손잡이 너비, 높이, 수평 각도가 손수레 운전에 필요한밀기, 들기, 회전 힘에 미치는 영향

김경아 ( Kyoung Ah Kim ),이호철 ( Ho Cheol Lee ),송영웅 ( Young Woong Song ) 한국안전학회(구-한국산업안전학회) 2011 한국안전학회지 Vol.26 No.1

This study evaluated the effects of the handle width(shoulder width, 1.25×shoulder width, 1.5×shoulder width), height(3 levels : knee, medium, knuckle) and horizontal angle(0°, 10°) on the pushing, lifting, and twisting strengths which were required for carrying single or two wheel barrows. Twelve healthy college students(male) participated in the experiment. In each experimental condition(3×3×2=18), the subjects exerted three forces(pushing, lifting, and twisting clockwise). The experimental conditions and three forces were tested in random order, and a minimum 2 minutes of rest was provided between exertions. Results showed that the mean and maximum pushing forces showed greater values when the horizontal angle was 0° than 10°(p=0.016). However, the three independent variables had no statistically significant effects on the lifting forces(p>0.1). The mean and maximum twisting forces increased as the handle width became larger(p<0.05). Also, there was a marginal effect of the horizontal angle(p=0.065) on the twisting force. From the results of this study, the horizontal angle of 0° and the wider handle width were suggested for the design of single-wheel barrows

어린이 놀이시설의 소재 색상에 따른 유해중금속 분석 연구

허선혜 ( Sun Hae Huh ),원종일 ( Jong Il Weon ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.2

The content of hazardous heavy metal of materials used in playground facility for children was investigated using X-ray fluorescence (XRF) and inductively coupled plasma (ICP) analyses, In order to examine the content of hazardous heavy metals according to the material color, four colors, i.e., green, red, yellow and blue, were categorized on the materials used. The highest lead content is observed in the yellow plastic samples. The yellow samples with relatively high lead content show that the chrome content is also high. This can explained that lead chromate, so-called chromium yellow, is normally used as a main pigment to express the yellow color. Therefore, it is concluded that hazardous heavy metal detected in the materials of playground facility for children is due to the pigments used for coloring. Based on above findings, the relationship between the color of materials used in playground facility for children and the content of hazardous heavy metal is discussed.

오토크레졸의 MSDS 연소특성치의 적정성 연구

하동명 ( Dong Myeong Ha ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.2

For the safe handling of o-cresol, this study was investigated the explosion limits of o-cresol in the reference data. The flash points and AITs(auto-ignition temperatures) by ignition delay time were experimented. The lower flash points of o cresol by using closed-cup tester were experimented in 77 ℃ and 80 ℃. The lower flash points of o-cresol by using open cup tester were experimented in 86 ℃ and 87 ℃. This study measured relationship between the AITs and the ignition delay times by using ASTM E659 tester for o-cresol. The AIT of o-cresol was experimented as 495 ℃. The lower explosion limit(LEL) by the measured the lower flash point for o-cresol was calculated as 1.27 Vol%.

철근콘크리트 공동주택의 평면확장을 위한 연결부의 전단성능 평가에 관한 연구

김동백 ( Dong Baek Kim ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.2

Nowadays, remodeling cases for some apartment like Hyundai through the support of government are reported. Conventionally, balcony and aisle are extended for additional private area or balcony which is supported by new frame is extended. In extension work at site, dowel bar is conventionally inserted in old concrete slab for connection with old and new slab, however, an examination for structural safety is rarely performed prior to construction, if ever, vertical load is only considered for structural analysis. When conventionally connected structures are exposed to earthquake, the old and new structures have individual earthquake behavior with different mode, which may lead the elimination of resistance to earthquake in new structures. As of this reason, new detailing connection system which can have light weight and sufficient ductility performance is developed for application to domestic extension works. Additionally, user manual and specification are also developed for fertilization of application for the developed technology.

국내 건설현장의 시스템비계 사용 현황 분석(2)

박종근 ( Jong Keun Park ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.2

It is a tendency for enterprises in the domestic construction field to harness the system scaffolding with an aim to securing safety, despite slight increase in terms of the construction cost. Nevertheless, given that putting the system into service in reality is not accurately surveyed by far and that safety standards and methods for safe work therewith are not yet established, hazardous factors involving the system scaffolding remain latent leaving unrecognized. In this regard, the current study attempts to understand the status of implementation and use of the system scaffolding in the local construction sites as for the year 2009 and the year 2013 through questionnaire surveying and in-depth interviewing, while further proposing, based on the result thereof, ways for activating introduction of the system scaffolding in an effective and systematic manner.

