• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1995년도 추계학술대회논문집
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• pp.172-180
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• 1995

Isothermal interrupted deformation behavior of 10vol.%SICp/AI-Si composites was investigated by hot torsion test at the temperature ranges from 27$0^{\circ}C$ to 43$0^{\circ}C$ and at strain rate range of 1.26X10-2~2.16X10-1/sec. With increasing pass strain, flow stresses were high compared to continuous deformation condition. Fractional softening was increased with temperature imterruption time and pass strain. Fractional softening of 10vol.%SiCp/AI-Si composites was lower than that of AI-Si matrix at 37$0^{\circ}C$. However at high temperature of 43$0^{\circ}C$, SiC particle promoted static softening, diminishing the dislocation density at the interface of AI-Si matrix and reinforcements, then this resulted in higher fractional softening in composites. Both of failure strain improved reducing the fracture of SiC particle and Si precipitates above 32$0^{\circ}C$, however at low temperature of 27$0^{\circ}C$, the softening effect by interrupted deformation was found to be negligible.

• Journal of Welding and Joining
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• 제2권1호
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• pp.49-57
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• 1984

The influence of weld defect, residual stress and microstructure on the Low Cycle Fatigue(L. C. F.) behaviour of AISI 304L austenitic stainless steel weldment has been studied. The specimens were welded by shielded metal are welding process, post weld heat treated(PWHT) at 900.deg.C for 1.5hrs, and tested under total strain controlled condition at room temperature. The results of the experiment showed that weld defect affected the L.C.F. behaviour of weldment deleteriously compared to the residual stress or microstructure, and it reduced the L.C.F. life about 70-80%. The PWHT exhibited beneficial effect on the L.C.F. behaviour and increased the L.C.F. life about 120%. This enhancement by PWHT was attributed to the removal of residual stress and recovery of weld metal ductility. The cyclic stress flow of as welded specimens showed intermediate cyclic softening, whereas those of heat treated specimens showed continuous cyclic hardening, and this difference was explained in terms of the residual stress removal and dislocation behaviour. Scanning electron microscopy studies of fatigue fracture surface showed that weld defects of large size and near weld surface were detrimental to the L.C.F. behaviour of weldment.

• 한국축산식품학회지
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• 제24권4호
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• pp.424-432
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• 2004

The handling and transport of broiler birds from farm to the processing factory is known to cause injury and dead. The preslaughter period can be compromised through thermal stress, emotional stress, starvation, dehydration, metabolic exhaustion, trauma to the skin and bone fraction resulting in bruising and dead. This paper focuses on the control points of individual post Harvest stages by reference to recent literature. In catching, the injuries and deads are caused from fracture of bone, skin damage and hipbone dislocation. It can be improved by training the catchers. The primary factor of dead during transportation is from thermal stress. It is related to stocking density, type of crate and vehicle, ventilation and transportation time. Of the factors, the ventilation is very important. The holding place should be built with consideration of protection from the hostile external environment. There were not much progresses in this area, however, many researches are conducting to focus on animal welfare in European Union. Recently, it is rapidly changed in marketing custom from whole carcass to portion cut in Korea. This means the increase of economic loss due to the mishandling at post harvest. The systematic approach is demanded for this area.

• Nuclear Engineering and Technology
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• 제43권5호
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• pp.421-428
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• 2011

The out-of-pile mechanical performance and microstructure of recrystallized Zr-1.5 Nb-S alloy was investigated. The strength of the recrystallized Zr-1.5Nb-O-S alloys was observed to increase with the addition of sulfur over a wide temperature range, from room temperature up to $300^{\circ}C$. A yield drop and stress serrations due to dynamic strain were observed at room temperature and $300^{\circ}C$. Wavy and curved dislocations and loosely knit tangles were observed after strained to 0.07 at room temperature, suggesting that cross slip is easier. At $300^{\circ}C$, however, dislocations were observed to be straight and aligned along the slip plane, suggesting that cross slip is rather difficult. At $300^{\circ}C$, oxygen atoms are likely to exert a drag force on moving dislocations, intensifying the dynamic strain aging effect. Oxygen atoms segregated at partial dislocations of a screw dislocation with the edge component may hinder the cross slip, resulting in the rather straight dislocations distributed on the major slip planes. Recrystallized Zr-Nb-S alloys exhibited ductile fracture surfaces, supporting the beneficial effect of sulfur in zirconium alloys. Oxidation resistance in air was also found to be improved with the addition of sulfur in Zr-1.5 Nb-O alloys.

