• Title/Summary/Keyword: 노치 형상

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Effect of Notch Geometries on Dynamic Stress Concentration Factor (노치 선단(균열 주위)의 기하학적 형상이 동적 응력집중계수(동적균열전파)에 미치는 영향)

  • O.S. Lee;H.S. Jeon;K.H. Byun
    • Journal of the Society of Naval Architects of Korea
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    • v.35 no.4
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    • pp.46-54
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    • 1998
  • In this paper, the erect of notch geometries on dynamic stress concentration was investigated by using the dynamic photoelasticity and the drop weight loading system Dynamic stress fields arisen by elastic wave through the loading system around various types of notch geometries were captured by using $10^6/sec$ frame rate Cranz-Shardin camera system with 12 photographic frames. We found that dynamic stress concentrations around the notch tip and comer were highly dependent on the change in notch geometries. The elders of dynamic stress singularity ware determined with respect to varying geometries of notches and we explained dynamic stress concentration in terms of the orders of dynamic stress singularity.

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Study on the Crack Generation Patterns with Change in the Geometry of Notches and Charge Conditions (노치 형상 및 장약조건의 변화에 따른 균열발생양상에 관한 연구)

  • Park, Seung-Hwan;Cho, Sang-Ho;Kim, Seung-Kon;Kim, Kwang-Yeom;Kim, Dong-Gyou
    • Tunnel and Underground Space
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    • v.20 no.1
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    • pp.65-72
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    • 2010
  • Crack-controlled blasting method which utilizes notched charge hole has been proposed in order to achieve smooth fracture plane and minimize the excavation damage zone. In this study, the blast models, which have a notched charge hole, were analyzed using dynamic fracture process analysis software to investigate the effect of the geometry of a notched charge hole and decoupling indexes of the charge hole on crack growth control in blasting. As a result, crack extension increased and damage crack decreased with the notch length. Ultimately, stress increment factors and resultant fracture patterns with different notch length and width were analyzed in order to examine the effect factors on the crack growth controlling in rock blasts using a notched charge hole.

A Study on the Variations of Impact Strength of Plastics for Various Thicknesses and Notch Formation (두께와 노치생성방법에 따른 플라스틱 수지의 충격강도 변화에 관한 연구)

  • Kim, Hyun;Lee, Dae-Seop;Lim, Jae-Soo;Lyu, Min-Young
    • Polymer(Korea)
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    • v.36 no.1
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    • pp.59-64
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    • 2012
  • The impact strength of material is considered the most important design factor for small and light products. Impact strength is a unique material property, thus the impact strength should not depend upon the geometry of specimen. However it varies according to specimen thickness, notching method, and notch shape. In this study, the variations of impact strength have been investigated according to thickness, notch shape, and notching method of specimen. Engineering plastics such as PC, ABS and POM have been used in this study. Experimental results showed impact strength increased as thickness decreasesd. PC showed the highest increment of impact strength when the thickness was thin. Fractured section of PC showed brittle fracture behavior when the specimen was thick. However it showed ductile fracture behavior when it was thin. The impact strength of in-mold notched specimen showed higher than that of milling notched specimen. PC showed the highest notch sensitivity among the materials used in this experiment.

Analysis of Multi-Mode Reflection and Transmission Coefficients of a Lamb Wave Across a Rectangular Notch (사각형 노치에 대한 램파의 다중 모드 반사와 투과 계수 해석)

  • Kim, Byung-Soo;Roh, Yong-Rae
    • The Journal of the Acoustical Society of Korea
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    • v.27 no.3
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    • pp.129-139
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    • 2008
  • The purpose of the present work is to derive the reflection and transmission coefficients of $S_0\;and\;A_0$ mode Lamb waves in relation to the geometry of a rectangular notch when the waves propagate across the notch in an elastic plate. Firstly, the excitable modes of the Lamb wave were analyzed with respect to the plate thickness. The scattering phenomena were divided into three independent processes according to the boundary shape of the notch and the direction of the wave propagation. Linear equations for each process were derived with corresponding free or continuous boundary conditions to analyze the scattered waves. By the rule of linear superposition, the waves scattered at each process were summed for each mode. Then the steady-state reflection and transmission coefficients of the scattered waves were determined so that the difference of energy flux between the incident and the scattered waves would remain within 4%.

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.

Effect of Wrinkling on Failure Behavior of Thin Membranes (얇은 막재에서 주름이 파괴거동에 미치는 영향)

  • Kim, Young-Ah;Woo, Kyeong-Sik
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.39 no.11
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    • pp.1005-1012
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    • 2011
  • In this paper, the effect of wrinkling on the failure behavior of thin membrane was studied using geometrically nonlinear shell element post-buckling analysis with global-local analysis strategy. In the analysis, double-edge notched and single-edge notched tensile specimen configurations were considered. The analyses were performed for both cases with allowing and suppressing the wrinkling deformation. The results were investigated focusing on the effect of wrinkle development on the variation of J-integral values at the cut tip. The effect of cut lengths and the specimen lengths were also systematically studied.

Evaluation of Notch Effect on the Dynamic Strain Aging Behavior of Carbon Steel Piping Material (탄소강 배관 재료의 DSA 거동에 미치는 노치 영향 평가)

  • Lee, Sa-Yong;Kim, Jin-Weon;Kim, Hong-Deok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.3
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    • pp.275-282
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    • 2012
  • In this study, tensile tests were performed using standard and notched-bar specimens under two different displacement rates and various temperatures, in order to investigate the effects of the stress and strain concentration at the notched section on the dynamic strain aging (DSA) behavior of carbon steel piping material. In addition, finite element simulations were conducted to evaluate quantitatively the stress and strain states for both types of specimen under uniaxial tensile loading. The results showed that serration and an increase in tensile strength, which are considered to be evidence of DSA in carbon steels, can be observed from tensile tests for notched-bar specimens. It was also found that the temperature region of DSA observed in the notched-bar specimens was higher than the DSA region observed in the standard tensile specimens tested under the same displacement rate. The results of finite element analysis showed that this behavior is associated with the high strain rate at the notched section, which is caused by the stress and strain concentration.

Fracture Analysis of Notched Laminated Composites using Cohesive Zone Modeling (응집영역 모델링 기법을 사용한 노치가 있는 적층복합재료의 파괴해석)

  • Woo, Kyeongsik;Cairns, Douglas S.
    • Composites Research
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    • v.30 no.2
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    • pp.149-157
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    • 2017
  • In this paper, fracture behavior of laminated composites with notch was studied by cohesive zone modeling approach. The numerical modeling proceeded by first generating 3 dimensional solid element meshes for notched laminated composite coupon configurations. Then cohesive elements representing failure modes of fiber fracture, matrix cracking and delamination were inserted between bulk elements in all regions where the corresponding failures were likely to occur. Next, progressive failure analyses were performed simulating uniaxial tensile tests. The numerical results were compared to those by experiment available in the literature for verification of the analysis approach. Finally, notched laminated composite configurations with selected stacking sequences were analyzed and the failure behavior was carefully examined focusing on the failure initiation and progression and the dominating failure modes.

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.