Pipe belt conveyor is a new type of environmentally friendly and efficient bulk conveying equipment.In the design of the roller,the belt and the driving motor of pipe belt conveyor,the sag resistance is a key paramete...Pipe belt conveyor is a new type of environmentally friendly and efficient bulk conveying equipment.In the design of the roller,the belt and the driving motor of pipe belt conveyor,the sag resistance is a key parameter.Meanwhile,the normal force between the conveyor belt and the roller group is the other important factor need be considered and has a great influence on the sag resistance.This paper analyzes a pipe belt conveyor with a diameter of 150 mm to study the calculation method of normal force.And the relationship between the normal force and the sag resistance is explored.Firstly,the normal force is decomposed into three components related to the forming force of belt,material gravity and belt gravity.So it can be expressed as a linear combination of these three quantities,and the coefficients of each component are obtained based on the dynamic analysis of belt-roller.The results show that the coefficient is mainly affected by the material filling rate,and is almost not affected by the distance between the rollers and the density of the material.The calculation method of the normal force is eventually obtained.Secondly,the normal force in the case of different material filling rates is tested by experiments,and the calculation method of the normal force is verified.Thirdly,the variation law of the sag resistance in the case of different roller group spacing and material filling rate is studied by the dynamic model.It is found that the roller group spacing and material filling rate affects the sag resistance by changing the normal force.There is a power function relationship between the sag resistance and the normal force.In the case of different roller group spacing and material filling rate,the relationship among the sag resistance and the normal force remains unchanged.This study results are of great significance to the design of pipe belt conveyor.展开更多
To solve the problems of low precision of weak feature extraction,heavy reliance on labor and low efficiency of weak feature extraction in X-ray weld detection image of ultra-high voltage(UHV)equipment key parts,an au...To solve the problems of low precision of weak feature extraction,heavy reliance on labor and low efficiency of weak feature extraction in X-ray weld detection image of ultra-high voltage(UHV)equipment key parts,an automatic feature extraction algorithm is proposed.Firstly,the original weld image is denoised while retaining the characteristic information of weak defects by the proposed monostable stochastic resonance method.Then,binarization is achieved by combining Laplacian edge detection and Otsu threshold segmentation.Finally,the automatic identification of weld defect area is realized based on the sequential traversal of binary tree.Several characteristic analysis dimensions are established for weld defects of UHV key parts,including defect area,perimeter,slenderness ratio,duty cycle,etc.The experiment using theweld detection image of the actual production site shows that the proposedmethod can effectively extract theweak feature information ofweld defects and further provide reference for decision-making.展开更多
For the static analysis of the sinking stage curved beam, a finite difference model was presented based on the proposed revised Vlasov equations. First, revised Vlasov equations for thin-walled curved beams with close...For the static analysis of the sinking stage curved beam, a finite difference model was presented based on the proposed revised Vlasov equations. First, revised Vlasov equations for thin-walled curved beams with closed sections were deduced considering the shear strain on the mid-surface of the cross-section. Then, the finite difference formulation of revised Vlasov equations was implemented with the parabolic interpolation based on Taylor series. At last, the finite difference model was built by substituting geometry and boundary conditions of the sinking stage curved beam into the finite difference formulation. The validity of present work is confirmed by the published literature and ANSYS simulation results. It can be concluded that revised Vlasov equations are more accurate than the original one in the analysis of thin-walled beams with closed sections, and that present finite difference model is applicable in the evaluation of the sinking stage curved beam.展开更多
A driver-pickup probe possesses better sensitivity and flexibility due to individual optimization of a coil.It is fre-quently observed in an eddy current(EC)array probe.In this work,a tilted non-coaxial driver-pickup ...A driver-pickup probe possesses better sensitivity and flexibility due to individual optimization of a coil.It is fre-quently observed in an eddy current(EC)array probe.In this work,a tilted non-coaxial driver-pickup probe above a multilayered conducting plate is analytically modeled with spatial transformation for eddy current nondestructive evalua-tion.Basically,the core of the formulation is to obtain the projection of magnetic vector potential(MVP)from the driver coil onto the vector along the tilted pickup coil,which is divided into two key steps.The first step is to make a projection of MVP along the pickup coil onto a horizontal plane,and the second one is to build the relationship between the pr,ojected MVP and the MVP along the driver coil.Afterwards,an analytical model for the case of a layered plate is established with the reflection and transmission theory of electromagnetic fields.The calculated values from the resulting model indicate good agreement with those from the finite element model(FEM)and experiments,which validates the developed analytical model.展开更多
