BACKGROUND Groove pancreatitis(GP)is a rare focal chronic pancreatitis of the pancreaticoduodenal groove that is usually diagnosed in chronic alcoholics.However,it is often difficult to differentiate from pancreatic o...BACKGROUND Groove pancreatitis(GP)is a rare focal chronic pancreatitis of the pancreaticoduodenal groove that is usually diagnosed in chronic alcoholics.However,it is often difficult to differentiate from pancreatic or periampullary cancers.In this study,we report a case of GP with the rare symptom of severe gastric outlet obstruction.CASE SUMMARY A 68-year-old man presented to our institution with severe gastric outlet obstruction accompanied by vomiting persisted for 3 days,severe electrolyte imbalance,and altered mental status with cardiac arrest.Differential diagnosis of cancers of the ampulla of Vater or duodenum was difficult due to discordant findings from preoperative imaging and an endoscopic biopsy of the lesion.In addition,the gastric outlet obstruction did not improve with conservative treatment;therefore,pancreatoduodenectomy was performed.Postoperatively,the histological findings revealed multiple cystic lesions in the duodenal wall that were collectively diagnosed as GP.The patient underwent a follow-up 3 years postoperatively and was found to have no postoperative sequelae.CONCLUSION In this case of GP,pancreatoduodenectomy safely treated severe gastric outlet obstruction when a cancer diagnosis could not be excluded.展开更多
Repairing the Ni-based superalloy component remains challenging due to the limited understanding of the role of the defect’s morphology on microstructure and related deformation responses.To address this issue,GH4099...Repairing the Ni-based superalloy component remains challenging due to the limited understanding of the role of the defect’s morphology on microstructure and related deformation responses.To address this issue,GH4099 Ni-based superalloy plate with U-shaped and V-shaped grooves was prepared and repaired by laser-directed energy deposition method using GH4099 powders.Both grooves exhibit three similar regions at the repaired interphase,which are the base metal region with equiaxed grains,repaired region with columnar or elongated equiaxed grains,and a transition region in between.High-temperature gradient in the repaired region induced a high density of substructures,and the repaired region in U-shaped grooves has an even higher temperature gradient due to fewer passes of the melted metal,which induces more metallic carbides in the subgrain boundaries and improves the tensile strength of the repaired samples.However,due to the steep side walls,local vortex might form at the bottom corner of the U-shaped groove,leaving macroscale holes and micro-cracks there.Such defects will decrease the alloy’s ductility.The relationship among groove morphology-macro-and microstructure-mechanical properties is then established,which suggesting the preferred V-shaped groove considering the flatter sidewall and more passes induced near equilibrium microstructure.展开更多
This study aims to develop an accurate calculation model of transmission torque and load-bearing capacity for hydro-viscous clutches(HVC)used in high-power vehicles,which is important to investigate the step-less spee...This study aims to develop an accurate calculation model of transmission torque and load-bearing capacity for hydro-viscous clutches(HVC)used in high-power vehicles,which is important to investigate the step-less speed regulation characteristics in a fan drive system.However,most of the existing models ignore the distribution differences of groove area along the radial direction,which may lead to significant deviations in calculating the mechanical property of friction pairs related to operating conditions and the engagement process.To fill this gap,a new calculation model for bearing capacity and frictional torque of friction pairs with different oil grooves is proposed,in which the traditional fixed contact area ratio coefficient for oil groove measurement is replaced by a more precise discrete micro-ring area ratio(DMAR)integration method.Then,a 32-degree-of-freedoms dynamic model of HVC at a fan drive system is established for the prediction of dynamic responses during speed regulation.Results show that friction pairs with different oil grooves have a direct influence on frictional torque and bearing capacity through the change of DMAR along the radial direction.The friction pairs with different groove structures have oscillation phenomena at the engagement steady-state boundary.Furthermore,a step-less speed regulation experimental setup is established to verify the correctness of the proposed model.It is demonstrated that the axial engagement force and the speed regulation curve predicted by the proposed method are in good agreement with the experimental data.The results could effectively predict the engagement dynamic characteristics.The numerical relationship among the structure parameters,the mechanical properties of friction pairs,and the speed regulation characteristics of the system are established through the proposed model,which lays a theoretical foundation for the structure design of friction plates and optimization of step-less speed regulation performance.展开更多
