This paper researches the vibration cuttiug mechanism for ultrahard coal seam by means of a selfmade test rig in the laboratory, when cutting tool was vibrating relatively to the coal specimen A new coal cutting metho...This paper researches the vibration cuttiug mechanism for ultrahard coal seam by means of a selfmade test rig in the laboratory, when cutting tool was vibrating relatively to the coal specimen A new coal cutting method-vibration coal cutting method,was advanced’ The influence on main cutting force and unit energy consumption was investigated by changing the paramaters of vibratiou and cutting.The test data show that the vibration cutting method can reduce significantly the main cutting force and unit energy consumption at given vibration waveform and cutting object.展开更多
Ultrawide bandgap semiconductor,e.g.,diamond,is considered as the next generation of semiconductor.Here,a new orthorhombic carbon allotrope(P2_(1)2_(1)2_(1)-C16)with ultrawide bandgap and ultra-large hardness is ident...Ultrawide bandgap semiconductor,e.g.,diamond,is considered as the next generation of semiconductor.Here,a new orthorhombic carbon allotrope(P2_(1)2_(1)2_(1)-C16)with ultrawide bandgap and ultra-large hardness is identified.The stability of the newly designed carbon is confirmed by the energy,phonon spectrum,ab-initio molecular dynamics and elastic constants.The hardness ranges from 88 GPa to 93 GPa according to different models,which is comparable to diamond.The indirect bandgap reaches 6.23 eV,which is obviously larger than that of diamond,and makes it a promising ultra-wide bandgap semiconductor.Importantly,the experimental possibility is confirmed by comparing the simulated X-ray diffraction with experimental results,and two hypothetical transformation paths to synthesize it from graphite are proposed.展开更多
There were only two kinds of superhard tool material at the past, i.e. diamond and cubic boron nitride (CBN). Manmade diamond and CBN are manufactured by the middle of 20th century. Various manufacturing methods and m...There were only two kinds of superhard tool material at the past, i.e. diamond and cubic boron nitride (CBN). Manmade diamond and CBN are manufactured by the middle of 20th century. Various manufacturing methods and manmade superhard materials were developed later. They were widely used in different industry and science areas. Recently, a new kind of superhard tool material, C 3N 4 coating film, had been developed. American physical scientists, A. M. Liu and M. L. Cohen, designed a new kind of inorganic compound C 3N 4 with the theory of molecule engineering. According to calculation, it can reach or even exceed the hardness of diamond, so material scientists and technique circles draw their attention to it. A high speed steel twist drill coated with C 3N 4 film is applied to the drilling hole process on steel workpiece in cutting tests, the tool life is increased greatly. When the C 3N 4 film is coated on the cemented carbide inserts, the cutting performance is improved, but is not good enough. The data of mechanical performance and cutting tests about this kind of new tool material is given in this paper, it shows that C 3N 4 has a promising future. The anti-wear ability of cutting tool increases sharply after C 3N 4 being coated on HSS tool. Coated HSS drill also has some benefit after being reground. The tool life prolongs after C 3N 4 being coated on cemented carbide inserts, but is not so long as that of C 3N 4 coated HSS tool. When machining PRCM with C 3N 4 thin-film coated cemented carbide tool, the cutting performance is poor and it is much better when machining PRCM with PCBN, PCD compound plates and CVD thick-film coated cutting tool. Some relative aspects need to be deeply discussed and researched, e.g. the existing coating techniques is not good enough and should be improved in the future, the film thickness should be optimized and try to find out the most effective value, the binding force and mutual effect between coated film and substrate need to be studied furtherly, etc.展开更多
文摘This paper researches the vibration cuttiug mechanism for ultrahard coal seam by means of a selfmade test rig in the laboratory, when cutting tool was vibrating relatively to the coal specimen A new coal cutting method-vibration coal cutting method,was advanced’ The influence on main cutting force and unit energy consumption was investigated by changing the paramaters of vibratiou and cutting.The test data show that the vibration cutting method can reduce significantly the main cutting force and unit energy consumption at given vibration waveform and cutting object.
基金supported by the National Natural Science Foundation of China(No.51875269)the Startup Foundation of Jiangsu University of Science and Technology(No.202100000135).
文摘Ultrawide bandgap semiconductor,e.g.,diamond,is considered as the next generation of semiconductor.Here,a new orthorhombic carbon allotrope(P2_(1)2_(1)2_(1)-C16)with ultrawide bandgap and ultra-large hardness is identified.The stability of the newly designed carbon is confirmed by the energy,phonon spectrum,ab-initio molecular dynamics and elastic constants.The hardness ranges from 88 GPa to 93 GPa according to different models,which is comparable to diamond.The indirect bandgap reaches 6.23 eV,which is obviously larger than that of diamond,and makes it a promising ultra-wide bandgap semiconductor.Importantly,the experimental possibility is confirmed by comparing the simulated X-ray diffraction with experimental results,and two hypothetical transformation paths to synthesize it from graphite are proposed.
文摘There were only two kinds of superhard tool material at the past, i.e. diamond and cubic boron nitride (CBN). Manmade diamond and CBN are manufactured by the middle of 20th century. Various manufacturing methods and manmade superhard materials were developed later. They were widely used in different industry and science areas. Recently, a new kind of superhard tool material, C 3N 4 coating film, had been developed. American physical scientists, A. M. Liu and M. L. Cohen, designed a new kind of inorganic compound C 3N 4 with the theory of molecule engineering. According to calculation, it can reach or even exceed the hardness of diamond, so material scientists and technique circles draw their attention to it. A high speed steel twist drill coated with C 3N 4 film is applied to the drilling hole process on steel workpiece in cutting tests, the tool life is increased greatly. When the C 3N 4 film is coated on the cemented carbide inserts, the cutting performance is improved, but is not good enough. The data of mechanical performance and cutting tests about this kind of new tool material is given in this paper, it shows that C 3N 4 has a promising future. The anti-wear ability of cutting tool increases sharply after C 3N 4 being coated on HSS tool. Coated HSS drill also has some benefit after being reground. The tool life prolongs after C 3N 4 being coated on cemented carbide inserts, but is not so long as that of C 3N 4 coated HSS tool. When machining PRCM with C 3N 4 thin-film coated cemented carbide tool, the cutting performance is poor and it is much better when machining PRCM with PCBN, PCD compound plates and CVD thick-film coated cutting tool. Some relative aspects need to be deeply discussed and researched, e.g. the existing coating techniques is not good enough and should be improved in the future, the film thickness should be optimized and try to find out the most effective value, the binding force and mutual effect between coated film and substrate need to be studied furtherly, etc.
