Numerical simulation of ferrofluid-lubricated rough elliptical contact with start-up motion

Abstract As exotic magnetic colloids, ferromagnetic ferrofluids have excellent tribological characteristics for many applications in mechanical environments. The anti-wear issues of extremely unstable technological conditions such as frequent start-up motions is an intractable challenge. The strategy of employing ferrofluid lubrication in the start-up motion from ultra-low speed to operating speed is a potential approach to improving the severe wear of rough elliptical contact. This paper presents a revised mixed lubrication model that accounts for magnetic field circumstances. Considering Gaussian random roughness, time-varying effect, and thermal effect, the lubrication equations are numerically calculated. First, four start-up modes are evaluated and compared; then the differences between ferrofluids and base oil are quantitatively studied. Furthermore, the influences of ferromagnetic particle size and magnetic field intensity on the film formation and wear of rough elliptical contact are discussed. Results show that ferrofluid lubrication is of great significance in wear reduction compared with base oil. The start-up motion with high accelerated speed is advantageous in film lubrication and wear reduction. Additionally, decreases in ferromagnetic particle size and increases in magnetic field intensity satisfactorily enhance the anti-wear performance of rough elliptical contact.