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Minimal adhesion surface area in tangentially loaded digital contacts
Alexander V Terekhov1, Vincent Hayward
1UPMC Univ Paris 06, UMR 7222, Institut des Systèmes Intelligents et de Robotique, Paris, France.
Journal of Biomechanics
|July 22, 2011
Summary
The transition from sticking to slipping during fingertip contact isn't instant. A new model predicts a "minimal adhesion surface area" phenomenon during partial slip, observed in some experimental data.
Area of Science:
- Biomechanics
- Tribology
- Friction and Adhesion
Background:
- The transition from static to kinetic friction in biological systems, like fingertip contact, is complex.
- Partial slip, where only portions of the contact surface adhere, is a key intermediate state.
- Understanding this transition is crucial for grasping manipulation and grip control.
Purpose of the Study:
- To develop a quasi-static model of the stick-to-slip transition for fingertip contact.
- To investigate the phenomenon of a diminishing stuck surface area under increasing tangential load.
- To compare model predictions with experimental finger-slip data.
Main Methods:
- Development of a quasi-static model for fingertip-planar surface contact.
- Analysis of partial slip dynamics based on friction coefficients.
- Processing of experimental finger-slip image data using an optic flow detection algorithm.
Main Results:
- The model predicts that if kinetic friction exceeds static friction, the stuck surface area decreases with load.
- A critical point, the 'minimal adhesion surface area,' was predicted where adhesion vanishes abruptly.
- Experimental data showed the minimal adhesion surface area phenomenon in 4 out of 10 trials.
Conclusions:
- The stick-to-slip transition is not instantaneous and involves partial slip.
- The minimal adhesion surface area is a predictable phenomenon under specific friction conditions.
- Experimental validation of the model was partial, suggesting further investigation is needed.
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