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열처리를 이용한 자동차 서스펜션 코일 스프링의 가속 피로 시험 방안에 대한 연구
신정규(J.K. Shin),신동열(D.Y. Shin),손태준(T.J. Sohn) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4
내구 시험은 제품의 내구성을 평가하는 방법으로 제품 개발의 마지막 단계이다. 자동차 부품 개발도 마찬가지인데, 특히 내구시험의 특성상 시간이 오래 걸리게 되는데, 이는 파손까지 한계 내구시험을 수행함에 있어 시간과 에너지가 필요한 고비용 시험의 특징이다. 이러한 내구시험의 시간 부하를 줄이기 위해 다양한 가속 내구 시험 기법이 제안되고 있다. 본 연구에서는 가속 내구 시험 기법 중 온도를 활용하는 방법으로 풀림(Annealing)을 이용하여 스프링 제품에 부여된 압축 잔류응력을 일부 완화시켜 내구 시험 시간을 단축함으로써 제품의 결함 부위를 빠르게 찾는 것에 있다. 스프링 제품에 대하여 풀림 열처리를 통한 가속 내구 수명 시험의 결과를 소개한다. (본문의 그림 참조) Fatigue test must be performed to check whether a product under development will endure the expected product life cycle or not. The test is characterized by time-consuming method and therefore, accelerated techniques are proposed by many researchers to reduce time and energy for fatigue test. Generally, suspension coil spring is manufactured by shot-peening to expand the product life. Recently, stress-peening process is additionally applied to meet the life over one million cycle time. If the fatigue test with coil spring as manufactured is performed, it will take one-million cycle time. A fatigue test is performed by 1 Hz, the test will be finished by 12 days. In this study, an accelerated fatigue test is proposed by heat-treated coil spring to reduce compressive residual stress on the entire coil spring. Depending on the temperature and its duration time, it is known that the residual stress is reduced. Under a selected heat treatment condition, a coil spring life cycle is reduced. This technique can be applied to the industrial field to reduce the fatigue test cost.
신정규(J.K.Shin),이정욱(J.W. Yi),이해주(H.J. Lee),박경진(G.J. Park) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
A rotor bar in an induction motor for electric railway is studied from a design viewpoint. The design<br/> process is divided into two stages; conceptual design and detailed design. In conceptual design, overall<br/> configuration is determined. A computer program is developed for the conceptual design. Various formulae<br/> are developed for analysis. They are derived from elementary and advanced elasticity. Design equations are<br/> made from the formulae and they are programmed with Graphic User Interface (GUI) for user convenience.<br/> Structural optimization is adopted for the detailed design. Finite element method is used for analysis. A design<br/> problem is defined to minimize mass or maximum stress while constraints are satisfied.
이상일(S.I. Yi),신정규(J.K. Shin),박경진(G.J. Park) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월
Optimum sensitivity analysis (OSA) is the process to find the sensitivity of optimum solution with respect to the parameter in the optimization problem. The prevalent OSA methods calculate the optimum sensitivity as a post-processing. In this research, a simple technique is proposed to obtain optimum sensitivity as a result of the original optimization problem, provided that the optimum sensitivity of objective function is required. The parameters are considered as additional design variables in the original optimization problem. And then, it is endowed with equality constraints to penalize the additional variables. When the optimization problem is solved, the optimum sensitivity of objective function is simultaneously obtained as Lagrange multiplier. Several mathematical and engineering examples are solved to show the applicability and efficiency of the method compared to other OSA ones.