Experimental and Numerical Analysis of the Effect of Segmentation on Modal Loss Factor of Constrained Layer Damped Beam

Abstract

This paper presents experimental investigation on the damping effects of constrained layer treatment by cutting the constraining layer and constrained layer of viscoelastic material (VEM). The constraining layer causes shear in the damping material as the structure deforms. The shear deformation occurring in the viscoelastic core is mainly responsible for the dissipation of energy. The shear deformation in the VEM is not significant in regions where the bending moment is maximal. Mostly only extensional deformation occurs in the damping layer. The local high-shear deformation in the damping material is produced by placing a cut at the region of highest curvature. Cutting both the constraining and the constrained layer, which leads to segmentation, increases the shear deformation at that position. This appropriate position of high bending moment for segmentation is obtained by MATLAB program. The modal loss factor of constrained layer damped (CLD) beam is obtained by half-power bandwidth method using FFT analyzer. The CLD beams are prepared as per ASTM Standard E 756-05. Extensive experiments are conducted by making number of separate segmented CLD beams of different viscoelastic damping materials. A three dimensional model of cantilever CLD beam has been used for numerical analysis. In this work, finite element commercial software MSC/NASTRAN is used to simulate the dynamic response of a CLD beam. The modal loss factor of constrained layer damped (CLD) beam is measured by Modal Strain Energy (MSE) Method. This is a new method for enhancement of damping capabilities of constrained layer damping. It is found that the performance of segmented CLD beam using passive treatment shows significant improvement in modal loss factor which leads to vibration attenuation of beam. The numerical results are corroborated with experimental data obtained for segmented CLD beam. The analyzed finite element models are found to provide reliable results and compared very well with experimentally acquired data.