In order to study the strength of the composite material plate problems, need to adopt a nondestructive testing method to obtain the specimen surface under the effect of high-speed impact regularity of shape. The proj...In order to study the strength of the composite material plate problems, need to adopt a nondestructive testing method to obtain the specimen surface under the effect of high-speed impact regularity of shape. The projection profilometry was used to measure the surface profile or the full field deformation. Furtherly, by using the Fourier transform algorithm, there is only one frame of captured image</span><span style="font-family:Verdana;"> which</span><span style="font-family:Verdana;"> is needed in the measurement, so that it can be introduced into the high speed impaction procedure measurement. An experimental system, which was contained with an impact setup and the projection profilometry measurement part, was constructed for the impaction action characteristic research. The metallic impact object can be launched by a gas gun or a spin fan, respectively. The detected object </span><span style="font-family:Verdana;">is</span><span style="font-family:Verdana;"> manufactured by composite materials. In order to increase the surface deformation measurement accuracy, the calibration method and the error was discussed with different calibration specimen. And then, the proposed profilometry measurement method is proved by the gas gun and spin fan projectile test. The surface deformation of the manufactured composite plates and fan case are measured in the impaction procedure. So that the impact action details can be described much more clearly than the traditional video monitoring method.展开更多
The fretting wear among the steel wires aggravates the wire rope’s fatigue damage,affects the service performance of the wire ropes,and threatens mine hoisting safety.In this paper,the practical friction behavior and...The fretting wear among the steel wires aggravates the wire rope’s fatigue damage,affects the service performance of the wire ropes,and threatens mine hoisting safety.In this paper,the practical friction behavior and wear mechanism among the wires in the wire rope are investigated.A series of tests were carried out on multiple steel wires in helical contact and tension–torsion coupling under different fretting parameters,twisting parameters,and lubrication conditions by self-made friction and wear testing machine.The results show that the coefficient of friction(COF)among the steel wires decreases slightly with increasing lateral loads and tension,and the effect of twist angle on the COF has opposite results under different lubrication conditions.Lateral loads,tension of the steel wires,twist angle,and lubrication condition all affect the fretting morphology among the steel wires.Fretting wear with larger twist angle structure leads to more energy loss.The energy loss of fretting is directly related to the fretting morphology among the contact surfaces,and the dissipated energy is lower in the two forms of complete slip and sticking.The wear depth and width increase with the increase of lateral loads,steel wire tension,and twist angle.And the wear width and depth under dry friction conditions are higher than those under oil lubrication conditions.In addition,the wear mechanism under dry friction conditions is mainly abrasive wear,adhesive wear,and fatigue wear.And the wear mechanism under oil lubrication conditions is mainly abrasive wear and fatigue wear.展开更多
To solve the problem of a low coal-loading rate being exhibited by the drum shearer on Chinese thin coal seams,systematic tests and research were performed to study the pivotal factors’influences on drum coal-loading...To solve the problem of a low coal-loading rate being exhibited by the drum shearer on Chinese thin coal seams,systematic tests and research were performed to study the pivotal factors’influences on drum coal-loading rate using a model test method.The effects of the drum hub diameter,cutting depth,vane helix angle,drum rotation speed and hauling speed on drum coal-loading rate were determined under circumstances of coal-loading with drum ejection and pushing modes,and reasons for these phenomena were analyzed.The results indicate that the influence of the drum cutting depth on the drum coal-loading rate is the most significant.The parameters of hub diameter,drum rotation speed and hauling speed can influence the drum coal-loading rate by cutting the coals’filling rate in the drum.The parameters of vane helix angle and drum rotation speed can influence drum coal-loading rates by influencing the ratio of cutting coals’tangential and axial speed in the drum.The coal-loading rate with drum ejection is clearly higher than that observed with drum pushing.Research in this study can provide support to design the drum structure and select drum operational parameters for a thin coal seam shearer.展开更多
Laser cladding with coaxial powder feeding is one of the new ponent to improve performance of its surface. In the process, processes applied to produce well bonding coating on the com- the clad material is transported...Laser cladding with coaxial powder feeding is one of the new ponent to improve performance of its surface. In the process, processes applied to produce well bonding coating on the com- the clad material is transported by the carrying gas through the coaxial nozzle, generating gas-powder flow. The powder feeding process in the coaxial laser cladding has important influence on the clad qualities. A 3D numerical model was developed to study the powder stream structure of a coaxial feeding nozzle. The predicted powder stream structure was well agreed with the experimental one. The validated model was used to explore the collision behavior of particles in the coaxial nozzle, as well as powder concentration distribution. It was found that the par- ticle diameter and restitution coefficient greatly affect the velocity vector at outlet of nozzle due to the collisions, as well as the powder stream convergence characteristics below the nozzle. The results indicated a practical approach to optimize the powder stream for the coaxial laser cladding.展开更多
