Bolt와 Band Strip으로 構成된 締結要素의 作用 토크 및 軸荷重 變化에 대한 構造解析

서용위 仁濟大學校 2006 仁濟論叢 Vol.21 No.1

Band strip과 볼트로 조립된 Suspension Band 구조물에 대해 나사의 토크가 부품의 구조적 안전성에 미치는 영향을 분석하였다. 볼트 토크에 의해서 발생하는 축하중과 이에 따른 응력상태를 유한요소 방법을 이용한 이론해석과 strain gage를 활용한 실험적 방법을 통해 그 결과를 비교하였다. 특히 실험에서는 볼트 토크만의 변화에 따른 band strip의 응력변화와, 토크와 부가적인 외부 축하중을 가했을 때의 응력변화 두 가지 경우에 대한 응력을 측정하여 Suspension Band의 안전성을 평가하였다. 실험 결과 볼트토크에 비례하여 Band 구조물의 등가응력은 증가하는 것으로 나타났다. 또한, 일정 토크와 부가적 외부 축하중이 동시에 작용했을 때 외부 축하중의 변화가 Band의 구조적 안전성에 미치는 영향은 거의 무시할 만 하였다. A suspension band assembled with band strip and bolt joint is analyzed for the structural safety under the applied bolt torques. The resultant stresses due to the corresponding axial forces by the applied torque were compared each other with the results obtained from the theoretical finite element and experimental strain gage methods. In the experiment, both cases of induced stresses were measured to evaluate the structural safety of the suspension band when the bolt torque alone is applied, and when both the torque and additional external axial force are applied. From the experimental results, it is found that the equivalent stresses of the band structure are proportional to the applied bolt torques. Also, additional external axial forces under the applied pre-torque had a negligible effect on the structural safety of the band structure.

직교 초정밀 다이아몬드 선삭에서 공구선단의 미세형상이 절삭에 미치는 영향

徐湧威 인제대학교 1998 仁濟論叢 Vol.14 No.1

공칭경사각이 서로 다른 천연 다이아몬드 공구인 세 개의 New Tool과 본 실험 전에 사용경력이 있는 Worn Tool 한 개를 사용하여 초정밀 직교 절삭실험을 행하였다. 실험전 공구인선의 미세형상을 AFM(Atomic Force Microscope)으로 측정한 후 절삭분력을 측정하여 이 미세형상의 차이에 의한 절삭분력비를 분석하였다. 실험결과 음의 공칭경사각의 변화에 의한 절삭분력비는 절삭깊이가 마이크로 미터 이하에서 음의 유효경사각의 변화에 의한 분력비의 변화 경향과 유사하였으며, 이 경우 공칭경사각보다는 유효경사각이 절삭메카니즘을 지배하는 것으로 나타났다. Experimental investigation of orthogonal ultraprecision diamond turning has been carried out using three new tools which are differing in nominal rake angles and one worn tool which has cutting history before the current study. Before cutting, detailed cutting tool edge was examined under the AFM. The resulting force ratio, based on the measured cutting force components, has been analysized to see the effect of the detailed cutting edge. The result shows that the force ratio from the tools with negative nominal rake angle showed similar trend with that from the tools with negative effective rake angle at submicrometer depths of cut. In this case, effective rake angle rather than nominal rake angle is shown to govern the cutting mechanism.

Abrasive Waterjet에 의한 원형절단 Kerf 형상의 특성

서용위 인제대학교 2012 仁濟論叢 Vol.27 No.1

A 10 mm thick A15052 was machined straightly and circularly using abrasive waterjets to investigate the machined quality. Experimental works were carried out under the pump pressure of 300 MPa and 0.3 mm orifice inner diameter with #80 garnet abrasives. The ranges of traverse rate applied were from 200 to 760 mm/min for straight cut and 100 to 460 mm/min for 10 mm diameter circular cut. After machining kerf widths at jet entry and exit, tapers and surface roughness of the surfaces were measured and compared each other for both the cuttings. The ratio of kerf width at jet entry for circular cut with respect to straight cut over the overlapped traverse rate of 200≤ v ≤ 480 mm/min was 1.15 and that at jet exit was 1.24, hence the kerf width for circular cut was appeared greater than that for straight cut. On the contrary, the taper generated at the identical range of traverse rate was rather smaller for circular cut by 90% compared with that of straight cut. Also the average surface roughness of circular cut surface was appeared to have about 96.7% of the straight cut surfaces over the overlapped traverse rate, indicated a little smoother surfaces for circular cut. Though not pronounced the surface topography of circular cut revealed to have more regular and repeating peaks and valleys in general within the range of current experimental study.

