• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.285-290
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• 2004

Low cycle fatigue tests are performed on the Inconel 617 that be used for a hot gas casing. The relation between strain energy density and numbers of cycles to failure is examined in order to predict the low cycle fatigue life of Inconel 617. The life predicted by the strain energy method is found to coincide with experimental data and results obtained from the Coffin-Manson method. Also the cyclic behavior of Inconel 617 is characterized by cyclic hardening with increasing number of cycle at room temperature.

• Structural Engineering and Mechanics
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• 제77권4호
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• pp.559-569
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• 2021

This study was conducted to investigate the residual bearing capacity of steel-concrete composite beams under high-cycle fatigue loading through experiments and theoretical analysis. Six test beams with stud connectors were designed and fabricated for static, complete fatigue, and partial fatigue tests. The failure modes and the degradation of several mechanical performance indicators of the composite beams under high-cycle fatigue loading were analyzed. A calculation method for the residual bearing capacity of the composite beams after certain quantities of cyclic loading cycles was established by introducing nonlinear fatigue damage models for concrete, steel beam, and shear connectors beginning with the material residual strength attenuation process. The results show that the failure mode of the composite beams under the given fatigue load appears to be primarily affected by the number of cycles. As the number of fatigue loadings increases, the failure mode transforms from mid-span concrete crushing to stud cutting. The bearing capacity of a 3.0-m span composite beam after two million fatigue cycles is degraded by 30.7% due to premature failure of the stud. The calculated values of the residual bearing capacity method of the composite beam established in this paper agree well with the test values, which indicates that the model is feasibly applicable.

• Nuclear Engineering and Technology
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• 제49권1호
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• pp.245-253
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• 2017

The relative displacement of a piping system installed between isolated and nonisolated structures in a severe earthquake might be larger when without a seismic isolation system. As a result of the relative displacement, the seismic risks of some components in the building could increase. The possibility of an increase in seismic risks is especially high in the crossover piping system in the buildings. Previous studies found that an elbow which could be ruptured by low-cycle ratcheting fatigue is one of the weakest elements. Fatigue curves for elbows were suggested based on component tests. However, it is hard to find a quantitative evaluation of the ultimate state of piping elbows. Generally, the energy dissipation of a solid structure can be calculated from the relation between displacement and force. Therefore, in this study, the ultimate state of the pipe elbow, normally considered as failure of the pipe elbow, is defined as leakage under in-plane cyclic loading tests, and a failure estimation method is proposed using a damage index based on energy dissipation.

• Restorative Dentistry and Endodontics
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• 제47권2호
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• pp.16.1-16.9
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• 2022

Objectives: This study compared the cyclic fatigue resistance of One Curve (C wire) and F6 Skytaper (conventional austenite nickel-titanium [NiTi]), and 2 instruments with thermos-mechanically treated NiTi: Protaper Next X2 (M wire) and Hyflex CM (CM wire). Materials and Methods: Ten new instruments of each group (size: 0.25 mm, 6% taper in the 3 mm tip region) were tested using a rotary bending machine with a 60° curvature angle and a 5 mm curvature radius, at room temperature. The number of cycles until fracture was recorded. The length of the fractured instruments was measured. The fracture surface of each fragment was examined with a scanning electron microscope (SEM). The data were analyzed using one-way analysis of variance and the post hoc Tukey test. The significance level was set at 0.05. Results: At 60°, One Curve, F6 Skytaper and Hyflex CM had significantly longer fatigue lives than Protaper Next X2 (p < 0.05). No statistically significant differences were found in the cyclic fatigue lives of One Curve, F6 Skytaper, and Hyflex CM (p > 0.05). SEM images of the fracture surfaces of the different instruments showed typical features of fatigue failure. Conclusions: Within the conditions of this study, at 60° and with a 5 mm curvature radius, the cyclic fatigue life of One Curve was not significantly different from those of F6 Skytaper and Hyflex CM. The cyclic fatigue lives of these 3 instruments were statistically significantly longer than that of Protaper Next.

