• 한국터널지하공간학회 논문집
• /
• 제16권6호
• /
• pp.573-584
• /
• 2014

본 연구에서는 로드헤더 커팅헤드 설계의 기본 사항인 절삭조건에 따른 커터작용력의 변화를 살펴보는 기초 연구를 진행하기 위하여 연암 및 보통암을 대상으로 하는 슬림 코니컬커터를 사용하여 받음각과 커터관입깊이, 커터간격의 조건에 따른 선형절삭시험을 수행하였다. 각 시험조건에서 커터작용력인 연직력, 절삭력, 구동력을 측정하였고 그 측정결과의 평균값을 사용하여 분석을 실시하였다. S/d비와 비에너지의 관계, 관입깊이와 비에너지의 관계, S/d비와 커터작용력의 관계로부터 받음각이 $50^{\circ}$, 커터간격이 12 mm, 커터관입깊이가 9 mm인 조건이 모르타르시험체에 대한 최적의 절삭조건임을 확인할 수 있었다. 특히 받음각이 $50^{\circ}$인 경우가 $45^{\circ}$인 경우에 비해 장비사양 설계를 위해 더 효과적임을 알 수 있었다.

• 터널과지하공간
• /
• 제30권6호
• /
• pp.591-602
• /
• 2020

기존의 전통적인 암석절삭방식의 한계점을 극복하고자 다양한 신개념의 암석절삭메커니즘이 연구되고 있으며, 그 중 언더커팅은 최근 연구가 수행되고 있는 기술이다. 본 논문에서는 언더커팅에 대한 기초연구로서 구동형 언더커팅에 의한 암석절삭메커니즘과 절삭에 관여하는 중요핵심변수들에 대하여 소개하였다. 구동형 언더커팅에 의한 절삭성능을 평가하기 위한 시험시스템을 구축하고 이를 활용하여 주요 핵심변수들을 변화시켜가며 구동형 언더커팅 디스크를 활용한 절삭시험을 수행하였다. 구동형 언더커팅 절삭시험으로부터 획득되는 3방향 커터작용력의 특성을 분석하였으며, ADC의 주요 절삭변수인 선형 이동속도, 법선압입깊이, 편심의 증가에 따라 3방향 커터작용력의 평균값과 최댓값은 모두 선형적으로 증가하는 결과를 나타내었다.

• 한국터널지하공간학회 논문집
• /
• 제16권6호
• /
• pp.585-597
• /
• 2014

본 연구에서는 받음각이 $45^{\circ}$인 경우에 대해 사각이 $0^{\circ}$와 $6^{\circ}$이고 S/d비가 1.3~12사이인 시험조건에 대해 슬림 코니컬커터를 사용하여 선형절삭시험동안 발생하는 커터작용력을 측정하였다. 각 시험조건에서 커터작용력인 연직력, 절삭력, 구동력을 측정하였고 그 측정결과의 평균값을 사용하여 분석을 실시하였다. 커터관입깊이가 깊어질수록 비에너지가 감소하였고 커터관입깊이에 따른 커터작용력의 변화는 사각이 $6^{\circ}$인 경우가 작게 나타났다. 이와 같은 결과로부터 사각이 $6^{\circ}$인 경우가 $0^{\circ}$인 경우에 비해 장비설계측면에서 효과적인 것으로 판단된다. 또한 $F_c/F_n$은 사각이 $6^{\circ}$일 때가 $0^{\circ}$인 경우에 비해 작게 나타났다. 그러나 사각이 있을 경우 구동력의 증가가 나타날 수 있으므로 이에 대한 고려가 필요하다.

• 한국생산제조학회지
• /
• 제7권2호
• /
• pp.9-14
• /
• 1998

One of the areas in the continuous casting process that up to this point, has not been definitively instrumented is a method of reliably locating the part of a continuously cast strand that remains liquid for a period after the outer portion has solidified. To solve the problem. Electromagnetic Trandsducers(EMAT) which operate across an air gap without the need for a coupling medium has been developed. The system was designed to employ a through transmission technique which enhanced the signal-to-noise ratio. The Al 75$\times$75mm and 75$\times$100mm simulators with 2, 4, 8, 16, 32 mm hole respectively has been produced in order to verify the developed EMAT system and to measure to liquid core in continuous casting strand. The system developed can be employed for the optimization of torch cutting speed and for the final cut length of the bloom as well as calculation of average bloom temperature.

