A TiA1N coating was deposited on a heat resistant steel X12CrMoWVNbN10-1-1 by vacuum arc ion plating. The tensile and fatigue properties of the coated steel were investigated at room temperature （RT） and 650 ℃. The...A TiA1N coating was deposited on a heat resistant steel X12CrMoWVNbN10-1-1 by vacuum arc ion plating. The tensile and fatigue properties of the coated steel were investigated at room temperature （RT） and 650 ℃. The results reveal that the TiA1N coating is compact, on which a small number of large particle and pits are present. The Ti/Al atomic ratio in the coating is about 0.94. The average hardness of the coating is 1 868 HV0.1 and the interface bonding force between TiAIN coating and the substrate is about 3 l N. The elastic modulus and the strength of the steel are improved by the deposition of TiAIN coating. The influence of the TiA1N coating on the tensile properties of the steel can be ignored at both RT and 650 ℃. Moreover, there is no obvious decrease of the fatigue limit of substrate when the steel is coated by the coating at the investigated temperature.展开更多
Squeezed quantum vacua seems to violate the averaged null energy conditions (ANEC’s), because they have a negative energy density. When treated as a perfect fluid, rapidly rotating Casimir plates will create vorticit...Squeezed quantum vacua seems to violate the averaged null energy conditions (ANEC’s), because they have a negative energy density. When treated as a perfect fluid, rapidly rotating Casimir plates will create vorticity in the vacuum bounded by them. The geometry resulting from an arbitrarily extended Casimir plates along their axis of rotation is similar to van Stockum spacetime. We observe closed timelike curves (CTC’s) forming in the exterior of the system resulting from frame dragging. The exterior geometry of this system is similar to Kerr geometry, but because of violation of ANEC, the Cauchy horizon lies outside the system unlike Kerr blackholes, giving more emphasis on whether spacetime is multiply connected at the microscopic level.展开更多
To improve the seeds pick-up precision of a vacuum plate seeder,it is important to accurately control the relative distance between suction plate and seeds layer in vibrating tray.Under the excitation of reciprocating...To improve the seeds pick-up precision of a vacuum plate seeder,it is important to accurately control the relative distance between suction plate and seeds layer in vibrating tray.Under the excitation of reciprocating vibration with a time varying interference in direction angle,the seeds motion is simulated using the discrete element method(DEM).By analyzing the seeds distribution characteristics,it was found that the seeds-mass-per-unit-area(SMA)was approximately plane distributed in the tray.Then,four square areas on the bottom of rectangular tray were divided symmetrically near the four vertices to measure the corresponding SMA respectively,and a monitoring plane model was established to predict the average SMA and total seeds mass in the tray.The prediction results of DEM simulation showed that the maximum and the mean relative errors were 6.75%and 2.85%.The influences of the normal vector of monitoring plane model and the standard deviation of SMA in four monitoring areas on the prediction errors were analyzed.A method for improving prediction accuracy by using linear regression correction was proposed,and the maximum and the mean relative errors could be reduced to 5.01%and 2.07%.When the tray was vibrated with the frequency of 11 Hz and the amplitude of 4 mm,experiments were carried out on the vacuum plate seeder test-rig.A Kalman filter was adopted to suppress the SMA measurement noise in four monitoring areas.Prediction results indicated that the maximum and the mean relative errors were 10.2%and 3.46%with the average SMA in range of 0.9-1.5 g/cm2,respectively.The paper can provide a basis for further study on the automatic control of suction plate motion according to the variation of seeds mass in the tray.展开更多
TiN,Ti1-xAIxN single layer coatings and TiN/Ti1-xAIxN multilayer coatings were deposited on SKH51 tool steel substrate by arc ion plating.The coatings were annealed in air to study the effect of aluminum and film stru...TiN,Ti1-xAIxN single layer coatings and TiN/Ti1-xAIxN multilayer coatings were deposited on SKH51 tool steel substrate by arc ion plating.The coatings were annealed in air to study the effect of aluminum and film structure on the oxidation performance.The surface morphology and structure were characterized by scanning electron microscopy and X-ray diffraction.The element distribution on the cross section was analyzed by electron probe microscopy.It is found that the oxidation resistance of these Ti1-xAlxN based coatings is mainly attributed to aluminum content in them.In comparison with the Ti1-xAlxN single layer coating,the TiN layer inserting into the Ti1-xAlxN in a multilayer coating increases the tendency of Ti diffusion toward the surface and forms a Ti-enriched top surface oxide layer,thus degrades the oxidation resistance.As far as the oxidation resistance is concerned in this study,Ti0.33Al0.67N single layer coating performs the best among all coatings.The kinetic of oxidation behavior of all coatings presents two definite stages.One is a slow oxidation growth which conforms to parabolic law,and the other presents severe mass gain with oxidation duration.The annealing time for severe oxidation initiation is responsible to Fe2O3formation in the oxide scale.展开更多
基金Funded by National Science Foundation of China(No.51172182)the Program for New Century Excellent Talents in University(No.NCET-08-0460)the 111 Project(No.B08040)
文摘A TiA1N coating was deposited on a heat resistant steel X12CrMoWVNbN10-1-1 by vacuum arc ion plating. The tensile and fatigue properties of the coated steel were investigated at room temperature （RT） and 650 ℃. The results reveal that the TiA1N coating is compact, on which a small number of large particle and pits are present. The Ti/Al atomic ratio in the coating is about 0.94. The average hardness of the coating is 1 868 HV0.1 and the interface bonding force between TiAIN coating and the substrate is about 3 l N. The elastic modulus and the strength of the steel are improved by the deposition of TiAIN coating. The influence of the TiA1N coating on the tensile properties of the steel can be ignored at both RT and 650 ℃. Moreover, there is no obvious decrease of the fatigue limit of substrate when the steel is coated by the coating at the investigated temperature.