• 한국압력기기공학회 논문집
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• 제16권2호
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• pp.58-67
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• 2020

This study presents cyclic stress-strain and tensile test results at room temperature (RT) and 316℃ using cold-worked TP304 stainless steel base and weld metals. By comparing the cyclic hardening/softening behavior and failure cycle of cold-worked materials with those of irradiated austenitic stainless steels, the feasibility of simulating the irradiation effect on cyclic deformation and failure behaviors of TP304 stainless steel base and weld metals was investigated. It was found that, in the absence of strain-induced martensite trasformation, cold-working could properly simulate the change in cyclic hardening/softening behavior of TP304 stainless steel base and weld metals due to neutron irradiation. It was also recognized that cold-working could adequately simulate the reduction in failure cycles of TP304 stainless steel base and weld metals due to neutron irradition in the low-cycle fatigue region.

• Journal of Welding and Joining
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• 제12권1호
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• pp.73-79
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• 1994

Low cycle fatigue test was performed by companion specimens method to compare the properties of cyclic strain for the weldments of controlled rolling steel CR60 and welding structural steel SM58Q. And the result does not showed any difference of low cycle fatigue life between weldments. Especially, the values of coefficient of cyclic plastic strain $C_{p}$ and exponent of cyclic plastic strain $K_{p}$ of heat affected zones of CR60 steel and SM58Q steel were same. And $C_{p}$ and $K_{p}$ of CR60 steel were equal to the values of weld it means a good combination between the base metal, the heat affected zone and the weld of CR60 steel.eel.eel.

• 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.

• Steel and Composite Structures
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• 제33권3호
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• pp.433-444
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• 2019

Fatigue failure of a grid structure using bolt-sphere joints is liable to occur in a high-strength bolt due to the alternating and reciprocal actions of a suspension crane. In this study, variable amplitude fatigue tests were carried out on 20 40 Cr steel alloy M30 high-strength bolts using an MTS fatigue testing machine, and four cyclic stress amplitude loading patterns, Low-High, High-Low, Low-High-Low, and High-Low-High, were tested. The scanning electron microscope images of bolt fatigue failure due to variable amplitude stress were obtained, and the fractographic analysis of fatigue fractures was performed to investigate the fatigue failure mechanisms. Based on the available data from the constant amplitude fatigue tests, the variable amplitude fatigue life of an M30 high-strength bolt in a bolt-sphere joint was estimated using both Miner's rule and the Corten-Dolan model. Since both cumulative damage models gave similar predictions, Miner's rule is suggested for estimating the variable-amplitude fatigue life of M30 high-strength bolts in a grid structure with bolt-sphere joints; the S-N fatigue curve of the M30 high-strength bolts under variable amplitude loading was derived using equivalent stress amplitude as a design parameter.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.5-8
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• 2002

The use of the co-cured joining method for composite structures is attractive due to several benefits. However, since the design stress level in cyclic loads is often smaller than the joint strength obtained from the static tensile load test, it is important to establish proper fatigue design criteria. Although some researchers have reported on co-cured joints, there are only a few papers published on the fatigue characteristics of co-cured joints. In this paper, the effect of bond parameters on the fatigue characteristics of a steel-composite co-cured double lap joint under cyclic tensile loads was experimentally investigated. We considered the surface roughness of the steel adherend and the stacking sequence of the composite adherend as bond parameters. A fatigue failure mechanism of the co-cured double lap joint was explained systematically by investigating the surfaces of failed specimens.

• International Journal of Ocean System Engineering
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• 제3권4호
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• pp.164-168
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• 2013

Tidal-current power is now recognized as a clean power resource. The turbine blade is the fundamental component of a tidal current power turbine. The kinetic energy available within a tidal current can be converted into rotational power by turbine blades. While in service, turbine blades are generally subjected to cyclic fatigue loading due to their rotation and the rotor-tower interaction. Predicting the fatigue life under a hydrodynamic fatigue load is very important to prevent blade failure while in service. To predict the fatigue life, hydrodynamic load data should be acquired. In this study, the vibration characteristics were analyzed based on three-dimensional unsteady simulations to obtain the cyclic fatigue load. Our results can be applied to the fatigue design of horizontal-axis tidal turbines.