• Journal of Biomedical Engineering Research
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• v.34 no.1
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• pp.1-7
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• 2013

According to the frequent use of mobile devices, risk of repetitive strain injury for the finger joints was increasing recently. The purpose of this study was to investigate the difference of muscular endurance limit of the thumb between adults and children. A total of thirty subjects (15 adults: $41.0{\pm}7.9$ years and 15 children: $9.5{\pm}2.7$ years) was recruited for this experiment. Maximum voluntary contraction (MVC) of the thumb was measured for 100 trials for each subject by using a push-pull gauge. From the maximum peak value obtained, three main factors (MVC, endurance limit, and fatigue index) were defined to quantify fatigue characteristics of the thumb flexor muscle. The experimental results showed that the mean of MVC, endurance limit, and fatigue index of the children were approximately 50% compared to the adults (p < 0.001). From the results of Pearson correlation test, the endurance limit was highly correlated with weight, age, hand length rather than height. Based on this study, children are more vulnerable to repetitive task using the thumb such as text/SNS messaging, gaming, and scrolling.

• Journal of the Korean Society of Safety
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• v.26 no.2
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• pp.1-5
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• 2011

In order to evaluate fatigue endurance for an ultra-light weight inline skate frame, FEM analysis was performed. Tensile properties and a S-N curve were determined through tensile and fatigue tests on a modified Al-7075+$S_c$ alloy. The yield and ultimate tensile strengths were 553.3 MPa and 705.5 MPa, respectively. The fatigue endurance limit of this alloy was 201.2 MPa. For evaluating the fatigue endurance of the inline skate frame, the S-N data were compared with the stress analysis results through FEM analysis of the frame. The maximum Von-Mises stress of the frame was determined 106 MPa through FEM analysis of the frame, assuming that the rider weight is 75 Kg. Conclusively, on the basis of fatigue limit, the inline skate frame has a safety factor of approximately 2.0.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.125-133
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• 2002

In this study, it was investigated about endurance limit and fatigue behavior of load carrying fillet welded cruciform joints according to welding methods of SMAW, SAW, MIG and FCAW commonly using for welding structures in present. Endurance limit carried omit highly in the order of SMAW, MIG, SAW, FCAW and fatigue crack propagation ratio carried out lowly in the order of SMAW, MIG, FCAW, SAW. By these results, it is needed to use SMAW or MIG welding methods for welding structures with small welding capacity and SAW or FCAW methods for large welding structures after due consideration about economic gains and operation efficiency of welding. Fatigue crack propagation ratio is more effected by strength of welding materials than endurance limit of welding materials according to welding methods.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.1
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• pp.38-44
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• 2003

In this study, endurance limit and fatigue behavior of load carrying fillet welded cruciform joints depending on commonly used welding methods such as SMAW, SAW, MIG and FCAW are investigated. In respect of endurance limit SMAW specimen showes highest result, and then MIG, SAW, FCAW in descending order. However, SMAW specimen showes lowest crack growth rate and it followed by MIG, FCAW, SAW. By these results, it is needed to use SMAW or MIG welding methods for welding structures with small welding capacity and SAW or FCAW methods for large welding structures with respect to economic benefits and operation efficiency of welding. It was also shown fatigue crack growth rate was more influenced by the strenght of welding materials than the endurance limit of welding materials.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.836-839
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• 2005

A limit switch box is used for a indicator of a valve actuator. This device indicates an opening and closing of a valve or throttle in a valve actuator. In a ship, equipments are required safety and robustness because of a rough environment and a specific condition during a voyage. However, the limit switch box is used in an indoor environment generally. In order to evaluate the endurance of the limit switch box used in an indoor environment, the endurance tests against salt water have been conducted. Experiment results showed that the limit switch box was corroded severely. Thus, this study developed a new limit switch box which can be used at an outdoor environment. The housing of the developed limit switch box was made by an stainless steel to prevent corrosion.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1979-1985
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• 2003

