• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.405-408
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• 2003

Generally, the life of casting mold is limited by fatigue fracture or dimensional inaccuracy originated from wear in high temperature. Although recent research of metallic materials in high temperature fatigue have been much accomplished, many studies on brittle material as a die steel in high temperature fatigue does not have been reported. Especially, the study on the fatigue behavior over the transformation temperature is not studied sufficiently because of its difficult analysis and experiment. Therefore, reliable results of brittle material in high temperature fatigue behavior are needed. In this paper, stress-strain curves and stress-life curves in die STD61 steel are carefully examined between room temperature and 90$0^{\circ}C$, as the basic experimental data are used to predict from fatigue life of casting mold.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1996년도 제23회 학술대회
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• pp.1-3
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• 1996

The characteristics of fretting wear are reviewed. Fretting damage depends on slip amplitude and classified into three groups: (1) an annular damage according to Mindlin's analysis at microslip region, (2) strong adhesive deformation without loose wear particles at the intermediate region, and (3) formation of fine oxide particles at the gross slip region. The critical slip amplitude of fretting is the boundary between (2) and (3). The boundary slip amplitude depends on normal load. The wear rate increases and saturates with increasing slip amplitude. But it is constant by considering the critical amplitude. The role of oxide particles are discussed. Three different actions are noted: accelerating wear, preventing wear and insignificant effect. The oxide shows two opposing effect depends on normal load and slip amplitude. This is related to the removal rate from the interface (abrasive action) and compaction rate at the interface to form a protective layer. The effect of oxidation is significant to determine the wear and friction. The diffusion of oxygen is restricted at the small amplitude. As a result, crack formation at the boundary is a predominant damage, related to fretting fatigue damage.

• 대한물리치료과학회지
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• 제20권1호
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• pp.17-25
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• 2013

The purpose of this research is to provide right information about deformation and to relieve fatigue of high-heels lovers. The research data includes 15 tests and survey on 71 female students. The result follows 1. Age of surveys is mostly 22, consisting 43.7% of all. The most frequently worn shoe kind is high heels that 45.1% of surveys wear 2. Female students those are 155~160cm high wear high heels most frequently, 40.8%. 3. The fatigue condition classified by hours of wearing: Surveys wearing high heels over 7 hours and 5~7 hours state starting to feel fatigue by 40.8%, 38.0% each, and the result was stastically significant 4. The appearance of pain on calf classified by hours of wearing: 35.2% of surveys answered they start to feel pain when worn high heels over 7 hours, and 33.8% of students answered 5~7 hours 5. The fatigue condition classified by kinds of shoes worn: 45.0% of the surveys felt tired when wearing high heels, 40.8% answered wearing heel inserted running shoes, and 14.0% for flat shoes. 6. The fatigue condition classified by heel height: 69.0% of survey answered they feel fatigue after wearing shoes with 5~9cm high heels, 21.1% answered under 3cm high heels, and 9.9% answered over 10cm heels(p<0.05) 7. The experience of cramp in calf cramp muscle classified by heel height: 69.0% of surveys experienced cramp when wearing 5~9cm high heels, 21.1% answered under 3cm high heels, 9.9% for over 10cm heels.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 제35회 춘계학술대회
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• pp.88-95
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• 2002

Fretting of fuel rod cladding material, Zircaloy-4 Tube, in PWR nuclear power plants must be reduced and avoided. Nowadays the introduction of surface treatments or coatings is expected to bean ideal solution to fretting damage since fretting is closely related to wear, corrosion and fatigue. Therefore, in this study the fretting wear experiment was peformed using TiAIN coated Zircaloy-4 tube as the fuel rod cladding and uncoated Zircaioy-4 tube as one of grids, especially concentrating on the sliding component. Fretting wear resistance of TiAIN coated Zircaloy-4 tubes was improved compared with that of TiN coated tubes and uncoated tubes and the fretting wear mechanisms were delamination and plastic flow following by brittle fracture at lower slip amplitude but severe oxidation and spallation of oxidative layer at higher slip amplitude.

• Tribology and Lubricants
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• 제7권1호
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• pp.40-45
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• 1991

Wear performances for dibutyl 3,5-di-t-butyl 4-hydroxy benzyl phosphonate (DBP) were invesitigated using the four ball test machine under sliding and also rolling contact conditions, and compared with ZDDP. DBP showed excellent antiwear performace compared with ZDDP under severe sliding contact. Also, DBP achieved a longer fatigue life than ZDDP under rolling contact conditions. The surface of the worn balls was observed using an optical microscope, and the wear derbis generated was measured using the Particle Quantifier (PQ).

