• Journal of the Korean Society of Safety
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• v.30 no.3
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• pp.1-6
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• 2015

Self-piercing riveting (SPR) is receiving more recognition as a possible and effective solution for joining automotive body panels and structures, particularly for aluminum parts and dissimilar parts. In this study, static strength and fatigue tests were conducted using coach-peel and cross-tension specimens with Al-5052 plates for evaluation of fatigue strength of the SPR joints. For the static experiment results, the fracture modes are classified into pull-out fracture due to influence of plastic deformation of joining area. During the fatigue tests for the coach-peel and cross-tension specimens with Al-5052, interface failure mode occurred on the top substrate close to the rivet head in the most cycle region. There were relationship between applied load amplitude $P_{amp}$ and life time of cycle N, $P_{amp}=715.5{\times}N^{-0.166}$ and $P_{amp}=1967.3{\times}N^{-0.162}$ were for the coach-peel and cross- tension specimens, respectively. The finite element analysis results for specimens were adopted for the parameters of fatigue lifetime prediction. The relation between SWT fatigue parameter and number of cycles was found to be $SWT=192.8N_f^{-0.44}$.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1127-1132
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• 2003

Suspension system of vehicle have enough endurance during its life time to protect passenger. Spring is one of major part of vehicle. Thus, a fatigue strength evaluation for leaf spring based on road load response was carried out. At first, strain of leaf spring is measured on the city condition and proving ground condition. And next, the damage analysis of road load response data was carried out. And fatigue test of leaf spring were also carried out. Based on -N life relation, fatigue life of leaf spring was evaluated at belgian mode, city mode and drawing test specification. After that, it is compared the design life of leaf spring and evaluated fatigue life by belgian mode, city mode and drawing test specification. From the above, the maximum load-fatigue life relation of leaf spring was defined by test. and new test target of belgian mode and city mode was proposed to accept design specification of leaf spring. It is expect that proposed test target can verify leaf spring fatigue endurance at specific road condition.

• Textile Coloration and Finishing
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• v.26 no.3
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• pp.181-186
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• 2014

This paper surveys improvement characteristics in muscle fatigue with bio-activity material imbedded fabric. For this purpose, the subjects wear the garment which is covered by bio-activity materials all over every day during 2 weeks of experimental period. After 2 weeks period, VAS(Visual Analogue Scale) index evaluation regarding muscle fatigue and pain has been conducted in comparison between before wearing and after so that we can evaluate the effect on muscle fatigue improvement. The effectiveness survey for testing products consists of improvement on krunkle, muscle fatigue and exercise capacity. As a result, 100% of test subject group completes a questionnaire with positive answer as above normal in every question. In addition the preference of testing products is researched in wearing comfort, activity and convenience. And it is marked above normal by 100% of test subject group as well. Moreover any kind of unusual skin reaction has not been detected in safety evaluation. Therefore this testing products is being judged as a beneficent product for improvement on muscle fatigue without any skin irritation.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.4
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• pp.212-219
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• 2001

The fatigue test was carried out to evaluate the fatigue characteristics of fire resistance steel for frame structure and heat affected zone (HAZ) by the one side Gas Metal Arc Welding (GMAW). In this paper, the fatigue crack growth behavior was investigated with the compact tension specimen of base metal and the HAZ according to chemical composition and rolling end temperature, respectively. And the acoustic emission signals obtained from the fatigue test were analyzed by the time-frequency analysis method as a nondestructive evaluation. Main results obtained are summarized as follows; The hardness was appeared softening phenomenon that weld metal and HAZ are lower than that of base metal. Fatigue life of welded specimen was longer than that of base metal. m was 3~4.5 in base metal and 3.8~5.8 in HAZ. The main frequency range of acoustic emission signal analyzed from time-frequency method is different with the range by noise and crack. Also, it could be classified that it was also generated by fracture mechanics of dimple, inclusion etc.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.4
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• pp.385-393
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• 2007

The strength evaluation of the most weakest junction part is required for the safety design of all structures. Most of all. in order to enhance the reliability and safety of the welding part. whose use is the highest, it is very important to establish the efficient structure manufacturing technology by studying and investigating the evaluation of fatigue strength in various environments. This study analyzed the relations of da/dN, and th according to the welding methods of SMAW, FCAW, and SAW. In the stage II. the value of stress intensity factor range was the highest in SMAW welding method of stress ration R=0.1, and appeared under the sequence of FCAW and SAW and as the completion section of stress intensity factor was low, threshold stress intensity factor was lowly formed in da/dN - The fatigue life of each welding method is sensitively worked in high stress ratio. judging from the fact that the width of life reduction increases in the high stress ratio zone compared to the width of life reduction in the low stress ratio zone. In the fatigue limit of welding methods before corrosion. the welding of SMAW and FCAW shows the same fatigue limit compared to Base metal, and SAW holds the lowest fatigue limit value.

• Journal of Power System Engineering
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• v.20 no.3
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• pp.29-35
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• 2016

Because of the severe service environment of the large marine vessel, the fatigue strength and its evaluation play an important role in design and maintenance of marine crankshaft. The aim of this work is to investigate the probability distribution of fatigue lives in crank throw forged steel and to develop the methodology for estimation of the probabilistic design fatigue strength. Detailed studies were performed on the constant amplitude axial loading fatigue test. The experiments were controlled by stress ratio of -1 and 15Hz frequency for each stress level. The considerable variability of fatigue life was observed in each stress level under rigidly controlled constant fatigue testing conditions. The fatigue life of crank throw forged steel was well followed the log-normal and Weibull distribution. In addition, it can be used for the estimation of probabilistic design fatigue strength by using the proposed methodology.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.4
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• pp.38-43
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• 2011

For the efficient and safe operation of nuclear power plant, evaluating quantitatively aging phenomenon of major components is necessary. Especially, typical aging parameters such as stresses and cumulative usage factors should be determined accurately to manage the lifetime of the plant facility. The 3-D finite element(FE) model is generated to calculate the aging parameters. Mechanical and thermal transfer functions called Green's functions are developed for the FE model with standard step input. The stress results estimated from transfer functions are verified by comparing with 3-D FE analyses results. Lastly, we suggest an effective fatigue evaluation methodology by using the transfer functions. The usefulness of the proposed fatigue evaluation methodology can be maximized by combining it with an on-line monitoring system.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.83-85
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• 2006

The purpose of this study is to evaluate the fatigue life at the rib weldment of generator shaft. In order to do it, the stress distributions at the weldment under design loading condition were evaluated using FEA and analytical approach. The fatigue strengths of the as welded and toe machined rib specimen were estimated using 3-points bending fatigue test. Based on the fatigue test results, the S-N curve far the rib weldment of the generator shaft with post treatment was established.

• Structural Engineering and Mechanics
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• v.44 no.4
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• pp.417-429
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• 2012

Taking the superficial temperature increment as the major fatigue damage indicator, the infrared thermography was used to predict fatigue parameters (fatigue strength and S-N curve) of welded joints subjected to fatigue loading with a high mean stress, showing good predictions. The fatigue damage status, related to safety evaluation, was tightly correlated with the temperature field evolution of the hot-spot zone on the specimen surface. An energetic damage model, based on the energy accumulation, was developed to evaluate the residual fatigue life of the welded specimens undergoing cyclic loading, and a good agreement was presented. It is concluded that the infrared thermography can not only well predict the fatigue behavior of welded joints, but also can play an important role in health detection of structures subjected to mechanical loading.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.1
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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.