• Structural Engineering and Mechanics
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• 제23권4호
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• pp.353-367
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• 2006

Two full-scale, precast, pretensioned box girders were subjected to shear-dominated loading, one under monotonic loads to failure and the other subjected to one-half million cycles of fatigue loads followed by monotonic ultimate loads. The number of cycles was selected to allow for comparison with previous research. The fatigue loads were applied in combination with occasional overloads. In the present study, fatigue loading reduced the shear capacity by only six percent compared to the capacity under monotonic loading. However, previous research on flexure-dominated girders subjected to the same number of repeated loads showed that fatigue loading changed the mode of failure from flexure to shear/flexure and the girder capacity dropped by 14 percent. The comparison of the measured data with calculated shear capacity from five different theoretical methods showed that the ACI code method, the compression field theory, and the modified compression field theory led to reasonable estimates of the shear strength. The truss model led to an overly conservative estimate of the capacity.

• 산업경영시스템학회지
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• 제24권68호
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• pp.1-7
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• 2001

A probabilistic model for fatigue life of a structural component is derived when the component is in a variable-amplitude loading environment. The physical mechanism which governs fatigue failure is used to model the fatigue life. Especially, the judgement of rotational symmetry in the-stress-intensity-factors results in the probability distribution for fatigue life. The probability distribution is related to the familiar truncated Gaussian distribution, which has a single parameter with a direct physical meaning.

• 콘크리트학회논문집
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• 제11권6호
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• pp.113-119
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• 1999

Fatigue failure is a phenomenon such that structures under cyclic service load is failed by sudden brittle manner. Therefore, in order to obtain structures safety against the fatigue failure during their service lifes, fatigue characteristics should be considered for design and analysis of the structures. As stress range of prestressed (PS) tendons, which governs fatigus characteristic of prestressed concrete (PSC) structures, increases with increased use of partial prestressig, it is more necessary to consider fatigue characteristics of PS tendons. In this paper, direct-tension fatigue experiments with special specimen-setting devices are carried out to obtain fatigue characteristics of domestic low relaxation PS strands having different diameters and PS strands connected with coupler. Then, allowable stress range of fatigue for PSC beams using low relaxation strands are presented for the fatigue examination of prestressed concrete beams applied cyclic loading.

• Steel and Composite Structures
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• 제25권5호
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• pp.571-579
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• 2017

The grid structure with bolt-sphere joints is widely adopted by industrial plants with suspending crane. The alternating reciprocating action of the suspending crane will cause fatigue problems of the grid structure with bolt-sphere joints with respect to the rod, the cone, the sealing plate, the bolt ball and the high strength bolt; while the fatigue of the high strength bolt is the key issue of fatigue failure. Based on efficient and smooth loading equipment with the AMSLER fatigue testing machine, this paper conducted a constant amplitude fatigue test on 18 M20 and 14 M30 high strength bolts with 40Cr material, and obtained 19 valid failure points, 9 unspoiled points with more than 2 million cycles, and 4 abnormal failure points. In addition, it established the constant amplitude fatigue design method, ${[{\Delta}{\sigma}]_{{2{\times}10}}{^6=58.91MPa}$, and analyzed the stress concentration and the fatigue fracture of high strength bolts. It can be explained that the geometrical stress concentration of high-strength bolt caused by spiral burr is severe.

• 대한금속재료학회지
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• 제46권2호
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• pp.80-87
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• 2008

Many researches related to the reliability of Pb-free solder joints with PCB (printed circuit board) surface finish under thermal or vibration stresses are in progress, because the electronics is operating in hash environment. Therefore, it is necessary to assess Pb-free solder joints life with PCB surface finish under thermal and mechanical stresses. We have investigated 4-points bending fatigue lifetime of Pb-free solder joints with OSP (organic solderability preservative) and ENIG (electroless nickel and immersion gold) surface finish. To predict the bending fatigue life of Sn-3.0Ag-0.5Cu solder joints, we use the test coupons mounted 192 BGA (ball grid array) package to be added the thermal stress by conducting thermal shock test, 500, 1,000, 1,500 and 2,000 cycles, respectively. An 4-point bending test is performed in force controlling mode. It is considered that as a failure when the resistance of daisy-chain circuit of test coupons reaches more than $1,000{\Omega}$. Finally, we obtained the solder joints fatigue life with OSP and ENIG surface finish using by Weibull probability distribution.

