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구경희(Kyoung-Hee Gu),이기식(Ki-Sik Lee),강석희(Seok-Hee Kang),강창룡(Chang-Yong Kang),박상현(Sang-Hyun Park),남기우(Ki-Woo Nam) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Ultra-high-strength steel structures are exposed to corrosive environments in service, and there is a risk of hydrogen assisted cracking(HAC) due to stress corrosion cracking and hydrogen embrittlement. In this paper, the HAC threshold stress intensity factor (KIHAC) and fatigue life of ultra-high-strength steel were evaluated by applying stress in a corrosive environment to prevent structures fracture. On the surface of the crack, grain boundaries were embrittled by corrosion, and the grains were clearly observed, and cracks in the surface direction propagated slightly, but cracks in the depth direction did not. Therefore, the HAC threshold stress intensity factor of the depth was determined as 1.96MPa·m<SUP>0.5</SUP>. The static fatigue limit of ultra-high strength steel (SKD11:HV670) was determined as 400MPa.
하경희,안종남,주선태,박구부,박기훈,김일석,진상근,Hah Kyoung-Hee,Ahn Chong-Nam,Joo Seon-Tea,Park Gu-Boo,Park Ki-Hoon,Kim Il-Suk,Jin Sang-Keun 한국축산식품학회 2006 한국축산식품학회지 Vol.26 No.1
This study was investigated the effect of aging at low temperature of seasoned pork with Korean traditional sauces. The samples, pork loins were cut by the shape of cube ($5{\times}15{\times}5\;cm$) and porks were seasoned with Korean tradition sauce such as soy sauce base (T1), red pepper sauce base (T2), and soybean sauce base (T3) in the same proportion of meat seasonings, respectively. The seasoned samples were stored, at $1{\pm}1^{\circ}C$ during 28 days. Surface meat color of seasoned pork was affected by the kind of sauces. Lightness of seasoned pork with soy sauce was decreased with increased in periods while red pepper sauce made it more red and soybean sauce produced a light seasoned pork, Lightness of inner meat color of seasoned pork was decreased with increased aging periods, and seasoned pork with soy sauce was lower compared to other treatments. TBARS of seasoned pork with soy sauce was lower compared to other treatments, and increased TBARS in all treatments with aging period. Total plate counts were increased with aging period, and those of seasoned pork with soy sauce were lower compared to other treatments. The microbial counts of Escherichia coli levels in all treatments was higher at the first day of aging periods. However Escherichia coli levels were decreased with increasing the aging period. Lactobacilli spp. of seasoned pork with soy sauce was not increased during aging periods, whereas other treatments were increased with aging period increased. 한국 전통 장류를 이용한 양념 돈육의 저장 안정성에 관한 연구로 돼지고기의 등심을 채취하여 $5{\times}15{\times}5\;cm$ 크기로 자른 후 육을 동일한 비율의 양념액에 침지하여 $1{\pm}1^{\circ}C$에서 28일간 숙성하면서 양념육(간장소스 양념육, T1; 고추장소스 양념육, T2; 된장소스 양념육, T3)의 품질 특성을 조사하였다. 양념육의 표면 육색은 소스의 영향을 많이 받았으며 간장 소스로 양념한 돈육의 명도는 낮게, 고추장소스로 양념한 돈육의 적색도는 높게, 된장 소스로 양념한 돈육의 명도는 높게 나타났다. 심부 육색의 명도는 모든 처리구에서 숙성기간에 따라 감소하였으며, 간장 소스로 양념한 돈육에서는 낮게 나타났다. TBARS는 간장 소스로 양념한 돈육이 다른 처리구에 비해 낮게 나타났으며 전 숙성기간 동안 증가하였다. 총균수는 모든 처리구에서 숙성기간에 따라 증가하였으며 간장 소스로 양념한 처리구가 다른 처리구에 비해 전 숙성기간 동안 낮은 총균수를 나타내었다. 대장균 수는 숙성 초기 $2.7{\sim}3.27\;log_{10}CFU/g$으로 다소 높게 나타났으나 숙성기간의 증가에 따라 처리구들에서 감소하였으며, 고추장 소스로 양념한 처리구는 숙성 14일에 된장소스로 양념한 처리구는 숙성 28일에 대장균이 나타나지 않았다. 유산균 수는 간장 소스로 양념한 처리구에서 숙성기간 동안 유산균수의 증가가 나타나지 않았으며, 고추장 소스로 양념한 처리구와 된장 소스로 양념한 처리구에서는 숙성기간에 따라 증가하였다.
레이저 및 초음파 피닝된 STS316L의 공식 부식에 관한 연구
구경희(Kyoung-Hee Gu),윤서현(Seo-Hyun Yun),남기우(Ki-Woo Nam) 대한기계학회 2022 大韓機械學會論文集A Vol.46 No.4
본 연구에서는 모재시험편, 초음파 피닝시험편, 레이저 피닝시험편을 FeCl3+HCl 용액에 침지하여 내공식성을 평가하였다. 초음파 피닝시험편은 초음파 해머핀의 충격에 의한 소성변형으로 표면 조직 입도가 작고, 깊이가 깊어질수록 모재의 조직 입도였다. 레이저 피닝시험편은 레이저 충격파에 의해 소성변형되었으나, 조직 입도의 크기 변화는 없었다. 모재시험편의 평균 비커스 경도는 약 153 HV, 초음파 피닝 및 레이저 피닝시험편의 표면 경도는 각각 약 290 및 250 HV였다. 세 가지 유형의 시험편에서 공식 부식이 관찰되었다. 레이저 피닝 및 초음파 피닝시험편은 모재보다 더 많은 공식 부식이 관찰되었다. The pitting resistance of as-received and laser and ultrasonically peened STS316L specimens was evaluated by immersion in FeCl₃ + HCl solution. The ultrasonically peened specimen had a smaller grain size owing to the plastic deformation caused by shocking induced via an ultrasonic hammer pin. However, the as-received grain size was observed at larger depths. The laser peening specimen was plastically deformed by the laser shock wave; however, no change in the grain size was observed. The average Vickers hardness of the as-received specimen was approximately 153 HV. The hardness values of the ultrasonically and laser peened specimens were approximately 290 and 250 HV, respectively. Pitting corrosion was observed for the three types of specimens. Notably, the laser and ultrasonically peened specimens exhibited a larger amount of pitting than that of the as-received specimen.