Laser assisted machining (LAM) has difficulties in estimating temperature after applying a LAM process due to its very small heat input area, large energy and movement. In particular, in the case of laser assisted t...Laser assisted machining (LAM) has difficulties in estimating temperature after applying a LAM process due to its very small heat input area, large energy and movement. In particular, in the case of laser assisted turning (LAT) process, it is more difficult to estimate the temperature after preheating because it has a shape of ellipse when a laser heat source is rotated. A prediction method and thermal analysis method for heat source shapes were proposed as a square shaped member was preheated. The temperature distribution was calculated according to the rotation of the member. Compared with the results of the former study, the maximum temperature of the calculation results, 1 407.1 ℃, is 8.5 ℃ higher than that of the square member, which is 1 398.6 ℃. In a LAT process for a square member, the maximum temperature is 1 850.8 ℃. It is recognized that a laser power control process is required because square members show a maximum temperature that exceeds a melting temperature at around a vertex of the member according to the rotation.展开更多
For laser assisted machining,shape of preheating laser heat source is changed irregularly because of complexity of material shape.So,the preheating temperature should be controlled by adjusting the feed rate or the la...For laser assisted machining,shape of preheating laser heat source is changed irregularly because of complexity of material shape.So,the preheating temperature should be controlled by adjusting the feed rate or the laser power.Thermal analyses of the laser assisted machining process for inclination planes were performed.By analyzing the obtained temperature profile,a proper feed rate control method was proposed according to the inclination angles.In addition,the temperature distribution of the cross section after feed rate control was predicted.The correlation equation between inclination angles and adjusted proper feed rate was proposed.The results of this analysis can be used to predict the preheating effect on workpiece and can be applied as a preheating temperature control method in laser assisted machining processes.展开更多
Temperature evolution in the laser aided direct metal deposition (LADMD) process has considerable influence on the micro-structure and properties of the final part. A 3D transient finite element model was developed to...Temperature evolution in the laser aided direct metal deposition (LADMD) process has considerable influence on the micro-structure and properties of the final part. A 3D transient finite element model was developed to study the temperature evolution during the multilayer LADMD process. To make the property analysis from thermal history easier, a critical temperature specific to thermal history was defined and the distribution of it in the part was also discussed. The simulation results indicated that the critical temperature can make the property analysis from thermal history easier. Thermal history of all the deposited materials was similar. It was also concluded that process parameters needed to be time-varying according to the real-time temperature field during the process.展开更多
Cube-like Ag-Ag2MoO4 composite has been successfully prepared in the presence of PVP (potyvinylpyrrolidone) via a facile microwave-assisted hydrothermal process. Studies of its photocatalytic performance in the deco...Cube-like Ag-Ag2MoO4 composite has been successfully prepared in the presence of PVP (potyvinylpyrrolidone) via a facile microwave-assisted hydrothermal process. Studies of its photocatalytic performance in the decomposition of RhB indicate that the cube-like Ag-Ag2MoO4 composite exhibits good catalytic activities under visible-light irradiation. The face that Ag pro- motes the absorption of visible light may be attributed to the surface plasmon resonance. Further XRD characterization after recycle photocatalytic tests confirms that partial Ag~ ions in Ag2MoO4 have been reduced to metallic Ag. Reaction temperature, reaction time and the amount of PVP have also been studied and found to play crucial roles in the formation of the cube-like microstructures.展开更多
基金Project(70004782)supported by the Regional Strategic Technology Development Program of the Ministry of Knowledge Economy(MKE),KoreaProject(2011-0017407)supported by National Research Foundation(NRF)of KoreaWork financially supported by the Second Stage of Brain Korea 21 Projects
文摘Laser assisted machining (LAM) has difficulties in estimating temperature after applying a LAM process due to its very small heat input area, large energy and movement. In particular, in the case of laser assisted turning (LAT) process, it is more difficult to estimate the temperature after preheating because it has a shape of ellipse when a laser heat source is rotated. A prediction method and thermal analysis method for heat source shapes were proposed as a square shaped member was preheated. The temperature distribution was calculated according to the rotation of the member. Compared with the results of the former study, the maximum temperature of the calculation results, 1 407.1 ℃, is 8.5 ℃ higher than that of the square member, which is 1 398.6 ℃. In a LAT process for a square member, the maximum temperature is 1 850.8 ℃. It is recognized that a laser power control process is required because square members show a maximum temperature that exceeds a melting temperature at around a vertex of the member according to the rotation.
基金Project(2011-0017407)supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MEST)
文摘For laser assisted machining,shape of preheating laser heat source is changed irregularly because of complexity of material shape.So,the preheating temperature should be controlled by adjusting the feed rate or the laser power.Thermal analyses of the laser assisted machining process for inclination planes were performed.By analyzing the obtained temperature profile,a proper feed rate control method was proposed according to the inclination angles.In addition,the temperature distribution of the cross section after feed rate control was predicted.The correlation equation between inclination angles and adjusted proper feed rate was proposed.The results of this analysis can be used to predict the preheating effect on workpiece and can be applied as a preheating temperature control method in laser assisted machining processes.
基金supported by the National Natural Science Foundation of China (Grant No. 10832011)
文摘Temperature evolution in the laser aided direct metal deposition (LADMD) process has considerable influence on the micro-structure and properties of the final part. A 3D transient finite element model was developed to study the temperature evolution during the multilayer LADMD process. To make the property analysis from thermal history easier, a critical temperature specific to thermal history was defined and the distribution of it in the part was also discussed. The simulation results indicated that the critical temperature can make the property analysis from thermal history easier. Thermal history of all the deposited materials was similar. It was also concluded that process parameters needed to be time-varying according to the real-time temperature field during the process.
基金supported by the National Basic Research Program of China (2013CB922102)the National Natural Science Foundation of China(21021062)the US National Science Foundation (CHE-1012173)
文摘Cube-like Ag-Ag2MoO4 composite has been successfully prepared in the presence of PVP (potyvinylpyrrolidone) via a facile microwave-assisted hydrothermal process. Studies of its photocatalytic performance in the decomposition of RhB indicate that the cube-like Ag-Ag2MoO4 composite exhibits good catalytic activities under visible-light irradiation. The face that Ag pro- motes the absorption of visible light may be attributed to the surface plasmon resonance. Further XRD characterization after recycle photocatalytic tests confirms that partial Ag~ ions in Ag2MoO4 have been reduced to metallic Ag. Reaction temperature, reaction time and the amount of PVP have also been studied and found to play crucial roles in the formation of the cube-like microstructures.