To investigate the control effect and flow mechanism of the L-shaped endwall groove on corner separation in the real compressor stage,a single stage axial flow compressor is selected as the research object and the L-s...To investigate the control effect and flow mechanism of the L-shaped endwall groove on corner separation in the real compressor stage,a single stage axial flow compressor is selected as the research object and the L-shaped grooves are introduced on the stator casing side.First,the experimental measurement is conducted on the optimal L-shaped groove obtained through a full factorial experimental design,and the results demonstrate that the optimal groove has a great control over the endwall flow.Moreover,the peak efficiency is improved by 0.9%and the stall margin is increased by 4.46%.Then,the flow field visualization of numerical results and analysis of variance method are employed to analyze the control mechanism and parameter control law of the L-shaped groove.It is found that the L-shaped groove can guide the skewed inlet endwall boundary layer towards the streamwise direction due to its confinement effect,thereby delaying the onset of corner separation and reducing the size of ring vortex.As a result,the aerodynamic performance of the compressor is enhanced.Furthermore,the groove depth and groove width play a significant role in controlling endwall flow among the three L-shaped groove design parameters.The larger groove depth and smaller groove width enhance the capability of the streamwise groove to constrain the endwall boundary layer,leading to a greater reduction in endwall loss.展开更多
Metamorphic mechanism has the advantages of variable topology and variable degrees of freedom, which can realize the requirements of multi-conditions and multi-tasks, and has a good application prospect. The configura...Metamorphic mechanism has the advantages of variable topology and variable degrees of freedom, which can realize the requirements of multi-conditions and multi-tasks, and has a good application prospect. The configuration transformation is prominent feature of the metamorphic mechanism. The number of constraints or properties of the kinematic pairs provided by the metamorphic kinematic pairs will change under certain conditions, its dynamic performance is much more complex than that of traditional kinematic pairs with immutable constraints. However, the clearance model about traditional kinematic pairs with immutable constraints established by long-term research is difficult to be directly applied to the metachromatic kinematic pairs. Referring to the experience of the traditional kinematic pairs with immutable constraints, the continuous contact model of Metamorphic Groove pin pair with clearance is established. According to the traditional continuous contact model of the kinematic pairs with immutable constraints, the forces between the elements of kinematic pair of the mechanism with clearance and the ideal mechanism without clearance are regarded as the same, and the inertia force and inertia moment of the components are also calculated according to the acceleration of the ideal mechanism. The clearance is regarded as a massless virtual bar with length r. For the rotating pair part, the massless virtual bar length r is the difference between the radius of the shaft and the hole, and for the sliding pair part, the massless virtual bar length r is half of the difference between the height of the slider and the guide groove. According to the new mechanism without gap after adding the imaginary bar, kinetic energy and potential energy of the system are calculated for the two configurations of mechanism with metamorphic Groove pin pair with clearance. The kinetic energy and potential energy of the system are calculated according to the new mechanism without clearance after adding the massless virtual bar. The kinetic energy, potential energy and generalized force are substituted into the Lagrangian equation to obtain the motion equation of the metamorphic mechanism, which lays the foundation for the dynamic performance study of the mechanism with metamorphic groove pin pair with clearance.展开更多
Taking the NACA0012 airfoil as the research object,the bio-inspired herringbone groove array,a new passive control method,is applied to relieve the flow separation under the large angle-of-attack conditions,and its ef...Taking the NACA0012 airfoil as the research object,the bio-inspired herringbone groove array,a new passive control method,is applied to relieve the flow separation under the large angle-of-attack conditions,and its effectiveness and mechanism in delaying airfoil stall are investigated by numerical simulations.The herringbone groove array is placed on the airfoil's upper surface near the trailing edge,and the effects of groove depth and yaw angle on the control effect are investigated.The results demonstrate that different designs of herringbone groove array can effectively broaden the stable operating range of the airfoil,and the application of herringbone groove array with a depth of only 0.00135 times the chord length and a yaw angle of 45°can result in a28.57%increase in the stable operating range.The flow details indicate that a pair of induced vortices with the same strength and opposite direction are formed near the converging line under the combined action of the accumulation effect of small-scale vortices in the grooves and the spanwise migration flow above the grooves.The induced vortices increase the mixing between the main flow and the boundary layer,allowing the boundary layer to gain sufficient energy to withstand the adverse pressure gradient at high angles of attack,effectively delaying airfoil stall.展开更多
