• Journal of Welding and Joining
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• 제27권1호
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• pp.90-94
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• 2009

In this study, a series of fatigue test was performed to evaluate the fatigue strength of butt welded specimens. Effective notch stress through finite element analysis was conducted to analyze the fatigue results. As a results, no significant decrease in fatigue strength was observed when backplates were present. The S-N curve that based on effective notch stress appeared a similar fatigue lift to FAT 225 curve without reference to existence of backplates.

• Structural Engineering and Mechanics
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• 제50권6호
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• pp.835-852
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• 2014

Despite the availability of other transport methods such as land and air transportations, marine transportation is the most preferred and widely used transportation method in the world because of its economical advantages. In service, ships experience cyclic loading. Hence, it can be said that fatigue fracture, which occurs due to cyclic loading, is one of the most critical failure modes for vessels. Accordingly, this makes fatigue failure prevention an important design requirement in naval architecture. In general, a ship structure contains many structural components. Because of this, structural modeling typically relies on Finite Element Analysis (FEA) techniques. It is possible to increase fatigue performance of the ship structures by using FEA in computer aided engineering environment. Even if literature papers as well as rules of classification societies are available to assess effect of fatigue cracks onto the whole ship structure, analytical studies are relatively scarce because of the difficulties of modeling the whole structure and obtaining reliable fatigue life predictions. As a consequence, the objective of this study is to improve fatigue strength of a mercantile vessel against fatigue loads via analytical method. For this purpose, the fatigue life of the mercantile vessel has been investigated. Two different type of fatigue assessment models, namely Coffin-Manson and Morrow Mean stress approaches, were used and the results were compared. In order to accurately determine the fatigue life of the ship, a nonlinear finite element analysis was conducted considering plastic deformations and residual stresses. The results of this study will provide the designer with some guidelines in designing mercantile vessels.

• 국제학술발표논문집
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• The 8th International Conference on Construction Engineering and Project Management
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• pp.257-264
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• 2020

Objective: To investigate test-retest reliability and responsiveness of Equivital Lifemonitor and photoplethysmography based wristwatch tools in assessing physiological parameters during a simulated fatigue task. Methods: Ten university students (Mean age, 30.6 ± 1.7 years) participated in this pilot study. Participants were asked to perform a 30-minute of a simulated fatigue task in an experimental setup in a lab. The physiological parameters (e.g., heart rate, heart rate variability, respiratory rate, electrodermal activity, and skin temperature) were measured at baseline and immediately after the fatigue task. An intraclass correlation coefficient (ICC2,1) was used to evaluate the test-retest reliability of each tool in assessing physiological measures. In addition, the responsiveness of each tool to measure changes from baseline to posttest was calculated using a standardized response mean. Results: The Equivital Lifemonitor has shown good to excellent test-retest reliability for the assessment of heart rate (ICC, 0.97), heart rate variability (ICC, 0.86), respiratory rate (ICC, 0.77), and local skin temperature (ICC, 0.76). However, photoplethysmography based wristwatch showed moderate to good test-retest reliability for the assessment of heart rate (ICC, 0.71), heart rate variability (ICC, 0.73), electrodermal activity (ICC, 0.80), and skin temperature (ICC, 0.72). A large standardized response mean (>0.8) indicates that both tools can capture the changes in heart rate, heart rate variability, respiratory rate, skin temperature, and electrodermal activity after a 30-minute of fatigue task. Conclusions: The Equivital Lifemonitor and photoplethysmography based wristwatch devices are reliable in measuring physiological parameters after the fatigue task. Additionally, both devices can capture the fatigue response after a simulated construction task. Future field studies with a larger sample should investigate the sensitivity and validity of these tools in measuring physiological parameters for fatigue assessment at construction sites.

• Structural Engineering and Mechanics
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• 제13권4호
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• pp.455-464
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• 2002

There is a growing demand to assess the remaining strength and endurance of existing composite steel and concrete bridge beams due to the aging infrastructure, increases in permissible vehicle weights and increases in their frequencies. As codes are generally dedicated to the design of new structures, new procedures are required to aid in the assessment of existing bridges to ensure that they are utilised to the full. In this paper, simple expressions are presented to perform partial-interaction analyses directly from full-interaction analyses, so that the beneficial effect of partial-interaction on the shear forces on the shear connectors can be utilised in assessment to extend the fatigue life of simply supported bridge beams and to determine the effect of remedial work if necessary. Use of the assessment technique is described by way of an illustrative example.

