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曺 棕 鉉 全南大學校開發硏究所 1964 農業科學技術硏究 Vol.2 No.-
Castor oil is dehydrated by heating at 240℃ under a pressure of 20mmHg with NaHSO₄ and NaHS0₃ as catalysts, and the dehydrated castor oil is combined with maleic anhydride as much as 9% while avoiding gel formation. By this result, oil's drying properties are somewhat lowered in proportion to the amount of combined maleic anhydride. However, after neutralizing the free acid radicals introduced to fatty acid. it readily emulsifies in water and it's dried coating shows better resistance against water. acid and alkalie.
SS41村 熔接部의 疲勞龜裂傳播에 미치는 殘留應力의 影響
李龍福,金鍾鉉,趙顯億 弘益大學校 1988 弘大論叢 Vol.20 No.2
In this study submerged arc welded the welding structural steel(SS41) was selected as an application model. On condition that stress ratios were 0.5, 0.3, 0.05, the relaxation of the residual stress was measured according to the number of repeated cycles, and the experimental values were compared with the values expected by the superposition of residual stress relaxation. The result are summarized as follows : 1. Welding residual stress is conspicuously reduced depend on the increase of repeated cycles, that is, the effect of welding residual stress on the crack propagation is gradually reduced with the increase of repeated cycles. 2. The error bet ween the experimental values and expected values which are considered only initial residual stress can be reduced by consideration of residual stress relaxation according to repeated cycles. The expected values depend on this method agree to experimental results of fatigue fracture behavior. 3. In case of welded metal, unlike base metal, rate of initial crack ropagation don't show up large difference because the difference of effective stress ratio(Reff) is decreased very much by addition to tensile residual stress.