Showing papers on "Constrained-layer damping published in 1990"

Vibration damper having extended temperature range and low temperature shock resistance

Abstract: Constrained layer damping structures are often based on viscoelastic layers of iso-octyl acrylate:acrylic acid or analogous copolymers. As the acrylic acid content is increased, the peak damping temperature also increases; unfortunately, however, the copolymer becomes more brittle and susceptible to shock, especially at low temperatures. Incorporating small amounts of rubbery polymer particles (especially core-shell polymers) in the viscoelastic copolymer alleviates this problem.

Effects of constrained-layer damping on the dynamics of a Type 4 in-line head suspension

Abstract: Experimental frequency-response functions were obtained for several Type 4 inline suspension assemblies with lateral excitation. Mode shapes are described for all the modes observed between 1 and 15 kHz. The effect of a constrained-layer damper on several of the most important modes is described. It is shown that the damper is not an optimal solution for reducing the amplitude of the sway mode for the Type 4 inline suspension. It is also shown that the partial effectiveness of the damper for the sway mode results primarily from the damper region near the base of the suspension, and that the tip region of the damper has a negligible contribution towards energy dissipation for this mode. Of the load beam modes investigated, the sway mode was most affected by the addition of mass to the slider. >

Effectiveness of section length optimization for constrained viscoelastic layer damping treatments

Abstract: It is well known that constrained viscoelastic layer damping treatments provide an effective means of passive control for structural vibration. These treatments dissipate vibrational energy by inducing shear strain in a thin layer of viscoelastic material. Our interest is in adding passive damping to a structure as an augmentation to active control. For such applications it is desirable to achieve high damping performance in a given frequency range with a minimum of added weight. Constrained layer damping treatments most commonly employ spatially continuous constraining layers over the entire viscoelastic layer. Plunkett and Lee have shown that the effectiveness of the damping treatment can be significantly increased by sectioning the constraining layer into segments of optimal length for the target frequency range. The authors have observed that few have recognized the degree of improvement achievable through this method. The purpose of this paper is to illustrate the effectiveness of the method, through examples. It is demonstrated that, for a particular laboratory structure, the damping of the modes of interest can easily be increased by a factor of 10 or more by properly sectioning the constraining layer. The structure considered is a simple aluminum flat bar which is the arm of a single link flexible robot experiment. The damping material is 3M ISD-11O, and the constraining layer is 10 mu steel shim. Data is presented to compare experimental results with theoretical and finite element predictions. Plunkett and Lee's theory is used for theoretical analysis. The finite element model was developed based on MSC/NASTRAN code.