• Title/Summary/Keyword: Rotary bending fatigue tester

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The Study on the Fatigue Life Prediction on Wheels through CAE (CAE를 이용한 자동차용 휠(wheel)의 피로수명 예측기법 연구)

  • 김만섭;고길주;김정헌;양창근;김관묵
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.2
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    • pp.117-122
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    • 2004
  • The fatigue life in wheels was predicted by simulating the experimental method using Finite-Element analysis. Based on a high frequency fatigue property, calculations of the stresses in wheels were performed by simulating the rotating bending fatigue test. Wheels made of an aluminum alloy(A356.2) were tested using a bending fatigue tester. Results from bending fatigue test showed a linear correlation between bending moment and stress amplitude. Consequently, Finite-Element calculations were performed by a linear analysis. In order to find stress-cycles curves, spoke parts of wheel were tested using a rotary bending fatigue tester. Also, highly accurate Finite-Element analysis requires regression lines and confidence intervals from these results. In conclusion, if the fatigue data related to the material and manufacturing procedure are reliable, the prediction on fatigue lift in wheels can be carried out with high accuracy.

The Evaluation of Fretting Fatigue Behavior on Rotary Bending Fatigue for Railway Axle Material (회전굽힘 피로 하에서의 철도 차축재료 프레팅 피로거동 평가)

  • Choi, Sung-Jong;Kwon, Jong-Wan
    • Transactions of the Korean Society of Automotive Engineers
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    • v.18 no.2
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    • pp.74-82
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    • 2010
  • Fretting damage can be observed in automobile and railway vehicle, fossil and nuclear power plant, aircraft etc. In the present study, railway axle material RSA1 used for evaluation of fretting fatigue life. Plain and fretting fatigue tests were carried out using rotary bending fatigue tester with proving ring and bridge type contact pad. Through these test, the following results are obtained: 1) it is found that the fretting fatigue limit of standard specimen decreased about 37% compared to the plain fatigue limit. 2) The early crack of Shinkansen type specimens initiated in contact area and final fractured below samp=214 MPa. 3) The early crack of all TGV type specimens initiated in rounded area and fractured. 4) Tire tracks and rubbed scars were observed in the oblique crack region and fatigue crack growth region of fracture surface. 5) The wear debris is observed on the contact surface, and oblique cracks at an earlier stage are initiated in contact area. These results can be used as useful data in a structural integrity evaluation of railway axle.

Fatigue Properties of Ti-Ni Shape Memory Alloy Wire Welded by Nd: YAG Laser

  • Kim, Y.S.;Kim, J.D.;Kil, B.L.
    • International Journal of Korean Welding Society
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    • v.3 no.1
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    • pp.39-44
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    • 2003
  • The welded specimens were made by butt welding of the 2 wires of 50mm length using the pulsed YAG laser. The laser welded wires were tested for investigating the shape memory effect and the ability of super elasticity. The fatigue properties of the welded wires were investigated using the rotary bending fatigue tester specially designed for wires. Moreover, the effect of defocusing distance during laser welding on the static and fatigue properties was Investigated. The shape memory effect and super elasticity of the laser welded wires were approximately identical with that of base metal at the test temperature below 353K. However, the welded wires were broken within elastic limit at the test temperature above 353k. Under the cyclic bending loading conditions, the welded wires could be useful only below the elastic limit, while the base metal had sufficient fatigue life even the stress induced M-phase region. The fatigue strength of the welded wires was about half of that of the base metal. The deterioration of the static and fatigue properties in the welded wires was proven to be from the large difference of the transformation behavior between the base metal and welded part that is caused by vaporization of Ni-content at the welded part during the welding process. The defocusing distance below 3mm acted more largely on lowering the strength of the welded wires than that of 6mm or 8mm.