• 한국재료학회지
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• 제27권6호
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• pp.318-324
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• 2017

In this study, two Fe-30Mn-0.2C-(1.5Al) high-manganese steels with different surface conditions were hydrogen-charged under high temperature and pressure; then, tensile testing was performed at room temperature in air. The yield strength of the 30Mn-0.2C specimen increased with decreasing surface roughness(achieved via polishing), but that of the 30Mn-0.2C-1.5Al specimen was hardly affected by the surface conditions. On the other hand, the tendency of hydrogen embrittlement of the two high-manganese steels was not sensitive to hydrogen charging or surface conditions from the standpoints of elongation and fracture behavior. Based on the EBSD analysis results, the small decrease in elongation of the charged specimens for the Fe-30Mn-0.2C-(1.5Al) high-manganese steels was attributed to the enhanced dislocation pile-up around grain boundaries, caused by hydrogen.

• Journal of Welding and Joining
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• 제22권3호
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• pp.69-76
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• 2004

Effects of friction stir welding parameters such as tool rotation speed and welding speed on the joints properties of 5052 Al alloys were studied in this study. A wide range of friction stir welding conditions could be applied to join 5052 AA alloy without defects in the weld zone except for certain welding conditions with a lower heat input. Microstructures near the weld zone showed general weld structures such as stir zone (SZ), thermo-mechanically affected zone (TMAZ) and heat affected zone (HAZ). Each zone showed the dynamically recrystallized grain, transient grain and structure similar to base metal's, respectively. Hardness distribution near the weld zone represented a similar value of the base metal under wide welding conditions. However, in case of 800 rpm of tool rotation speed, hardness of the stir zone had a higher value due to the fine grain with lots of dislocation tangle, a higher angle grain boundary and some of Al3Fe particles. Except joints with weld defects, tensile strength and elongation of the joints had values similar to the base metal values and fracture always occurred in the regions approximately 5mm away from the weld center.

• 한국기계기술학회지
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• 제13권2호
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• pp.115-121
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• 2011

The size of hydrogen molecule is not so small as to invade into the lattice of material, and therefore, hydrogen invades into the material as atom. Hydrogen movement is done by diffusion or dislocation movement in the near crack tip or plastic deformation. Hydrogen appeared to have many effects on the mechanical properties of the Cr-Mo steel alloys. The materials for this study are 1.25Cr-0.5Mo and 2.25Cr-1Mo steels used at high temperature and pressure. The hydrogen amount obtained by theoretical calculation was almost same with the result solved by finite element analysis. The distribution of hydrogen concentration and average concentration was calculated for a flat specimen. Also, finite element analysis was employed to simulate the redistribution of hydrogen due to stress gradient. The calculation of hydrogen concentration diffused into the material by finite element method will provide the basis for the prediction of delayed fracture of notched specimen. The distribution of hydrogen concentration invaded into the smooth and notched specimen was obtained by finite element analysis. The hydrogen amount is much in smooth specimen and tends to concentrate in the vicinity of surface. Hydrogen embrittlement susceptibility of notched specimen after hydrogen charging is more remarkable than that of smooth specimen.

• Clinics in Shoulder and Elbow
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• 제22권3호
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• pp.154-158
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• 2019

The incidence of heterotopic ossification in adolescents appears to be lower than in adults. There exist very few reports of heterotopic ossification with total bony ankylosis in child or adolescent populations. We describe a case of total bony ankylosis of the elbow secondary to heterotopic ossification, in a 14-year-old female. Total ankylosis of the elbow at 45 degrees of flexion was noted 6 months postsurgery, and complete surgical excision of the heterotopic mass was performed. After an additional one-time dose of radiation therapy and nonsteroidal anti-inflammatory drug medication, full range of motion was obtained without any recurrence or other complications, up to the last follow-up of 30 months.