• 대한기계학회논문집A
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• 제29권5호
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• pp.655-662
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• 2005

This paper investigates the improvement of accuracy and fatigue life of the developed counter pressurized microcellular gears of polyacetal. It is shown that the fatigue life and operational characteristics of the counter pressurized microcellular gears are more improved than conventional injection molded plastic gears by the dynamic gear durability test. For the cases of test sea.5. conventional injection molded sea.5(SGea.) and counter pressurized microcellular gears(CGear) are manufactured. Durability test is performed on both conventional lnjection molded gears and counter pressurized microcellular gears. Accuracy variation and operational characteristics on fatigue life, wear and tooth surface temperature of CGear and Scear are compared and represented. Operational characteristics of the proposed counter pressurized microcellular gears show a good result in this research. The durability limit of counter pressurized microcellular gears is also obtained, and represented by a function of unit load as well as by a function off-factor.

• 한국해양공학회지
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• 제23권2호
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• pp.74-80
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• 2009

Surface hardening treatments, such as using the high-frequency induction hardening method, are widely used to increase the fatigue life and prevent the failure of materials by locally increasing the surface hardness. This method, in particular, brings an improvement in static strength by compressive residual surface stress due to the hardening. In this study, the mechanical properties of high-frequency induction hardened SCM440 steel were investigated. These results were also compared with those for base metal and a Q/T (tempering after quenching) treatment specimen. The test results showed that partially high-frequency induction hardened SCM440 steel specimens were more improved in static strength, surface hardness, fatigue limit, and anti-wear than the base metal and Q/T treatment specimens. In particular, the fatigue limit of the high-frequency induction hardened SCM440 steel increased by more than about 52% compared to that of base metal and by about 25% compared to that of the Q/T specimen.

• 한국염색가공학회지
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• 제23권1호
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• pp.60-68
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• 2011

The effect of compression wear for sport performance and muscle function was investigated based on the physiological test and electromyograph(EMG). The EMG test was used to study muscle activity after fitting the compression wear during exercise. It showed slight difference between men and women testee groups in the results of anaerobic, aerobic, fatigue, and EMG test due to muscle content in the body. In addition, the exercise performance was increased to some extent even the muscle activity was decreased. It is estimated that the compression effect to muscle by the compression wear decreased the muscle vibration and improved blood circulation which helped the entire sport performance. However, it is necessary to study the effect of compression wear in long-term wearing in the future study.

• 여성건강간호학회지
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• 제10권3호
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• pp.235-243
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• 2004

Purpose: The purpose of this study was to measure the effects of aroma inhalation on fatigue and quality of sleep of postpartum mothers. Method: The study design was a non-equivalent control group pre-post design. 51 Postpartum mothers were assigned either to a control group or to an experimental group that was exposed to aromas through inhalation for 6 days. Subjects in the experimental group were instructed to wear a necklace filled with Lavender and Eucalyptus oil from 2:00 PM to 8:00 PM every day. Fatigue was measured using the Rhoten Fatigue Scale. Sleep duration, night arousal frequency and sleep satisfaction were used to assess the quality of sleep. Result: There was a significant difference in the score of fatigue following the treatment between the experimental and control groups (t=-2.79 p=.00). However, there was no significant difference in sleep duration, frequency of night arousal and sleep satisfaction following aroma inhalation between two groups. Conclusion: This intervention appears to be effective in reducing the fatigue in postpartum mothers.

• Restorative Dentistry and Endodontics
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• 제46권2호
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• pp.18.1-18.13
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• 2021

Composite resins are the most commonly used dental restorative materials after minimally invasive dental procedures, and they offer an aesthetically pleasing appearance. An ideal composite restorative material should have wear properties similar to those of tooth tissues. Wear refers to the damaging, gradual loss or deformation of a material at solid surfaces. Depending on the mechanism of action, wear can be categorized as abrasive, adhesive, fatigue, or corrosive. Currently used composite resins cover a wide range of materials with diverse properties, offering dental clinicians multiple choices for anterior and posterior teeth. In order to improve the mechanical properties and the resistance to wear of composite materials, many types of monomers, silane coupling agents, and reinforcing fillers have been developed. Since resistance to wear is an important factor in determining the clinical success of composite resins, the purpose of this literature review was to define what constitutes wear. The discussion focuses on factors that contribute to the extent of wear as well as to the prevention of wear. Finally, the behavior of various types of existing composite materials such as nanohybrid, flowable, and computer-assisted design/computer-assisted manufacturing materials, was investigated, along with the factors that may cause or contribute to their wear.