Study Of The Supersonic Sliding On The Surface Of Elastic Solids

Sliding friction is the type of resistive effect that resists the relative tangential motion of objects,and the force of resistance is the sliding friction force.Friction forces exist in all aspects of engineering applications and it results in energy dissipation in the form of heat,sound or noise,wear,deformation: change of surface texture,etc.The study of the supersonic sliding on the surface of elastic solids was the focus of this thesis.It was to study the sliding and friction behavior for the subsonic,transonic,and supersonic regimes under both frictionless and friction-defined sliding conditions.The research works in this thesis were studied using 2D plane stress models with the commercial finite element solver,Abaqus FEA/Standard.These works are presented as follows:1.The friction force is always known as the force which resists the relative motion of objects.There has always been the need to reduce or possibly overcome the friction force since its discovery.In this study,the effects of the propagation of the elastic waves on the tangential force between a slider and an elastic substrate were studied using Newton's laws of motion.It was found that the friction force is not always a resistive force,but it can also provide a pushing force in specific cases in which the propagation of the elastic waves is considered.2.A slider-substrate sliding system was modeled under the frictionless condition to investigate if the deformation of the substrate will exist and its effect on the slider during the supersonic sliding.The friction behavior for the frictionless supersonic sliding on the surface of elastic solids was studied using two different constant tangential pulling forces.The numerical results for this frictionless supersonic sliding did not agree with the classical theoretical result(? =0: F_f= 0).Because they have shown the existence of sliding resistance during the frictionless supersonic motion.The results in this research provided insights into the understanding of the sliding and friction behavior for the supersonic sliding on the surface of elastic solids.3.When the slider is in a sliding motion with the substrate,energy is dissipated to friction according to Amontons' second law of friction.In this study,a sliding mechanism that is in the reverse direction to stone skipping was proposed for friction reduction using supersonic sliding speed.To reduce the effect of geometry on the friction force,the results were analyzed using the normalized conventional friction force or coefficient.The results have shown that the proposed sliding mechanism achieved a low normalized effective friction coefficient through the generation of a pushing force that was proportional to the normal load of the slider.4.Finally,under dry sliding condition,the use of the benchmark unstructured elastic substrate for the supersonic sliding has shown high friction effects in the sound barrier.Due to this reason,a new kind of substrate was proposed over the benchmark unstructured substrate for the supersonic sliding and textured its surface for friction reduction.The computational results were analyzed using the normalized friction coefficient to reduce the effect of geometry on the friction coefficient.The results have shown that the proposed substrate eliminated the sound barrier effect and had a steady friction behavior during the supersonic sliding with high friction reduction after its surface texture.