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정영화(Jung Young Hwa),김익겸(Kim lk Gyeom),남왕현(Nam Wang Hyone),장동휘(Chang Dong Huy) 강원대학교 산업기술연구소 2000 産業技術硏究 Vol.20 No.1
The 4-point bending tests have been performed in order to estimate the effect of TIG-dressing on fatigue strength and fatigue characteristics quantitatively for nonload-carrying fillet welded joints subjected to pure bending. As a result of fatigue tests, fatigue strengths of as-welded specimens have satisfied the grade of fatigue strength prescribed in specifications of korea, AASHTO and JSSC. Fatigue strength at 2 million cycles of TIG-dressing specimens have increased compared with as-welded specimens. As the result of beachmark tests, fatigue cracks occurred at several points, where the radius of curvature and flank angle in the weld bead toes were low, and grew as semi-elliptical cracks, then approached to fracture, As a result of finite element analysis, stress concentration factor in weld bead toes has closely related to the flank angle and radius of curvature, and between these, the radius of curvature has more largely mechanics approaches, the crack correction factor than flank angle. As a result of fracture mechanics approaches, the crack correction factor of test specimens has largely affected on stress gradient correction factor in case a/t is below 0.4 from the relations between stress intensity factor range estimated from FEM analysis and fatigue crack growth rate, fatigue life has been correctly calculated.
정영화(Jung Young Hwa),남왕현(Nam Wang Hyone),장동휘(Chang Dong Huy) 강원대학교 산업기술연구소 2001 産業技術硏究 Vol.21 No.1
This study is finding the most appropriate model of kangwondo watershed. To synthesize each hydrograph, It is found to several parameters which are used in existing hydrographes. then the synthestic hydrograph is compared and investigated wish many hydrographes of the rivers in kanwondo. These methods, Nakayasu, Clark, SCS are used to calculate the run-off of this watershed. When the calculated run-off is compared with real rating-curves, then it is found that the SCS method using the Clark’s concentrantion time is the best way on this area having large watershed, long river length and gentle water slope, the Nakayasu method is more suitable on this area having small watershed, short river length and steep water slope. Also it is founded from analyzing run-off hydrographes, peak run-off and peak time that the Clark’s method applied Kirpich’s concentration time way is suitable in the area of kanwondo.
역량스펙트럼 방법을 이용한 철근 콘크리트 교각의 내진성능 평가
송종걸,장동휘,정영화 江原大學校 産業技術硏究所 2004 産業技術硏究 Vol.24 No.A
To evaluate seismic performance of reinforced concrete piers two procedures for capacity spectrum method are presented. The capacity spectrum procedures include the reduction factor-ductility-period(R_(μ)-μ-T)relationship in order to construct the inelastic demand spectra from the elastic demand spectra. Application of the procedures are illustrated by example analysis. Maximum displacements estimated by the procedures are compared to those by inelastic time history analysis for several artificial earthquakes. The results show that the maximum displacements estimated by the procedures are, on overall, smaller than those by the inelastic time history analysis.
정영화,남왕현,장동휘 江原大學校 産業技術硏究所 2001 産業技術硏究 Vol.21 No.B
In the study, the fatigue strength improvement and mechanism have been estimated by the Spot-Heating treatment on welded bead toes. For this, web-gusset specimens were made without residual stresses and the others with residual stresses imposed by Spot-Heating. The 4-point bending tests were performed in order to estimate the effect of spot-heating on fatigue strength and fatigue characteristics quantitatively for non load-carrying fillet welded joints subjected to pure bending. As a result of fatigue test, fatigue strength of As-Welded specimen for non load-carrying fillet welded joints subjected to pure bending has satisfied the grade of fatigue prescribed in specifications of korea, AASHTO and JSSC. As compare with As-Welded specimen and Spot-Heating specimen have increased about 20% for the fatigue strength at 7.7×106 cycles. The Spot-Heating by reformation of the residual stress on welded bead toes has greatly affected the fatigue crack propagation life, but has slightly affected the fatigue crack initiation life.
정영화,김익겸,남왕현,장동휘 강원대학교 산업기술연구소 2000 産業技術硏究 Vol.20 No.A
The 4-point bending tests have been performed in order to estimate the effect of TIG-dressing on fatigue strength and fatigue characteristics quantitatively for nonload-carrying fillet welded joints subjected to pure bending. As a result of fatigue tests, fatigue strengths of as-welded specimens have satisfied the grade of fatigue strength prescribed in specifications of korea, AASHTO and JSSC. Fatigue strength at 2 million cycles of TIG-dressing specimens have increased compared with as-welded specimens. As the result of beachmark tests, fatigue cracks occurred at several points, where the radius of curvature and flank angle in the weld bead toes were low, and grew as semi-elliptical cracks, then approached to fracture, As a result of finite element analysis, stress concentration factor in weld bead toes has closely related to the flank angle and radius of curvature, and between these, the radius of curvature has more largely mechanics approaches, the crack correction factor than flank angle. As a result of fracture mechanics approaches, the crack correction factor of test specimens has largely affected on stress gradient correction factor in case a/t is below 0.4 from the relations between stress intensity factor range estimated from FEM analysis and fatigue crack growth rate, fatigue life has been correctly calculated.