• 한국터널지하공간학회 논문집
• /
• 제16권2호
• /
• pp.181-191
• /
• 2014

본 연구는 선형절삭시험 중에 동일한 커터 링 형상을 가진 더블디스크커터와 싱글디스크커터에 발생하는 커터작용력과 각 디스크커터 축에 발생하는 축응력 및 토크를 평가하였다. 선형절삭시험 결과, 선형절삭실험 중에 발생한 더블디스크커터의 연직력과 회전력의 평균값은 싱글디스크커터의 약 두 배 내외인 것으로 측정되었다. 더블디스크커터의 축에 작용하는 축응력의 평균값 역시 연직력과 마찬가지로 싱글디스크커터의 두 배 정도로 나타났지만, 토크의 경우에는 전체적으로 낮은 측정값을 보여 비교의 의미가 없는 것으로 판단되었다. 하지만 더블디스크커터의 연직력의 평균값이 직경 432 mm(17인치) 디스크커터의 허용하중을 상회하기 때문에 테이퍼 롤러 베어링의 내구성능에 대한 검토가 필요한 것으로 판단되었다. 또한 더블디스크커터 축에 작용하는 축응력은 싱글디스크커터의 약 두 배 정도로 발생하였지만, 일반적으로 사용하는 디스크커터 축 재료의 항복강도를 고려할 때 적용 상에 문제가 없는 것으로 나타났다.

• 생물환경조절학회지
• /
• 제22권3호
• /
• pp.284-290
• /
• 2013

본 연구는 시설재배에서 참외를 수확할 수 있는 로봇의 엔드이펙터를 개발하기 위한 전단계로서, 참외의 엔드이펙트 중에서 소프트 핸드링이 가능한 그립퍼와 참외줄기를 절단하는 커터를 설계하기 위해 참외의 기하학, 압축, 절단, 마찰 특성 등을 분석하였다. 그 결과 참외의 길이는 평균 108mm, 직경은 중간지점에서 평균 70mm, 중량은 평균 188g, 부피는 평균 333mL, 진원도는 평균 3.8mm로 나타났다. 참외의 중량(W)에 대하여 길이(L)와 직경(D2)을 변수로 하는 식 $W=L^a{\times}D_2^b$로부터 비선형 회귀분석을 실시한 결과 a는 2.0279, b는 -0.9998의 상수값을 가지는 상관관계가 있는 것으로 나타났다. 참외줄기의 지름은 평균 3.8mm이며, 참외 줄기는 중심으로부터 반경 5mm 범위 내에서 대부분 분포하였다. 참외의 항복치와 압축강도, 경도의 평균값은 각각 $36.5N/cm^2$, $185.7N/cm^2$, $636.7N/cm^2$이며, 참외 줄기의 절단력과 절단강도는 각각 $2.87{\times}10^{-2}N$와 $5.60N/cm^2$로 나타났다. 참외의 마찰계수는 고무가 0.609으로 가장 높게 나타났고, 그 다음으로 알루미늄이 0.393, 스테인레스강이 0.177, 테프론이 0.079로 나타났다. 분석된 자료를 토대로 엔드이펙터 설계시 동작에 따른 위치 오차와 안전율을 감안하여, 그립퍼의 및 커터의 크기, 선회반경, 설치위치, 구동모터의 동력, 재료 및 재질의 선정 등에 적용할 수 있을 것으로 판단되었다.

• International Journal of Precision Engineering and Manufacturing
• /
• 제9권4호
• /
• pp.74-78
• /
• 2008

High-speed tool steels are extensively used in tooling industries for manufacturing cutting tools, forming tools, and rolls. Electrical discharge machining (EDM) has been found to be an effective process for machining these extremely hard and difficult-to-cut materials. Extensive research has been conducted to identify the optimum machining parameters for EDM with different tool steels. This paper presents a fundamental study of the surface characteristics of SKH-51 tool steel machined by micro-EDM, with particular focus on obtaining a better surface finish. An RC pulse generator was used to obtain a better surface finish as it produces fine discharge craters. The main operating parameters studied were the gap voltage and the capacitance while the resistance and other gap control parameters were kept constant. A negative tungsten electrode was used in this study. The micro-EDM performance was analyzed by atomic force microscopy to determine the average surface roughness and the distance between the highest peak and lowest valley. The topography of the machined surface was observed using a scanning electron microscope and a digital optical microscope.

