• Title/Summary/Keyword: variable amplitude fatigue

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Fatigue Life Estimation Using the Multi-Axial Multi-Point Load Counting Method under Variable Amplitude Loading (가변진폭하중하에서 다축-다점 하중 Counting method를 이용한 피로수명평가)

  • Lee, W.S.;Lee, H.W.
    • Journal of the Korean Society for Precision Engineering
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    • v.14 no.6
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    • pp.22-27
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    • 1997
  • In general, the load which acts on the structure is almost independent of time in many locations. In this case. It is difficult to estimate the life with the service load history, because the structure is on the multi- axial and multi-point loading states. In this study, the service load of the excavator which is widely used in industry field was calculated using measured cylinder pressures and displacements. The fatigue life was estimated using the multi-axial and multi-point load counting method. Service load history of 4 pin joint which act independently each other is yielded by mult-axial and multi-point load counting method. The stress spectrum is yielded by superposition of the results of FEM stress analysis applied unit load. Palm- gren-Miner's cumulative Damage is 0.000804 for Von Mises equivalent stress sequence by one side fillet weld S-N curve. This result agress with Bench test results. As a result of this study, the fatigue life esti- mation using the multi-axial and multi-axial and multi-point load counting method is useful.

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The Delamination and Fatigue Crack Propagation Behavior in A15052/AFRP Laminates Under Cyclic Bending Moment (반복-굽힘 모멘트의 진폭에 따른 A15052/AFRP 적층재의 층간분리 영역과 피로균열진전 거동)

  • Song, Sam-Hong;Kim, Cheol-Ung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.8
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    • pp.1277-1286
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    • 2001
  • Aluminum 5052/Aramid Fiber Reinforced Plastic(Al5052/AFRP) laminates are applied to the fuselage-wing intersection. The Al5052/AFRP laminates suffer from the cyclic bending moment of variable amplitude during the service. Therefore, the influence of cyclic bending moment on the delamination and the fatigue crack propagation behavior in Al5052/AFRP laminate was investigated in this study. Al5052/AFRP laminate composite consists of three thin sheets of Al5052 and two layers of unidirectional aramid fibers. The cyclic bending moment fatigue tests were performed with five different levels of bending moment. The shape and size of the delamination zone formed along the fatigue crack between Al5052 sheet and aramid fiber-adhesive layer were measured by an ultrasonic C-scan. The relationships between da/dN and ΔK, between the cyclic bending moment and the delamination zone size, and between the fiber bridging mechanism and the delamination zone were studied. Fiber failures were not observed in the delamination zone in this study. It represents that the fiber bridging modification factor should turn out to increase and that the fatigue crack growth rate should decrease. The shape of delamination zone turns out to be semi-elliptic with the contour decreased non-linearly toward the crack tip.

Cumulative Damage Characteristics of Concrete Subjected to Variable Amplitude Loadings (반복하중을 받는 콘크리트의 누가손상 특성)

  • Byun, Keun Joo;Kim, Moon Kyum;Han, Sang Hoon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.7 no.1
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    • pp.43-54
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    • 1987
  • Cumulative damage characteristics of concrete, on which rapetitive loads are applied, are investigated. Preliminarily, a series of uniaxial compression tests on cylindrical specimens of plain concrete is carried out to find out that, among various factors, stress levels of repetitive loadings and loading order are the most governing factors of cumulative damage of concrete. Based on this preliminary study, fatigue tests are carried out applying two levels of stresses, stepwisely. As a result, it is found that characteristics of cumulative damage of concrete are governed by nonlinear relationships and do not follow Miner's linear theory. It is also observed that cumulative damage characteristics and static strengths of concrete vary with loading history of stresses. Empirical equations which may be useful in predicting fatigue characteristics and remaining life of concrete stuctures are proposed for concrete subjected two stress levels.

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Experimental Study on Structural Performance of Steel Slit Damper According to Restrained Out-of-plane Deformation (면외변형 구속에 따른 강재슬릿댐퍼의 구조성능에 관한 실험적 연구)

  • Jin-Woo Kim;U-Jin Kwon;Kwang-Yong Choi;Young-Ju Kim;Hae-Yong Park
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.27 no.1
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    • pp.86-94
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    • 2023
  • In this study, a supplementary detail capable of restraining out-of-plane deformation was proposed for steel slit dampers, and a constant amplitude cyclic loading test was performed with the application of the proposed detail and the shape ratio of the damper as variables. Repeated hysteresis and cumulative plastic deformation according to the test results were analyzed. Repeated hysteresis of the slit damper with the proposed detail showed a stable spindle-shaped hysteresis within the set variable range, and no out-of-plane deformation of the damper was observed until ultimate state. It was confirmed that the restraining panel effect through the application of the proposed details is effective in terms of both the strength and deformation capacity of the damper. In addition, experimental parameters for the fatigue curve evaluation of slit dampers were derived in this study. Based on the results, it is judged that quantitative comparison of structural performance with various types of seismic devices will be possible in the future.