Effect of Various Type of Nanoparticles on Mechanical and Tribological Properties of Wear-Resistant PEEK + PTFE-Based Composites

The mechanical and tribological properties of polyetheretherketone (PEEK)- and PEEK + PTFE (polytetrafluoroethylene)-based composites loaded with and four types of nanoparticles (carbonaceous, metallic, bimetal oxide, and ceramic) under metal- and ceramic-polymer tribological contact conditions were investigated. It was found that loading with the nanofillers in a small content (0.3 wt.%) enabled improvement of the elastic modulus of the PEEK-based composites by 10–15%. In the metal–polymer tribological contact, wear resistance of all nanocomposites was increased by 1.5–2.3 times. In the ceramic-polymer tribological contact, loading PEEK with metal nanoparticles caused the intensification of oxidation processes, the microabrasive counterpart wear, and a multiple increase in the wear rate of the composites. The three component “PEEK/10PTFE/0.3 nanofillers” composites provided an increase in wear resistance, up to 22 times, for the metal–polymer tribological contact and up to 12 times for the ceramic-polymer one (with a slight decrease in the mechanical properties) compared to that of neat PEEK. In all cases, this was achieved by the polymer transfer film formation and adherence on the counterparts. The various effects of the four types of nanoparticles on wear resistance were determined by their ability to fix the PTFE-containing transfer film on the counterpart surfaces.

A Segmented Preprocessing Method for the Vibration Signal of an On-Load Tap Changer

The vibration signal of an on-load tap changer (OLTC) consists of a series of sharp vibration bursts, and its fault feature in certain periods is easily missed. This study considered that preprocessing the vibration signal of the OLTC in segments could effectively solve the aforementioned problem. First, the collection of the signal is discussed, the waveform characteristics of the vibration signal when the OLTC was in normal action was described, and the selection of the signal was analyzed. Second, the time domain characteristics and frequency spectrum analyses were carried out to demonstrate the necessity of segmented preprocessing. Further, the segmented preprocessing method for the vibration signal of the OLTC was presented. Finally, the main mechanical faults of the OLTC were simulated, and the vibration signals were collected to carry out the fault diagnosis experiment on the OLTC. The experimental results showed that the accuracy of the fault diagnosis increased from 94.30% of the nonsegmented preprocessing to 98.46% of the segmented preprocessing. The increase was greater, especially for contact wear faults. The method was successfully applied to the actual project.

A dynamic contact wear model of ball bearings without or with distributed defects

A dynamic contact wear model of ball bearings consisting of wear degree and position distribution is proposed by integrating the developed contact wear model, multi-body dynamics and raceway waviness or ball diameter differences. Subsequently, the dynamic wear characteristics, not only for the ideal bearing under different axial and radial loads, but also for the bearing with above defects are analysed. The influences of load, typical waviness orders and amplitude on the wear of each ball against both raceways are evaluated and qualitatively validated. Finally, the dynamic characteristics of ball bearings with one ball larger are discussed, and then vibration frequency and wear rates distinction are verified by the experiment with working-surface roughness measurement as a way for wear rate assessment.