FRICTION: FROM MACRO- TO MICRO-SCALE
| Quand ? |
Le 10/10/2016, de 11:00 à 11:00 |
|---|---|
| Où ? | Centre Blaise Pascal, LR6 |
| Participants |
Frédéric Restagno |
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Friction is a common phenomenon that occurs when to objects are force to move tangentially relatively to each other. During this seminar, we shall present an introduction to the classical laws of friction known as the Amontons and Coulomb laws in a historic perspective. Figure 1 : Car hold by two interleaved phonebooks. Copyrights France 5/2p2l. We will then focus on a simple question related to friction which was first asked by the frenche TV-show "On n'est pas que des cobayes": why can we hold a car with two interleaved phonebooks. We have studied the force needed to separate two books as a function of the number of sheets, the thickness of the sheets, and the interleaving distance in a systematic way [1]. We have shown that the strength of the system is due to the operator : the person, car, truck amplifies any small friction arising from the normal force acting on the boundaries of the stack. We have proposed for the first time a model that captures all the data into a single mastercurve. We will show that this very macroscopical study allows us to get some information about the adhesion forces induced by the capillary forces between the paper pages [2]. The study of this complex network provides insight into friction with some connections to MEMS, mooring a ship, interactions between DNA and bacteriophage capsid, and even a toy known as the Chinese finger trap.
[1] H. Alarcón, T. Salez, C. Poulard, J.-F. Bloch, É. Raphaël, K. Dalnoki-Veress, and F. Restagno, Phys. Rev. Lett. 116, (2016).
[2] Restagno, F., Ursini, C., Gayvallet, H., & Charlaix, É. (2002). Aging in humid granular media. Physical review E, 66(2), 021304.