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하경준(KYUNG-JUN HA),박경동(KYUNG-DONG PARK) 한국해양공학회 2003 韓國海洋工學會誌 Vol.17 No.3
Shot peening is an effective method of improving the fatigue strength of components and structures. The compressive residual stress produced by surface plastic deformation with shot peening is usually regarded as the major factor in increasing fatigue strength. In this study, the influence of shot peening on corrosion was investigated. Spring steel immersed in 3.5% NaCl prior was used to evaluate the effect of shot peening on fatigue properties. The immersion test was performed on the five kinds of specimens with shot peened and unpeened. The distributions of residual stresses of shot peened spring steels were measured in an X-ray diffraction apparatus, using the two-point method. Corrosion potential, polarization curve, residual stress, etc. were investigated, based on the experimental results. From test results, the effect of shot peening on the corrosion was evaluated.
압력용기용 강의 응력비에 따른 저온 피로균열 진전특성에 관한 연구
박경동(KYUNG-DONG PARK),하경준(KYUNG-JUN HA),박형동(HEYOUNG-DONG PARK) 한국해양공학회 2001 韓國海洋工學會誌 Vol.15 No.3
In this study, CT specimens were prepared from Pressure Vessel Steel which was used for pressure vessel plates for room and low temperature service. And we got the following characteristics from fatigue crack growth test carried out in the environment of room and low temperature at 25℃, -30℃, -60℃, -80℃, -100℃ and -120℃ and in the range of stress ratio of 0.05 and 03 by means of opening mode displacement. At the constant stress ratio, the threshold stress intensity factor range △K<SUB>th</SUB> in the early stage of fatigue crack growth (Region Ⅰ) and stress intensity factor range △K in the stable of fatigue crack growth (Region Ⅱ) was increased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region. The straight line slope relation of logarithm da/dN -△K in Region Ⅱ, that is, the fatigue crack growth exponent m increased with descending temperature at the constant stress ratio. It was assumed that the fatigue crack growth rate da/dN is rapid in proportion to descending temperature in Region Ⅱ and the cryogenic-brittleness greatly affect a material with decreasing temperature.
압력용기용 강의 저온 피로크랙 하한계 특성에 관한 연구(Ⅱ)
박경동(KYUNG-DONG PARK),김정호(JUNG-HO KIM),정찬기(CHAN-GI JUNG),하경준(KYUNG-JUN HA) 한국해양공학회 2000 韓國海洋工學會誌 Vol.14 No.3
In this study, CT specimens were prepared from ASTM SA516 Gr. 70 which wasused for pressure vessel plates for room and low temperature service. And we got the following characteristics from fatigue crack growth test carried out in the environment of room and low temperature at 25℃, -60℃, -80℃ and -100℃ and in the range of stress ratio of 0.05, 0.3 by means of opening mode displacement. At the constant stress ratio, the threshold stress intensity factor range △K<SUB>th</SUB> in the early stage of fatigue crack growth (Region Ⅰ) and stress intensity factor range △K in the stable of fatigue crack growth (Region Ⅱ) were increased in proportion to descending temperature. It was assumed that the fatigue resistance characteristics and fracture strength at low temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region. The straight line slope relation of logarithm da/dN -△K in Region Ⅱ, that is, the fatigue crack growth exponent m increased with descending temperature at the constant stress ratio. It was assumed that the fatigue crack growth rate da/dN is rapid in proportion to descending temperature in Region Ⅱ and the cryogenic-brittleness greatly affect a material with decreasing temperature.