Grooved tuning forks with hierarchical structures have become some of the most widely used piezoelectric quartz microelectromechanical system devices;however,fabricating these devices requires multi-step processes due...Grooved tuning forks with hierarchical structures have become some of the most widely used piezoelectric quartz microelectromechanical system devices;however,fabricating these devices requires multi-step processes due to the complexity of etching of quartz,particularly in specific orientations of the crystal lattice.This paper proposes a one-step fabrication strategy that can form a complete hierarchical structure with only a single etching process using novel lithography patterns.The core principle of this strategy is based on the effect of the size of the groove patterns on quartz etching,whereby trenches of varying depths can be created in a fixed etching time by adjusting the width of the hard mask.Specifically,the device outline and grooved structure can be completed using a seamlessly designed etching pattern and optimized time.Furthermore,the etching structure itself influences the etching results.It was found that dividing a wide trench by including a wall to separate it into two narrow trenches significantly reduces the etching rate,allowing for predictable tuning of the etching rate for wider grooves.This effectively increases the usability and flexibility of the one-step strategy.This was applied to the manufacture of an ultra-small quartz grooved tuning fork resonator with a frequency of 32.768 kHz in a single step,increasing production efficiency by almost 45%and reducing costs by almost 30%compared to current methods.This has great potential for improving the productivity of grooved tuning fork devices.It can also be extended to the fabrication of other quartz crystal devices requiring hierarchical structures.展开更多
Mode matching method is used to analyze the scattering characteristics of thecircular-to-circular groove waveguide junction. Matching the electric fields and magnetic fields atthe boundary of the junction, and multipl...Mode matching method is used to analyze the scattering characteristics of thecircular-to-circular groove waveguide junction. Matching the electric fields and magnetic fields atthe boundary of the junction, and multiplying the mode functions of the circular waveguide andcircular groove waveguide on both sides of the boundary equation, the scattering matrix equation isobtained, the scattering coefficients can be obtained from the equation. Then the scatteringcharacteristics of the iris with circular window in circular groove waveguide are analyzed. At lastthe convergent problem is discussed; when choosing a suitable mode group, convergent numericalresults are obtained, and the frequency response of the iris' scattering coefficients is also given.展开更多
A rotary swaging machine was applied to fabricating pipe reduction for miniature inner grooved copper tube （MIGCT） heat pipes. Compared with conventional swaging method, the axial feed of the designed rotary swaging...A rotary swaging machine was applied to fabricating pipe reduction for miniature inner grooved copper tube （MIGCT） heat pipes. Compared with conventional swaging method, the axial feed of the designed rotary swaging machine was reached by a constant pushing force. The deformation of grooves in pipe reduced section during rotary swaging was analyzed. The shrinkage and extensibility of pipe reduction were measured and calculated. Furthermore, four aspects, including outer diameter, surface roughness, extensibility and processing time of pipe reduction, which were influenced by the pushing force, were considered. The results show that the tube wall thickness increases gradually along the z-axis at sinking section. However, the outer diameters, surface roughness and micro-cracks at reduced section tend to decrease along the z-axis. Besides, the effect of variation in the pushing force on the extensibility is limited while an increase in the pushing force results in a decrease of surface roughness. Therefore, a large pushing force within the limit is beneficial to pipe reduction manufacturing during rotary swaging process.展开更多