基金Supported by National Natural Science Foundation of China (Grant No. 51705144)Hunan Provincial Science and Technology Major Project of China (Grant No. 2015GK1003)Jiangsu Provincial Mine Electromechanical Equipment Key Laboratory Development Fund of China (Grant No. JSKL-MMEE-2018-2)
文摘Pipe belt conveyor is a new type of environmentally friendly and efficient bulk conveying equipment.In the design of the roller,the belt and the driving motor of pipe belt conveyor,the sag resistance is a key parameter.Meanwhile,the normal force between the conveyor belt and the roller group is the other important factor need be considered and has a great influence on the sag resistance.This paper analyzes a pipe belt conveyor with a diameter of 150 mm to study the calculation method of normal force.And the relationship between the normal force and the sag resistance is explored.Firstly,the normal force is decomposed into three components related to the forming force of belt,material gravity and belt gravity.So it can be expressed as a linear combination of these three quantities,and the coefficients of each component are obtained based on the dynamic analysis of belt-roller.The results show that the coefficient is mainly affected by the material filling rate,and is almost not affected by the distance between the rollers and the density of the material.The calculation method of the normal force is eventually obtained.Secondly,the normal force in the case of different material filling rates is tested by experiments,and the calculation method of the normal force is verified.Thirdly,the variation law of the sag resistance in the case of different roller group spacing and material filling rate is studied by the dynamic model.It is found that the roller group spacing and material filling rate affects the sag resistance by changing the normal force.There is a power function relationship between the sag resistance and the normal force.In the case of different roller group spacing and material filling rate,the relationship among the sag resistance and the normal force remains unchanged.This study results are of great significance to the design of pipe belt conveyor.
文摘To solve the problems of low precision of weak feature extraction,heavy reliance on labor and low efficiency of weak feature extraction in X-ray weld detection image of ultra-high voltage(UHV)equipment key parts,an automatic feature extraction algorithm is proposed.Firstly,the original weld image is denoised while retaining the characteristic information of weak defects by the proposed monostable stochastic resonance method.Then,binarization is achieved by combining Laplacian edge detection and Otsu threshold segmentation.Finally,the automatic identification of weld defect area is realized based on the sequential traversal of binary tree.Several characteristic analysis dimensions are established for weld defects of UHV key parts,including defect area,perimeter,slenderness ratio,duty cycle,etc.The experiment using theweld detection image of the actual production site shows that the proposedmethod can effectively extract theweak feature information ofweld defects and further provide reference for decision-making.
基金Project(IRT1292)supported by Fund for Changjiang Scholars and Innovative Research Team in University(PCSIRT)China+2 种基金Project(51475456)supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development(PAPD)of Jiangsu Higher Education InstitutionsChina
文摘For the static analysis of the sinking stage curved beam, a finite difference model was presented based on the proposed revised Vlasov equations. First, revised Vlasov equations for thin-walled curved beams with closed sections were deduced considering the shear strain on the mid-surface of the cross-section. Then, the finite difference formulation of revised Vlasov equations was implemented with the parabolic interpolation based on Taylor series. At last, the finite difference model was built by substituting geometry and boundary conditions of the sinking stage curved beam into the finite difference formulation. The validity of present work is confirmed by the published literature and ANSYS simulation results. It can be concluded that revised Vlasov equations are more accurate than the original one in the analysis of thin-walled beams with closed sections, and that present finite difference model is applicable in the evaluation of the sinking stage curved beam.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61701500,51677187,and 51465024)
文摘A driver-pickup probe possesses better sensitivity and flexibility due to individual optimization of a coil.It is fre-quently observed in an eddy current(EC)array probe.In this work,a tilted non-coaxial driver-pickup probe above a multilayered conducting plate is analytically modeled with spatial transformation for eddy current nondestructive evalua-tion.Basically,the core of the formulation is to obtain the projection of magnetic vector potential(MVP)from the driver coil onto the vector along the tilted pickup coil,which is divided into two key steps.The first step is to make a projection of MVP along the pickup coil onto a horizontal plane,and the second one is to build the relationship between the pr,ojected MVP and the MVP along the driver coil.Afterwards,an analytical model for the case of a layered plate is established with the reflection and transmission theory of electromagnetic fields.The calculated values from the resulting model indicate good agreement with those from the finite element model(FEM)and experiments,which validates the developed analytical model.