文摘Squeezed quantum vacua seems to violate the averaged null energy conditions (ANEC’s), because they have a negative energy density. When treated as a perfect fluid, rapidly rotating Casimir plates will create vorticity in the vacuum bounded by them. The geometry resulting from an arbitrarily extended Casimir plates along their axis of rotation is similar to van Stockum spacetime. We observe closed timelike curves (CTC’s) forming in the exterior of the system resulting from frame dragging. The exterior geometry of this system is similar to Kerr geometry, but because of violation of ANEC, the Cauchy horizon lies outside the system unlike Kerr blackholes, giving more emphasis on whether spacetime is multiply connected at the microscopic level.
文摘To improve the seeds pick-up precision of a vacuum plate seeder,it is important to accurately control the relative distance between suction plate and seeds layer in vibrating tray.Under the excitation of reciprocating vibration with a time varying interference in direction angle,the seeds motion is simulated using the discrete element method(DEM).By analyzing the seeds distribution characteristics,it was found that the seeds-mass-per-unit-area(SMA)was approximately plane distributed in the tray.Then,four square areas on the bottom of rectangular tray were divided symmetrically near the four vertices to measure the corresponding SMA respectively,and a monitoring plane model was established to predict the average SMA and total seeds mass in the tray.The prediction results of DEM simulation showed that the maximum and the mean relative errors were 6.75%and 2.85%.The influences of the normal vector of monitoring plane model and the standard deviation of SMA in four monitoring areas on the prediction errors were analyzed.A method for improving prediction accuracy by using linear regression correction was proposed,and the maximum and the mean relative errors could be reduced to 5.01%and 2.07%.When the tray was vibrated with the frequency of 11 Hz and the amplitude of 4 mm,experiments were carried out on the vacuum plate seeder test-rig.A Kalman filter was adopted to suppress the SMA measurement noise in four monitoring areas.Prediction results indicated that the maximum and the mean relative errors were 10.2%and 3.46%with the average SMA in range of 0.9-1.5 g/cm2,respectively.The paper can provide a basis for further study on the automatic control of suction plate motion according to the variation of seeds mass in the tray.
基金the financial supports from the project of the Innovation Center of China(Grant No. 11C26214403099)the Science and Technology Project of Guangdong Province(Grant No.2010B090400172)
文摘TiN,Ti1-xAIxN single layer coatings and TiN/Ti1-xAIxN multilayer coatings were deposited on SKH51 tool steel substrate by arc ion plating.The coatings were annealed in air to study the effect of aluminum and film structure on the oxidation performance.The surface morphology and structure were characterized by scanning electron microscopy and X-ray diffraction.The element distribution on the cross section was analyzed by electron probe microscopy.It is found that the oxidation resistance of these Ti1-xAlxN based coatings is mainly attributed to aluminum content in them.In comparison with the Ti1-xAlxN single layer coating,the TiN layer inserting into the Ti1-xAlxN in a multilayer coating increases the tendency of Ti diffusion toward the surface and forms a Ti-enriched top surface oxide layer,thus degrades the oxidation resistance.As far as the oxidation resistance is concerned in this study,Ti0.33Al0.67N single layer coating performs the best among all coatings.The kinetic of oxidation behavior of all coatings presents two definite stages.One is a slow oxidation growth which conforms to parabolic law,and the other presents severe mass gain with oxidation duration.The annealing time for severe oxidation initiation is responsible to Fe2O3formation in the oxide scale.