파이프 서포트의 좌굴특성에 대한 지지조건의 영향

이진섭 ( Jin Seop Lee ),이연수 ( Yeon Su Lee ),오태근 ( Tae Keun Oh ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.2

Recently, a lot more disasters in the temporary structures happen because the stabilities of the temporary structures are disregarded by the reduction of the unit cost, using defective materials, the existing materials and so on. Pipe supports, which are one of the temporary structures, are basically used for the most constructing works such as buildings, bridges, plants and so on. In the most sites, adequate support installations of the pipe supports have not been performed although the presence of the guideline legally and institutionally. In this study, therefore, the collapse accidents of the pipe supports were investigated on the basis of theoretical analysis as well as the buckling tests by simulating the site support condition. Both the theocratical analysis and test results show that the buckling load in the fixed ends is at least 4 times larger than one in the pinned ends. This results will be utilized for safety assurance as well as accident prevention the in the field application.

셀프 피어싱 리베팅한 Al-5052 접합부의 피로강도 평가

강세형 ( Se Hyung Kang ),황재현 ( Jae Hyun Hwang ),김호경 ( Ho Kyung Kim ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.3

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 pamp and life time of cycle N, P(amp)=715xN(-0.166) and P(amp)=1967.3xN(-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).

CFRP 적층판의 충격손상이 잔류 굽힘 피로강도에 미치는 영향

양용준 ( Yong Jun Yang ),양인영 ( In Young Yang ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.3

CFRP composites are used as primary structural members in various industrial fields because their specific strength and specific stiffness are excellent in comparison to conventional metals. Their usage is expanding to high added-value industrial fields because they are more than 50% lighter than metals, and have excellent heat resistance and wear resistance. However, when CFRP composites suffer impact damage, destruction of fiber and interface delamination occur. This causes an unexpected deterioration of strength, and for this reason it is very difficult to ensure the reliability of the excellent mechanical properties. Therefore, for the destruction mechanism in bending with impact damage, this study investigated the reinforcement data regarding various external loads by identifying the consequential strength deterioration. Specimens were damaged by impact with a steel ball propelled by air pressure. Decrease in bending strength caused by the tension and compression of the impact side, and depending on the lamination direction of fiber and interface inside the specimen. From the bending test it was found that the bending strength reduced when the impact energy increased. Especially in the case of compression on the impact side, as tensile stress occurred at the damage starting point, causing rapidfailure and a substantially reduced failure strength.

접지시스템에 사용되는 접속요소의 열화특성 분석

길형준 ( Hyoung Jun Gil ),송길목 ( Kil Mok Shong ),김영석 ( Young Seok Kim ),김종민 ( Chong Min Kim ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.2

This paper describes the analysis of deterioration characteristics for connection factor used in grounding system. The connection method of grounding system is specified in IEC standard. In order to analyze the deterioration characteristics for connection factor, deterioration test was carried out when the connection factor was buried in salt water and underground. The test connection factors were C-type sleeve, clamp, and exothermic welding. As a consequence, most of the connection factor was corroded, and the electrical resistance decreased after deterioration. The analytical results can be used to establish the safety of grounding system.

전동차 제동장치의 고장데이터와 비용함수를 고려한 유지보수 정책에 관한 연구

한재현 ( Jae Hyun Han ),김종운 ( Jong Woon Kim ),구정서 ( Jeong Seo Koo ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.3

Railway vehicle equipment goes back again to the state just before when failure by the repair. In repairable system, we are interested in the failure interval. As such, a statistical model of the point process, NHPP power law is often used for the reliability analysis of a repairable system. In order to derive a quantitative reliability value of repairable system, we analyze the failure data of the air brake system of the train line 7. The quantitative value is the failure intensity function that was modified, converted into a cost-rate function. Finally we studied the optimal number and optimal interval in which the costs to a minimum consumption point as cost-rate function. The minimum cost point was 194,613 (won/day) during the total life cycle of the braking system, then the optimal interval were 2,251days and the number of optimal preventive maintenance were 7 times. Additionally, we were compared to the cost of a currently fixed interval(4Y) and the optimum interval then the optimal interval is 3,853(won/day) consuming smaller. In addition, judging from the total life, “fixed interval” is smaller than 1,157 days as “optimal interval”.