To analyze the influence of surface texture on friction properties of Crl2MoV＇, ordinary grinder and spinning technology were adopted to obtain the grooved surface morphology of samples, and then the impact of spindl...To analyze the influence of surface texture on friction properties of Crl2MoV＇, ordinary grinder and spinning technology were adopted to obtain the grooved surface morphology of samples, and then the impact of spindle speed and feed in z-direction on surface morphology in the process of spinning was studied. In addition, the corresponding friction coefficient of sample was obtained through friction and wear tests. The results show that the peak clipping and the valley filling were conducted on the grinding surface, which could improve the surface roughness effectively and make the grinding trench-type wear scar more uniform. Both the area ratio of groove and groove spacing increased initially and then decreased with the increase of the spindle speed or the feed in z-direction. As a kind of micro-process, the groove could influence the friction coefficient of sample surface, whose distribution was beneficial to the reduction of friction coefficient. Compared with the surface obtained through ordinary grinding, grooved surface morphology through spinning technology was more conductive to reduce the friction coefficient, which could be reduced by 25%. When the friction coefficient of sample was reduced to the minimum, the texture of groove corresponded had an optimal area ratio and an optimal groove spacing, 37.5% and 27.5 μm, respectively.展开更多
A FEM model for a failed industrial example of roll forging was established to analyze the generation mechanisms of the mismatch of size and shape of two spring board.To demonstrate the formulation of these defects,th...A FEM model for a failed industrial example of roll forging was established to analyze the generation mechanisms of the mismatch of size and shape of two spring board.To demonstrate the formulation of these defects,the bites condition and contact status between rectangular groove and workpiece during rolling the first and second spring boards were analyzed.Then,a new oval-diamond groove combining oval groove and diamond groove was presented to eliminate these defects.By analyzing field variables under the same deformation degree,the larger friction can be obtained on the contact surface of workpiece and the oval-diamond groove.The physical experiment validates that the oval-diamond groove can eliminate these defects effectively,and the size of part is in good agreement with design requirement.展开更多
The current research on secondary O-ring seals used in mechanical seals has begun to focus on their dynamic properties.However,detailed analysis of the dynamic properties of O-ring seals in spiral groove gas face seal...The current research on secondary O-ring seals used in mechanical seals has begun to focus on their dynamic properties.However,detailed analysis of the dynamic properties of O-ring seals in spiral groove gas face seals is lacking.In particular a transient study and a difference analysis of steady-state and transient performance are imperative.In this paper,a case study is performed to gauge the effect of secondary O-ring seals on the dynamic behavior(steady-state performance and transient performance)of face seals.A numerical finite element method(FEM)model is developed for the dynamic analysis of spiral groove gas face seals with a flexibly mounted stator in the axial and angular modes.The rotor tilt angle,static stator tilt angle and O-ring damping are selected to investigate the effect of O-ring seals on face seals during stable running operation.The results show that the angular factor can be ignored to save time in the simulation under small damping or undamped conditions.However,large O-ring damping has an enormous effect on the angular phase difference of mated rings,affecting the steady-state performance of face seals and largely increasing the possibility of face contact that reduces the service life of face seals.A pressure drop fluctuation is carried out to analyze the effect of O-ring seals on the transient performance of face seals.The results show that face seals could remain stable without support stiffness and O-ring damping during normal stable operation but may enter a large-leakage state when confronting instantaneous fluctuations.The oscillation-amplitude shortening effect of O-ring damping on the axial mode is much greater than that on the angular modes and O-ring damping prefers to cater for axial motion at the cost of angular motion.This research proposes a detailed dynamic-property study of O-ring seals in spiral groove gas face seals,to assist in the design of face seals.展开更多
The coupling effect among the flow of fluid film, the frictional heat of fluid film and the thermal deformation of sealing rings is inherent in mechanical seals. The frictional heat transfer analysis was carded out to...The coupling effect among the flow of fluid film, the frictional heat of fluid film and the thermal deformation of sealing rings is inherent in mechanical seals. The frictional heat transfer analysis was carded out to optimize the geometrical parameters of the sealing rings, such as the length, the inner radius and the outer radius. The geometrical parameters of spiral grooves, such as the spiral angle, the end radius, the groove depth, the ratio of the groove width to the weir width and the number of the grooves, were optimized by regarding the maximum bearing force of fluid film as the optimization objective with the coupling effect considered. The depth of spiral groove was designed to gradually increase from the end radius of spiral groove to the outer radius of end face in order to decrease the weakening effect of thermal deformation on the hydrodynamic effect of spiral grooves. The end faces of sealing rings were machined to form a divergent gap at inner radius, and a parallel gap will form to reduce the leakage rate when the thermal deformation takes place. The improved spiral groove mechanical seal possesses good heat transfer performance and sealing ability.展开更多
