| This work is motivated by the realization that the phenomena of noise and vibration caused by frictional contact in mechanical systems must be related to the properties of the contact. This thesis provides predominantly a theoretical investigation of the mechanical interaction of two surfaces in frictional contact.;Three parameters of interest to vibration response are considered that include equivalent (macroscopic) contact stiffness, damping and friction function (contact tangential-to-normal load ratio). The equivalent parameters are obtained through micronscale consideration of surface interactions and their statistical summation. Initially, elastic and elastic-plastic interactions of surfaces are treated leading to the mathematical formulations of tangential and normal components of contact force and stiffness. In developing the elastic-plastic model the plastic asperity concept is forwarded and is shown to be expedient in ascertaining the elastic and plastic parts of force and stiffness components. The plastic asperity leads to the concept of ultimate-stress asperity. Utilizing the surface, plastic and ultimate-stress asperities, mathematical formulations of contact damping, energy loss and wear are developed.;The analytical work is extended further by including the visco-elastic properties at the contact. The dynamic response of a spring-mass-damper in frictional contact with a moving platform is considered. The equations for contact stiffness as well as viscoelastic characteristics are implemented in the equations of motion of mass-spring-damper system. It is shown that the formulation of contact stiffness and force allows the inclusion of frictional contact without the necessity of including friction/velocity relation phenomenologically. That is no assumption of friction/velocity relation is made in the formulation of the governing differential equations. Friction is obtained together with the resulting dynamic response of the system. It is demonstrated that the contact and the mechanical system have a mutual influence, i.e. effect and feedback.;The research has resulted in three contact models that include the accounts of elastic, elastic-plastic and viscoelastic effects of interacting surfaces. Additional contributions of this research entail the model for prediction of wear and estimation of contact damping. |
