• 대한기계학회논문집 C: 기술과 교육
• /
• 제4권2호
• /
• pp.93-99
• /
• 2016

엔진 성능 혹은 효율의 극대화는 엔진 구성품들을 점점 더 극한의 환경에서 장시간 운용되게 요구하고 있다. 이를 위해 엔진 제작사 혹은 연구소는 초내열합금, 냉각 설계 최적화, 열차폐 코팅 개선 등의 노력과 동시에 재료 모델링, 유한요소해석, 최적설계 등의 수치 해석 기법을 적용하여 좀 더 정교한 설계 및 해석을 수행하고 있다. 본 연구에서는 연소기 뒤에 위치하는 1 단 고압터빈 노즐의 끝벽 냉각 설계와 열차폐 코팅에 따른 일방향 응고 재료인 1 단 고압터빈 블레이드의 저주기 피로 수명에 대한 영향을 고찰하고자 한다. 이를 위해 경계 조건인 고온 및 고압의 연소 가스에 의한 노즐 및 블레이드의 금속 온도는 복합 열 전달 해석을 통해 얻고, 이 결과를 받아 블레이드의 구조 해석 및 저주기 피로수명을 평가하여 노즐 냉각설계와 열차폐 코팅의 영향을 분석하였다.

• 디자인학연구
• /
• 제11권2호
• /
• pp.47-57
• /
• 1998

본 연구는 중소기업의 측면에서 산학협동 참여 행동에 영향을 미치는 요인을 조사하였다. 광주, 전남지역의 375 중소기업을 대상으로 실증분석 조사하였으며 대상기업의 제품디자인 최근 상황을 시장에서의 경쟁적 지위 측면에서 조사하였다. 연구결과는 대상기업들이 대학과의 산학협동 활동은 매우 적으나 제품디자인 개발을 목적으로 대학과 긴밀한 관계구축을 원하고 있는 것으로 나타났다. 산학협동 연구 및 공동개발을 희망하는 기업과 희망하지 않는 기업을 구분시키는 요인을 조사하기 위하여 다양한 t-검증을 실시하였다. 그 결과 경제수단으로서 디자인의 중요성을 인식, 현재의 디자인 능력수준, 디자인 관련특허권 보유 유무가 산학협동 참여 의사에 큰 영향을 미치고 있다고 나타났다. 본 연구는 중소기업과 대학 간의 산학협동을 높일 수 있는 방안을 제시하는데 시사점을 제공하고자 하였다.

• Archives of Plastic Surgery
• /
• 제35권3호
• /
• pp.279-282
• /
• 2008

Purpose: It is known that the chronic absence of unilateral breast can cause spine curvature. The artificial breast manufactures take up the position of that possibility. This study was designed to evaluate the influence of the mastectomy on the spine and appearance of scoliosis among women who wanted delayed breast reconstruction. ted delayed breast reconstruction. Methods: The study population consisted of 47 women who underwent delayed breast reconstruction at our Department of Plastic Surgery from April 2001 to May 2007. The whole spine anteroposterior and lateral X-ray was taken to evaluate the Cobb's angle. As a general rule a Cobb angle of 10 is regarded as a minimum angulation to define scoliosis. We evaluated Cobb's angle and drew a correlation between the duration of the mastectomy state and the weight of the mastectomy specimen. Results: There were no family history of scoliosis, and no numbness or weakness in the upper or lower extremities. They had normal reflex and experienced no tenderness of the perispinal area. The Spearman Correlation Coefficient between Cobb's angle and the period that took time from the mastectomy to the X-rays and analysis between Cobb's angle and specimen weight was 0.032 and-0.115. there were no correlation between Cobb's angle and time, or between Cobb's angle and specimen weight. Conclusion: lthough the patients attribute their back pain and distorted posture to having received an one-sided mastectomy, it is unlikely that one-sided mastectomy causes spinal deformity and scoliosis.