文摘BACKGROUND Groove pancreatitis(GP)is a rare focal chronic pancreatitis of the pancreaticoduodenal groove that is usually diagnosed in chronic alcoholics.However,it is often difficult to differentiate from pancreatic or periampullary cancers.In this study,we report a case of GP with the rare symptom of severe gastric outlet obstruction.CASE SUMMARY A 68-year-old man presented to our institution with severe gastric outlet obstruction accompanied by vomiting persisted for 3 days,severe electrolyte imbalance,and altered mental status with cardiac arrest.Differential diagnosis of cancers of the ampulla of Vater or duodenum was difficult due to discordant findings from preoperative imaging and an endoscopic biopsy of the lesion.In addition,the gastric outlet obstruction did not improve with conservative treatment;therefore,pancreatoduodenectomy was performed.Postoperatively,the histological findings revealed multiple cystic lesions in the duodenal wall that were collectively diagnosed as GP.The patient underwent a follow-up 3 years postoperatively and was found to have no postoperative sequelae.CONCLUSION In this case of GP,pancreatoduodenectomy safely treated severe gastric outlet obstruction when a cancer diagnosis could not be excluded.
基金support of the Mount Taishan Industrial Leading Talent Project.
文摘Repairing the Ni-based superalloy component remains challenging due to the limited understanding of the role of the defect’s morphology on microstructure and related deformation responses.To address this issue,GH4099 Ni-based superalloy plate with U-shaped and V-shaped grooves was prepared and repaired by laser-directed energy deposition method using GH4099 powders.Both grooves exhibit three similar regions at the repaired interphase,which are the base metal region with equiaxed grains,repaired region with columnar or elongated equiaxed grains,and a transition region in between.High-temperature gradient in the repaired region induced a high density of substructures,and the repaired region in U-shaped grooves has an even higher temperature gradient due to fewer passes of the melted metal,which induces more metallic carbides in the subgrain boundaries and improves the tensile strength of the repaired samples.However,due to the steep side walls,local vortex might form at the bottom corner of the U-shaped groove,leaving macroscale holes and micro-cracks there.Such defects will decrease the alloy’s ductility.The relationship among groove morphology-macro-and microstructure-mechanical properties is then established,which suggesting the preferred V-shaped groove considering the flatter sidewall and more passes induced near equilibrium microstructure.
基金Supported by the National Natural Science Foundation of China(Grant Nos.52475089,52035002)National Key Research and Development Program of China(Grant No.2021YFB2011400)the Chongqing Natural Science Foundation(Grant No.CSTB2022NSCQ-MSX1243).
文摘This study aims to develop an accurate calculation model of transmission torque and load-bearing capacity for hydro-viscous clutches(HVC)used in high-power vehicles,which is important to investigate the step-less speed regulation characteristics in a fan drive system.However,most of the existing models ignore the distribution differences of groove area along the radial direction,which may lead to significant deviations in calculating the mechanical property of friction pairs related to operating conditions and the engagement process.To fill this gap,a new calculation model for bearing capacity and frictional torque of friction pairs with different oil grooves is proposed,in which the traditional fixed contact area ratio coefficient for oil groove measurement is replaced by a more precise discrete micro-ring area ratio(DMAR)integration method.Then,a 32-degree-of-freedoms dynamic model of HVC at a fan drive system is established for the prediction of dynamic responses during speed regulation.Results show that friction pairs with different oil grooves have a direct influence on frictional torque and bearing capacity through the change of DMAR along the radial direction.The friction pairs with different groove structures have oscillation phenomena at the engagement steady-state boundary.Furthermore,a step-less speed regulation experimental setup is established to verify the correctness of the proposed model.It is demonstrated that the axial engagement force and the speed regulation curve predicted by the proposed method are in good agreement with the experimental data.The results could effectively predict the engagement dynamic characteristics.The numerical relationship among the structure parameters,the mechanical properties of friction pairs,and the speed regulation characteristics of the system are established through the proposed model,which lays a theoretical foundation for the structure design of friction plates and optimization of step-less speed regulation performance.
