• Title/Summary/Keyword: Stress Concentration

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A Study on the Effect of Stress Concentration Factor Determined by 3D-ESPI System on the Fatigue Life (3D-ESPI 시스템을 이용하여 결정된 응력집중계수가 피로수명에 미치는 영향에 관한 연구)

  • 김경수;심천식
    • Journal of Ocean Engineering and Technology
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    • v.16 no.1
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    • pp.46-51
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    • 2002
  • Fatigue life estimation by the theoretical stress concentration factors are, in general, considerably different from test results. And in calculating stress concentration factor, it is very difficult to consider actual geometry and material property which are the notch shapes, imperfections or defects of materials such as porosities inclusions and casting defects, etc. Therefore, the paper deals with the experimental method to find out the more exact stress concentration factors by measuring the strain distributions on each specimen by 3D-ESPI(Electronic Speckle Pattern Interferometry) System. Then the fatigue lives are compared between theoretical calculations using stress concentration factors determined by 3D-ESPI system and fatigue test results.

A Study on the Stress Concentration Phenomenon of a Dissimilar Joints (이종재 접합부에서의 응력집중현상에 관한 연구)

  • 조상명;김영식
    • Journal of Welding and Joining
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    • v.10 no.1
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    • pp.35-42
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    • 1992
  • In this study, the stress concentration phenomenon for the dissimilar joints(ceramic-metal) bonded by thermal treating using a soft-insert metal(copper) was investigated with the aid of FEM(finite element method) under the load condition of uniform tension. The analysis was carried out by the supposing that stress states are plane stress or plane strain and elastic or elastic-plastic. And the Von Mises yield criterion and the incremental theory as plastic flow were adopted in this analysis. As the summarized results obtained, the stress concentration phenomenon was severer as the soft insert metal was thicker, in plane strain than in plane stress and in elastic-plastic state than in elastic state. Furthermore, the inducing mechanism of stress concentration was well expressed by the constraint forces(Fc) generated between the soft and the hard material.

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Estimation of stress concentration factor in bolt jointed structure with variable preload (체결력에 따른 볼트 결합구조물의 응력집중계수 평가)

  • 송준혁
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 1998.03a
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    • pp.298-303
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    • 1998
  • Most of mechanical structures are combined of substructures such as beam and/or plates. There are few system with unibody structures but are not a few systems with united body structures. Generally the dynamic analysis of whole structures is perform ed under alternating load. However, the analysis of each joint area is more important than others for zero severity. This paper presents the results of analysis of concentration stress in bolt jointed structure with variable preload. At frist, a static vibration test was performed to find out a nominal stress of bolt joint ed plates from the relationship between natural frequency and nominal stress. Then a concentration stress was computed at contact point between bolt and plate in the structure. It is believed that the proposed method has promising implications for safer design with fatigue quality index of stress concentration factor and has merit for cost down and saving time at the beginning of vehicle development.

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An Analysis of stress concentration and crack in injection mold by cavity pressure (사출금형에서 내압에 의한 응력집중 및 크랙 분석)

  • Choi, Sung-Hyun;Hang, Su-Jin;Choi, Sung-Ju;Lyu, Min-Young
    • 한국금형공학회:학술대회논문집
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    • 2008.06a
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    • pp.159-162
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    • 2008
  • High pressure is involved during injection molding operation specially packing phase. Cracks in the mold are often occurred by high cavity pressure. In this study, structural analysis of mold has been performed using commercial softwares, Abaqus and Ansys, to investigate cause of crack in the injection mold. Structural analysis contains four cases: stress distribution according to the cavity pressure, stress concentration according to the boundary conditions, stress concentration for inter-locking design of mold, and stress concentration for distributed cavity pressure. Through this study it was observed that the locations of stress concentrations were coincident with locations of crack. Robust mold design is being required to withstand high cavity pressure.