• 한국대기환경학회지
• /
• 제9권3호
• /
• pp.191-199
• /
• 1993

This paper describes the results of a systematic study to determine the characteristics of particle generated from various types of asbestos containing material(ACM) and manmade fiber material(MMFM) during operations of cutting and grinding in laboratory and workplace. Tests were conducted with a specially designed glove box which allowed complete sampling of the generated asbestos fibers. Specificially, air measurements were made during ACM and MMFM installation in building. All personal air samples collected were identified by polarized light microscopy(PLM), X-ray diffraction(XRD) and scanning electron microscope with energy dispersive X-ray analysis(SEM/EDXA). Also, the samples were counted by phase contrast microscope(PCM) in order to compare the results with the permissible exposure standard for workplace. Results indicate that the characterisitcs of fibers found in the roofing sheet, the ceiling and the wall insulation boards were identical to those of asbestos, while the characteristics of fibers found in the ceiling insulation board, the floor tile and the sprayed on insulation products in parking area were identical to those of asbestos, while the characteristics of fibers found in the ceiling insulation board, the floor tile and the sprayed on insulation products in parking area were identical to those of rock wool. The concentrations of airborne fibers from various building materials cut by a grinder for 5 minutes were in the ranges of 0.09 $\sim$ 1.71 fibers/cc(f/cc). The highest concentration(1.71f/cc) was found during grinding the wall insulation board which also contains rock wool. The airborne fiber concentrations generated by installing at workplace were ranged from 0.0009 to 0.029 f/cc. All asbestos fibers from the ceiling insulation board at workplace were less than 20$\mu$m in length and more than 20% of them had the average aspect ratio greater than 20. Therefore, for the purpose of decreasing asbestos and man-made fiber concentrations at the workplace, the ceiling and wall board should use strong binding material to increase the binding force with fiber. Also, the permissible exposure standard for workplace(2.0f/cc) in Korea should be constituted below the maximum avaiable concentration measured at glove box.

• 한국기계가공학회지
• /
• 제20권11호
• /
• pp.36-42
• /
• 2021

This study was conducted to analyze the effect of the gear specification and gear quality corresponding to the macro geometry on the gear transmission error. The two pairs of gears with large and small transmission errors were selected for calculation, and two pairs of gears were manufactured with different gear quality. The test gears were manufactured by two different gear specifications with ISO 5 and 8 gear quality, respectively. The transmission error measurement system consists of an input motor, reducer, encoders, gearbox, torque meter, and powder brake. To confirm the repeatability of the test results, repeatability was confirmed by performing three repetitions under all conditions, and the average value was used to compare the transmission error results. The transmission errors of the gears were analyzed and compared with the test results. When the gear quality was high, the transmission error was generally low depending on the load, and the load at which the decreasing transmission error phenomenon was completed was also lower. Even when the design transmission error according to the gear specification was different, the difference of the minimum transmission error was not large. The transmission error at the load larger than the minimum transmission error load increased to a slope similar to the slope of the analysis result.

• Asian-Australasian Journal of Animal Sciences
• /
• 제32권4호
• /
• pp.585-591
• /
• 2019

Objective: This study investigated carcass characteristics and meat quality of purebred Pakchong 5, crossbred pigs sired by Pakchong 5, and crossbred pigs sired by Duroc. Methods: Forty-eight pigs (average body weight of 22.25 kg) were composed of three groups as purebred Pakchong 5 (PP), Large $White{\times}Landrace$ pigs sired by Pakchong 5 (LWLRP), and Large $White{\times}Landrace$ pigs sired by Duroc (LWLRD). Each group consisted of eight gilts and eight barrows. At 109-day-raising period, pigs were slaughtered, and carcass characteristics were evaluated. Longissimus thoracis (LT) muscles from left side of carcasses were evaluated for meat quality and chemical composition. Data were analyzed using general linear model procedure, where group, sex, and their interaction were included in the model. Results: The PP had greater carcass, total lean, and ham percentages than crossbred pigs (p<0.05). LWLRP had thicker backfat and more carcass fat percentage than LWLRD (p<0.05). There were no differences (p>0.05) on cutting percentages from tender loin, loin, boston butt, and picnic shoulder among groups. The PP and LWLRP had larger loin eye area (LEA) than LWLRD (p<0.05). Gilts had more loin percentage and lower $L^*$ value than barrows (p<0.05). No meat color parameters ($L^*$, $a^*$, and $b^*$) were affected by groups (p>0.05). PP and LWLRP had larger muscle fiber diameters than LWLRD (p<0.05). However, water holding capacity, Warner-Bratzler shear force values, and chemical composition of LT were not affected by group or sex (p>0.05). Conclusion: Pakchong 5 purebred has good carcass and lean percentages. Compared to Duroc crossbred pigs, Pakchong 5 crossbreds have similar carcass and lean percentages, larger LEA, and slightly more carcass fat, with comparable meat quality and chemical composition. Pakchong 5 boars are more affordable for very small- to medium-scale pig producers.