• 한국산업융합학회 논문집
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• 제27권3호
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• pp.509-517
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• 2024

Purpose : The study examined the knowledge and health education about first aid of college students. Methods : The survey had done from October to December, 2022. Total subjects in this study were 205. The collected data were analyzed by SPSS 24.0 program. Results : Regarding the difference in first aid knowledge according to the first aid education characteristics of the subjects, significant differences were observed in experience of first aid training (t=6.54, p(.01), necessity of first aid training (t=3.60, p(.01), and number of first aid training sessions (F=5.40, p(.01). In the case of first aid education experience, first aid education was necessary, and the knowledge score was the highest tn the three or more training sessions. As for the contents of first aid education, action tips in case of emergency, fracture, dislocation, sprain was the highest, and rescue and transport was the lowest. Conclusion : Continuous and systematic first aid education for college students is needed, and it is absolutely necessary to develop an advanced treatment education program to revitalize it.

• 대한정형외과스포츠의학회지
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• 제10권2호
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• pp.94-99
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• 2011

목적: 겨울철 스포츠로서 스키와 스노우 보드를 즐기는 인구가 점차 증가하여 대중화 되고 있다. 안전 장비에 대한 인식도 발전하여 스키나 스노우 보드에서 헬멧의 착용도 늘었고, 이 영향으로 두부나 안면부 손상의 비율은 감소하였다. 그러나 헬멧의 착용이 경추부 손상에 어떠한 영향을 미치는 지에 대하여 아직 잘 알려지지 않았다. 따라서 이에 대한 연구를 통하여 경추부손상의 감소를 위한 효과적인 보호장비의 개발에 도움이 되고자 조사하였다. 대상 및 방법: 2009년 12월부터 2010년 3월까지, 2010년 12월부터 2011년 3월까지 2시즌 동안 국내 대형 리조트에서 스키 및 스노우 보드 손상으로 의무 시설에 내원한 환자 14,538명 중 경추부 손상으로 내원한 658명을 대상으로 하였으며, 남자 432명, 여자 226명이 내원하였고, 상급자 273명 초급자 385명 이었다. 이들을 대상으로 헬멧을 착용 한 군과 착용하지 않은 군으로 나누어 경추 손상 비율, 수상 기전, 손상의 정도 및 진단된 질환에 대하여 조사하였다. 각각의 군은 SPSS 12.0(SPSS Inc., Chicago, IL, USA)를 사용하여 통계학적으로 처리 하였다. 결과: 스키 손상으로 인한 환자는 312명, 스노우 보드 손상은 346명 이었으며, 헬멧을 착용한 수상자는 스키 143명, 스노우 보드 140명 이었다. 각 질환 별 분류는 단순 염좌 292명, 타박상 359명, 경추부 골절 6명, 탈구 1명이며, 수상 원인 별 분류에서 대인 충돌 287명, 대물 충돌 212명, 혼자서 넘어진 경우 108명, 낙상 39명, 기타 12명으로 나타났다. 헬멧을 쓴 경우 스키 78명/스노우 보드 70명에서 단순 염좌 였고, 스키 64명/스노우 보드 68명에서 타박상으로 나타났으며, 스키 1명/ 스노우 보드 2명에서 경추부의 골절이나 탈구가 발생하였다. 헬멧을 쓴 경우 헬멧을 착용하지 않은 경우에 비하여 경추부 염좌의 빈도는 통계학적으로 유의하게 높았으며(p<0.001), 헬멧을 착용하지 않은 경우 헬멧을 착용한 경우에 비하여 좌상의 빈도가 유의하게 높았다(p<0.05). 그러나 골절, 탈구에서는 헬멧을 쓴 경우와 그렇지 않은 경우를 비교하였을 때 수상빈도의 유의한 증가는 관찰되지 않았다(p>0.05). 결론: 본 연구에서 헬멧이 스키와 스노우 보드에서 공히 추가적인 경추 손상의 발생과 심각도를 증가시키지 않았고, 대인 손상시에 헬멧의 사용은 경추부 염좌의 빈도가 통계학적으로 유의하게 증가되었으나 좌상의 빈도는 감소하였다. 그러나 추가적인 생체 역학적 연구가 필요 할 것으로 사료된다.