Instability Induced by Dry Friction

A theoretical analysis of the dynamic behavior of mechanical systems characterized by coupled e-lements subjected to friction force from the sliding surface is proposed. With reference to systems with one degree of freedom, and approximating the friction force as a piecewise linear function, i.e. straight line segments with a suitable slope, the positioning errors in the stop phase are studied. Dimensionless analytical relations used to predict the size of positioning errors and dimensionless diagrams are provided. Furthermore the influence of the dry friction on the dynamics of a system with two degrees of freedom is proposed. The model system consists of a body of mass m1, constrained by means of a spring and a damper to a driving support, moving relatively to its counterpart of mass m2. In the conditions stability of the position of equilibrium vibrations due the static friction and the support’s velocity have been pointed out.