基金financially supported by the National Natural Science Foundation of China(No.52176045)the National Science and Technology Major Project of China(No.J2019-I-0011-0011)。
文摘To investigate the control effect and flow mechanism of the L-shaped endwall groove on corner separation in the real compressor stage,a single stage axial flow compressor is selected as the research object and the L-shaped grooves are introduced on the stator casing side.First,the experimental measurement is conducted on the optimal L-shaped groove obtained through a full factorial experimental design,and the results demonstrate that the optimal groove has a great control over the endwall flow.Moreover,the peak efficiency is improved by 0.9%and the stall margin is increased by 4.46%.Then,the flow field visualization of numerical results and analysis of variance method are employed to analyze the control mechanism and parameter control law of the L-shaped groove.It is found that the L-shaped groove can guide the skewed inlet endwall boundary layer towards the streamwise direction due to its confinement effect,thereby delaying the onset of corner separation and reducing the size of ring vortex.As a result,the aerodynamic performance of the compressor is enhanced.Furthermore,the groove depth and groove width play a significant role in controlling endwall flow among the three L-shaped groove design parameters.The larger groove depth and smaller groove width enhance the capability of the streamwise groove to constrain the endwall boundary layer,leading to a greater reduction in endwall loss.
文摘Metamorphic mechanism has the advantages of variable topology and variable degrees of freedom, which can realize the requirements of multi-conditions and multi-tasks, and has a good application prospect. The configuration transformation is prominent feature of the metamorphic mechanism. The number of constraints or properties of the kinematic pairs provided by the metamorphic kinematic pairs will change under certain conditions, its dynamic performance is much more complex than that of traditional kinematic pairs with immutable constraints. However, the clearance model about traditional kinematic pairs with immutable constraints established by long-term research is difficult to be directly applied to the metachromatic kinematic pairs. Referring to the experience of the traditional kinematic pairs with immutable constraints, the continuous contact model of Metamorphic Groove pin pair with clearance is established. According to the traditional continuous contact model of the kinematic pairs with immutable constraints, the forces between the elements of kinematic pair of the mechanism with clearance and the ideal mechanism without clearance are regarded as the same, and the inertia force and inertia moment of the components are also calculated according to the acceleration of the ideal mechanism. The clearance is regarded as a massless virtual bar with length r. For the rotating pair part, the massless virtual bar length r is the difference between the radius of the shaft and the hole, and for the sliding pair part, the massless virtual bar length r is half of the difference between the height of the slider and the guide groove. According to the new mechanism without gap after adding the imaginary bar, kinetic energy and potential energy of the system are calculated for the two configurations of mechanism with metamorphic Groove pin pair with clearance. The kinetic energy and potential energy of the system are calculated according to the new mechanism without clearance after adding the massless virtual bar. The kinetic energy, potential energy and generalized force are substituted into the Lagrangian equation to obtain the motion equation of the metamorphic mechanism, which lays the foundation for the dynamic performance study of the mechanism with metamorphic groove pin pair with clearance.
基金supported by the National Natural Science Foundation of China(No.52306058)the Natural Science Foundation of Tianjin Municipal Science and Technology Commission,China(No.22JCQNJC00050)。
文摘Taking the NACA0012 airfoil as the research object,the bio-inspired herringbone groove array,a new passive control method,is applied to relieve the flow separation under the large angle-of-attack conditions,and its effectiveness and mechanism in delaying airfoil stall are investigated by numerical simulations.The herringbone groove array is placed on the airfoil's upper surface near the trailing edge,and the effects of groove depth and yaw angle on the control effect are investigated.The results demonstrate that different designs of herringbone groove array can effectively broaden the stable operating range of the airfoil,and the application of herringbone groove array with a depth of only 0.00135 times the chord length and a yaw angle of 45°can result in a28.57%increase in the stable operating range.The flow details indicate that a pair of induced vortices with the same strength and opposite direction are formed near the converging line under the combined action of the accumulation effect of small-scale vortices in the grooves and the spanwise migration flow above the grooves.The induced vortices increase the mixing between the main flow and the boundary layer,allowing the boundary layer to gain sufficient energy to withstand the adverse pressure gradient at high angles of attack,effectively delaying airfoil stall.
