• Title, Summary, Keyword: Bending Fatigue Strength

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A Study on Bending Fatigue Strength of One Side Fillet Welded T-Joint by SM 490A steel (Sm 490A강으로 제작된 T형 편면용접이음재의 굽힘피로강동에 관한 연구)

  • 엄동석;강성원;이태훈;이해우;조수형
    • Journal of Welding and Joining
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    • v.16 no.5
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    • pp.134-141
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    • 1998
  • In this study, a fillet size for bending fatigue strength of one side fillet welded T-joint, used in box type girder and other welding structure, was investigated by bending fatigue test with or without edge preparation and burn through, with variation of joint shape. As a result, the following conclusions were obtained. (1) In one side fillet welded T-joint, the larger the leg length, the greater the bending fatigue strength. The increase in bending fatigue strength. (2) One side filet welded T-joint with edge preparation showed higher bending fatigue strength than that with twofold-large leg length and without edge preparation. (3) In one side fillet welded T-joint without edge preparation, both manual welding and automatic welding were carried out with same condition. In this case, automatic welding shoed deeper penetration and more increased horizontal leg length than manual welding, so that automatic welding offers grater bending fatigue strength. (4) For one side fillet welded T-joint without edge preparation, the ratio(h/t) of the leg length (h) and the main plate thickness (t) in which toe crack can occur was 1.2 over. (5) In one side fillet welded T-joint with edge preparation, the burn through led to reduced bending fatigue strength. However, this bending fatigue strength was higher than that of one side fillet welded T-joint without edge preparation and with a larger leg length.

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Bending Fatigue Strength of Carburized and Induction Hardened Gears (침탄 및 고주파 열처리한 치차의 굽힘피로강도 평가)

  • Kim, W.D.;Choi, B.I.;Han, S.W.;Kim, J.H.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.2 no.6
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    • pp.1-8
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    • 1994
  • To enhance the strength of gears for transmission, Generally caburizing heat treatment is applied. But there are some problems in this technology the distortion of gears during heat treatment process, and the discontinuity of manufacturing process. For these reasons, the high frequency induction hardening process is widely used. This method is one of the surface hardening process to improve the wear resistance and fatigue life of the machine components. In this study, to compare the bending fatigue strength of caburized gear with that of induction hardened gear, bending fatigue testing of gears with two different cases was performed by using an electrohydraulic servo-controlled fatigue testing machine and double tooth bending fatigue test fixture. Fatigue life distributions at constant stress levels were established directly from fatigue data. For gear design, the fatigue strength distribution at specified life is more important. This distribution is obtained by statical transformation from fatigue life distribution. Reliability of bending fatigue strength was estimated by P-S-N curves and Weibull distribution.

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Fatigue Strength of Fillet Weldment under Out-of-plane Bending Load (필릿 용접부의 면외굽힘하중에 대한 피로강도)

  • 강성원;한상혁;김화수;백영민
    • Journal of the Society of Naval Architects of Korea
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    • v.40 no.1
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    • pp.28-35
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    • 2003
  • Fatigue tests of transverse fillet weldment were performed under out-of-plane bending loads. Significant increase of the fatigue strength was observed under out-of-plane bending loads, compared to the one under in-plane loads (axial loads). Applicability of the crack propagation analysis using LEFM for the surface crack of fillet weldment were investigated as well, in parallel with the fatigue tests. For the rational assessment of the fatigue strength of welded ship structures where combined stresses of the in-plane axial stress and the out-of-plane bending stress are induced simultaneously due to complexity of applied load and structural geometry, further investigation is recommended for the effect of the out-of-plane bending stress on the fatigue strength of weldment.

A Study on Evaluation of Bending Fatigue Strength in SCM415 Carburized Spur Gear (SCM415 침탄치차의 굽힘피로강도평가에 관한 연구)

  • 류성기
    • Journal of the Korean Society of Marine Engineering
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    • v.22 no.6
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    • pp.763-770
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    • 1998
  • This paper deals with evaluation of bending fatigue strength in SCM415 carburized spur gears. The constant stress amplitude fatigue test is performed by using an electrohydraulic servo-controlled pulsating tester. The S-N curves are obtained and the enhanvement of fatigue strength due to carburized treatment is clarified. In this study the improvement of fatigue strength is assumed to be caused by an increase of both hardness and residual stress and experimental formula has been proposed for the estimation of bending fatigue strength of carburized gears. The effect of surface conditions on the fatigue strength is evaluated quantitatively and it is close to the relative surface condition factor used in the ISO strength rating formula.

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Characteristic of Fatigue Properties with Tension and Bending Loading Using High Strength Steel Wire (고강도 강선의 인장 및 회전굽힘 피로특성)

  • U, Byeong-Cheol;Kim, Sang-Su;Kim, Byeong-Geol;Seo, Chang-Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.1
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    • pp.161-167
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    • 2001
  • The overhead transmission wires operating both at warm temperature and tighten state for a long period of time in a power transmission plant are degraded by air pollution, wind, creep and slip between steel wire and aluminium conductor. The objective of this study is to investigate to investigate the characteristics of fatigue properties with tension and bending loading of a high carbon steel wire. The fatigue behaviors have been carried out by tension-tension, 4 points bending and 3 points bending loading. In the present study, a conventional fatigue strengths between 4 points bending and tension-tension fatigue were determined by Gerber, Sorderberg and Goodmans theory and we investigated S-N diagram for bending and tensile loading.