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Photoelastic Stress Analysis of the Abutment Surrounding Tissue According to Shape of the Proximal Plate of the RPI Clasp (압축하중시 RPI clasp의 3가지 다른 proximal plate 형태에 따른 지대치 주위조직의 광탄성 응력 분석)

  • Choi, Jung Soo;Kim, Busob
    • Journal of Technologic Dentistry
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    • v.34 no.4
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    • pp.473-482
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    • 2012
  • Purpose: The purpose of this study was to investigate the stress distribution of the surrounding tissues according to 3 proximal plate types of the RPI clasp. Methods: The removeable partial denture which mandibular right and left second premolars and mandibular molars were lost was attached to a three dimensional photo elastic epoxy resin model. Then 120N of vertical load was applied. After 3-dimensional photoelastic stress analysis was used to record the isochromatic fringe patterns. Results: Kratochvil type guiding plane exhibited little uniform stress distribution on load center and alveolar ridge, but higher stress concentration on buccal surface of second premolar. Krol type guiding plane exhibited the stress concentration on the front of load center and relatively higher stress concentration on buccal surface of first premolar. However, this type had no effect on canine. Researcher type guiding plane showed the stress concentration on second premolar and molar, but the little stress distribution on first premolar. Conclusion: In all types, excessive stress concentration was appeared and three types were not significant different.

Analysis of the Change of Polyamine during the Cold Treatment in Spring Radish Young Cotyledons and Hypocotyls (봄무우 유식물의 자엽과 하배축에서 저온처리동안 Polyamine 농도 변화의 분석)

  • Lee, Sung Chang;Park, Jae Won;Cho, Bong-Heuy
    • Analytical Science and Technology
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    • v.12 no.1
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    • pp.75-79
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    • 1999
  • The concentration of polyamine and the relationship between the concentration of PA and cold resistance were analysed during the cold stress in the cotyledons and hypocotyls of young spring radishes. The concentration of PUT was increased during the cold stress in the cotyledons and the concentration of PUT and SPD was changed significantly all the stress time. From the results, we suggested that PUT and SPD were synthesized against cold stress or separated from the bound PA during the cold stress. But, the concentration of SPM was not significantly changed during the cold stress. Only SPD existed in the control hypocotyls. The concentration of SPD was increased during the cold stress, but was decreased dramatically during continusly cold stress. The reactivity against stress of hypocotyls was generally more sensitive during the cold treatment than that of the cotyledons because of the lower concentration of PA in the hypocotyls. PUT and SPD were responsible for the resistance of cold stress in the cotyledons and PA did not play an important role on the resistance of cold stress in the hypocotyls. In this study we suggest that PUT and SPD were responsible for the increase of the resistance against the cold stress.

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The Study on Stress Distibution of a Slotted Plate (슬롯 을 갖는 平板 의 應力分布擧動 에 관한 硏究)

  • 송삼홍
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.6 no.4
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    • pp.367-376
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    • 1982
  • Stress concentration mainly occurs near holes and notches. Then local stress is larger than nominal stress. It is necessary that stress concentration phenomena are studied because it can act as a cause of fracture of material. In order to analyze fracture of material including holes, stress concentration factor and stress distribution must be studied more carefully. In this paper the stress concentration and distribution of a slotted plate is examined. Hardened 7:3 brass plate with 4 different slots including a circular hole is used. And ratios of slot length to its root radius are 1, 2, 3, 24, 4. The stress distribution is measured by using strain gages attached to the plate with variable width. And obtained experimental data are adjusted by using calibrated gage factor.

Effects of Ni Concentration on Residual Stress in Electrodeposited Ni Thin Film for 63Ni Sealed Source (63Ni 밀봉선원용 Ni 전기도금 박막에서 Ni 농도가 잔류응력에 미치는 영향)

