Friction and wear performance of polyether ether ketone(PEEK)polymers in three lubrication regimes

This experimental study investigates the friction and wear of three coatings commonly used in industrial applications,particularly in hydrodynamic bearings.The three materials under investigation were Babbitt,polyether ether ketone(PEEK)reinforced with 15%carbon fibers,and PEEK reinforced with 20%carbon fibers.The first polymer material was extruded,while the other was produced by fused deposition modelling(FDM).The materials were subjected to sliding tests in a pin-on-disc configuration,with a steel ball serving as the counter surface.The tests were conducted at room temperature,with a load of 10 N and under three different lubrication conditions:dry,grease,and oil.The linear speed was set at 0.3 m/s for the dry and semi-solid lubrication tests,while for the oil tests,the speed was set at 0.25 m/s.The greases used had consistency grades of NGLI 000 and NGLI 2.An ISO VG 68 circulation oil was used for the oil lubrication tests.Additionally,thermodynamic analyses were performed under the most severe conditions(i.e.,dry)to investigate the steel-Babbitt and steel-PEEK contact.

Dynamic, thermal, and vibrational analysis of ball bearings with over-skidding behavior

The term“over-skidding”indicates that the cage rotational speed ratio exceeds the theoretical value as ball purely rolls on the raceway.Different from the skidding phenomenon that occurs in low-load and high-speed bearing,over-skidding usually occurs in large-size angular contact bearings,and it is still difficult to suppress under high load conditions.The main forms of damage to the raceway by over-skidding are spinning and gyro slip.To further explore the vibration characteristics and thermal effects of this phenomenon,a set of over-skidding tests of an angular contact bearing with a bore diameter of 220 mm were conducted on an industrial-size test bench.Through the experiment,the influence of axial load,rotational speed,and lubrication conditions on the occurrence of over-skidding were determined.Based on a previous dynamics model,the heat generation and thermal network models were integrated in the present study to predict the over-skidding and its thermal behavior.The model was validated in terms of the measured degree of over-skidding and temperature rise.The results showed that the degree of over-skidding reaches up to 12%of the theoretical value,and the friction power loss of the ball-pocket accounts for 30%of the total power loss.The analysis of the vibration signal showed a strong correlation between the bearing vibration characteristics and over-skidding behavior,thereby providing a way to indirectly measure the degree of over-skidding.