• Title/Summary/Keyword: S-N 피로특성곡선

Search Result 24, Processing Time 0.02 seconds

Fatigue Analysis of Prestressed Concrete Composite Girder Bridges (프리스트레스트 콘크리트 합성거더 교량의 피로해석)

  • 김지상;오병환
    • Magazine of the Korea Concrete Institute
    • /
    • v.5 no.4
    • /
    • pp.135-144
    • /
    • 1993
  • A fatigue analysis procedure for prestressed concrete composite girder bridges is established, which includes the time-dependent effects of component materials. The procedure can take into account the movement of neutral axis depth as crack develops and give quite good agreement with experimental results available. It is also assured that Korean Standard prestressed concrete composite girder has enough fatigue resistance. The procedure in this paper gives a way to express the fatigue capacity of prestressed concrete beams in the form of S-N curve, which can be utilized under variable amplitude fatigue load.

Surface Crack Behavior and the Fatigue Life Prediction of Notched Specimens (표면균열의 거동과 피로수명예측에 관한 연구)

  • 서창민;이정주;정은화;박희범
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.12 no.5
    • /
    • pp.1097-1103
    • /
    • 1988
  • This paper deals with surface crack behavior and the fatigue life prediction of notched specimens using the relation between surface crack length, a, and the cycle ratio, $N/N_{f}$. From the $a-N\;/\;N_{f}$ curves, UC(the upper limit curve), LC(the lower limit curve) and MC(the middle limit curve) were assumed and utilized to predict the fatigue life and crack growth rate. The data computed from the three assumed curves were compared with the experimental data. It has been found that in the stable crack growth region ($N/N_{f}=0.3-0.8$) fatigue life can be predicted within 20% errors. Using the characteristics of $a-N\;/\;N_{f}$ curve, it is possible to predict the $da/dN-K_{max}$ curve, the $da/dN-{\Delta}K_{{\varepsilon}_t}$ curve, and the $S-N_{f}$ curve.

Improvement of Fatigue-Proof Characteristics of Link Members Under Impact Loadings by a Spring-Actuated Mechanism (스프링구동 메커니즘의 충격 하중을 받는 링크부재의 내피로 특성 향상)

  • 안길영;박상후;이부윤;김원진;오일성
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.20 no.4
    • /
    • pp.158-164
    • /
    • 2003
  • The air circuit breaker (ACB) with the spring-actuated mechanism was studied to improve the fatigue-proof characteristics of its link. The low-cycle fatigue fracture phenomenon occurred on the critical link, called h-link, of ACB from the repeated rapid closing and opening operations. To analyze the cause of failure, dynamic FE-analysis on the b-link part of ACB was performed considering tile velocity and acceleration of the links per time as boundary conditions, which were obtained by using ADAMS. Also, the S-N curve obtained by experiments was used to investigate requirement on the fatigue-proof characteristics. Then, to reduce the maximum tensile stress on the h-link, three types of h-link were examined and one of them was selected.

Probabilistic Analysis of Fatigue Behavior of Induction Hardened Steel (고주파 열처리된 SAE1055 강의 피로거동 및 이의 확률론적 평가)

  • Lee, Seon-Ho;Lee, Seung-Pyo;Kang, Ki Weon
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.37 no.3
    • /
    • pp.429-436
    • /
    • 2013
  • This study considers how the fatigue behavior and probabilistic properties of SAE1055 steel are related to its hardness level. SAE1055 steel was heat-treated using induction hardening. Five types of specimens were prepared (A: base material, B: through hardened material with HV390, C: through hardened material with HV510, D: through hardened material with HV700, and E: surface hardened material with HV700). Fatigue tests were performed under a stress ratio of R = -1 using a 4-point rotary bending fatigue tester. The fatigue behaviors were greatly influenced by the hardness, but the fatigue limit did not increase over a hardness of HV510. In addition, the effect of the hardness level on the failure mechanism was evaluated using a scanning electron microscope. The probabilistic properties of the fatigue life were investigated using a probabilistic S-N approach, and the effect of the hardness level on these properties was evaluated using a residue analysis.

