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티타늄 합금판재(Ti-6Al-4V)의 온간 소성변형특성(2)
박진기(J. G. Park),박노광(N. K. Park),김영석(Y. S. Kim),J. H. Kim 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
Titanium alloy sheets have excellent specific strength and corrosion resistance as well as good performance at high temperature. Recently, titanium alloys are widely employed not only aerospace parts but also bio prothesis and motorcycle However, due to the low formability and large spring back at room temperature, titanium alloy sheets were usually formed by slow forming or hot forming with heating die and specimen. In the sheet metal forming area, FE simulation technique to optimize forming process is widely used. To achieve high accuracy FE simulation results, Identification of material properties and deformation characteristic such as yield function are very important. In this study, uniaxial tensile of Ti-6Al-4V alloy sheet with thickness of 1.0㎜ were performed at elevated temperature of 400℃~600℃. Also, uniaxial compression tests with special jig were performed characterize the yield locus of Ti-6AI-4V alloy sheet at 600℃. The experimental results for yield locus are compared with new yield function which was proposed in this study. The new yield function can describe not only the anisotropic of material but also asymmetry behavior between tension and compression.
티타늄 합금판재(Ti-6Al-4V)의 고온 소성변형특성(1)
박진기(J. G. Park),김정한(J. H. Kim),박노광(N. K. Park),김영석(Y. S. Kim) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
Titanium alloy sheets have excellent specific strength and corrosion resistance as well as good performance at high temperature. Recently, titanium alloys are widely employed not only aerospace parts but also bio prothesis and motorcycle However, due to the low formability and large spring back at room temperature, titanium alloy sheets were usually formed by slow forming or hot forming with heating die and specimen. in the sheet metal forming area, FE simulation technique to optimize forming process is widely used. To achieve high accuracy FE simulation results, Identification of material properties and deformation characteristic such as yield function are very important. In this study, uniaxial tensile and biaxial tensile test of Ti-6Al-4V alloy sheet with thickness of 1.0mm were performed at elevated temperature of 873K. Biaxial tensile tests with cruciform specimen were performed until the specimen was breakdown to characterize the yield locus of Ti-6Al-4V alloy sheet. The experimental results for yield locus are compared with the theoretical predictions based on Von Mises, Hill, Logan-Hosford, and Balat’s model. Among these Logan-Hosford’s yield criterion well predicts the experimental results.
비타민 A와 D의 공급제한이 거세 한우의 육질등급에 미치는 영향
김완영,박진기,조성용,남기택,여준모,Kim, W.Y.,Park, J.K.,Cho, S.Y.,Nam, K.T.,Yeo, J.M. 국립한국농수산대학교 교육개발센터 2016 현장농업연구지 = Journal of practical agricultural resear Vol.18 No.1
Sixty Hanwoo steers(15 months of age; 409±29.2 kg of BW) were used to evaluate the effects of dietary vitamins A and D restriction on carcass characteristics. Steers were allotted randomly to 1 of 4 treatments: Control(diet supplemented with vitamins A, D and E), -A (diet supplemented with vitamins D and E), -D(diet supplemented with vitamins A and E) and -AD(diet supplemented with vitamin E only). Steers were fed the experimental diet for a period of 8 months(until 23 months of age), and then supplemented with vitamins A and D at 0.05% of the diet(as fed-basis) from 24 to 26 months of age, and at 0.1% of the diet from 27 to 31 months of age(harvesting time). Dietary restriction of vitamins A and D did not affect DM intake, daily gain and feed conversion ratio. But the concentration of serum retinol was significantly(P<0.05) decreased by vitamin A restriction with the lowest concentration being seen at 23 months of age(345.0 ㎍/L and 326.7㎍/L for control and -D treatment versus 169.3 ㎍/L and 175.4 ㎍/L for -A and -AD treatments). The serum concentration of 25(OH)D<sub>3</sub> was also decreased significantly(P<0.05) by vitamin D restriction and the lowest concentration was seen at 18 months of age(53.7ng/ml and 61.8ng/ml for control and - A treatment versus 24.0 ng/ml and 24.5 ng/ml for -D and -AD treatments). After the restriction period of vitamins A and D, the concentrations of retinol and 25(OH)D<sub>3</sub> for - A, -D and -AD treatments were recovered at those of control. Dietary restriction of vitamins A and D did not affect carcass weight, backfat thickness, ribeye area, quality grade and yield grade. But marbling score was significantly increased by vitamin A restriction compared with control(6.73, 6.87 and 5.73 for -A, -AD and control, respectively). The results of the present study suggested that dietary vitamin A restriction could improve marbling score in Hanwoo steers.
