Direct milling of sand molds is an important development in rapid manufacturing of sand molds. Direct milling is an effective method for manufacturing single or small batches of cast parts. This paper describes experi...Direct milling of sand molds is an important development in rapid manufacturing of sand molds. Direct milling is an effective method for manufacturing single or small batches of cast parts. This paper describes experimental investigations to find sand blocks with the appropriate strength, to describe wear patterns of different tools (high-speed steel (HSS), carbide, and polycrystalline diamond (PCD) tools), and to analyze sand mold cutting mechanisms. The results show that the PCD tool outperformes the other tools in terms of tool life. Average flank wear and micro-tipping are the dominant tool failure modes in the sand mold milling process. With a flank wear limit of 0.3 mm, the PCD tool works continuously for about 70 h under the experimental conditions. The experimental results show that the cutting mechanism for direct milling sand molds differs from metal cutting.展开更多
The shoots with good functional leaves were selected, from which cutting slips with the length of about 20 cm were cut, and 2 nodes were left for the ones with long sections. All leaves could be kept or 1/3 of each le...The shoots with good functional leaves were selected, from which cutting slips with the length of about 20 cm were cut, and 2 nodes were left for the ones with long sections. All leaves could be kept or 1/3 of each leaf could be cut. The cutting depth was that making the bottom node touch the substrate, and the cutting slips with short nodes should have 1/3 of the length insert in the soil. Each pot was planted with 2 - 3 cutting slips, and the substrate around the cutting slips was pressed by hands, followed by enough watering. And then white plastic bags were used to cover the pots, which were then placed in the place with the shading rate of 75%. The method had low costs but good landscape effect, promising with good development prospects, which could provide references for the promotion of out- of-season rapid propagation technology of Antigonon leptopus in tropical areas.展开更多
Both Cu60Ni38Co2 and Cu60Ni40 alloy were naturally cooled after rapid solidification from the liquid phase.The transformation law of the microstructure characteristics of the rapidly solidified alloy with the change o...Both Cu60Ni38Co2 and Cu60Ni40 alloy were naturally cooled after rapid solidification from the liquid phase.The transformation law of the microstructure characteristics of the rapidly solidified alloy with the change of undercooling(ΔT)was systematically studied.It is found that the two alloys experience the same transformation process.The refinement structures under different undercoolings were characterized by electron backscatter diffraction(EBSD).The results show that the characteristics of the refinement structure of the two alloys with low undercooling are the same,but the characteristics of the refinement structure with high undercooling are opposite.The transmission electron microscopy(TEM)results of Cu60Ni38Co2 alloy show that the dislocation network density of low undercooled microstructure is lower than that of high undercooled microstructure.By combining EBSD and TEM,it could be confirmed that the dendrite remelting fracture is the reason for the refinement of the low undercooled structure,while the high undercooled structure is refined due to recrystallization.On this basis,in the processing of copper base alloys,there will be serious work hardening phenomenon and machining hard problem of consciousness problems caused by excessive cutting force.A twodimensional orthogonal turning finite element model was established using ABAQUS software to analyze the changes in cutting speed and tool trajectory in copper based alloy ultrasonic elliptical vibration turning.The results show that in copper based alloy ultrasonic elliptical vibration turning,cutting process parameters have a significant impact on cutting force.Choosing reasonable process parameters can effectively reduce cutting force and improve machining quality.展开更多
基金Supported by the National Natural Science Foundation of China(No. 50775092)the China International Science and Technology Cooperation Project (No. 2008DF71250)
文摘Direct milling of sand molds is an important development in rapid manufacturing of sand molds. Direct milling is an effective method for manufacturing single or small batches of cast parts. This paper describes experimental investigations to find sand blocks with the appropriate strength, to describe wear patterns of different tools (high-speed steel (HSS), carbide, and polycrystalline diamond (PCD) tools), and to analyze sand mold cutting mechanisms. The results show that the PCD tool outperformes the other tools in terms of tool life. Average flank wear and micro-tipping are the dominant tool failure modes in the sand mold milling process. With a flank wear limit of 0.3 mm, the PCD tool works continuously for about 70 h under the experimental conditions. The experimental results show that the cutting mechanism for direct milling sand molds differs from metal cutting.
基金Supported by the Special Fund for the Research,Development,Demonstration and Popularization of Applied Technology of Hainan Province(ZDXM-2015001)
文摘The shoots with good functional leaves were selected, from which cutting slips with the length of about 20 cm were cut, and 2 nodes were left for the ones with long sections. All leaves could be kept or 1/3 of each leaf could be cut. The cutting depth was that making the bottom node touch the substrate, and the cutting slips with short nodes should have 1/3 of the length insert in the soil. Each pot was planted with 2 - 3 cutting slips, and the substrate around the cutting slips was pressed by hands, followed by enough watering. And then white plastic bags were used to cover the pots, which were then placed in the place with the shading rate of 75%. The method had low costs but good landscape effect, promising with good development prospects, which could provide references for the promotion of out- of-season rapid propagation technology of Antigonon leptopus in tropical areas.
基金Funded by the Basic Research Projects in Shanxi Province(202103021224183)。
文摘Both Cu60Ni38Co2 and Cu60Ni40 alloy were naturally cooled after rapid solidification from the liquid phase.The transformation law of the microstructure characteristics of the rapidly solidified alloy with the change of undercooling(ΔT)was systematically studied.It is found that the two alloys experience the same transformation process.The refinement structures under different undercoolings were characterized by electron backscatter diffraction(EBSD).The results show that the characteristics of the refinement structure of the two alloys with low undercooling are the same,but the characteristics of the refinement structure with high undercooling are opposite.The transmission electron microscopy(TEM)results of Cu60Ni38Co2 alloy show that the dislocation network density of low undercooled microstructure is lower than that of high undercooled microstructure.By combining EBSD and TEM,it could be confirmed that the dendrite remelting fracture is the reason for the refinement of the low undercooled structure,while the high undercooled structure is refined due to recrystallization.On this basis,in the processing of copper base alloys,there will be serious work hardening phenomenon and machining hard problem of consciousness problems caused by excessive cutting force.A twodimensional orthogonal turning finite element model was established using ABAQUS software to analyze the changes in cutting speed and tool trajectory in copper based alloy ultrasonic elliptical vibration turning.The results show that in copper based alloy ultrasonic elliptical vibration turning,cutting process parameters have a significant impact on cutting force.Choosing reasonable process parameters can effectively reduce cutting force and improve machining quality.
