Aluminum-silicon （Al-Si） alloy is very difficult to machine and diamond tools are considered by far the best choice for the machining of these materials. Experimental results in the machining of the Al-Si alloy with...Aluminum-silicon （Al-Si） alloy is very difficult to machine and diamond tools are considered by far the best choice for the machining of these materials. Experimental results in the machining of the Al-Si alloy with diamond coated inserts are presented. Considering the fact that high adhesive strength and fine surface morphology play an importance role in the applications of chemical vapor deposition （CVD） diamond films, multilayer technique combining the hot filament CVD （HFCVD） method is proposed, by which multilayer diamond-coating on silicon nitride inserts is obtained, microcrystalline diamond （MCD）/ nanocrystalline diamond （NCD） film. Also, the conventional monolayer NCD and MCD coated inserts are produced for comparison. The as-deposited diamond films are characterized by field emission scanning electron microscopy （FE-SEM） and Raman spectrum. All the CVD diamond coated inserts and uncoated insert endure the aluminum-silicon alloy turning to estimate their cutting performances. Among all the tested inserts, the MCD/NCD coated insert exhibits the perfect behavior as tool wear due to its very low flank wear and no diamond peeling.展开更多
Piezoelectric bar-shaped resonators were proposed to act as hardness sensors in the 1960 s and stiffness sensors in the 1990 s based on the contact impedance method.In this work, we point out that both multilayer and ...Piezoelectric bar-shaped resonators were proposed to act as hardness sensors in the 1960 s and stiffness sensors in the 1990 s based on the contact impedance method.In this work, we point out that both multilayer and unimorph（or bimorph） piezoelectric actuators could act as stiffness/modulus sensors based on the principle of mechanical contact resonance. First, the practical design and the performance of a piezoelectric unimorph actuator–based stiffness sensor were presented. Then the working principle of piezoelectric multilayer actuator–based stiffness sensors was given and verified by numerical investigation. It was found that for these two types of resonance-based sensors, the shift of the resonance frequency due to contact is always positive, which is different from that of the contact impedance method. Further comparative sensitivity study indicated that the unimorph actuator–based stiffness sensor is very suitable for measurement on soft materials, whereas the multilayer actuator–based sensor is more suitable for hard materials.展开更多
Tribological properties of chemical vapor deposition (CVD) diamond films greatly affect its application in the mechanical field. In this paper, a novel multilayer structure is proposed, with which multilayer diamond f...Tribological properties of chemical vapor deposition (CVD) diamond films greatly affect its application in the mechanical field. In this paper, a novel multilayer structure is proposed, with which multilayer diamond films are deposited on silicon carbide by hot filament CVD (HFCVD) method. The different micrometric diamond grains are produced by adjusting deposition parameters. The as-deposited multilayer diamond films are characterized by scanning electron microscope (SEM) and white-light interferometry. The friction tests performed on a reciprocating ball-on-plate tribometer suggest that silicon carbide presents the friction coefficient of 0.400 for dry sliding against silicon nitride (Si3N4) ceramic counterface. With the water lubrication, the corresponding friction coefficients of silicon carbide and as-deposited multilayer diamond films further reduce to 0.193 and 0.051, respectively. The worn surfaces indicate that multilayer diamond films exhibit considerably high wear resistance.展开更多
基金Project(50975177)supported by the National Natural Science Foundation of China
文摘Aluminum-silicon （Al-Si） alloy is very difficult to machine and diamond tools are considered by far the best choice for the machining of these materials. Experimental results in the machining of the Al-Si alloy with diamond coated inserts are presented. Considering the fact that high adhesive strength and fine surface morphology play an importance role in the applications of chemical vapor deposition （CVD） diamond films, multilayer technique combining the hot filament CVD （HFCVD） method is proposed, by which multilayer diamond-coating on silicon nitride inserts is obtained, microcrystalline diamond （MCD）/ nanocrystalline diamond （NCD） film. Also, the conventional monolayer NCD and MCD coated inserts are produced for comparison. The as-deposited diamond films are characterized by field emission scanning electron microscopy （FE-SEM） and Raman spectrum. All the CVD diamond coated inserts and uncoated insert endure the aluminum-silicon alloy turning to estimate their cutting performances. Among all the tested inserts, the MCD/NCD coated insert exhibits the perfect behavior as tool wear due to its very low flank wear and no diamond peeling.
基金financial support of the National Natural Science Foundation of China (Grant11090331)Support from the Chinese National Programs for Scientific Instruments Research and Development (Grant 2012YQ03007502)
文摘Piezoelectric bar-shaped resonators were proposed to act as hardness sensors in the 1960 s and stiffness sensors in the 1990 s based on the contact impedance method.In this work, we point out that both multilayer and unimorph（or bimorph） piezoelectric actuators could act as stiffness/modulus sensors based on the principle of mechanical contact resonance. First, the practical design and the performance of a piezoelectric unimorph actuator–based stiffness sensor were presented. Then the working principle of piezoelectric multilayer actuator–based stiffness sensors was given and verified by numerical investigation. It was found that for these two types of resonance-based sensors, the shift of the resonance frequency due to contact is always positive, which is different from that of the contact impedance method. Further comparative sensitivity study indicated that the unimorph actuator–based stiffness sensor is very suitable for measurement on soft materials, whereas the multilayer actuator–based sensor is more suitable for hard materials.
基金the National Natural Science Foundation of China (No. 50975177)
文摘Tribological properties of chemical vapor deposition (CVD) diamond films greatly affect its application in the mechanical field. In this paper, a novel multilayer structure is proposed, with which multilayer diamond films are deposited on silicon carbide by hot filament CVD (HFCVD) method. The different micrometric diamond grains are produced by adjusting deposition parameters. The as-deposited multilayer diamond films are characterized by scanning electron microscope (SEM) and white-light interferometry. The friction tests performed on a reciprocating ball-on-plate tribometer suggest that silicon carbide presents the friction coefficient of 0.400 for dry sliding against silicon nitride (Si3N4) ceramic counterface. With the water lubrication, the corresponding friction coefficients of silicon carbide and as-deposited multilayer diamond films further reduce to 0.193 and 0.051, respectively. The worn surfaces indicate that multilayer diamond films exhibit considerably high wear resistance.