超精密加工 工作物 表面下層의 構造的 擧動

徐湧威 인제대학교 2001 仁濟論叢 Vol.16 No.1

초정밀가공 정삭시의 절삭분력을 이용하여 공작물 표면하층의 구조적 거동을 Slider model로 이상화하여 이론적으로 예측하였다. 공작물 표면하층의 전체적인 응력분포는 탄성해석과 소성해석 결과가 서로 유사한 형태를 보였으며 등가응력은 절삭방향의 전방하향으로 치우쳐져 있고 후방으로는 Trailing edge 형태의 거동을 보였다. 소성변형층 두께의 이론적 예측치는 New tool의 경우 50-100nm, Worn tool의 경우는 1.02-1.09 ㎛로 유사한 경우의 실험치 2-3㎛ 보다 낮게 나타났다. 이 표면 소성변형층 두께 예측 결과는 표면완전성의 개선을 위한 후속공정의 정밀도에 따라 유용하게 이용될 수 있을 것이다. Using the published data in literatures for ultraprecision finish machining, subsurface structural behavior of a workpiece has been theoretically predicted by idealization of the process as a slider model on a semi-infinite body. The stress distributions of the workpiece subsurface showed similar pattern for two results of elastic analysis and elasto-perfectly plastic analysis, and the direction of the equivalent stress was downward toward the cutting direction and had trailing edge at the back. The theoretically estimated ranges of plastically deformed thickness for new tool were 50-100 nm, and were 1.02-1.09 ㎛ for worn tool, which showed smaller than the experimental results of 2-3 ㎛ for similar cases.

구조용 강과 열가소성 플라스틱의 연삭입자 워터넷가공 특성

서용위 인제대학교 2011 仁濟論叢 Vol.26 No.1

Structural steel SS400 and engineering thermoplastic MC Nylon have been cut under various cutting conditions using abrasive waterjet machining(AWJM) technology. The 3, 12, and 20 ㎜ thick SS400 and 15, 32, 42 ㎜ thick MC Nylon were cut under the pump pressure of 250-320 ㎫ and the standoff distance(SOD) of 2-5 ㎜ using a 1.0 ㎜ focusing tube with 0.3 ㎜ diamond nozzle. After cutting the quality of the specimen in terms of kerf width, taper, and surface finish were measured to characterize the machinability of the materials. The maximum traverse rate for the largest thickness reached up to 180 ㎜/min for SS400, and 330 ㎜/min for MC Nylon, and were linearly increased for smaller thicknesses and higher pump pressures. The kerf taper for MC Nylon was greater than that of SS400 which indicates that the plastics can generate greater taper than metals under the similar AWJM conditions. The overall trend of machined surface roughness appeared to be somewhat higher near the jet entry and showed decreasing and increasing pattern as approaching toward jet entry of the machined surface. The SEM observation revealed that the machined surface of MC Nylon has many fine plowing and micro burrs with curled ends jut out from the surface, which seems to deteriorate the surface quality. This seems to be due to the intrinsic viscoelastic long chained characteristics of polymerized thermoplastics.

Waterjet Peening에 의해 생성된 표면특성의 변화에 관한 연구

서용위 인제대학교 2010 仁濟論叢 Vol.25 No.1

Structural carbon steel SM45C was waterjet peened in air to investigate the induced residual stresses and resulting surface characteristics of the material, Experimental works were carried out under the pump pressure of 100-300 MPa, standoff distance(SOD) of 20-60 mm, traverse rate from 40 to 100 mm/min using fanjet nozzle with 0,33 mm in inner diameter and diffusion angles of 10, 15 and 20 °. After the peening the erosion-peening transition in terms of SOD, characteristics of the surface topography, and resulting residual stresses were evaluated using surface roughness tester and X-ray diffraction equipment. The erosion-peening transition was revealed to occur in the range of 10-58 mm SOD and erosion was generated at higher pressures, slower traverse rates and shorter SODs on the surface of the material. The peened surface topography appeared to have deep valleys and high peaks relative to the rounded shapes before peening, also the average increase in surface roughness Ra before and after the peening was measured to have less than 0,2 ㎛ for all the peening conditions. The maximum compressive residual stress of -406.9 MPa were induced, which corresponds to about 68% of the ultimate tensile strength of the material, The result of superior surface quality along with high compressive residual stress generated by the in-air waterjet peening showed a feasible application of this process for the precise surface treatment of machine elements.

