Tribology Letters

, 67:126 | Cite as

On the Gravity-Driven Sliding Motion of a Planar Board on a Tilted Soft Porous Layer

  • Zenghao Zhu
  • Rungun Nathan
  • Qianhong WuEmail author
Original Paper


In this paper, we report a novel experimental study to investigate the gravity-driven sliding motion of a planar board over a tilted soft porous layer. A laser displacement sensor was used to measure the motion of the board, while a high-speed camera was adopted to capture the detailed compression of the porous layer when the board glided over it. The pore pressure generation, as a result of the compression, was recorded by pressure sensors mounted on the bottom surface of the porous layer. One finds that, the pressure distribution agrees well with the theory developed by Wu and Sun (Med Sci Sports Exerc 43:1955–1963, 2011). Extensive parametric study was performed by varying the center of gravity of the planar board, the tilted angle and the porous material. Consistent agreement between the theoretical predictions and experimental results was obtained. It shows that, the effect of soft porous lubrication is enhanced when the center of gravity moves toward to the trailing edge of the planar board, or the tilted angle of the porous layer is increased, or a smoother fibrous surface is used.

Graphic Abstract


Porous media Soft lubrication Permeability Pore pressure Sliding motion 



This research was supported by the National Science Foundation under Award No. 1511096. The authors would like to acknowledge Mr. Lu An for helping in SEM analysis of the testing materials, and Mr. Bchara Sidnawi and Mr. James Reynolds for manuscript proof-reading. The technical support from Mr. Chris Townend and Mr. Zach Nowasad are greatly appreciated.

Supplementary material

11249_2019_1238_MOESM1_ESM.mp4 (1.6 mb)
The sliding motion of the planar board on the porous layer is recorded by a high-speed camera at the moment when the geometric center of the board gliding through the absolute location S = 98.9 mm. We provide herein two videos which represent two different D/L ratios when θ = 17.5° and the porous material is cotton fibers. Video 1 is for D/L = 1.42, while Video 2 is for D/L = 0.17. It is clearly shown in these two videos the instantaneous compression of the porous layer. Supplementary material 1 (MP4 1633 kb)
11249_2019_1238_MOESM2_ESM.mp4 (1.2 mb)
Supplementary material 2 (MP4 1261 kb)


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Villanova Cellular Biomechanics and Sports Science LaboratoryVillanovaUSA
  2. 2.Department of Mechanical EngineeringVillanova UniversityVillanovaUSA
  3. 3.Division of EngineeringPenn State BerksReadingUSA

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