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최성삼,구양,허정식,Choi, S.S.,Koo, Y.,Heo, J.S. 한국기계가공학회 2002 한국기계가공학회지 Vol.1 No.1
In the grinding process, the degree of the sharpness in wheel gram affects the surface roughness and the dimensional accuracy. If a wheel with dull grains is used, the grinding force will be increased and the surface roughness deteriorated. To produce a precision component, the magnitude of parameters related to the wear amount of a grinding wheel has to be limited. In this study, a variation of the grinding force and the surface roughness were measured to seek the machining characteristics of the W A and CBN wheels. From the wear amount of the grinding wheel and the removal rate of workpiece, the grinding ratio was calculated. And also the wheel life was determined at a rapid decreasing point of the grinding ratio. The difference between the surface of wheel-workpiece before grinding and after wheel life was clearly verified with a microscopic photo.
0.5T<sub>m</sub> 이하에서의 AZ31 마그네슘합금의 크리이프 변형과 단시간 파단수명예측
강대민,안정오,전성호,구양,심성보,Kang, D.M.,An, J.O.,Jeon, S.H.,Koo, Y.,Sim, S.B. 한국소성가공학회 2008 소성가공 : 한국소성가공학회지 Vol.17 No.8
The initial strain, the applied stress exponent, the activation energy, and rupture time in AZ31 magnesium alloy have been measured in order to predict the deformation mechanism and rupture life of creep over the temperature range of 423-443K. Creep tests were carried out under constant applied stress and temperature, and the lever type tester and automatic temperature controller was used for it, respectively. The experimental results showed that the applied stress exponent was about 9.74, and the activation energy for creep, 113.6KJ/mol was less than that of the self diffusion of Mg alloy including aluminum. From the results, the mechanism for creep deformation seems to be controlled by cross slip at the temperature range of 423-443K. Also the higher the applied stress and temperature, the higher the initial strain. And the rupture time for creep decreased as quadratic function with increasing the initial strain in double logarithmic axis.