산·학·연·관 컨소시엄 할성화 방안에 관한 고찰

徐湧威,元種厦 인제대학교 1998 仁濟論叢 Vol.14 No.2

현대의 기업환경은 기술변화가 가속화되고 단일기술보다는 인접기술과 연계된 복합 및 융합화 기술의 필요가 증대됨에 따라 산업체가 모든 기술을 독자개발 하거나 핵심기술을 보유한다는 것은 거의 불가능해졌다. 따라서 투자효율의 극대화 및 기술의 공유를 위해서 산ㆍ학ㆍ연ㆍ관 협동의 필요성이 제기된다. 이로써 자원과 기술을 공유하거나 교류나 활용하는 등의 상호보완이 가능하며 시너지 효과를 거둘 수 있다. 특히 이러한 협력관계 중에서 대학이 선도적인 역할을 하여야 한다. 산학협동이 활성화되기 위해서는 무엇보다도 각 주체상호간의 신뢰가 중요하다. 중소기업의 입장에서는 최소의 비용으로 최대의 효과를 창출하려는 노력뿐만 아니라 특정 고유분야에 역량을 집중해야 한다. 대학의 입장에서는 수행 연구과제로부터 반드시 실용적 결과를 도출하겠다는 의지가 있어야 할 것이다. 국가경쟁력 제고는 국가경제의 중요한 관건이며, 이러한 경쟁력은 기술력에서부터 시작된다. 산학협동은 교육기관인 대학과 산업현장인 기업간의 협력을 말하는 것이며, 기업이 제공하는 현장을 대학에서 익히고 대학에서 개발한 기술을 기업에서 상품화하는 것으로 이해할 수 있다. 이들간의 상호 보완과 이해의 폭을 넓히기 위해서는 실효성 있는 제도 및 지원시책이 완비되어야 한다. In modern industrial environment the technological advancement is accelerated and the need for joining of adjacent technologies are increased to make complex or melting technologies, hence it is almost impossible for each industry to develop by itself or to have core technologies. To maximize the effect of investment and to utilize developed technologies the necessity of the collaboration is claimed among industries, universities, research institutes and (local) government. Through the collaboration, resources and technologies which the institutes hold can be exchanged, utilized, and complemented each other to bring a synergy effect. Among those institutes, universities must play a key role. The most important factor to make the consortium successful would be the credibility among the participants. From the point of view of the small and medium sized industries, they have to create the maximum effect with least cost but also have to concentrate on their unique areas of technological development. For the universities, they have to have a strong willingness to make their research topic a useful results. The national competitiveness is a key factor for the national economy, and this competitiveness may be due to the technological achievement. To have the mutual complementation and understanding among the interest parties for the consortium, effective and realistic regulations and supporting polices or laws must be completed.

김해시 벤처기업 유치를 위한 방안

원종하,서용위 인제대학교 김해발전연구소 1998 김해발전연구 Vol.2 No.1

Abrasive Waterjet Machining Characteristics of Epoxy Plastics

서용위(Yongwie Seo) 한국자동차공학회 2007 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-

Engineering epoxy plastic material was machined with abrasive waterjet (AWJ) to investigate its machinability under various cutting conditions. Maximum traverse rates for a couple of thicknesses of the material were experimentally determined. The characteristics of kerf width and surface quality generated by the AWJ machining were investigated. The kerf width was comparable with the focus tube size at the jet entry and the surface roughness was ranged several micrometers near the jet entrance region, and was observed to increase at the jet exit of the workpiece. The overall range of the AWJ machined surface roughness was identified in the scope of the experimental study, and some of the operating conditions were recommended for acceptable surface quality.

Waterjet Peening에 의한 SUP9강의 압축잔류응력 유발 최적조건

서용위(Yongwie Seo),조지룡(Ji Ryong Cho),임익섭(Ik-Sub Lim),여명헌(Myeong-Heon Yeo) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.11

Waterjet peening of spring steel SUP9 was conducted in-air to investigate the optimum peening conditions for the induced compressive residual stress which is beneficial to improve the endurance limit. The erosion-peening transition was identified as a critical standoff distance within the experimental envelope. Using X-ray diffraction technique the residual stresses generated by the waterjet peening was measured and analyzed to characterize the optimum peening conditions for the maximum compressive stress on the specimen surface. Also the surface roughnesses of peened specimen were measured at the non-eroded surfaces and the results represented the superior surface quality with minimal changes in surface topography before and after the peening process.