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Aluminum Alloy 용접재의 피로균열성장거동 연구
정영석(Young-Seok Chung),최용식(Yong-Shick Choy),이환우(Hwan-Woo Rhee) 한국해양공학회 1989 韓國海洋工學會誌 Vol.3 No.1
The fatigue crack growth behavior in a type Al-Alloy 5052-H38 welded joint was investigated. In particular experimental results on the effects of redistributed compressive residual stress over various stress(R=0.l, 0.3, 0.5) on the mode I fatigue crack growth behavior were reviewed. At the low ΔK region, the increased ΔK compared with ΔKe?? at the same da/dN in the welds is attributed to compressive residual stress introduced by welding. This effect was analyzed in the present paper by means of superposition concept of stress intensity factor whereby the applied stress intensity factor range was decreased to some lower effective value. As a rule, the value of Kres decreased gradually with increasing ΔKapp values, which is most pronounced at lower ΔK values. This behavior is attributable to a redistribution of residual stress in the specimen as the crack advances, and to residual stress relaxation. The higher applied tensile mean load(that is, higher values or the stress ratio, R)diminished the influence of compressive residual stress.
영전압 스위칭 PWM 하프 브릿지 컨버터의 모델링 및 분석
강정일(Jeong-il Kang),정영석(Young-Seok Jung),노정욱(Chung-Wook Roh),윤명중(Myung-Joong Youn) 전력전자학회 1997 전력전자학술대회 논문집 Vol.1997 No.-
The circuit effects due to the transformer primary side series equivalent inductance in the Zero Voltage Switching Pulse Width Modulated Half Bridge DCIDC Converter and its impact on the effective duty are analyzed. The steady state equations and the small signal model of the converter are derived incorporating the effects of the complementary control and the utilization of transformer primary side series equivalent inductance. The open loop plant dynamics are analyzed on the basis of the model derived. The model predictions are confirmed by experimental measurements.