文摘Grooved tuning forks with hierarchical structures have become some of the most widely used piezoelectric quartz microelectromechanical system devices;however,fabricating these devices requires multi-step processes due to the complexity of etching of quartz,particularly in specific orientations of the crystal lattice.This paper proposes a one-step fabrication strategy that can form a complete hierarchical structure with only a single etching process using novel lithography patterns.The core principle of this strategy is based on the effect of the size of the groove patterns on quartz etching,whereby trenches of varying depths can be created in a fixed etching time by adjusting the width of the hard mask.Specifically,the device outline and grooved structure can be completed using a seamlessly designed etching pattern and optimized time.Furthermore,the etching structure itself influences the etching results.It was found that dividing a wide trench by including a wall to separate it into two narrow trenches significantly reduces the etching rate,allowing for predictable tuning of the etching rate for wider grooves.This effectively increases the usability and flexibility of the one-step strategy.This was applied to the manufacture of an ultra-small quartz grooved tuning fork resonator with a frequency of 32.768 kHz in a single step,increasing production efficiency by almost 45%and reducing costs by almost 30%compared to current methods.This has great potential for improving the productivity of grooved tuning fork devices.It can also be extended to the fabrication of other quartz crystal devices requiring hierarchical structures.
文摘Mode matching method is used to analyze the scattering characteristics of thecircular-to-circular groove waveguide junction. Matching the electric fields and magnetic fields atthe boundary of the junction, and multiplying the mode functions of the circular waveguide andcircular groove waveguide on both sides of the boundary equation, the scattering matrix equation isobtained, the scattering coefficients can be obtained from the equation. Then the scatteringcharacteristics of the iris with circular window in circular groove waveguide are analyzed. At lastthe convergent problem is discussed; when choosing a suitable mode group, convergent numericalresults are obtained, and the frequency response of the iris' scattering coefficients is also given.
基金Project (U0834002) supported by the Key Program of NSFC Guangdong Joint Funds of ChinaProjects (51005079, 20976055) supported by the National Natural Science Foundation of China+1 种基金Project (10451064101005146) supported by the Natural Science Foundation of Guangdong Province, ChinaProject (20100172120001) supported by Specialized Research Fund for the Doctoral Program of Higher Education, China
文摘A rotary swaging machine was applied to fabricating pipe reduction for miniature inner grooved copper tube （MIGCT） heat pipes. Compared with conventional swaging method, the axial feed of the designed rotary swaging machine was reached by a constant pushing force. The deformation of grooves in pipe reduced section during rotary swaging was analyzed. The shrinkage and extensibility of pipe reduction were measured and calculated. Furthermore, four aspects, including outer diameter, surface roughness, extensibility and processing time of pipe reduction, which were influenced by the pushing force, were considered. The results show that the tube wall thickness increases gradually along the z-axis at sinking section. However, the outer diameters, surface roughness and micro-cracks at reduced section tend to decrease along the z-axis. Besides, the effect of variation in the pushing force on the extensibility is limited while an increase in the pushing force results in a decrease of surface roughness. Therefore, a large pushing force within the limit is beneficial to pipe reduction manufacturing during rotary swaging process.
