnical Society
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    • v.15 no.5
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    • pp.125-139
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    • 1999
  • It is difficult to evaluate the shear strength of weathered residual soils because of the difficulties of undisturbed sampling. In this study, a sampling device, direct shear box with shoe, was developed in order to get undisturbed samples easily for direct shear tests, and undisturbed samples could be successfully obtained. Through direct shear tests on undisturbed samples, the shear strength was evaluated with the variation of saturated conditions. In order to consider the effect of disturbance on the shear strength, a static compaction device was developed, and then it was found that undisturbed samples show greater shear strengths than the disturbed ones under natural water contents and similar strengths to the ones under soaked conditions. Further, the shear strength evaluated from direct shear tests was compared with the result of triaxial tests on undisturbed samples, and soaked strengths of the former were similar to the latter. As the result of stability analyses on an actual failed slope, it was found that the shear strength can be evaluated reasonably using direct shear box with shoe.

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Fatigue Life Evaluation Model for Welded feints Based on Nominal Stress and Residual Stress Relaxation (잔류응력 완화를 고려한 공칭응력 기반 용접재의 피로수명 평가 모델)

  • 구병춘;양승용;정흥채;최성규
    • Proceedings of the KWS Conference
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    • 2004.05a
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    • pp.249-251
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    • 2004
  • According to our fatigue tests carried out at 20 ㎐, R=0.1 on transversely butt-welded joints, fatigue strengths of as-welded specimens, that is, specimens having residual stress are higher than those of annealed specimens in short hie range, but vice verse in long life range. This behavior seems to be concerned mainly with residual stress relaxation by applied loading. After analyzing the welding process, we conducted finite element analysis to quantify the degree of residual stress relaxation. By taking into account residual stress relaxation, modified Goodman diagram, and nominal stress, we evaluated the fatigue life of the welded joint from the S-N curve for the parent material. The estimated results are in a good agreement with the experimental results.

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Material Characteristics of Traditional Bricks used in the Royal Tomb of King Muryeong, Gongju, Korea and Its Reproduction Bricks (무령왕릉에 사용된 전돌과 재현 전돌의 재료학적 특성)

  • Kwon, Yang Hee;Hong, Sung Gul
    • Journal of Conservation Science
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    • v.30 no.3
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    • pp.287-298
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    • 2014
  • This study investigates the material properties of the traditional bricks used in the royal tomb of King Muryeong. Compressive strengths, thermal conductivities, absorptance and the rate of residual moisture are measured by non-destructive experiments. Compressive strength of the traditional bricks is estimated by using the ultrasonic wave velocity and the absorptance. Based on the experimental results, the predicted compressive strengths using the ultrasonic wave velocity are unsuitable for the traditional bricks due to the rough surface and thickness variation of the specimens. The strengths using the absorptance are more suitable than those using the velocity because the predicted average strengths (28.69 MPa ~ 33.19 MPa) are close to building materials like normal strength concrete. In addition, the methods using the absorptance are not influenced by surface and thickness conditions of the specimens. The average thermal conductivities of the bricks measured by using Mathis TCi are close to those of soils (1.58 W/mK). The absorptance and the rate of residual moisture of the bricks are 1.6 % ~ 15 %, 0 % ~ 0.7 %, respectively.

MSD가 존재하는 시편에 대한 잔류강도 평가

  • 신규인;김태순;박재학
    • Proceedings of the Korean Institute of Industrial Safety Conference
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    • 1998.05a
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    • pp.77-82
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    • 1998
  • The residual strength of a specimen with MSD was investigated experimentally and numerically. The used materials for specimens are 2024-T3 and S50C. In each specimen, one main crack and 4 small cracks are machined by using electrical discharge wire cutting and saw cutting. The residual strengths are measured for 3 cases of crack configurations, and the measured values are compared with the values obtained numerically by using elasto-plastic average uncracked ligament stress link-up criteria.

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Influence of Hygrothermals on Residual Fatigue Bending Strength of CFRP Composite Laminates (CFRP적층재의 잔류피로굽힘강도애 미치는 열습의 영향)

  • 박노식;임광희;양인영
    • Journal of the Korean Society of Safety
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    • v.12 no.2
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    • pp.27-36
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    • 1997
  • This paper evaluates the static and fatigue bending strengths of CFRP (carbon fiber reinforced plastic) laminates subjected to hygrothermals. The specimens which had different stacking composition, orthotropic and quasi-isotropic laminated plates, were prepared for this experiment. A steel ball launched by the air gun collides against CFRP laminates to generate impact damages, and the 3-point fatigue bending test is carried out by using the impacted laminates to investigate the influence of hygrothermals on the effect on the residual bending fatigue strength of CFRP laminates.

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Residual Strength of Damaged Tubulars under Combined Axial Compression, Hydrostatic Pressure and End Bending Moment (복합 하중에 대한 손상 원통의 잔류강도)

  • Cho, Sang-Rai;Gwak, Dong-Il
    • Journal of Ocean Engineering and Technology
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    • v.3 no.2
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    • pp.118-124
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    • 1989
  • In this paper a design formula has been proposed to predict the residual strength of damaged tubulars subjected to combined axial copression, hydrostatic pressure and end bending loadings. A theoretical analysis method was employed to calculate the residual strengths, in which the geometric configuration of damaged tubulars is realistically described using empirically derived equations. The predictions using this method have been compared with relevent experimental results to demonstrate their validity and accuracy. A rigorous parametric study has been conducted using the method, and then a design formula has been derived based upon the parametric study results.

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Residual Strength of Damaged Tubulars under Combined Axial Compression, Hydrostatic Pressure and End Bending Moment (복합 하중에 대한 손상 원통의 잔류강도)

  • Cho, Sang-Rai;Gwak, Dong-Il
    • Journal of Ocean Engineering and Technology
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    • v.3 no.2
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    • pp.618-618
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    • 1989
  • In this paper a design formula has been proposed to predict the residual strength of damaged tubulars subjected to combined axial copression, hydrostatic pressure and end bending loadings. A theoretical analysis method was employed to calculate the residual strengths, in which the geometric configuration of damaged tubulars is realistically described using empirically derived equations. The predictions using this method have been compared with relevent experimental results to demonstrate their validity and accuracy. A rigorous parametric study has been conducted using the method, and then a design formula has been derived based upon the parametric study results.

Analysis of the residual strengths and failure mechanisms in laminated composites under impact loading

  • Park, K.C.;Kim, M.S.
    • Journal of the Korean Society for Precision Engineering
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    • v.11 no.3
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    • pp.105-121
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    • 1994
  • In this paper, we proposed the two-parameter model for predicting the residual strength in CFRP laminated composites subjected to high velocity impact and developed and formulated it based upon Cparino's by using the ratio of impact and the normalized residual strength. Critical indentation was obtained by the statical indentation tests. Impact tests were carried out through air-gun type impact equipment with the velocities varied 30-100m/sec. Projectiles were steel balls with 5 and 7mm in diameter. Test material was carbon/epoxy. The specimens were composed of [ .+-. 45 .deg. /0 .deg. /90 .deg. ]$\_$2/ and [ .+-. 45 .deg. ]$\_$4/stacking sequences and had 0.75$\^$T/*0.26$\^$W/*100$\^$L/(mm) dimension. Results from the proposed model were in good agreement with the test data. And failure mechanism due to high velocity impact is given here to examine the initation and deveolpment of damage by fractography and ultrasonic image system. The effects of the 0 .deg. -direction ply position and the amount to damage area on the residual strength are considered here.