• Journal of Welding and Joining
• /
• 제34권1호
• /
• pp.59-67
• /
• 2016

The automotive manufactures increase their use of lightweight materials to improve fuel economy and energy usage has a significant influence on the choice of developing materials. To meet this requirements manufacturers are replacing individual body parts with lightweight metals, for these the process treating and painting surfaces is changing. The pre-coated steels are newly developed to avoid the conventional complex and non-environmental painting process in the body-in-white car manufacturing. The development of new joining techniques is critically needed for pre-coated steel sheets, which are electrically non-conductive materials. In the present study, dissimilar combination of pre-coated steel and galvanized steel sheets were joined by the self-piercing rivet, adhesive bonding and hybrid joining techniques. The tensile shear test and free falling high speed crash test were conducted to evaluate the mechanical properties of the joints. The highest tensile peak load with large deformation was observed for the hybrid joining process which has attained 48% higher than the self-piercing rivet. Moreover, the hybrid and adhesive joints were observed better strain energy compared to self-piercing rivet. The fractography analyses were revealed that the mixed mode of cohesive and interfacial fracture for both the hybrid and adhesive bonding joints.

• 한국산학기술학회논문지
• /
• 제11권9호
• /
• pp.3155-3160
• /
• 2010

최근 자동차 산업은 고효율 자동차의 개발에 박차를 가하고 있으며 이에 따라 차체 경량화 및 내식성 방지를 위한 고강도강 및 도금강의 사용이 증가하고 있다. 이에 따라 본 연구에서는 자동차 차체에 쓰이는 3종의 다른 강판에 대하여, 겹침 순서에 따른 용접 특성을 시뮬레이션 기법을 이용하여 분석하였다. 자동차 차체에 많이 사용되는 EDDQ 급의 도금강판 0.7t와 인장강도 440 MPa급의 440R 1.2t, 그리고 AHSS (Advanced High Strength Steel)인 DP 590 0.2t 판재에 대하여 겹치기 순서에 따른 용접 특성을 시뮬레이션 하였고, 너겟 성장 곡선 및 전류에 따른 너겟의 크기로 그 용접성을 분석하였다. 또한 용접 시 발생되는 각 접촉부의 접촉저항을 이용하여 겹침순서에 따른 너겟의 크기를 분석하였으며, 이를 통해 최적의 겹치기 순서를 제안할 수 있었다.

• 한국의류학회지
• /
• 제34권1호
• /
• pp.126-137
• /
• 2010

This study examines the effects of trust and commitment on firm performance in the apparel manufacturer-contractor relationships. A total of 92 apparel manufactures participated in the study. Factor analysis, Cronbach's alpha coefficient, and multiple regression analysis were conducted for the statistical analysis. Two factors of trust were identified: credibility and benevolence. Two factors of commitment were identified: affective commitment and calculative commitment. Three factors of firm performance were identified: customer service performance, finance performance, and product performance. The credibility of the apparel manufacture in a contractor had a significant positive effect on the affective commitment of an apparel manufacturer and on the calculative commitment in a contractor. Meanwhile, the benevolence of the apparel manufacture on a contractor had a significant positive effect on the affective commitment of an apparel manufacturer on a contractor. The credibility of the apparel manufacture on a contractor was positively related to customer service performance, finance performance, and product performance. The benevolence of the apparel manufacture on a contractor was positively related to customer service performance and finance performance of an apparel manufacture. The affective commitment of the apparel manufacture in a contractor was positively related to service performance. The calculative commitment of the apparel manufacture on a contractor was positively related to finance performance and to the product performance of an apparel manufacture. The results of this study provides practical guidelines toward exchange partners of apparel manufacturers as to how to facilitate from performance in apparel manufacturer-contractor relationships.

• 산업공학
• /
• 제13권3호
• /
• pp.378-387
• /
• 2000

As the globalization of manufacturing companies continues, the scope of dependence between these companies and distributors, and other suppliers are growing very rapidly since no one company manufactures or distributes the whole product by themselves. And, the need to increase the efficiency of the whole supply chain is increasing. This paper deals with a multi-plant lot-sizing problem(MPLSP) which happens in a decentralized manufacturing system of a supply chain. In this study, we assume that the whole supply chain is driven by a single source of independent demand and many levels of dependent demands among manufacturing systems in the supply chain. We consider setup cost, transportation cost and time, and inventory holding cost as a decision factor in the MPLSP. The MPLSP is decomposed into two sub-problems: a planning problem of the whole supply chain and a lot-sizing problem of each manufacturing system. The supply chain planning problem becomes a pure linear programming problem and a Generalized Goal Decomposition method is used to solve the problem. Its result is used as a goal of the lot-sizing problem. The lot-sizing problem is solved using the CPLEX package, and then the coefficients of the planning problem are updated reflecting the lot-sizing solution. This procedure is repeated until termination criteria are met. The whole solution process is similar to Lagrangian relaxation method in the sense that the solutions are approaching the optimum in a recursive manner. Through experiments, the proposed closed-loop hierarchical planning and traditional hierarchical planning are compared to optimal solution, and it is shown that the proposed method is a very viable alternative for solving production planning problems of decentralized manufacturing systems and in other areas.