基金Project(51275543)supported by the National Natural Science Foundation,ChinaProject(KJ1603804)supported by the Research Projects of Chongqing Commission of Science and Technology,China
文摘To analyze the influence of surface texture on friction properties of Crl2MoV＇, ordinary grinder and spinning technology were adopted to obtain the grooved surface morphology of samples, and then the impact of spindle speed and feed in z-direction on surface morphology in the process of spinning was studied. In addition, the corresponding friction coefficient of sample was obtained through friction and wear tests. The results show that the peak clipping and the valley filling were conducted on the grinding surface, which could improve the surface roughness effectively and make the grinding trench-type wear scar more uniform. Both the area ratio of groove and groove spacing increased initially and then decreased with the increase of the spindle speed or the feed in z-direction. As a kind of micro-process, the groove could influence the friction coefficient of sample surface, whose distribution was beneficial to the reduction of friction coefficient. Compared with the surface obtained through ordinary grinding, grooved surface morphology through spinning technology was more conductive to reduce the friction coefficient, which could be reduced by 25%. When the friction coefficient of sample was reduced to the minimum, the texture of groove corresponded had an optimal area ratio and an optimal groove spacing, 37.5% and 27.5 μm, respectively.
基金Project(51275543)supported by the National Natural Science Foundation of ChinaProject(cstc2009aa3012-1)supported by the Key Program of Chongqing Science and Technology Foundation,China
文摘A FEM model for a failed industrial example of roll forging was established to analyze the generation mechanisms of the mismatch of size and shape of two spring board.To demonstrate the formulation of these defects,the bites condition and contact status between rectangular groove and workpiece during rolling the first and second spring boards were analyzed.Then,a new oval-diamond groove combining oval groove and diamond groove was presented to eliminate these defects.By analyzing field variables under the same deformation degree,the larger friction can be obtained on the contact surface of workpiece and the oval-diamond groove.The physical experiment validates that the oval-diamond groove can eliminate these defects effectively,and the size of part is in good agreement with design requirement.
基金Supported by National Key Basic Research Program of China(973Program,Grant No.2012CB026003)National Science and Technology Major Project of China(Grant No.ZX06901)
文摘The current research on secondary O-ring seals used in mechanical seals has begun to focus on their dynamic properties.However,detailed analysis of the dynamic properties of O-ring seals in spiral groove gas face seals is lacking.In particular a transient study and a difference analysis of steady-state and transient performance are imperative.In this paper,a case study is performed to gauge the effect of secondary O-ring seals on the dynamic behavior(steady-state performance and transient performance)of face seals.A numerical finite element method(FEM)model is developed for the dynamic analysis of spiral groove gas face seals with a flexibly mounted stator in the axial and angular modes.The rotor tilt angle,static stator tilt angle and O-ring damping are selected to investigate the effect of O-ring seals on face seals during stable running operation.The results show that the angular factor can be ignored to save time in the simulation under small damping or undamped conditions.However,large O-ring damping has an enormous effect on the angular phase difference of mated rings,affecting the steady-state performance of face seals and largely increasing the possibility of face contact that reduces the service life of face seals.A pressure drop fluctuation is carried out to analyze the effect of O-ring seals on the transient performance of face seals.The results show that face seals could remain stable without support stiffness and O-ring damping during normal stable operation but may enter a large-leakage state when confronting instantaneous fluctuations.The oscillation-amplitude shortening effect of O-ring damping on the axial mode is much greater than that on the angular modes and O-ring damping prefers to cater for axial motion at the cost of angular motion.This research proposes a detailed dynamic-property study of O-ring seals in spiral groove gas face seals,to assist in the design of face seals.
文摘The coupling effect among the flow of fluid film, the frictional heat of fluid film and the thermal deformation of sealing rings is inherent in mechanical seals. The frictional heat transfer analysis was carded out to optimize the geometrical parameters of the sealing rings, such as the length, the inner radius and the outer radius. The geometrical parameters of spiral grooves, such as the spiral angle, the end radius, the groove depth, the ratio of the groove width to the weir width and the number of the grooves, were optimized by regarding the maximum bearing force of fluid film as the optimization objective with the coupling effect considered. The depth of spiral groove was designed to gradually increase from the end radius of spiral groove to the outer radius of end face in order to decrease the weakening effect of thermal deformation on the hydrodynamic effect of spiral grooves. The end faces of sealing rings were machined to form a divergent gap at inner radius, and a parallel gap will form to reduce the leakage rate when the thermal deformation takes place. The improved spiral groove mechanical seal possesses good heat transfer performance and sealing ability.