김완영,박진기,여준모,Kim, W.Y.,Park, J.K.,Yeo, J.M. 국립한국농수산대학교 교육개발센터 2015 현장농업연구지 = Journal of practical agricultural resear Vol.17 No.1
Vitamin A exerts a broad range of effects on many essential life processes. But, since vitamin A is known to negatively affect the development of adipocytes, extensive research has been conducted to improve marbling score in beef cattle by feeding vitamin A-deficient diets. In Japan, the method of fattening Wagyu cattle using vitamin A-deficient diets has been widely adapted. Recently, the method of feeding vitamin A-deficient diets in Korean native cattle (Hanwoo) has been spread by feed companies and TMR plants. But proper guidelines in feeding vitamin A-deficient diets should be provided, otherwise it can adversely affect the health of cattle. To maximize marbling score, a controlled level of vitamin A in blood needs to be maintained and the proper period for feeding vitamin A-deficient diets should be adapted. This review was conducted to highlight the regulatory effects of vitamins A on adipocyte differentiation, and offer a potential guideline for improving beef quality grades in Hanwoo.
김완영,박진기,조성용,남기택,여준모,Kim, W.Y.,Park, J.K.,Cho, S.Y.,Nam, K.T.,Yeo, J.M. 국립한국농수산대학교 교육개발센터 2016 현장농업연구지 = Journal of practical agricultural resear Vol.18 No.1
Vitamin D plays a vital role in maintaining blood concentrations of Ca and P. In lipid metabolism, vitamin D is also known to negatively affect the development of adipocytes, but it has received little attention with regard to improve marbling score in beef cattle via restricting its supply. Recently, the method of feeding fat soluble vitamins(including vitamin D)-deficient diets in Korean native cattle (Hanwoo) has been spread by feed companies and TMR plants. But proper guidelines in feeding vitamin D-deficient diets should be provided, otherwise it can adversely affect the health of cattle. To maximize marbling score, a controlled level of vitamin D in blood needs to be maintained and the proper period for feeding vitamin D-deficient diets should be provided. This review was conducted to highlight the regulatory effects of vitamins D on adipocyte differentiation, and provide information on improving beef quality grades in relation to feeding vitamin D-deficient diets in beef cattle.
친환경농산물 인증기관의 신뢰도 제고방안 - 민간인증기관 설문조사 결과를 바탕으로 -
신용광,박진기,Shin, Y.K.,Park, J.K. 국립한국농수산대학교 교육개발센터 2015 현장농업연구지 = Journal of practical agricultural resear Vol.17 No.1
The purposes of this study is to draw up some measures for improving the reliability of certificate bodies of environmentally-friendly agricultural products in Korea. For the purpose, this study investigated the current states of certification system through a survey of the private certificate bodies. Based on the survey, the main goals of this study are as follows : First, the main reason of providing the certification services is the academic-industrial collaboration(21.7%) followed by the revenue seeking of the organizations (20.0%). Second, the average number of cases per private certificate bodies is 277 cases for 1,195 farms, and the average net revenue per authority is estimated as 16.84 million Won with the average total revenue of 262.09 million Won and the average total cost of 255.04 million Won. Third, in order to improve the reliability of the certificate bodies requires a variety of policy options.