• 한국정밀공학회지
• /
• 제18권4호
• /
• pp.142-150
• /
• 2001

Automotive manufactures have taken more interests in tailored sheet metals for improving the rigidity, weight reduction, crash durability, and cost savings so that their application to auto-bodies has been increased. However, since the tailored sheet metals do not behave like un-welded sheet metals in press forming operations, the stamping engineers no longer rely only on conventional forming techniques. Futhermore, there is no clear understanding of the characteristics of welded metal which influence the overall press formability of tailored sheet metals. Recently, the computer simulations are prevailing for the evaluation of the formability. Unfortunately, the mechanical property of tailored sheet metal has to be quantitatively defined in the simulation. In this study, the analytical equations are formulated in order to find the mechanical properties of the welded metal in the tailored sheet metal welded by co$_2$laser. Based on force distribution assumption, the constitutive behavior of the welded metal is investigated using uniaxial tensile test results of base metals and tailored sheet metal. Then, the strength coefficient, work-hardening exponent, and plastic strain ratio of laser-welded metal are calculate from those of base metals and tailored sheet metal. In addition, the existence of weld defects in the welded metal is indirectly detected by examining the slop of strength coefficient of the welded metal.

• 대한교통학회지
• /
• 제22권4호
• /
• pp.57-68
• /
• 2004

자동차 리콜제도를 선진화시키는 것은 자동차의 결함으로 발생하는 교통사고로부터 인간의 생명을 보호한다는 측면뿐만 아니라 결함 없는 자동차의 제작에 기여하여 결국에는 자동차 산업의 대외경쟁력을 강화시켜 자동차 산업을 발전시키는 데에도 매우 중요한 사항이다. 자기인증제는 제작사의 자율권을 최대한 부여한다는 취지에서 도입된 제도지만 제작된 자동차에 대한 사전검증 및 승인 없이 시장에 판매된다는 측면에서 자동차 결함의 발생 가능성은 그 만큼 크다. 따라서 자동차 리콜제도의 정착은 선택적 사항이 아닌 필수적인 과제이다. 분석결과 자동차 리콜제도는 여러 가지 이유로 인해서 자동차 제작사와 소비자 모두로부터 개선을 요구받고 있다. 본 연구에서는 리콜관련 법 제도에 대한 분석, 제작사와 소비자에 대한 의견조사를 수행하였으며 이를 토대로 문제점을 분석하고 향후의 정책방안을 제시하였다. 제시된 정책방안은 리콜대상 및 범위의 명확한 설정, 결함정보의 신속한 수집, 결함 판정의 객관성을 확보, 리콜에 대한 지속적인 모니터링 수행 등으로 구분할 수 있다.

• 한국자동차공학회논문집
• /
• 제16권1호
• /
• pp.86-92
• /
• 2008

Recently, the use of tubes in the manufacturing of the automobile parts has increased and therefore many automotive manufactures have tried to use hydro-forming technology. The hydro-forming technology may cause many advantages to automotive applications in terms of better structural integrity of the parts, lower cost from fewer part count, material saving, weight reduction, lower spring-back, improved strength and durability and design flexibility. In this study, the whole process of front engine cradle (or front sub-frame) parts development by tube hydro-forming using steel material having tensile strength of 440MPa grade is presented. At the part design stage, it requires feasibility study and process design aided by CAE (Computer Aided Design) to confirm hydro-formability in details. Effects of parameters such as internal pressure, axial feeding and geometry shape on automotive sub-frame by hydro-forming process were carefully investigated. Overall possibility of hydro-formable sub-frame parts could be examined by cross sectional analyses. Moreover, it is essential to ensure the formability of tube material on every forming step such as pre-bending, preforming and hydro-forming. At the die design stage, all the components of prototyping tools are designed and interference with press is examined from the point of geometry and thinning.