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The paper presents the basic features of the steady-state performance of a two-degree of freedom system consisting of a main linear spring mass system under periodic forcing, the motion of which acts parametrically on the motion of an attached absorber system. Terms, nonlinear in the absorber motion, act back on the main mass and with appropriate choice of tuning parameters, “absorption” of the main mass response can be obtained. Experimental results for this type of device are compared with a theoretical solution obtained from a first order asymptotic approximation. Comparison is also made with the performance of a linear tuned and damped absorber.

The Hu-Washizu variational principle in linear elasticity in which displacement, strain, and stress can be independently varied is extended, for application to dynamic problems, to include independent variation of the velocities associated with the displacements. Such independent variation is of value in the construction of approximate theories for beams and plates.

In this paper the numerical and experimental response of a two degree of freedom, discontinuously nonlinear rotor system, which is subject to excitation by out-of-balance is considered. The nonlinearity in the form of a discontinuous stiffness is effected by a radial clearance between the elastically supported rotor and an elastically supported outer ring. The rotor is placed eccentrically within this ring so that it is just touching one side of the inner bearing housing. The equations of motion for the system are presented and the numerical techniques used to solve them are described. A description of a corresponding experimental rig is presented, along with details of the procedures used to investigate its response. By employing various chaos and spectral analysis techniques comparison is made between the results obtained from the two methods of investigation. Reasonable correlation is found. Subsequently, the results from further numerical simulations are presented which investigate the effect on the systems response when various system parameters are altered systematically. These show that the response of the system is extremely sensitive to changes in these parameters and that chaos can exist over large regions of the parameter space.