• Title/Summary/Keyword: Notch stress

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Contact Singular Stress with Relief Notch by Using Dynamic Photoelasticity (동적광탄성 실험에 의한 응력이완 노치부근에서의 접촉특이응력해석)

  • 이억섭;황시원;나경찬
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.1
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    • pp.55-62
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    • 1996
  • The dynamic photoelastic technique has been utilized to investigate the possibility of relieving the large local singular stresses which are induce in the corner of a right angled indenter. The indenter compresses a semi-infinite body dynamically with an impact load applied on the top of the indenter. The effect of geometric changes to the indenter in terms of the diameter (d) and the location (ℓ) of the notch on the relieving of the dynamic contact stresses are investigated. A multi-spark-high speed camera with twelve sparks was used to take dynamic photographs. The contact singular stresses were found to be released by introducing the relief notch along the indenter. The optimal location and geometry of the relief notch need further experimental investigation.

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The Notch Effects on the Fatigue fracture Behaviour of Ferrite-Martensite Dual Phase Steel (페라이트-마르텐사이트 이상조직강의 피로파괴거동에 미치는 노치효과)

  • 도영민
    • Journal of the Korean Society of Safety
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    • v.18 no.3
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    • pp.46-53
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    • 2003
  • For the tensile tests of the F.E.M., microvoids are created by the boundary separation process at the martensite boundary or neighborhood and at inclusions within the fracture. to grow to the ductile dimple fracture. For the case of the M.E.F., microvoids created at the discontinuities of the martensite phase which exists at the grain boundary of the primary ferrite are grown to coalescence with the cleavage cracks induced at the interior of the ferrite, which as a result show the discontinuous brittle fracture behavior. In spite of their similar tensile strengths, the fatigue limit and the notch sensitivity of the M. E.F. is superior to those of the F.E.M., The M.E.F. is much more insensitive to notch than F.E.M. from the stress concentration factor($\alpha$).

Notch Fatigue Analysis Based on the Actual Bead Shape of Welded Joint (용접연결부의 실제 비드형상을 고려한 노치피로해석법)

  • Yang, Park-Dal-Chi;Park, Chi-Mo
    • Journal of the Society of Naval Architects of Korea
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    • v.46 no.4
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    • pp.417-423
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    • 2009
  • This paper is concerned with the fatigue behaviour of welded joints by the notch stress approach. The actual welded shape is complex and 3-dimensional that may influence greatly the fatigue strength. The purpose of the paper is to present a way of modelling the actual weld bead shape by using a 3-D Laser scanner for experimental models of steel plates with longitudinal fillet welds, and applying its results to a proper notch stress method for the fatigue strength. The present approach to assess the fatigue strength is quite promising with application to a variety of welded joints and effects of weld profiling to fatigue strength.

Study of cracks in compressed concrete specimens with a notch and two neighboring holes

  • Vahab, Sarfarazi;Kaveh, Asgari;Shirin, Jahanmiri;Mohammad Fatehi, Marji;Alireza Mohammadi, Khachakini
    • Advances in concrete construction
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    • v.14 no.5
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    • pp.317-330
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    • 2022
  • This paper investigated computationally and experimentally the interaction here between a notch as well as a micropore under uniaxial compression. Brazilian tensile strength, uniaxial tensile strength, as well as biaxial tensile strength are used to calibrate PFC2d at first. Then, uniaxial compression test was conducted which they included internal notch and micro pore. Experimental and numerical building of 9 models including notch and micro pore were conducted. Model dimensions of models are 10 cm × 10 cm × 5 cm. Joint length was 2 cm. Joints angles were 30°, 45° and 60°. The position of micro pore for all joint angles was 2cm upper than top of the joint, 2 cm upper than middle of joint and 2 cm upper than the joint lower tip, discreetly. The numerical model's dimensions were 5.4 cm × 10.8 cm. The fractures were 2 cm in length and had angularities of 30, 45, and 60 degrees. The pore had a diameter of 1 cm and was located at the top of the notch, 2 cm above the top, 2 cm above the middle, and 2 cm above the bottom tip of the joint. The uniaxial compression strength of the model material was 10 MPa. The local damping ratio was 0.7. At 0.016 mm per second, it loaded. The results show that failure pattern affects uniaxial compressive strength whereas notch orientation and pore condition impact failure pattern. From the notch tips, a two-wing fracture spreads almost parallel to the usual load until it unites with the sample edge. Additionally, two wing fractures start at the hole. Both of these cracks join the sample edge and one of them joins the notch. The number of wing cracks increased as the joint angle rose. There aren't many AE effects in the early phases of loading, but they quickly build up until the applied stress reaches its maximum. Each stress decrease was also followed by several AE effects. By raising the joint angularities from 30° to 60°, uniaxial strength was reduced. The failure strengths in both the numerical simulation and the actual test are quite similar.