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LASER WELDING OF TI-NI SHAPE MEMORY ALLOY WIRE

  • Kim, Young-Sik;Kim, Jong-Do
    • Proceedings of the KWS Conference
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    • 2002.10a
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    • pp.139-144
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    • 2002
  • Ti-50.9at%Ni wires were welded using pulsed YAG laser. The laser welded wires were tested for investigating the shape memo교 effect and the ability of super elasticity. The fatigue properties of the welded wires were investigated using the rotary bending fatigue tester specially designed for wires. Moreover, the effect of defocusing distance during laser welding on the static and fatigue properties was investigated. The shape memory effect and super elasticity of the laser welded wires were approximately identical with that of base metal at the test temperature below 353K. However, the welded wires were broken within elastic limit at the test temperature above 353k. Under the cyclic bending loading conditions, the welded wires could be useful only below the elastic limit, while the base metal had sufficient fatigue life even the stress induced M-phase region. The fatigue strength of the welded wires was about half of that of the base metal. The deterioration of the static and fatigue properties in the welded wires was proven to be from the large difference of the transformation behavior between the base metal and welded part that is caused by vaporization of Ni-content at the welded part during the welding process. The defocusing distance below 3mm acted more largely on lowering the strength of the welded wires than that of 6mm or 8mm.

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Evaluation of Fretting Fatigue Behavior for Railway Axle Material (철도 차축재료의 프레팅 피로거동 평가)

  • Choi, Sung-Jong;Kwon, Jong-Wan
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.5
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    • pp.139-145
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    • 2007
  • Fretting is a kind of surface damage mechanism observed in mechanically jointed components and structures. The initial crack under fretting damage occurs at lower stress amplitude and lower cycles of cyclic loading than that under plain fatigue condition. This can be observed in automobile and railway vehicle, fossil and nuclear power plant, aircraft etc. In the present study, railway axle material RSA1 used for evaluation of fretting fatigue life. Plain and fretting fatigue tests were carried out using rotary bending fatigue tester with proving ring and bridge type contact pad. Through these experiments, it is found that the fretting fatigue limit decreased about 37% compared to the plain fatigue limit. In fretting fatigue, the wear debris is observed on the contact surface, and oblique cracks at an earlier stage are initiated in contact area. These results can be used as useful data in a structural integrity evaluation of railway axle.

A Study on Stress Analysis and Fatigue Behaviors of Carbonitried Cr-Mo(SCM415) Steel -About Various Factors Having an Effect on Fatigue Strength- (침탄질화 처리된 크롬-몰리브덴(SCM415)강의 피로거동 및 응력해석 -피로강도에 영향을 주는 제 인자를 중심으로 -)

  • 송삼홍;이상훈
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.8
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    • pp.135-144
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    • 1998
  • In this research, the fatigue behaviors of Cr-Mo(SCM415) steel and carbonitrided CrMo(SCM415) steel are examined. The description of experiments in detail as follows. For SCM415 and carbonitried Cr-Mo(SCM415) steel, smooth specimens and hole defected specimens are fabricated and tested under a rotary bending tester, respectively. By performing the rotary bending fatigue test for smooth and hole defected specimens, the characteristics of the fatigue strength are examined for parameters such as tensile strength, hardness at surface, and residual stresses.

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A Study on the Fatigue Properties of Ti-Ni Shape Memory Alloys (Ti-Ni계 형상기억 합금의 피로특성에 관한 연구)