Effect of internal Stress on the Strength of PZT Cermics (PZT 세라믹스의 강도에 미치는 내부응력의 영향)

  • 태원필;윤여범;김송희
    • Journal of the Korean Ceramic Society
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    • v.33 no.1
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    • pp.49-55
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    • 1996
  • The aim of this study is to investigate the change of bending strength and fatigue strength in the unpoled and poled Pb(Zr, Ti)O3 ferroelectrics of tetragonal morphotropic phase boundary (MPM) and rhombohedral com-position in terms of internal stress which is measured by XRD method. Before poling treatment the highest bending strength was found in rhombohedral composition. After poling treatment the bending strength decreas-ed in all compositions but it decreased most remarkably in tetragonal composition. The most prominent de-crease of bending strength after poling treatment in tetragonal was attributed to the occurrence of microcracks due to highanisotropic internal stress around grain boundary which was induced of bending strength after poling in MPB and rhombohedral composition was not due to the occurrence of microcracks but to the increase in tensile internal stress perpendicular to the direction of crack propagation by domain alignment. Fatigue strength was higher before poling treatment than after poling treatment for various compositions.

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FATIGUE STRENGTH OF FILLET WELDED STEEL STRUCTURE UNDER OUT-OF-PLANE BENDING LOAD

  • Kang, Sung-Won;Kim, Wha-Soo;Paik, Young-Min
    • Proceedings of the KWS Conference
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    • pp.113-120
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    • 2002
  • The effect of out-of-plane loads on the fatigue strength of welded steel structures is examined through fatigue tests with weldment of two fillet weld joint types. The results of the fatigue tests are compared with those under axial loads, on the basis of the hot spot stress range at the weld toe. From the result of the comparison, a method on how to incorporate the effect of the out-of-plane bending stress is proposed using design S-N curves derived from fatigue tests under the axial load. The proposed method is useful for rational assessment of the fatigue strength of fillet-welded structures, where combined stresses of the in-plane axial stress and the out-of-plane bending stress are induced simultaneously due to the complexity of applied loads and structural geometry.

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A Study on the Evaluation of Bending Fatigue Strength in Shaving Gears (세이빙기어의 굽힘피로강도 평가에 관한 연구)

  • 박준철
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • pp.93-99
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    • 2000
  • This study deals with the evaluation of bending fatigue strength in shaving gears, We manufactured gears using manufacture processes that are currently used in most gears manufacturing companies. The test gears are hobbed then the tooth surface are treated by a combination of shaving carbonizing and shot peening. The constant stress amplitude fatigue test is performed by using an electrohydraulic servo-controlled pulsating tester. The S-N curves are obtained and illustrated. In this study we investigated the effect of shaving process and shot peening on fatigue strength, The effect of shaving process ad shot peening on the fatigue strength is evaluated quantitatively,. The enhancement of fatigue strength due to shaving process and shot peening is clarified

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An Evaluation of Bending Fatigue Strength for Cold Forged Bevel Gear (냉간단조 베벨기어의 굽힘피로강도 평가)

  • 김재훈;사정우;김덕회;이상연
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.1
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    • pp.61-67
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    • 2000
  • Gears are the most commonly used parts in automotive and industrial applications. One of most common modes of gear failures is tooth breakage, which is usually produced by the bending fatigue failure. It is important to manufacture the gears which can withstand the applied stresses in view of safety and economic requirement. This paper deals with bending fatigue strength for cold forged bevel gear. Especially, to compare fatigue characteristics for manufacturing processes difference, bending fatigue tests of bevel gears made by three different processes respectively. Results indicate that the fatigue strength of bevel gear is improved by cold forging process. Intergranular fracture is found on fatigue fracture surface, and dimples are observed on final fracture surface. The fatigue failure cannot be considered as a deterministic quantity, but must be characterized statistically. This study proposes a method to estimate bending fatigue lift of the bevel gear using the probability-load-life and Weibull analysis.

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Characteristic of fatigue properties with tension and bending loading using high strength steel wire (고강도 강선의 인장 및 회전굽힘 피로특성)

  • Woo, Byung-Chul;Kim, Sang-Soo;Kim, Byung-Guel;Suh, Chang-Min
    • Proceedings of the KSME Conference
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    • pp.274-279
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    • 2000
  • The overhead transmission wires operating both at warm temperature and tighten state for a long period of time in a power transmission plant are degraded by air pollution, wind, creep and slip between steel wire and aluminium conductor. The objective of this study is to investigate a high carbon steel wire. We tested for basic mechanical properties and 3 types fatigue behavior, tension-tension, 4 points bending and 3 points bending fatigues. In this study, a conventional fatigue strengths between 4 points bending and tension-tension fatigue were determined by Gerber, Sorderberg and Goodman's theory and we investigated S-N diagram for bending and tensile loading.

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