• 한국정밀공학회지
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• 제17권1호
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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.

• 대한토목학회논문집
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• 제7권2호
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• pp.9-20
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• 1987

아스팔트포장(鋪裝) 공용성(供用性)을 저하(低下)시키는 하나의 원인(原因)으로 피로균열파괴(疲勞龜裂破壞)를 들 수 있다. 본(本) 연구(硏究)에서는 아스팔트혼합물(混合物)의 피로파괴(疲勞破壞)에 미치는 재료특성(材料特性)의 영향(影響)에 대해서 검토(檢討)를 하고 밀입도(密粒度)아스팔트 콘크리트에 대한 반복(反覆)휨변형율제어어시험(變形率制御試驗)을 하여 피로파괴포락선(疲勞破壞包絡線)을 구(求)했다. 다음에 탄성이론(彈性理論)의 결과(結果)와 피로파괴포락선(疲勞破壞包絡線)으로부터 온도(溫度) 아스팔트층(層)두께 하층(下層)의 탄성계수(彈性係數)와 피로파괴회수(疲勞破壞回數)의 관계를 고찰(考察)했다.

• 한국철도학회논문집
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• 제5권2호
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• pp.118-124
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• 2002

The failure probability of wheel beyond 10$\^$7/ cycles is achieved by the strengths-stress interference model for the evaluation of fatigue strength and reliability in the wheel, From plane bending fatigue test results, the fatigue life (N$\_$f/) for the smooth and 200㎛ holed specimens can be represented as $\sigma$$\_$a/ = 1326N$\_$f/$\^$-0.10/ and $\sigma$$\_$a/ = 2894N$\_$f/$\^$-0.18/. Respectively, fatigue strength of the wheel at beyond 10$\^$7/cycles was about 332 MPa. And, the fatigue strength for the specimen with a micro hole (d=200㎛) which simulated an inclusion on the wheel surface was about 235 MPa. Thus, a micro hole (d=200㎛) caused about 30% reduction of fatigue strength of the specimen. The failure probabilities for the smooth and micro-holed specimens, derived from the strength-stress interference model, are 0.0148% and 13.05%, respectively. The current finding suggests that at least 200 ㎛ sized inclusion, which might be produced during manufacturing process, will cause a critical effect on integrity of the railway vehicle.

• 대한기계학회논문집
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• 제13권3호
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• pp.451-460
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• 1989

본 논문에서는 기계용 부품소재로 많이 사용되는 SM45C에 대하여 이온질화 처리시 N$_{2}$:H$_{2}$ 가스조성비 변화에 따른 효과가 반복인장-압축하중을 받는 부식피로파괴의 거동에 미치는 영향을 중점적으로 연구하였다.

• 대한기계학회논문집
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• 제19권8호
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• pp.1869-1875
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• 1995

The adhesively bonded tubular single lap joint shows a nonlinear relationship between the applied torque and the resulting displacement under the static-torsional loading, which is induced from the nonlinear properties of the adhesive. However the torque transmission capability in the case of the dynamic-torsional loading is much less than that in the case of the static-torsional loading, the stress level of the adhesive is usually in the region of the linear stress and strain relation and the stress distributions of the joint can be obtained by the linear analysis. In this paper, a failure model for the adhesively bonded tubular single lap joint under the torsional fatigue loading was developed with respect to the adhesive thickness that was a critical factor in predicting the static torque transional-cyclic loadings was proposed.