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이금화,구경희,김재훈,윤서현,권영국,남기우,Lee, Gum-Hwa,Gu, Kyoung-Hee,Kim, Jae-Hoon,Yun, Seo-Hyun,Kwon, Yung-Kug,Nam, Ki-Woo 한국산업융합학회 2022 한국산업융합학회 논문집 Vol.25 No.5
Using the fatigue limit (△σ<sub>unsm</sub>) and residual stress (σ<sub>r</sub>) of the UNSM smooth specimen, the harmless maximum crack depth (α<sub>hml</sub>) according to the crack aspect ratio (As) was evaluated. α<sub>hml</sub> evaluated the reliability in the relationship between the minimum crack depth (α<sub>NDI1</sub>, α<sub>NDI2</sub>) detectable by nondestructive inspection(NDI) and the crack depth (α<sub>25</sub>, α<sub>50</sub>) that reduces the fatigue limit by 25% and 50%. All α<sub>hml</sub> was determined by the crack depth. The α<sub>hml</sub> of 80N UNSM with high σ<sub>r</sub> and high △σ<sub>unsm</sub> was found to be large. σ<sub>r</sub> in the depth direction had a much effect on α<sub>hml</sub>. Since α<sub>hml</sub>>α<sub>50</sub>(As=0.6-0.1) and α<sub>hml</sub>>α<sub>25</sub>, α<sub>25</sub> and α<sub>50</sub>(some range) can secure the safety and reliability. Since α<sub>hml</sub><α<sub>50</sub> (As=1. 0-0. 6), it cannot be made harmless by UNSM. So safety and reliability cannot be secured. α<sub>NDI1</sub> and α<sub>NDI2</sub> are larger than α<sub>25</sub>, α<sub>25</sub> cannot be detected by NDI. α<sub>NDI1</sub> and α<sub>NDI2</sub> are smaller than α<sub>50</sub>, α<sub>25</sub> can detected by NDI.
서브제로 온도 및 시간이 다른 STS316L의 탄성파 특성
이금화,구경희,탁영준,권영국,신기항,남기우,Lee, Gum-Hwa,Gu, Kyoung-Hee,Tak, Young-Joon,Kwon, Yung-Kug,Shin, Ki-Hang,Nam, Ki-Woo 한국산업융합학회 2022 한국산업융합학회 논문집 Vol.25 No.5
In this study, STS316L rolled at five rolling degrees were treated with two types of subzero temperatures for 10, 30, and 60 minutes, respectively, and the dominant frequencies of elastic waves was investigated. The dominant frequency was higher as the subzero temperature was lower and the subzero treatment time was longer at each rolling degree. On the other hand, the dominant frequency was higher as the elongation decreased. In the time-frequency analysis for subzero temperature and time of the specimen with a rolling degree of 33%, the dominant frequency was higher at a subzero temperature of -196℃ than -50℃ regardless of subzero treatment time.