A crosshead slipper-guide system,which bears a significant thrust force,is an essential friction pair in low-speed marine diesel engines.Owing to the low moving speed of the crosshead slipper during engine startup,it ...A crosshead slipper-guide system,which bears a significant thrust force,is an essential friction pair in low-speed marine diesel engines.Owing to the low moving speed of the crosshead slipper during engine startup,it is difficult to form good hydrodynamic lubrication between the crosshead slipper and guide.Therefore,a detailed analysis of the crosshead slipper during engine startup is needed.In this study,a new transient tribo-dynamic model for a crosshead slipper during the engine startup process is presented.The model consists of a mixed lubrication model of the crosshead slipper-guide and dynamic models of the piston assembly,crosshead assembly,connecting rod,and crankshaft.The tribo-dynamic performances of the crosshead slipper during startup and under the rated conditions were simulated and compared.The results show that the tribo-dynamics of the crosshead slipper during the startup process are significantly different from those under the rated conditions.Some measures beneficial for the low friction of a crosshead slipper-guide under the rated conditions may significantly increase the friction loss of the crosshead slipper-guide system during the startup process.展开更多
When the oil supply is not adequate to maintain the ideal lubrication,angular contact ball bearing will enter into the starved lubrication regime resulting in the potential performance degradation and consequently the...When the oil supply is not adequate to maintain the ideal lubrication,angular contact ball bearing will enter into the starved lubrication regime resulting in the potential performance degradation and consequently the severe failures.To study the effects of starved lubrication on the performance of angular contact ball bearing,this paper first proposes a multi-degree-of-freedom(DOF)tribo-dynamic model by introducing five-DOF inner ring,six-DOF balls,and six-DOF cage.The model considers the starved lubrication in the ball-raceway contact and the full multi-body interactions between the bearing components.With different ball-raceway starvation degrees being analyzed,the effects of starved lubrication on the bearing tribo-dynamic performance are first revealed.By comparison,it is found that the oil film thickness,the skidding performance,and the traction forces in the ball-raceway contact are significantly influenced by the starvation degrees.It is also found that the starvation-induced change of the ball-pocket contact force is dramatical under combined loads,and the maximum contact force under this load condition increases with the increasing starvation degrees.展开更多
The topography of gear meshing interfaces is one of the key factors affecting the dynamic characteristics of the gear transmission system.In order to obtain the contact characteristics of meshing gear pair with differ...The topography of gear meshing interfaces is one of the key factors affecting the dynamic characteristics of the gear transmission system.In order to obtain the contact characteristics of meshing gear pair with different surface micro-topographies,an interface feature model and a tribo-dynamics coupling model for the gear system are proposed in this paper.The effects of the gear tooth surface micro-topography on the oil film distribution,contact damping and friction are considered.The time-varying meshing stiffness and the static transmission error are included in the abovementioned models.An exemplary gear pair is analyzed using the proposed models to investigate the influence of the surface micro-topography on the dynamic characteristics of gear system under different micro-topographies and input torque conditions.Simulation results show that the effects of gear tooth micro-topography on the gear dynamic responses(including the friction and the vicious damping at the gear meshing interface and the vibration in the direction of offline of action)are highly dependent on the regularity of tooth surface.The vibration and noise can be significantly controlled by manufacturing a regular gear tooth profiles instead of random profiles.展开更多
The thermal elastohydrodynamic lubrication characteristics of a modified gear system under a dynamic load were investigated,including the influence of the modification coefficient and vibrations.Based on the dynamic t...The thermal elastohydrodynamic lubrication characteristics of a modified gear system under a dynamic load were investigated,including the influence of the modification coefficient and vibrations.Based on the dynamic theory of gear systems,a six-degree-of-freedom tribo-dynamics model was established.Thermal elastohydrodynamic lubrication characteristics of a modified gear system under vibrations and a static load were analyzed.The results showed that the positive transmission gear system exhibited the better lubrication effect compared with other transmission types.A thick lubricating oil film could be formed,and the friction coefficient between the teeth and the oil film flash temperature were the smallest.As the modification coefficient increased,the lubrication condition was continuously improved,and the scuffing load capacity was enhanced.The increment of the modification coefficient increased the meshing stiffness of the gear system but reduced the stiffness of the oil film.展开更多
基金This study was supported by the Research Project of High Technological Vessels:Development of Low Speed Marine Engines(Grant No.MC-201501-D01-03)the National Natural Science Foundation of China(Grant No.51875344).
