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<p>This study presents the characteristics of transient elastohydrodynamic lubricating film thickness and its rate of change when subjected to the influence of an oscillatory entrainment speed. The effects of entrainment velocity amplitude, nominal velocity, load and frequency on the relative film thickness variations are described in detail. Oscillatory contact surface entrainment speed was performed to simulate transient response of elastohydrodynamic lubrication. The Reynolds equation, film thickness equation considering surface deformation, and load balancing equation are concurrently solved utilizing the Newton–Raphson technique in conjunction with the Gauss–Seidel iteration method. The numerical findings indicated that the fluctuation in film thickness at the contact centerline caused by fluctuating speed primarily relies on two factors: the frequency of entrainment velocity and the amplitude of relative entrainment velocity. The contact demonstrates quasi-static behavior at low frequencies, with the solution closely resembling steady-state solutions for instantaneous velocity at a specific time. With increased frequency, the transient effects increase leading to changes in the inlet film propagation in the central region and a reduction in film thickness to be diminished. For small velocity amplitude, the film thickness varies harmonically. As the velocity amplitude increases, the amplitude of these variations also increases. However, along with the increase in amplitude, the shape of the film thickness becomes distorted and asymmetric. The novelty of this research, following the validation of the numerical solution, lies in studying the impact of previously unstudied operational parameters, such as load and a spectrum of frequencies, on the behavior of elastohydrodynamic lubricated contacts. Additionally, a comprehensive physical explanation will be provided concerning the behavior of these contacts, especially in terms of film thickness and pressure profiles at different time snapshots, in conjunction to the squeeze film velocity and entrainment velocity.</p>

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Film thickness variations under transient conditions of speed oscillation in point contact elastohydrodynamic lubrication

  • 期刊论文

  • 发表日期：

    2025年5月20日

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  • Mohamed Fahmy Abd Al-Samieh

摘要

This study presents the characteristics of transient elastohydrodynamic lubricating film thickness and its rate of change when subjected to the influence of an oscillatory entrainment speed. The effects of entrainment velocity amplitude, nominal velocity, load and frequency on the relative film thickness variations are described in detail. Oscillatory contact surface entrainment speed was performed to simulate transient response of elastohydrodynamic lubrication. The Reynolds equation, film thickness equation considering surface deformation, and load balancing equation are concurrently solved utilizing the Newton–Raphson technique in conjunction with the Gauss–Seidel iteration method. The numerical findings indicated that the fluctuation in film thickness at the contact centerline caused by fluctuating speed primarily relies on two factors: the frequency of entrainment velocity and the amplitude of relative entrainment velocity. The contact demonstrates quasi-static behavior at low frequencies, with the solution closely resembling steady-state solutions for instantaneous velocity at a specific time. With increased frequency, the transient effects increase leading to changes in the inlet film propagation in the central region and a reduction in film thickness to be diminished. For small velocity amplitude, the film thickness varies harmonically. As the velocity amplitude increases, the amplitude of these variations also increases. However, along with the increase in amplitude, the shape of the film thickness becomes distorted and asymmetric. The novelty of this research, following the validation of the numerical solution, lies in studying the impact of previously unstudied operational parameters, such as load and a spectrum of frequencies, on the behavior of elastohydrodynamic lubricated contacts. Additionally, a comprehensive physical explanation will be provided concerning the behavior of these contacts, especially in terms of film thickness and pressure profiles at different time snapshots, in conjunction to the squeeze film velocity and entrainment velocity.