  • Yoon, Pilgeun;Park, Deok-Yong
    • Journal of the Korean institute of surface engineering
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    • v.50 no.1
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    • pp.29-34
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    • 2017
  • Chloride plating solution was fabricated by dissolving metal Ni powders in a mixed solution with HCl and de-ionized water. Effects of $Ni^{2+}$ and saccharin concentrations in the plating baths on current efficiency, residual stress, surface morphology and microstructure of Ni films were studied. In the case of $0.2M\;Ni^{2+}$ concentration, current efficiency was decreased to about 65 % with increasing saccharin concentration, but, in the case of $0.7M\;Ni^{2+}$ concentration, it was shown more than 90 % with the increase of saccharin concentration. Residual stress of Ni thin film was appeared to be about 400 MPa up to 0.0244 M saccharin concentration at the $0.2M\;Ni^{2+}$ concentration and surface morphology with severe cracks was observed in the range of 0.0487~0.0975 M saccharin concentration. Residual stress of Ni thin films was measured to be about 750 MPa without saccharin addition and 114~148 MPa at the range of 0.0097~0.0975 M saccharin concentration for the $0.7M\;Ni^{2+}$ concentration. Relatively low residual stress values (114~148 MPa) of the Ni films at the range of 0.0097~0.0975 M saccharin concentration may be resulted from codeposition of S from saccharin. Ni films at $0.7M\;Ni^{2+}$ concentration showed smooth surface morphology and were independent of saccharin concentration. Ni films at $0.7M\;Ni^{2+}$ concentration consist of FCC(111), FCC(200), FCC(220) and FCC(311) peaks and the intensities of FCC(111) and FCC(200) peaks increased with increasing saccharin concentration. Also, the average grain size decreased with increasing saccharin concentration from about 30 nm to about 15 nm.

Effect of the Semi-circular Relieving Groove on the Stress Concentration at the Fillet of the Stepped Bar under Axial Tension (축인장하(軸引張下)의 평판(平板)의 단부(段部) Fillet 근처(近處)의 Relieving Groove가 응력집중(應力集中)에 미치는 영향(影響))

  • Hyo-Chul,Kim
    • Bulletin of the Society of Naval Architects of Korea
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    • v.6 no.2
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    • pp.5-10
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    • 1969
  • A stepped bar with seimi-circular stress relieving groove near the fillet was subjected by axial tension in a polarized light field. On the stress concentration factor, the effect of the ratios of the fillet radius, the distance between two relieving grooves and the groove radius to the breath of the narrower portion of the stepped bar have been investigate. Observing the stress concentration in 48 models with various proportions, the conclusion arrived at were as follow: 1) If the fillet radius of the stepped bar is larger than half breadth of the narrower portion, the reduction of the stress concentrations can not be expected. 2) If the fillet radius is smaller than half breadth of the narrower portion of the stepped bar, the stress concentration can be droped to the reasonable range. 3) When the groove radius is larger than a quarter of the difference between the distance of two relieving grooves and the breadth of the stepped bar and smaller than a half of that, the stress concentration factors can have their possible minimum value. 4) When the sun of the breadth of the narrower portion of the stepped bar and twice of the relieving groove radius is smaller than the distance between two relieving grooves, minimum stress concentration can be obtained.

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Estimation of Dynamic Stress Concentration Factor by Infrared Thermography Stress Analysis (적외선 열화상 응력측정법에 의한 동적 응력집중계수 예측)

  • Choi, Man-Yong;Kang, Ki-Soo;Park, Jeong-Hak;Ahn, Byung-Wook;Kim, Koung-Suk
    • Journal of the Korean Society for Precision Engineering
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    • v.25 no.5
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    • pp.77-81
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    • 2008
  • Structural components subjected to high frequency vibrations, such as those used in vibrating parts of gas turbine engines, are usually required to avoid resonance frequencies. Generally, the operating frequency is designed at more than resonance frequencies. When a vibrating structure starts or stops, the structure has to pass through a resonance frequency, which results in large stress concentration. This paper presents the transient thermoelastic stress analysis of vibrating cantilever beam using infrared thermography and finite element method (FEM). In FEM, stress concentration factor at the 2nd resonance vibration mode is calculated by the mode superposition method of ANSYS. In experiment, stress distributions are investigated with infrared thermography and dynamic stress concentration factor is estimated. Experimental result is agreed with FEM result within 10.6%. The advantage of this technique is a better immunity to contact problem and geometric limitation in stress analysis of small or micro structures.