EXISTENCE AND UNIFORM DECAY ESTIMATES FOR THE FOURTH ORDER WAVE EQUATION WITH NONLINEAR BOUNDARY DAMPING AND INTERIOR SOURCE

In this paper, we consider the initial boundary value problem for the fourth order wave equation with nonlinear boundary velocity feedbacks f(1)(u(vt)), f(2)(u(t)) and internal source vertical bar u vertical bar(rho)u. Under some geometrical conditions, the existence and uniform decay rates of the solutions are proved even if the nonlinear boundary velocity feedbacks f(1)(u(vt)), f(2)(u(t)) have not polynomial growth near the origin respectively. By the combination of the Galerkin approximation, potential well method and a special basis constructed, we first obtain the global existence and uniqueness of regular solutions and weak solutions. In addition, we also investigate the explicit decay rate estimates of the energy, the ideas of which are based on the construction of a special weight function phi(t) (that depends on the behaviors of the functions f(1)(u(vt)), f(2)(u(t)) near the origin), nonlinear integral inequality and the Multiplier method.