### Abstract

In this paper, pure squeeze elastohydrodynamic lubrication motion of circular contacts with couple stress lubricant is explored at impact loading. On the basis of microcontinuum theory, the transient modified Reynolds equation is derived. Then it is solved simultaneously with the elasticity deformation equation and ball motion equation, thus obtaining the transient pressure profiles, film shapes, normal squeeze velocities, and accelerations. The simulation results reveal that the effect of the couple stress is equivalent to enhancing the lubricant viscosity, which would also enlarge the damper effect. Therefore, as the characteristic length of the couple stress fluid increases, the pressure spike and the dimple form earlier the maximum pressure and the film thickness increase, and the diameter of the dimple, the rebounding velocity, the maximum value of the relative impact force, and the acceleration decrease. Furthermore, the fact that the contact central pressure for a ball impacting and rebounding from a lubricated surface reached two peaks during the total impact period is proved numerically in this analysis. As the effect of couple stress increases, the first and second peaks form earlier; as the total impact time decreases, the pressure of the first peak increases and that of the second peak decreases. Moreover, the phase shift between the time of the peak value of the squeeze acceleration and the zero value of the squeeze velocity increases with increasing the characteristic length of the couple stress fluid.

Original language | English |
---|---|

Article number | 011010 |

Journal | Journal of Tribology |

Volume | 130 |

Issue number | 1 |

DOIs | |

Publication status | Published - 2008 Jan 1 |

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### All Science Journal Classification (ASJC) codes

- Mechanics of Materials
- Mechanical Engineering
- Surfaces and Interfaces
- Surfaces, Coatings and Films

### Cite this

*Journal of Tribology*,

*130*(1), [011010]. https://doi.org/10.1115/1.2805430

}

*Journal of Tribology*, vol. 130, no. 1, 011010. https://doi.org/10.1115/1.2805430

**Effects of couple stress on elastohydrodynamic lubrication at impact loading.** / Chu, Hsiao Ming; Li, Wang-Long; Chang, Yuh Ping; Huang, Huan Chang.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Effects of couple stress on elastohydrodynamic lubrication at impact loading

AU - Chu, Hsiao Ming

AU - Li, Wang-Long

AU - Chang, Yuh Ping

AU - Huang, Huan Chang

PY - 2008/1/1

Y1 - 2008/1/1

N2 - In this paper, pure squeeze elastohydrodynamic lubrication motion of circular contacts with couple stress lubricant is explored at impact loading. On the basis of microcontinuum theory, the transient modified Reynolds equation is derived. Then it is solved simultaneously with the elasticity deformation equation and ball motion equation, thus obtaining the transient pressure profiles, film shapes, normal squeeze velocities, and accelerations. The simulation results reveal that the effect of the couple stress is equivalent to enhancing the lubricant viscosity, which would also enlarge the damper effect. Therefore, as the characteristic length of the couple stress fluid increases, the pressure spike and the dimple form earlier the maximum pressure and the film thickness increase, and the diameter of the dimple, the rebounding velocity, the maximum value of the relative impact force, and the acceleration decrease. Furthermore, the fact that the contact central pressure for a ball impacting and rebounding from a lubricated surface reached two peaks during the total impact period is proved numerically in this analysis. As the effect of couple stress increases, the first and second peaks form earlier; as the total impact time decreases, the pressure of the first peak increases and that of the second peak decreases. Moreover, the phase shift between the time of the peak value of the squeeze acceleration and the zero value of the squeeze velocity increases with increasing the characteristic length of the couple stress fluid.

AB - In this paper, pure squeeze elastohydrodynamic lubrication motion of circular contacts with couple stress lubricant is explored at impact loading. On the basis of microcontinuum theory, the transient modified Reynolds equation is derived. Then it is solved simultaneously with the elasticity deformation equation and ball motion equation, thus obtaining the transient pressure profiles, film shapes, normal squeeze velocities, and accelerations. The simulation results reveal that the effect of the couple stress is equivalent to enhancing the lubricant viscosity, which would also enlarge the damper effect. Therefore, as the characteristic length of the couple stress fluid increases, the pressure spike and the dimple form earlier the maximum pressure and the film thickness increase, and the diameter of the dimple, the rebounding velocity, the maximum value of the relative impact force, and the acceleration decrease. Furthermore, the fact that the contact central pressure for a ball impacting and rebounding from a lubricated surface reached two peaks during the total impact period is proved numerically in this analysis. As the effect of couple stress increases, the first and second peaks form earlier; as the total impact time decreases, the pressure of the first peak increases and that of the second peak decreases. Moreover, the phase shift between the time of the peak value of the squeeze acceleration and the zero value of the squeeze velocity increases with increasing the characteristic length of the couple stress fluid.

UR - http://www.scopus.com/inward/record.url?scp=42149146068&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=42149146068&partnerID=8YFLogxK

U2 - 10.1115/1.2805430

DO - 10.1115/1.2805430

M3 - Article

VL - 130

JO - Journal of Tribology

JF - Journal of Tribology

SN - 0742-4787

IS - 1

M1 - 011010

ER -