• 한국해양공학회지
• /
• 제30권5호
• /
• pp.341-348
• /
• 2016

The fatigue damage caused by wide band loadings has generally been predicted using fatigue damage models in the frequency domain rather than a rain-flow counting method in the time domain because of its computation cost. This study showed that these fatigue damage models can be simplified in the form of normalized fatigue damage as a function of the S-N curve slope and bandwidth parameters. Based on numerical simulations of various wide band spectra, it was found that fatigue damage models in the form of normalized fatigue damage with one S-N curve slope and two bandwidth parameters( α₁ , α₂ ) provided less reasonable fatigue damage. Therefore, an additional bandwidth parameter needs to be considered based on a sensitivity study using various neural networks, which proved that α_1-5 would be the dominant factor of a fatigue damage model as an additional bandwidth parameter.

• 항공우주시스템공학회지
• /
• 제14권6호
• /
• pp.58-67
• /
• 2020

In this study, finite element fatigue analysis combined with a fatigue correlation factor is proposed to predict the bending fatigue life of a gear in an electro-mechanical aircraft actuator. First, stress-life curves are obtained for the gear material via a round bar fatigue test. Subsequently, stochastic stress-life (P-S-N) curves are derived for 50% and 1% failure probabilities, separately. The curves are applied to the fatigue analysis model of a single gear tooth, and the effect of the fatigue correction factor is analyzed. The analytical P-S-N curves reflecting the fatigue correction factor matched the experimental data. This shows that the analytical fatigue life is reliable and that the analysis technique is effective.

• 소성∙가공
• /
• 제24권4호
• /
• pp.264-271
• /
• 2015

In the current study, a method was proposed to quantitatively predict the wear and fatigue life of a shearing die in order to determine an effective replacement period for the die. The shearing die model of a retainer manufacturing process was used for the proposed method of quantitative life prediction. The retainer is produced through shearing steps, such as piercing and notching. The shearing die of the retainer is carefully controlled because the dimensional accuracy of the retainer is critical. The fatigue life for the shearing die was predicted using ANSYS considering S-N curves of STD11 and Gerber’s equation. The wear life for the shearing die was predicted using DEFORM-3D considering the Archard’s wear model. Experimental shearing of the retainer was conducted to verify the effectiveness of the proposed method for predicting die life. The fatigue failure of the shearing die was macroscopically measured. The wear depth was measured using a 3D coordinate measuring machine. The results showed that the wear and fatigue life in the FE analysis agree well with the experimental results.

• 한국강구조학회 논문집
• /
• 제10권3호통권36호
• /
• pp.423-435
• /
• 1998

본 연구에서는 기존의 강교에서 흔하게 발견되고 있는 맞대기 용접부의 용입불량으로 인한 부재의 피로강도 저하도를 정량적으로 평가하고자 하였다. 이를 위하여 강교량의 재료로 널리 사용되고 있는 SWS490강으로 제작된 완전용입 및 용입깊이가 서로 다른 불완전용입 맞대기 용접시험편을 대상으로 일정진폭하중시험을 수행하여 S-N선도를 산출하고 이를 비교 검토하였으며, 파괴역학적 방법을 이용하여 불완전용입 용접재의 피로수명을 계산하였다. 본 연구의 결과로서, 완전용입 용접재의 경우 AASHTO의 피로강도등급선도와의 비교에서 피로한도값은 A등급보다 높은 값을 보였고, S-N선도의 기울기는 5.57로 매우 높게 나타났다. 불완전용입 용접재의 경우 불완전용입깊이 D가 증가함에 따라 피로강도가 감소하는데, D=14.7mm인 경우 AASHTO의 E'등급보다 낮게 나타난다. 불완전용입 용접재의 파손거동에서 피로균열은 내부 용접루트 선단부에서 a/c가 매우 작은 반타원형 표면균열의 형태로 발생하고, 시험체의 두께방향으로 진전하여 최종파손을 유발한다. 파괴역학적 방법을 이용한 불완전용입 용접재의 피로수명을 평가하기 위하여 3차원 반타원형 균열형상에 대한 응력확대계수 K를 유한요소해석으로 구하였다. 여기서 얻어진 K값과 실험으로 얻어진 Paris식의 상수를 이용하여 불완전용입 용접재의 피로수명을 계산하여 비교하였다. 그리고 실제 불완전용입 맞대기용접부의 파손으로 붕괴사고가 발생한 성수대교의 수직재에 본 연구결과를 적용하여 피로수명을 계산해 보았다.