Fretting is a kind of surface degradation mechanism observed in mechanical components and structures. The fretting damage decreases in 50-70% of the plain fatigue strength. This may be observed in the fossil power plant and the nuclear power plant used in special environments and various loading conditions. The thermal degradation of material is observed when the heat resisting steel is exposed for long period time at the high temperature. In the present study, the degraded 1Cr-0.5Mo steel used for long period time at high temperature (about 515$^{\circ}C$) and artificially reheat-treated materials are prepared. These materials are used for evaluating an effect of thermal aging on the fretting fatigue behavior. Through the experiment, it is found that the fretting fatigue endurance limit of the reheat-treated 1Cr-0.5Mo steel decreased about 46% from the non-fretting fatigue endurance limit, while the fretting fatigue endurance limit of the degraded 1Cr-0.5Mo steel decreased about 53% from the non-fretting fatigue endurance limit. The maximum value of fatigue endurance limit difference is observed as 57%(244 MPa) between the fretting fatigue of degraded material and non-fretting fatigue of reheat-treated material. These results can be a basic data to a structural integrity evaluation of heat resisting steel considered to thermal degradation effect.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1334-1338
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• 2005

A limit switch box is used for an indicator of a valve actuator. This device indicates an opening and closing of a valve or a throttle in the valve actuator. In a ship, equipments require safety and robustness because of a rough environment and a specific condition during a voyage. However, the limit switch box has been used in an indoor environment generally. This study developed a new limit switch box which can be used at an outdoor environment. This study designed the new limit switch box. The housing of the limit switch box was made by an aluminum die cast method with surface painting after anodizing or chromate coating. In order to evaluate the endurance of the housing, the endurance tests against salt water have been conducted. Experiment results showed that the proposed device provides a reliable performance against salt water.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.226-227
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• 2005

In this study, it was investigated about endurance and fatigue crack propagation rate of according to welding methods of SMAW and FCAW commonly using for welding structures in present. Endurance limits carried out highly in the order of SMAW, FCAW and fatigue crack propagation rate out lowly in the order of SMAW, FCAW. By these results, it is needed to used SMAW welding methods for welding structures with small welding capacity and FCAW methods for large welding structures after consideration about economic gains and operation efficiency of welding. Fatigue crack propagation rate is more effected by strength of welding materials than endurance limit of welding materials according to welding methods..

• Journal of the Korean Society for Heat Treatment
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• v.6 no.3
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• pp.166-177
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• 1993

Bending fatigue strength tests were made for VC coated die steels which were coated by immersing in a molten borax bath and for hardened die steels which were quenched and tempered, in order to clarify the effect of VC coating at $1000^{\circ}C$ and $1025^{\circ}C$. The material used in this investigation was a representative cold and hot die steels STD11, STD61. The results obtained are as follows. 1) The endurance limit of VC coated die steels was a little lower than that of hardened die steels. It is considered to be mainly due to the decfl.lase of hardness in the substrates. Accordingly, the endurance limit reo covered almost to the level of hardened die steels by an additional diffusion treatment. 2) The initiation point of fatigue fracture of VC coated die steels in reversed bening was on the substrate just under the VC layer. Hence, the endurance limit is corrected to the hardness of this part. 3) But, there is a considerable scatter in this relationship and the endurance limit of VC coated die steels was a little lower than that of hardened die steels with equal hardness. These results suggest that the fatigue strength of VC coated die steels is determined not only by the hardness but also by other factors. For example. the residual stress in the substrate just under VC coating layer is one of the factors besides hardness which is mainly related to the retained austenite(${\gamma}_R$).

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.899-903
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• 2004

A limit switch box is used for a indicator of a valve actuator. This device indicates an opening and closing of a valve or throttle in a valve actuator. In ship, equipments are required safe and robust because of a rough environment and a specific condition during a voyage. However, the limit switch box is used in an indoor environment generally. Thus, a new limit switch box must be developed which can be used at an outdoor environment. This study designed the limit switch box. The housing of the limit switch box was made by an aluminium die cast method with surface painting after anodizing or chromate coating. In order to evaluate the endurance of the housing, the endurance tests against salt water have been conducted. Experiment results showed that the proposed device provides a reliable performance against salt water.