Effects of Tuned Mass Damper on Fixed-Fixed 3D Nonlinear String Resting on Nonlinear Elastic Foundation

This paper studies the vibration of a nonlinear 3D-string fixed at both ends and supported by a nonlinear elastic foundation. Newton's second law is adopted to derive the equations of motion for the string resting on an elastic foundation. Then, the method of multiple scales (MOMS) is employed for the analysis of the nonlinear system. It was found that 1: 3 internal resonance exists in the first and fourth modes of the string when the wave speed in the transverse direction is a(2) approximate to 101.5 and the elasticity coefficient of the foundation is k(y) = 9 pi(4). Fixed point plots are used to obtain the frequency responses of the various modes and to identify internal resonance through observation of the amplitudes and mode shapes. To prevent internal resonance and reduce vibration, a tuned mass damper (TMD) is applied to the string. The effects of various TMD masses, locations, damper coeffcients (g(s)), and spring constants (f(s)) on overall damping were analyzed. The 3D plots of the maximum amplitude (3D POMAs) and 3D maximum amplitude contour plots (3D MACPs) are generated for the various modes to illustrate the amplitudes of the string, while identifying the optimal TMD parameters for vibration reduction. The results were veri fied numerically. It was concluded that better damping effects can be achieved using a TMD mass ratio m(D) = 0.3-0.5 located near the middle of the string. Furthermore, for damper coeffcient g(s) = 0: 9, the use of spring constant f(s) = 9-13 can improve the overall damping.