• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.58-63
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• 2002

This study has performed rotary bending fatigue testing that smooth specimen using SM45C materials and notched specimen whose radii were R6, R4 and R2, were processed in 3% NaCl aqueous solutions or in the air. The results are as followed; 1. In the air fatigue limit at 10$^{7}$ cycles remarkably reduced as notch radius goes small. 2. In 3% NaCl aqueous solution fatigue strength at 10$^{6}$ cycles also had large range of reduction as notch radius goes small. 3. Comparing fatigue strength in the air, fatigue strength at 10$^{6}$ cycles in 3% NaCl aqueous solution reduced by 46.2% at smooth specimen, 55.3% at R6 notch radius, 45.8% at R4 and 39.7% at R2 respectively. 4. The reason that fatigue strength reduced in the reduction of notch radius sire was because the surface of notch exposed in corrosion was small and consequently it was less corroded.

• International Journal of Korean Welding Society
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• v.2 no.1
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• pp.33-39
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• 2002

The effect of out-of-plane loads on the fatigue strength of welded steel structures is examined through fatigue tests with weldment of two fillet weld joint types. The results of the fatigue tests are compared with those under axial loads, on the basis of the hot spot stress range at the weld toe. From the result of the comparison, a method on how to incorporate the effect of the out-of-plane bending stress is proposed using design S-N curves derived from fatigue tests under the axial load. The proposed method is useful for rational assessment of the fatigue strength of fillet-welded structures, where combined stresses of the in-plane axial stress and the out-of-plane bending stress are induced simultaneously due to the complexity of applied loads and structural geometry.

• Transactions of Materials Processing
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• v.23 no.2
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• pp.110-115
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• 2014

Low cycle fatigue characteristics are very important in the development of automobile suspension parts. Fatigue properties using the strain life approach are usually obtained from low cycle fatigue tests. However, low cycle fatigue testing requires a lot of time and cost. In the current study, an attempt to estimate low cycle fatigue properties of high strength steel sheet from tensile test and tensile simulations is performed. In addition, low cycle fatigue testing was conducted to compare the fatigue properties obtained from tensile testing and simulations. In conclusion, the results effectively predict the low cycle fatigue properties. However, some deviations still exist.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.312-316
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• 1996

Flexural fatigue strength of reinforced concrete members can be controlled by fatigue characteristics of concrete and reinforcing bars because the reinforced concrete members are composite members consisted of the concrete and the reinforcing bars. Since the fatigue characteristics of the reinforcing bars are different from static strength characteristics of those, it is necessary to obtain the fatigue characteristics of reinforcing bars directly from fatigue test. In this paper, the fatigue characteristics like fatigue strength of reinforcing bars with different diameters and different yield-strengths are obtained experimentally and the analysis and comparison of fatigue test results are presented. For the experiment, most widely used reinforcing bars manufactured by two domestic companies were randomly selected and direct tension fatigue tests were performed.

• 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.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.1
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• pp.21-26
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• 2000

This study deals with effects of heat-treatment on the fatigue strength of SNC815 spur gears. The test gears are heat-treated by two different treatments. After carburization, one group of the test gears is quenched directly, while the other group is fumace cooled, reheated then quenched. The fatigue test at a constant stress amplitude is performed by using an electrohydraulic servo-controlled pulsating tester. The S-N curves are obtained and illustrated. By comparing the estimated strength with the experimental results, the validity of the previous experimental formula, presented by the author for estimating the fatigue strength of carburized gears, was discussed on these tested gears.

• Journal of Welding and Joining
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• v.20 no.5
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• pp.99-105
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• 2002

One of the important advantage of adhesive bonded joint can combine the different materials. The joint that bonded by structural adhesive bond must keep a large force and its strength is affected by some environmental factors such as temperature and submergence time in water. In order to advance the fatigue strength of adhesive bonded joint, mostly put a surface treatment on the surface. This study was researched the effect of air temperature, submergence time, submergence temperature and surface treatment on the fatigue strength. We found that submergence temperature has the most effect and low plasma treatment specimens have the most fatigue strength.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1051-1055
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• 2003

Aluminum carbody for rolling stocks is light and perfectly recycled, but includes severe defects which are very dangerous to fatigue strength. Structural integrity assessment for the carbody by static load test has been performed up to date. In this study, to evaluate fatigue strength of the aluminum carbody of urban transit unit. a testing method to simulate dynamic loading condition was proposed and the fatigue strength of the carbody was evaluated. The dynamic load test results showed that the alternating stress ranges were different from the estimated ranges based on the static test results. Excessive stress ranges at the center are thought to come from the flexible motion of the carbody. published fatigue test data for aluminum components, but variation of alternating acceleration along the length due to flexibility of carbody yielded unexpected results. Because fatigue strength based on the static test results may be overestimated at the center, modification of testing method is necessary.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.2
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• pp.191-195
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• 2009

After developing the pre-crack to simulate a damaged reinforced concrete beam, fatigue test was conducted on the beam repaired by GFRP Bar and GSP embedded method. In the result of fatigue test, most residual displacement and crack of the experimental beams occurs in the early loading cycle and an increasing rate of these due to number of cycles were insignificant. Comparing with a non-repaired beam, a static strength of the repaired beam greatly increased, but fatigue strength decreased. In S-N curves, fatigue strength of the beam repaired by GFRP Bar and GSP was 58%, 52% of the static strength respectively.

• Journal of the Korean Society for Heat Treatment
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• v.11 no.4
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• pp.247-257
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• 1998

In order to evaluate the relation between prior structure and fatigue strength on a induction surface hardened medium carbon steel(SAE1050M) for automotive drive shafts, torsional fatigue test were conducted with various cases of different hardened depths and applied loads. Prior structures of the steel such as pearlite, fine pearlite and spheroidal pearlite were prepared by conventional nomalizing, tempering after quenching and spheroidized annealing, respectively. Maximum torsional fatigue strength can be obtained when the case depth is 18~25% diameter of the bar in each prior structure. The effect of case depth on the torsional fatigue strength was different depending on applied load to specimen, but the most good fatigue life was shown in the case of pearlitic structure when the case depth was 4.0~5.5mm(18~25% of bar diameter). Among three different prior structures, energy consumption, to obtain high strength or to get the same case depth, was the most saved in the case of pearlitic structure.