  • S.Y Kim;S. Miyazaki
    • Journal of Advanced Marine Engineering and Technology
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    • v.21 no.5
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    • pp.482-490
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    • 1997
  • The effects of strain amplitude. test temperature and stress on the fatigue properties for Ti-Ni wires were investigated using a rotary bending fatigue tester specially designed for wires. The fatigue test results were discussed in connection with the static tensile properties. The DSC measurement was conducted after fatigue test in order to clarify the change of transformation behavior due to the progress of fatigue. Under the temperature below or near the Af, the strain amplitude($\varepsilon_a$)-failure life (Nf) curve showed to be composed of three straight lines with two turning points. Of the 2 turning points, the upper one was coincident with the elastic limit strain and the lower one with the proportional limit strain. With rising of the test temperature above Af, the pattern of $\varepsilon_a$-Nf curve changed gradually to composition of 2 straight lines. The $\varepsilon_a$-Nf curve shifted depending on test temperature. In the short and medium life zones, the higher the temperature was, the shorter the fatigue life. However, in the long life zone, above the Af temperature, the fatigue life was not affected by the temperature. The transformation enthalpy measured after fatigue test was dependent on Nf, $\varepsilon_a$, and test temperature.

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The Characteristics of Fatigue Cracks Emanating from Micro Hole Defects Located Opposite Position of the Shaft Cross Section (축 단면 내 대칭 위치의 미소 원공 결함에서 발생한 피로균열 특징)

  • Song, Sam-Hong;Bae, Jun-Su;Ahn, Il-Hyuk
    • Proceedings of the KSME Conference
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    • 2001.06a
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    • pp.211-216
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    • 2001
  • The components with the circular cross section have the symmetric combination parts for rotating balance and the crack emanates from the symmetric combination parts. The symmetric cracks from symmetric combination parts make a decrease in the component fatigue life more than single crack. In this study, to estimate the behavior of symmetric cracks, the fatigue test was performed using rotary bending tester on the specimen with a symmetric defects in circular cross section. The material used in this study is Ni-Cr-Mo steel alloy. Under the same stress, the result from the rotary bending fatigue test turned out that the symmetric cracks made a decrease in the fatigue life by 35% more than single crack and the relation between log a and cycle ratio $N/N_f$ obtained linearly.

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The Influence of the Small Circular Hole Defect on the Fatigue Crack Propagation Behavior in Aluminum Alloys (알루미늄 합금재의 피로크랙 전파거동에 미치는 미소원공결함)

  • Kim, G.H.;Lee, H.Y.
    • Journal of Advanced Marine Engineering and Technology
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    • v.32 no.6
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    • pp.834-840
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    • 2008
  • We carried out fatigue testing with materials of aluminum alloyC7075-T6, 2024-T4) by rotary bending fatigue tester. We investigated fatigue limit, fatigue crack initiation, fatigue crack propagation behavior and possibility of fatigue life prediction to the different small circular hole defect. The summarized result are as follows; Fatigue limit of the smooth specimens were related tensile strength and yield strength. In case of more large applied stress and small circular hole crack defect, the fatigue crack was grown rapidly. The fatigue crack propagation behavior proceed at according to inclusion. Fatigue crack propagation ratio appeared instability and retardation phenomenon in the first half of fatigue life but appeared stability and replied in the latter half. On other hand, this experimental data of the materials are appeared fatigue life predictability.

Quantitative Evaluation for the Internal Defect Size Governing the Fatigue Life in Ductile Irons (구상흑연주철의 피로수명을 지배하는 내재결함부 크기는 정량적 평가)

  • 김진학;김민건
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.11
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    • pp.2742-2748
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    • 2000
  • In this study, the quantitative evaluation was performed by examination for gatigue crack origin in two prepared ductile irons specimens which have different microstructures using rotary bending fatigue tester, Series A has mixed microstructure. ferrite plus pearlite, and series B has bainitic microstructure. Obtained main results are as follows. The scatterings of fatigue strength were observed on σ(sub)α-Ν diagram of both specimen series, and it is observed that scatterings of series A were more serious. It is reasonable to evaluate the size of mesocrack range by means of √A(원문참조), where A means the area of mesocrack range including globular graphite nodule. As a result of reconsideration for the fatigue data by introduction of K(sub)α-Ν diagram, the scattrings of fatigue life were, remarkably. reduced. Therefore, it is more reasonable to evaluate of mesocrack range on fatigue life by parameter K(sub)α rather than σ(sub)α.