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New insight into the mechanisms of static and kinetic friction

EU-funded scientists have provided further insight into the dynamics underlying the transition from static to kinetic friction along heterogeneous interfaces. The results may help address important problems in various fields, including mechanical engineering, geology, biology and robotics.
New insight into the mechanisms of static and kinetic friction
Within the EU-funded project CASCADE (Frictional shear crack dynamics along heterogeneous interfaces), scientists conducted experimental and numerical work in an effort to provide a more comprehensive picture of the onset of sliding and, in particular, of the dynamics of shear cracks along heterogeneous interfaces.

The project started with the development, testing and calibration of an optomechanical device that monitors the frictional contact between a rough elastomer and a rigid substrate. First, the dynamics of the slip field were measured using a high-speed camera and digital image processing. Then, using image segmentation, scientists measured the dynamics of the real contact area along the interface.

As a result, the device served as a tool for first tests of classical models for the incipient tangential loading of the contact between the smooth rigid sphere and the rough elastomeric plane. In addition, it allowed study of the influence of a variety of system parameters on the static friction strength of the rough interface.

Scientists shed light on the dependence of the real contact area on the tangential force applied to the contact interface. They also studied the influence of the thickness of a soft solid coating deposited on the rigid substrate and concluded that, contrary to common belief, shear strength is not a material constant.

Experimental activities were supported by modelling work. The team developed a multi-scale model for unravelling the mechanisms behind the rupture dynamics of a multi-contact interface. Using the model, scientists were able to reproduce for the first time the transition from fast to abnormally slow fronts propagating along the interface. Modelling work also led to classification of the various types of possible shear crack fronts, and provided important insight into the mechanisms behind the selection of front speeds.

Overall, CASCADE's experimental and modelling work led to obtaining further insight into the mechanisms behind the transition of static to kinetic friction.

Related information

Keywords

Static, kinetic friction, heterogeneous interfaces, shear crack, frictional contact
Record Number: 190551 / Last updated on: 2016-11-18
Domain: Industrial Technologies
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