• Journal of Welding and Joining
• /
• 제22권3호
• /
• pp.50-55
• /
• 2004

S-N fatigue tests were conducted to investigate the fatigue strength of small diameter socket and butt welded joints made of carbon steels. Experimental parameters were pipe diameter, throat depth, shape of socket welds and welding procedure. Filler metals used in SMAW and GTAW procedure were E9016-G with diameter of 4.0 m and ER70S-G with diameter of 2.4 m. API 5L Gr.B pipes were adopted as a small diameter branch pipes. All socket fittings were machined from ASTM A105 carbon steel. Tensile strength was not affected by the welding procedure. Fatigue strength in socket weld joints increased with increasing pipe diameter, area of weld metal and weld leg length of pipe side.

• 대한토목학회논문집
• /
• 제5권4호
• /
• pp.113-119
• /
• 1985

본(本) 논문(論文)에서는 휨하중을 받는 콘크리트의 피로특성 및 피로신뢰성이 연구(硏究)되었다. 콘크리트보에 대한 피로실험이 수행되었으며, 피로하중은 4 점하중 상태로 작용되었다. 본(本) 실험결과(實驗結果)로부터 S-N 관계가 얻어졌으며, 콘크리트의 휨피로 강도를 예측하기 위한 공식(公式)이 도출되었다. 또한 본(本) 논문(論文)에서는 콘크리트의 휨피로에 대한 확률론적 해석방법이 제안되었다. 본(本) 연구결과(硏究結果) 콘크리트의 피로거동을 서술하는 데는 Weibull 분포가 적절한 것으로 나타났다.

• 한국자동차공학회논문집
• /
• 제16권4호
• /
• pp.63-68
• /
• 2008

The fatigue characteristics of bevel gear used for differential gear of automobile was investigated in this paper. From the A-N(Almen intensity-Number of fracture)curve of bevel gear it was shown that there was a specific time that have a maximum fatigue life. Optimal peening condition was 65m/s of project velocity and 8min of project time. Fatigue life was also investigated from the S-N curve between optimal peened specimen and unpeened specimen. Another very significant point is that the crack initiation of bevel gear by shot peening was generated in the subsurface from fractography. This paper shows that shot peening process tremendously improve fatigue characteristics of bevel gear.

• 대한기계학회논문집A
• /
• 제24권9호
• /
• pp.2353-2360
• /
• 2000

Statistical fatigue properties of metallic materials are increasingly required for reliability design purpose. In this study, static and fatigue tests were conducted and the normal, log-normal, two -parameter Weibull distributions at the 5% significance level are compared using the Kolmogorov-Smirnov goodness-of-fit test. Parameter estimation were compared with experimental results using the maximum likelihood method and least square method. It is found that two-parameter Weibull distribution and maximum likelihood method provide a good fit for static and fatigue life data. Therefore, it is applicable to the static and fatigue life analysis of the spheroidal graphite cast iron. The P-S-N curves were evaluated using log-normal distribution, which showed fatigue life behavior very well.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.394-399
• /
• 2004

In order to secure the safety of power steering system, it is necessary to perform the strength and the fatigue analysis of pulley in this paper. The applied stress distribution of the pulley subject to combined loads condition was obtained using finite element analysis. Based on these results, the fatigue life of the pulley with the variation of the fatigue strength was evaluated using durability analysis simulator. The optimal hole size to improved the safety of the pulley was investigated using parametric study. Moreover, the predicted fatigue life cycle with the simulator was verified by experimental tests.

• 대한기계학회논문집A
• /
• 제39권12호
• /
• pp.1207-1212
• /
• 2015

진동리퍼는 암반의 파쇄와 리핑 작업을 동시에 하기 위해서 개발된 장비이며 기존의 암반 파쇄용 유압 브레이커와 작동 원리가 다르다 진동리퍼의 기진력을 투스로 전달하는 기어박스-생크 용접부는 매우 중요한 부분이며 진동리퍼의 기계적 건전성의 예측이 필수적이다. 본 연구는 생크소재 및 용접재료의 변화에 따른 접부의 피로수명 예측을 목적으로 하고 있다. 생크의 재료는 Hadox-hituf, AR 400을 사용하였고 접금속은 CSF-71T, CSF-81T를 사용하였다. 피로시험은 응력비 R=0에서 각 재료조건에 대해서 수행하였다. P-S-N 선도는 JSME-S002 규정에 맞춰 파괴확률 10%, 50%, 90%에 대해서 나타냈으며 수명 예측 식을 도출하였다.