A Study on Growth Behavior of Small Fatigue Crack in 304 Stainless Steel at Elevated Temperatures (고온하 304 스테인레스강의 작은 표면구열의 성장거동에 관한 연구)

  • 서창민;김영호
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.14 no.1
    • /
    • pp.87-95
    • /
    • 1990
  • Rotating bending fatigue tests of an authentic steel 304 were performed at various temperatures such as room temperature, $538^{\circ}$ and $593^{\circ}C$. The plastic replica method was also applied in order to estimate the fatigue life on the basis of serial observation of small fatigue crack initiation and growth on the pit specimen surface. The fatigue crack growth behavior of 304 stainless steel was investigated within the frame work of elastic-plastic fracture mechanics within a narrow scatterband in spite of different stress levels at elevated temperature as at room temperature. The growth law of small surface crack is determined uniquely by the term. $\DELTA\sigma^{n}a$ where $\DELTA\sigma$ is the stress amplitude, a is the crack length, and n is a constant. It is found that the small crack growth behavior is basically equivalent to the S-$N_{f}$ relationship, where S and $N_{f}$ are stress and number of cycles to failure, and the fatigue life prediction is in good agreement with the experimental results.

Evaluation of Fatigue Life Characteristic of a Real Waterwork Pipe Using the Probability Density Function (확률밀도함수를 이용한 상수도 실 배관의 피로수명 특성 평가)

  • Choi, Jung-Hun;Koo, Jae-Mean;Seok, Chang-Sung;Song, Weon-Keyu
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.32 no.9
    • /
    • pp.707-712
    • /
    • 2008
  • The fatigue characteristics of a material or a structure are generally derived from fatigue tests of standard specimens. However, test results of standard specimens are different from those of real structures or components. Therefore, to calculate more accurate fatigue life, the geometrical effect and surface condition must be considered by comparing test results of standard specimens with those of real structures or components. Thus the object of this paper is to evaluate the fatigue characteristics of a real waterwork pipe. Also, to evaluate fatigue characteristic based on life distribution, the statistical fatigue characteristics were analyzed by the normal distribution and related data of P-S-N curve.

Fatigue Behavior of Composites with different Fiber Orientation (섬유 방향에 따른 복합재 피로특성에 관한 연구)

  • Kang, Tae-Young;An, Hyo-Seong;Chun, Heoung-Jae;Park, Jong-Chan
    • Composites Research
    • /
    • v.34 no.2
    • /
    • pp.77-81
    • /
    • 2021
  • Due to the high specific strength and stiffness of the composite materials, the composite materials have been extensively used in various industries. In particular, carbon fiber reinforced composites are widely used in many mechanical structures. In addition, since carbon fiber reinforced composites have anisotropic properties, to understand the fatigue behavior of composites with different fiber orientation is very important for the efficient structural design. Therefore, in this paper, the effect fiber orientation on the fatigue life of composite materials was experimentally evaluated. For this purpose, tensile and fatigue tests were performed on the off-axis specimens (0°, 10°, 30°, 45°, 60°, 90°) of the composite materials. As a result of the fatigue tests, the fatigue strength of the composites decreased significantly as the fatigue strength slightly deviated from 0 degrees. On the other hand, the more deviated, the less decreased. This is because the role of supporting the load of fibers decreased as the stacking angle increased. In addition, the fatigue behavior was analyzed by introducing a fatigue strength ratio (Ψ) that eliminates the fiber orientation dependence of the off-axis fatigue behaviors on the unidirectional composites. The off-axis fatigue S-N lines can be reduced to a single line regardless of the fiber orientation by using the fatigue strength ratio (Ψ). Using the fatigue Ψ-N line, it is possible to extract back to any off-axis fatigue S-N lines of the composites with different fiber orientations.