• Journal of Welding and Joining
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• 제24권2호
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• pp.48-56
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• 2006

The fatigue strength of the welds is affected by such factors as the weld geometry, microstructures, tensile properties and residual stresses caused by fabrication. It is very important to evaluate the structural integrity of the welds in nuclear power plant because the weldment undergoes the most of damage and failure mechanisms. In this study, the fatigue assessments for a reactor vessel outlet nozzle with the weldment to the piping system are performed considering the welding residual stresses as well as the effect of local brittle zone in the vicinity of the weld fusion line. The analytical approaches employed are the microstructure and mechanical properties prediction by semi-analytical method, the thermal and stress analysis including the welding residual stress analysis by finite element method, the fatigue life assessment by following the ASME Code rules. The calculated results of cumulative usage factors(CUF) are compared for cases of the elastic and elasto-plastic analysis, and with or without residual stress and local brittle zone effects, respectively. Finally, the fatigue life of reactor vessel outlet nozzle weld is slightly affected by the local brittle zone and welding residual stresses.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.853-858
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• 2004

In order to develop a high speed train, various conditions have been considered. Fatigue strength assessment by the fluctuation of pressure is an important one. When high speed train passing though tunnels, the pressure wave is generated in tunnels and pressure variation by the wave is acting on carbody structure with dynamic load repeatedly. In this study, formulation for reliability based fatigue assessment method has been performed when the high speed train passes through tunnels. The formulation was based on structural reliability index method and followed the proposed ISO method. The result by this study would be a good guidance to calculate the fatigue life and reliability index of body structure.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.274-279
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• 2001

Creep-fatigue crack growth behavior was experimentally measured particularly when a crack was located in the heat affected region of 1Cr-0.5Mo steel. Load hold times of the tests for trapezoidal fatigue waveshapes were varied among 0, 30, 300 and 3,600 seconds. Time-dependent crack growth rates were characterized by the $C_t$-parameter. It was found that the crack growth rates were the highest when the crack path was located along the fine-grained heat affected zone(FGHAZ). Cracks located in other heat affected regions had a tendency to change the crack path eventually to FGHAZ. Creep-fatigue crack growth law of the studied case is suggested in terms of $(da/dt)_{avg}$ vs. $(C_t)_{avg}$ for residual life assessment.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.336-341
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• 2003

In this paper, resonance durability analysis technique is presented for the fatigue life assessment considering dynamic effect of a vehicle system. In the resonance durability analysis, the frequency response and the dynamic load on frequency domain are used. Multi-body dynamic analysis, finite element analysis, and fatigue life prediction method are applied for the virtual durability assessment. To obtain the frequency response and the dynamic load, the computer simulations running over typical pothole and Belgian road are carried out by utilizing vehicle dynamic model. The durability estimations on the rear suspension system of the passenger car are performed by using the presented technique and compared with the quasi-static durability analysis. The study shows that the fatigue life considering resonant frequency of vehicle system can be effectively estimated in early design stage.

• Journal of Mechanical Science and Technology
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• 제20권12호
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• pp.2136-2146
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• 2006

A study on a creep-fatigue crack growth behavior has been carried out for a cylindrical structure with weldments by using a structural test and an evaluation according to the assessment procedures. The creep-fatigue crack growth behavior following the creep-fatigue crack initiation has been assessed by using the French A16 procedure and the conservatism for the present structural test has been examined. The structural specimen is a welded cylindrical shell made of 316 L stainless steel (SS) for one half of the cylinder and 304 SS for the other half. In the creep-fatigue test, the hold time under a tensile load which produces the primary nominal stress of 45 MPa was one hour at $600^{\circ}C$ and creep-fatigue loads of 600 cycles were applied. The evaluation results for the creep-fatigue crack propagation were compared with those of the observed images from the structural test. The assessment results for the creep-fatigue crack behavior according to the French Al6 procedure showed that the Al6 is overly conservative for the creep-fatigue crack propagation in the present case with a short hold time of one hour.

• 종양간호연구
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• 제12권2호
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• pp.117-124
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• 2012

Purpose: The purpose of this study was to assess pain, sleep disturbance, fatigue, and the quality of life and to identify the impact of pain, sleep disturbance and fatigue on the quality of life in patients with pancreatic cancer undergoing chemotherapy. Methods: Data were collected from June to July, 2010. Participants were recruited from Y university hospital in Seoul. Research instruments included numeric rating scale for pain, Functional Assessment Chronic Illness Therapy-Functional Well-Being (FACIT-FWB): General Factor 5 (GF5) for sleep disturbance, Functional Assessment of Cancer Therapy-General (FACT-G) for quality of life, and FACT-Fatigue for fatigue. Results: The quality of life for cancer patients had a significant relationship with pain, sleep disturbance, and fatigue. The significant factors influencing quality of life were pain, sleep disturbance, and fatigue that explained 52.6% of the variance. Conclusion: Patients with pancreatic cancer undergoing chemotherapy experienced pain, fatigue, and sleep disturbance which led to a negative effect on quality of life. The results suggest that intervention program to improve quality of life could reduce pain, fatigue, and sleep disturbance of pancreatic cancer patients undergoing chemotherapy.