Facile wear failure monitoring of commercial bearing alloys using I-kaz method

• Correlation of noise signal and wear response via air-borne method due to sliding action.
• Friction coefficient of A7075 bearing alloys against steel was in the range of 0.02–0.13.
• Three distinct regions in the wear stages; the running-in, the steady state and the severe wear.
• Z̵∞ values were applicable to predict the K′ value with the accuracy of 96–99%.

Numerous methods have been well developed in the area of bearing monitoring. This paper presents an experimental study of wear monitoring of connecting rod bearings type AA7075-T6 within audio frequency signals; f < 20 kHz against a AISI4340 hardened steel via air-borne with the aid of tribometer. The objective of this study is to determine the correlation between the noise signals and wear responses via air-borne method generated due to the sliding wear action. The wear tests were carried out by using a pin-on-disc configuration at a range of sliding speed 5.24, 7.85 and 9.95 m/s. A set of sliding distance was utilised, ranging from 20 to 160 km at a fixed load of 200 N. The test was performed under a lubricated sliding condition using a SAE40 type lubricant to imitate the actual operation of the connecting rod bearings. Presented results were obtained using a microphone 40SC type which was located 10 mm from the pin-on-disc contact. The extracted noise was represented as numerical descriptor of I-kaz coefficient, Z̵∞ using MATLAB software. From the analysis, it was noted that the specific wear rate K′, value was proportional to an increase of sliding velocity in which K′ lies in between 1.36 and 7.96 × 10−8 mm3/Nm. Based on the morphology investigation, it was found that under a lubricated test, parallel grooves and craters up to 10 μm in size were present, indicating the occurrence of the abrasive action of fresh abrasive action caused by the entrapment of hard debris particles that protruded soft mating materials thus, resulting a higher coefficient of friction. Oxides formation in adhesive junction was attributed to yield a lower friction, and this was clearly supported by X-ray diffraction spectra on worn surfaces. Furthermore, from the microstructure observation of worn surfaces it was also strongly suggested that a combination of adhesion, abrasion, fatigue and delamination wear mechanisms had occurred. Detailed changes in wear responses were analysed and displayed in I-kaz™ 3D spaces. This approach is capable of determining bearing condition, thus allowing the end-user to monitor the wear rate and the degradation of the bearings.