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송진태,권종상 대한금속재료학회(대한금속학회) 1980 대한금속·재료학회지 Vol.18 No.3
AISI 4340鋼의 强度와 靭性에 미치는 高溫加工熱處理(HTMT)의 效果에 대하여 調査硏究하였다. 本 實驗에서 HTMT는 austenite安定 領域中 低溫部인 850℃에서 行하였다. 加工度는 0%에서 58%까지, 燒戾溫度는 室溫을 비롯하여 250℃에서 650℃까지 각각 行하였고, 현미경조직은 광학현미경, 透過電子顯微鏡(TEM)과 走査電子顯微鏡(SEM)을 利用하여 관찰하였다. 本 硏究에 의하면 HTMT한 경우에는 HTMT를 하지않은 것에 비하여 强度와 靭性이 向上되었고, HTMT를 통해 加工度가 클수록 그리고 燒戾溫度가 높을수록 subgrain구조가 形成되어 微細化 되어갔다. HTMT를 받은 4340鋼의 强度와 靭性의 向上은 組織의 subgrain化에 기인하며 加工後 550℃에서 燒戾시킨 鋼의 强靭化에 기여하는 主要한 强化機構는 結晶組織의 微細化라 思慮된다. An investigation was carried out on the effect of high temperature thermomechanical treatment (HTMT) on the strength and toughness of AISI 4340 steel. HTMT was carried out at 850℃ which is in the lower temperature range of the stable austenized region, and the degree of working was between 0% and 58%. The tempering temperature was between 250℃ and 650℃ including room temperature and microstructures of specimens were observed by optical microscope, transmission electron microscope(TEM), and scanning electron microscope (SEM). The results showed that HTMT increased the strength and toughness of steel compared to conventional heat-treatment and produced the subgrain structures which become finer with increasing degree of working and tempering temperature. It seems that the improvement in strength and toughness of this steel resulting from HTMT is attributed to the formation of subgrain structure, and the refinement of structure is the predominent factor contributing to improved strength and toughness of the steels tempered at 550℃.
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송진태,권종상 대한금속재료학회(대한금속학회) 1980 대한금속·재료학회지 Vol.18 No.5
高硅素의 Fe-Si 合金粉末로 되는 壓粉燒結鐵心의 磁氣的性質과 硬度를 조사하고 그들의 特性을 金屬組織學的인 面에서 고찰하였다. 粒度를 달리하는 各各의 Fe-6.5% Si粉末을 8∼9ton/㎠ 의 壓力으로 成形시켰고 壓粉體는 1250℃∼1400℃의 수소분위기속에서 燒結되었다. Fe-6.5% Si壓粉燒結鐵心의 자기특성은 壓粉體의 밀도가 클수록 向上되었고 소결온도가 높을수록 우수하였다. 特히 保磁力과 기계적성질(硬度)은 鐵粉末鐵心보다 우수하였고 一般硅素電磁鋼板이 比較하여 손색이 없었다. 結論的으로 6.5%Si을 함유하는 高硅素鋼壓粉鐵心의 자기특성은 먼저 壓粉體의 密度를 될수 있는 대로 크게 하고 다음에 높은 은도에서 소결할 때, 보다 우수한 값을 가졌다. 그리고 그 磁化機構는 고온소결에 의한 氣孔의 제거와 조직의 粗大化에 기인하는 것이라 思慮되었다. 그리하여 密度는 壓粉燒結鐵心의 자기적성질과 기계적 성질을 向上시키는 支配的인 因子이라 믿어진다. Magnetic properties and hardness of sintered cores made of Fe-Si alloy powder containing high silicon were studied and the mechanism bringing about their characteristics is examined by metallographic methods. Fe-6.5%Si powders with different particle sizes were compacted under pressures of 8∼9ton//㎠ and sintered at 1250℃∼1400℃ in hydrogen atmosphere. The magnetic properties of Fe-6.5%Si sintered cores were improved with increasing the green density of core and sintering temperature. Especially, coercive force and hardness of sintered cores compared favorably with compressed iron powder cores and were almost comparable to electrial steel sheets. It may be concluded that the higher the density the better the magnetic properties of compacted core, high temperature sintering provides further improvement to them, and their mechanism is attributed to the elimination of porosity and the coarse-grained microstructures. Therefore, it seems that density (or porosity) is the predominant factor controlling magnetic properties and mechanical properties of compacted core.
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황선홍,박선우,손종상,박정미,권성주,최익선,김영호,Hwang, S.H.,Park, S.W.,Son, J.S.,Park, J.M.,Kwon, S.J.,Choi, I.S.,Kim, Y.H. 대한의용생체공학회 2011 의공학회지 Vol.32 No.2
The femoral nerve innervates the quadriceps muscles and its dermatome supplies anteromedial thigh and medial foot. Paralysis of the quadriceps muscles due to the injury of the femoral nerve results in disability of the knee joint extension and loss of sensory of the thigh. A child could walk independently even though he had injured his femoral nerve severely due to the penetrating wound in the medial thigh. We measured and analyzed his gait performance in order to find the mechanisms that enabled him to walk independently. The child was eleven-year-old boy and he could not extend his knee voluntarily at all during a month after the injury. His gait analysis was performed five times (GA1~GA5) for sixteen months. His temporal-spatial parameters were not significantly different after the GA2 or GA3 test, and significant asymmetry was not observed except the single support time in GA1 results. The Lower limb joint angles in affected side had large differences in GA1 compared with the normal normative patterns. There were little knee joint flexion and extension motion during the stance phase in GA1 The maximum ankle plantar/dorsi flexion angles and the maximum knee extension angles were different from the normal values in the sound side. Asymmetries of the joint angles were analyzed by using the peak values. Significant asymmetries were found in GA1with seven parameters (ankle: peak planter flexion angle in stance phase, range of motion; ROM, knee: peak flexion angles during both stance and swing phase, ROM, hip: peak extension angle, ROM) while only two parameters (maximum hip extension angle and ROM of hip joint) had significant differences in GA5. The mid-stance valleys were not observed in both right and left sides of vertical ground reaction force (GRF) in the GA1, GA2. The loading response peak was far larger than the terminal stance peak of vertical ground reaction curve in the affected side of the GA3, GA4, GA5. The measured joint moment curves of the GA1, GA2, GA3 had large deviations and all of kinetic results had differences with the normal patterns. EMG signals described an absence of the rectus femoris muscle activity in the GA1 and GA2 (affected side). The EMG signals were detected in the GA3 and GA4 but their patterns were not normal yet, then their normal patterns were detected in the GA5. Through these following gait analysis of a child who had selective injuries on the knee extensor muscles, we could verify the actual functions of the knee extensor muscles during gait, and we also could observe his recovery and asymmetry with quantitative data during his rehabilitation.
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