Papers by Author: Li Qin Wang

Abstract: The dynamic model of the cage in high-speed ball bearing was developed according to the geometry and force relationship between bearing elements. Based on this dynamic model, cage instability was researched through mass center whirl. The effect of clearance ratio, load and bearing rotation speed on cage instability were studied by taking type 7004 angular ball bearing as an example. The results shown that the increase of clearance ratio and radial load makes cage stability lowered, and the cage stability could be enhanced by increasing the axial load and bearing rotation speed.

Abstract: Radial lip seals made from PTFE composites are used more frequently for sealing of crank shafts in automotive and aerospace industries. Due to the seal loses materials and finally fails. Through experiment on a test rig, the tribology performance of seal can be predicted. Because of the non-linear elasto-viscoplastc material properties of PTFE composites, the finite element analysis (FEA) is adopted. A modified iterative remeshing method is adopted in wear process. The lip wears out according to the contact pressure of the node on the contact surface. Comparisons between numerical simulation and short-term service are made. The results show that the maximum of contact pressure decreased and width increased with wear time added, and the maximum of contact pressure moves toward the lip tip. Finally, it reaches lip tip, the phenomenon of uneven contact pressure was disappeared.

Abstract: Semi-dynamic method is employed to calculate the local stiffness of angular contact ball bearing, accounting for the influence of geometrical deflects caused by shaft coaxiality in the process of bearing assemble. The effect of coaxiality on the bearing deflect is computed, and the relationship of local bearing stiffness to coaxiality is analyzed.

Abstract: The tribological performances of mixed PTFE-based composites were evaluated on the MM-200 block-on-ring test rig under dry friction condition. The following filler contents: carbon fiber (CF), flake graphite (FG) and spherical graphite (SG) were adopted to investigate their effects on the tribological performances of the composites. The experiments were carried out by a four levels orthogonal table-L₁₆（4³）, and the experiment data were deal with the methods of range and variance analysis. The results shown that all the filler contents could reduce wear, and the wear rate was stable when the content of fillers were more than 10 wt.%. The degrees of three fillers affecting the wear of composites were CF>FG>SG, and that affecting the friction coefficient were SG>CF>FG. The friction coefficient decreased with increasing the contents of SG, increased with that of CF, first decreased and then increased with that of FG. When the contents of FG is 15 wt.%, the friction coefficient is the lowest. The main worn form was adhesion wear.

Abstract: In this paper, the gear acceleration noise model is first built up. The theoretical formula for calculating meshing acceleration noise is developed by dynamic analysis. Base on the impact theory, we first treat the gear meshing behavior as two variable radius cylinders, construct dynamics model, and then according to the industry standard to calculate sound pressure value one meter away by simulation,. Finally, we obtain the optimize equation according to the relation of parameters and noise.

Abstract: According to roller profile modification method, several commonly used modified rollers were selected into the bearing dynamic analysis combined with dynamic model of bearing. As the three types of modified roller an example, simulation program was established to analyze the load distribution of loaded roller under the working conditions of upright loading and offset loading of bearing, respectively. The effects of modified roller on bearing dynamic parameters were discussed. The results provided optimal direction for bearing selection and design under different working conditions.

Abstract: In this work, the feasibility of using planetary ball milling for coating bearing balls with a self-lubricating film was investigated. Bearing balls with appropriate amount of MoS2 powder were put into vacuumed stainless steel vials and ball milled. With proceeding of ball milling, thickness of the self-lubricating film increased at first and then decreased. X-ray diffraction (XRD) and X-ray photoelectron spectrum (XPS) results revealed that the surface of the self-lubricating film was MoS2 and the inner region was a mixture of iron molybdenum alloys (Fe3Mo, FexMoy), MoS2 and FeS. Friction coefficient between the self-lubricating film and bear steel was 0.06~0.1.

Abstract: The friction and wear performances of Si3N4 ceramics sliding against bearing steel and to find optimal operating condition against M50 bearing steel couples under high vacuum surroundings were investigated. The tests were studied on the ball-disk machine under different loads and steady sliding velocity. The worn surfaces of tested samples were examined using optical microscope，SEM and XPS. The results showed that the friction coefficient of Si3N4 was decided by the applied load, the critical load of Si3N4’ friction coefficient was 10N applied load; The critical load of Si3N4’ specific wear rate was 5N applied load, the specific wear rate of Si3N4 drop rapidly as the applied load exceeded the critical load; The dominant wear mechanisms of Si3N4 ceramics were adhesion wear, brittle facture and furrow wear in vacuum.