The properties of damping vibrations by a layer of carbon nanotubes on the lateral surface of a piston

As a result of applying the hydrodynamic lubrication theory in the piston-cylinder group of a combustion engine, the authors have obtained the opportunity for practical elimination of abrasion of this unit. However, it turns out that in the case of the engine start, especially after a longer standstill and before the oil film is formed, the piston lateral surface’s micro-roughness comes into direct contact with the cylinder bearing surface. For this reason, manufacturers more and more commonly apply a special layer on the lateral surface of a piston, which decreases the friction force and eliminates very damaging effects of the so-called semi-dry friction. It turns out that applying an enriching layer on the lateral surface of the piston may result in an additional effect, which is not usually associated with the pistoncylinder unit. This effect is the damping of torsional vibrations. Thus, despite the seemingly insignificant properties of materials which the elements of the kinematic pair are made of, as a result of the occurrence of the layer with specific properties on these elements, one may find that these layers – even when they are separated by the oil film – can change the parameters of collaboration of the elements of the kinematic pair. In particular, it concerns generating and damping vibrations, and in such circumstances frictional losses may also be subject to change, which is the main domain of the conducted research presented in this paper. The article analyzes various effects which are caused by applying a special layer formed of carbon nanotubes (NCT in short) on the lateral surface of the piston.