文摘A crosshead slipper-guide system,which bears a significant thrust force,is an essential friction pair in low-speed marine diesel engines.Owing to the low moving speed of the crosshead slipper during engine startup,it is difficult to form good hydrodynamic lubrication between the crosshead slipper and guide.Therefore,a detailed analysis of the crosshead slipper during engine startup is needed.In this study,a new transient tribo-dynamic model for a crosshead slipper during the engine startup process is presented.The model consists of a mixed lubrication model of the crosshead slipper-guide and dynamic models of the piston assembly,crosshead assembly,connecting rod,and crankshaft.The tribo-dynamic performances of the crosshead slipper during startup and under the rated conditions were simulated and compared.The results show that the tribo-dynamics of the crosshead slipper during the startup process are significantly different from those under the rated conditions.Some measures beneficial for the low friction of a crosshead slipper-guide under the rated conditions may significantly increase the friction loss of the crosshead slipper-guide system during the startup process.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.52130502 and 51875344)the Research Project of State Key Laboratory of Mechanical System and Vibration(Grant No.MSVZD202107)。
文摘When the oil supply is not adequate to maintain the ideal lubrication,angular contact ball bearing will enter into the starved lubrication regime resulting in the potential performance degradation and consequently the severe failures.To study the effects of starved lubrication on the performance of angular contact ball bearing,this paper first proposes a multi-degree-of-freedom(DOF)tribo-dynamic model by introducing five-DOF inner ring,six-DOF balls,and six-DOF cage.The model considers the starved lubrication in the ball-raceway contact and the full multi-body interactions between the bearing components.With different ball-raceway starvation degrees being analyzed,the effects of starved lubrication on the bearing tribo-dynamic performance are first revealed.By comparison,it is found that the oil film thickness,the skidding performance,and the traction forces in the ball-raceway contact are significantly influenced by the starvation degrees.It is also found that the starvation-induced change of the ball-pocket contact force is dramatical under combined loads,and the maximum contact force under this load condition increases with the increasing starvation degrees.
基金Projects(51905053,51805051)supported by the National Natural Science Foundation of ChinaProject(cstc2019jcyj-bshX0119)supported by the Chongqing Postdoctoral Science Foundation,China。
文摘The topography of gear meshing interfaces is one of the key factors affecting the dynamic characteristics of the gear transmission system.In order to obtain the contact characteristics of meshing gear pair with different surface micro-topographies,an interface feature model and a tribo-dynamics coupling model for the gear system are proposed in this paper.The effects of the gear tooth surface micro-topography on the oil film distribution,contact damping and friction are considered.The time-varying meshing stiffness and the static transmission error are included in the abovementioned models.An exemplary gear pair is analyzed using the proposed models to investigate the influence of the surface micro-topography on the dynamic characteristics of gear system under different micro-topographies and input torque conditions.Simulation results show that the effects of gear tooth micro-topography on the gear dynamic responses(including the friction and the vicious damping at the gear meshing interface and the vibration in the direction of offline of action)are highly dependent on the regularity of tooth surface.The vibration and noise can be significantly controlled by manufacturing a regular gear tooth profiles instead of random profiles.
基金Projects(51575289,51705270)supported by the National Natural Science Foundation of China。
文摘The thermal elastohydrodynamic lubrication characteristics of a modified gear system under a dynamic load were investigated,including the influence of the modification coefficient and vibrations.Based on the dynamic theory of gear systems,a six-degree-of-freedom tribo-dynamics model was established.Thermal elastohydrodynamic lubrication characteristics of a modified gear system under vibrations and a static load were analyzed.The results showed that the positive transmission gear system exhibited the better lubrication effect compared with other transmission types.A thick lubricating oil film could be formed,and the friction coefficient between the teeth and the oil film flash temperature were the smallest.As the modification coefficient increased,the lubrication condition was continuously improved,and the scuffing load capacity was enhanced.The increment of the modification coefficient increased the meshing stiffness of the gear system but reduced the stiffness of the oil film.