文摘In order to study the strength of the composite material plate problems, need to adopt a nondestructive testing method to obtain the specimen surface under the effect of high-speed impact regularity of shape. The projection profilometry was used to measure the surface profile or the full field deformation. Furtherly, by using the Fourier transform algorithm, there is only one frame of captured image</span><span style="font-family:Verdana;"> which</span><span style="font-family:Verdana;"> is needed in the measurement, so that it can be introduced into the high speed impaction procedure measurement. An experimental system, which was contained with an impact setup and the projection profilometry measurement part, was constructed for the impaction action characteristic research. The metallic impact object can be launched by a gas gun or a spin fan, respectively. The detected object </span><span style="font-family:Verdana;">is</span><span style="font-family:Verdana;"> manufactured by composite materials. In order to increase the surface deformation measurement accuracy, the calibration method and the error was discussed with different calibration specimen. And then, the proposed profilometry measurement method is proved by the gas gun and spin fan projectile test. The surface deformation of the manufactured composite plates and fan case are measured in the impaction procedure. So that the impact action details can be described much more clearly than the traditional video monitoring method.
基金supported by the National Natural Science Foundation of China(No.51975572)the Program for Changjiang Scholars and Innovative Research Team in University(No.IRT_16R68)+1 种基金The authors also thank the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions,Chinathe Top-notch Academic Programs Project(TAPP)of Jiangsu Higher Education Institutions,China.
文摘The fretting wear among the steel wires aggravates the wire rope’s fatigue damage,affects the service performance of the wire ropes,and threatens mine hoisting safety.In this paper,the practical friction behavior and wear mechanism among the wires in the wire rope are investigated.A series of tests were carried out on multiple steel wires in helical contact and tension–torsion coupling under different fretting parameters,twisting parameters,and lubrication conditions by self-made friction and wear testing machine.The results show that the coefficient of friction(COF)among the steel wires decreases slightly with increasing lateral loads and tension,and the effect of twist angle on the COF has opposite results under different lubrication conditions.Lateral loads,tension of the steel wires,twist angle,and lubrication condition all affect the fretting morphology among the steel wires.Fretting wear with larger twist angle structure leads to more energy loss.The energy loss of fretting is directly related to the fretting morphology among the contact surfaces,and the dissipated energy is lower in the two forms of complete slip and sticking.The wear depth and width increase with the increase of lateral loads,steel wire tension,and twist angle.And the wear width and depth under dry friction conditions are higher than those under oil lubrication conditions.In addition,the wear mechanism under dry friction conditions is mainly abrasive wear,adhesive wear,and fatigue wear.And the wear mechanism under oil lubrication conditions is mainly abrasive wear and fatigue wear.
基金Project(2012AA062104)supported by the National High Technology Research and Development Program of ChinaProject(51704178)supported by the National Natural Science Foundation of China+1 种基金Project(ZR2017MEE034)supported by Natural Science Foundation of Shandong Province,ChinaProject(2018T110700)supported by China Postdoctoral Science Foundation
文摘To solve the problem of a low coal-loading rate being exhibited by the drum shearer on Chinese thin coal seams,systematic tests and research were performed to study the pivotal factors’influences on drum coal-loading rate using a model test method.The effects of the drum hub diameter,cutting depth,vane helix angle,drum rotation speed and hauling speed on drum coal-loading rate were determined under circumstances of coal-loading with drum ejection and pushing modes,and reasons for these phenomena were analyzed.The results indicate that the influence of the drum cutting depth on the drum coal-loading rate is the most significant.The parameters of hub diameter,drum rotation speed and hauling speed can influence the drum coal-loading rate by cutting the coals’filling rate in the drum.The parameters of vane helix angle and drum rotation speed can influence drum coal-loading rates by influencing the ratio of cutting coals’tangential and axial speed in the drum.The coal-loading rate with drum ejection is clearly higher than that observed with drum pushing.Research in this study can provide support to design the drum structure and select drum operational parameters for a thin coal seam shearer.
基金supported by the National Natural Science Foundation of China(Grant Nos.11272316 and 11272317)a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Laser cladding with coaxial powder feeding is one of the new ponent to improve performance of its surface. In the process, processes applied to produce well bonding coating on the com- the clad material is transported by the carrying gas through the coaxial nozzle, generating gas-powder flow. The powder feeding process in the coaxial laser cladding has important influence on the clad qualities. A 3D numerical model was developed to study the powder stream structure of a coaxial feeding nozzle. The predicted powder stream structure was well agreed with the experimental one. The validated model was used to explore the collision behavior of particles in the coaxial nozzle, as well as powder concentration distribution. It was found that the par- ticle diameter and restitution coefficient greatly affect the velocity vector at outlet of nozzle due to the collisions, as well as the powder stream convergence characteristics below the nozzle. The results indicated a practical approach to optimize the powder stream for the coaxial laser cladding.
基金Project supported by the National Basic Research Program(973)of China(No.2014CB049404)the National Key Research and Development Program(No.2016YFC0600905)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in University(No.IRT_16R68)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),China