Mechanical Properties of a Lining System under Cyclic Loading Conditions in Underground Lined Rock Cavern for Compressed Air Energy Storage (복공식 지하 압축공기에너지 저장공동의 내압구조에 대한 반복하중의 역학적 영향평가)

  • Cheon, Dae-Sung;Park, Chan;Jung, Yong-Bok;Park, Chul-Whan;Song, Won-Kyong
    • Tunnel and Underground Space
    • /
    • v.22 no.2
    • /
    • pp.77-85
    • /
    • 2012
  • In a material, micro-cracks can be progressively occurred, propagated and finally lead to failure when it is subjected to cyclic or periodic loading less than its ultimate strength. This phenomenon, fatigue, is usually considered in a metal, alloy and structures under repeated loading conditions. In underground structures, a static creep behavior rather than a dynamic fatigue behavior is mostly considered. However, when compressed air is stored in a rock cavern, an inner pressure is periodically changed due to repeated in- and-out process of compressed air. Therefore mechanical properties of surrounding rock mass and an inner lining system under cyclic loading/unloading conditions should be investigated. In this study, considering an underground lined rock cavern for compressed air energy storage (CAES), the mechanical properties of a lining system, that is, concrete lining and plug under periodic loading/unloading conditions were characterized through cyclic bending tests and shear tests. From these tests, the stability of the plug was evaluated and the S-N line of the concrete lining was obtained.

Fatigue Reliability Evaluation of Steel-Composite High-Speed Railway Bridge with Tuned Mass Damper (동조질량감쇠기를 장착한 강합성형 고속철도교의 피로신뢰성 평가)

  • Kang, Soo-Chang;Seo, Jeong-Kwan;Koh, Hyun-Moo;Park, Kwan-Soon
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.9 no.5 s.45
    • /
    • pp.1-10
    • /
    • 2005
  • This study proposes a fatigue reliability evaluation procedure for steel-composite high-speed railway bridge based on dynamic analysis and investigates the effectiveness of Tuned Mass Damper(TMD) in terms of the extension of fatigue life of the bridge. For the fatigue reliability evaluation, the limit state is determined using S-N curve and linear fatigue-damage accumulation. Dynamic analyses are peformed repeatedly to consider the uncertainties of train-velocity and damping ratio of the bridge. The distribution of random variables related to fatigue damage for the intended service life is then statistically estimated from analytical results. Finally, the fatigue reliability indices are obtained by means of the Advanced First-Order Second-Moment (AFOSM) method. Through numerical simulation of a steel-composite bridge of 40m span, the effectiveness of TMD on fatigue life of the bridge is examined and the results are presented.

Variation of Fatigue Properties in Nanoskinned Ti-6Al-4V - Rotating Bending and Axial Loading Tension-Compression Cycle - (Ti-6Al-4V 재의 UNSM 처리에 의한 피로특성변화 - 회전굽힘 피로시험과 축하중 인장압축 피로시험 비교 -)

  • Suh, Min-Soo;Pyoun, Young-Shik;Suh, Chang-Min
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.36 no.4
    • /
    • pp.443-449
    • /
    • 2012
  • Nanoskins were fabricated on a Ti-6Al-4V material by carrying out various surface treatments, i.e., deep rolling, laser shot peening, and ultrasonic nanocrystal surface modification (UNSM). These surface treatments are newly developed techniques and are becoming more popular for industrial applications. Fatigue tests were carried out using material test system (MTS); these tests included the axial loading tension-compression fatigue test (R = -1, RT, 5 Hz, sinusoidal wave) and rotating bending fatigue test (R = -1, RT, 3200 rpm). The analysis of the crack initiation pattern in the UNSM-treated material indicated that the crack was interior originating in the axial loading tension-compression cycle, and was surface originating in the bending fatigue test. UNSM treatment significantly improved the fatigue strength for the regime of above $10^6$ cycles that S-N curve of rotating bending stress clearly show the performance of a 5 mm titanium specimen after UNSM treatment is similar to that of an untreated 6 mm titanium specimen.