The Stress Distribution and Improvement of fatigue Strength for Notched Materials by Shot Peening (Shot peening 가공에 의한 노치재의 응력분포와 피로강도의 개선)

  • Lee, Seung-Ho;Kim, Hei-Song
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.7 no.5
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    • pp.120-126
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    • 1998
  • Second step shot peening was applied on both smooth specimen and U-notch specimen in order to investigate the stress distribution and the improvement in fatigue strength. Various experiments and measurements such as rotary bending fatigue test and the measurement of compressive residual stress were performed. The results showed that the fatigue strength of second step shot peened specimens increased by 34 percent compared to that of unpeened ones. Compressive residual stress also considerably increased, which resulted in the increase of fatigue strength. finite element analysis showed that shot peening is effective in decreasing the bending stress by external force. The effectiveness of shot peening in reducing the compressive residual stress was anticipated by the superposition of the concentrated stress and the compressive residual stress.

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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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A Study on Fracture Criterion of PMMA Plates Having a V-Notch with an End Hole (단공 (端孔) V-노치가 있는 PMMA 판의 파괴기준에 관한 연구)

  • Choo, Won Chul;Cho, Sang Bong;Yun, Jon Do
    • Journal of the Korean Society for Precision Engineering
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    • v.33 no.10
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    • pp.865-873
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    • 2016
  • The aim of this study was to examine the validity of fracture criterion for PMMA plates that have a V-notch with an end hole. The predicted stress intensity factors and crack initiation angles by the fracture criterion based on the maximum circumferential stress and the novozhilov's criteria were compared with the experimental results. By increasing the radius of end hole, the differences of predicted stress intensity factors and experimental results increased, possibly due to the plastic zone size. The results indicated that when the radius of end hole is < 1 mm, the fracture criterion would be useful.

Fatigue Assessment of Butt Welded Specimen According to the Existence of the Backplate (Backplate의 유무에 따른 맞대기 용접 시험편의 피로강도 평가)

  • Han, Ju-Ho;Kim, Seong-Min;Lee, Woo-Il;Kang, Sung-Won;Kim, Myung-Hyun
    • Journal of Welding and Joining
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    • v.27 no.1
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    • pp.90-94
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    • 2009
  • In this study, a series of fatigue test was performed to evaluate the fatigue strength of butt welded specimens. Effective notch stress through finite element analysis was conducted to analyze the fatigue results. As a results, no significant decrease in fatigue strength was observed when backplates were present. The S-N curve that based on effective notch stress appeared a similar fatigue lift to FAT 225 curve without reference to existence of backplates.

Fatigue Assessment of High Strength Steel with Butt Welded Joints for the Root Gap Difference (고강도강 맞대기 용접 시험편의 루트갭 변경에 따른 피로강도 평가)

  • Kim, Ho-Jung;Kang, Sung-Won;Kim, Myung-Hyun
    • Journal of the Society of Naval Architects of Korea
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    • v.48 no.1
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    • pp.56-61
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    • 2011
  • In this study, a series of fatigue tests was conducted to evaluate fatigue strength for the root gap difference with high strength steel with butt welded joints. A finite element analysis using effective notch stress method was also performed to compare effective notch factors each other with butt welded specimens made by copper backing. The results of fatigue tests were classified according to the root gap difference. Fatigue life of butt welded specimens is presented for determining the root gap of high strength steel with butt welded joints in terms of fatigue strength. Then effective notch stress was applied to interpret fatigue strength of butt welded specimen model which is reflected actual measured dimensions. As a result, fatigue strength of high strength steel with butt welded specimens is increased by root gap gets longer in length.

Influence of Notch Change on Corrosion Fatigue Fracture in F.E.M. Dual phase Steel of SS41 Steel (SS41강의 F.E.M.복합조직강에서 노치변화가 부식피로파괴에 미치는 영향)

  • 도영민;이규천
    • Journal of the Korean Society of Safety
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    • v.16 no.2
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    • pp.44-50
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    • 2001
  • The rotated bending fatigue test was conducted in air md in 3.5% NaCl salt solution to investigate the fatigue fracture behaviour of raw material and F.E.M dual phase steel made from raw material(SS41) by a suitable heat treatment. This study has compared the initial microcrack creation of material by tensile test with that by fatigue test. And the rotated bending test of cantilever type under the condition of 3.5% NaCl salt solution and air has investigated the corrosion fatigue fracture behaviour with the variation of stress concentration factor determined by each of notch shapes. The initial microcrack have been developed in fragile grainboundary with general corrosion occurring in raw material : in the pits built up by corrosion in F.E.M. dual phase steel because pits bring out stress concentration. It is small that the degree of decrease in corrosion fatigue life for F.E.M. dual phase steel compared with raw material because the notch sensitivity of F.E.M. dual phase steel is lower than raw material in reason of characteristics with two-phase construction.

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