Abstract
In this study, the effects of ultrasonic nanocrystal surface modification (UNSM) technology on the fatigue life of needle roller bearings were investigated. The fatigue life of the untreated and UNSM-treated needle roller bearings was evaluated using a roller fatigue tester at various contact stress levels, under oil lubrication conditions. It was found that the fatigue life of the UNSM-treated needle roller bearing was extended by approximately 34.3% in comparison with the untreated one. The results of the surface roughness and surface hardness of the needle roller bearings before and after UNSM technology were compared and discussed in order to understand the role of UNSM technology in improving fatigue life. It was found that the application of UNSM technology to the needle roller bearings can improve their fatigue life by reducing the friction coefficient and increasing the wear resistance, which may be attributed to the reduction in surface roughness from 0.50 µm to 0.15 µm and also the increase in surface hardness from 58 HRC to 62 HRC.
Highlights
A bearing is one of the important mechanical components and is indispensable in almost all industries, such as steel, automotive, power plant equipment, and aerospace. [1]
The results show the improvement in the fatigue life of the ultrasonic nanocrystal surface modification (UNSM)-treated specimen by
The longest fatigue life at 1484 Mpa contact stress was found to be a 70.1% increase in the fatigue life of the UNSM-treated bearing compared to the untreated specimen
Summary
A bearing is one of the important mechanical components and is indispensable in almost all industries, such as steel, automotive, power plant equipment, and aerospace. [1]. The effect of ultrasonic nanocrystal surface modification (UNSM) technology on the fatigue life of needle roller and angular ball bearings was investigated. These bearings are widely used in rear wheel drive transmission, constant velocity joints and mechanical pumps. Surface and microstructure-related damage such as flaking, cracking and wear, is caused by friction and fretting during the operation and can affect the fatigue life of bearings [6] In this regard, it is necessary to improve the fatigue life of bearings by controlling the surface properties of bearing raceways. A UNSM technology, which was developed in South Korea, is applied to the surface of the inner and outer raceways of bearings to improve the fatigue life by reducing the surface roughness, increasing the strength, and transferring a tensile residual stress into compressive residual stress
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