Constrained-layer damping

About: Constrained-layer damping is a research topic. Over the lifetime, 795 publications have been published within this topic receiving 15758 citations.

Bending and torsional vibration control of composite beams through intelligent constrained-layer damping treatments

Abstract: This paper is to develop a mathematical model to predict bending, twisting, and axial vibration response of a composite beam with intelligent constrained layer (ICL) or active constrained layer (ACL) damping treatments. In addition, preliminary experiments are conducted on composite beams to evaluate this new technique. The ICL composite beam model is obtained by integrating the existing ICL composite plate model proposed by Shen. When the plate width (along the x-axis) is much smaller than the plate length (along the y-axis), integration of the ICL composite plate equations and linearization of displacement fields with respect to x leads to a set of equations that couples bending, tosional, and axial vibrations of a composite beam. The equations of motion and associated boundary conditions are normalized and rearranged in a state-space matrix form, and the vibration response is predicted through the distributed transfer function method developed by Yang and Tan. A numerical example is illustrated on a composite beam with bending-torsion coupling stiffness. Numerical results show that ICL damping treatments may or may not reduce coupled bending and torsional vibrations of a composite beam simultaneously. When the deflection is fed back to actuate the ICL damping treatment, a sensitivity analysis shows that only those vibration modes with significant bending response are suppressed simultaneously with their torsional components. In the preliminary experiments, two different ICL setups are tested on a composite beam without bending-torsion coupling. Damping performance of both ICL setups agrees qualitatively with existing mathematical models and experimental results obtained from other researchers. The damping performance, however, is not optimized due to the availability of materials and their dimensions in the laboratory. An optimization strategy needs to be developed to facilitate design of ACL damping treatments with maximized damping performance.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Dynamic Optimization of Constrained Layer Damping Structure for the Headstock of Machine Tools with Modal Strain Energy Method

Abstract: Dynamic stiffness and damping of the headstock, which is a critical component of precision horizontal machining center, are two main factors that influence machining accuracy and surface finish quality. Constrained Layer Damping (CLD) structure is proved to be effective in raising damping capacity for the thin plate and shell structures. In this paper, one kind of high damping material is utilized on the headstock to improve damping capacity. The dynamic characteristic of the hybrid headstock is investigated analytically and experimentally. The results demonstrate that the resonant response amplitudes of the headstock with damping material can decrease significantly compared to original cast structure. To obtain the optimal configuration of damping material, a topology optimization method based on the Evolutionary Structural Optimization (ESO) is implemented. Modal Strain Energy (MSE) method is employed to analyze the damping and to derive the sensitivity of the modal loss factor. The optimization results indicate that the added weight of damping material decreases by 50%; meanwhile the first two orders of modal loss factor decrease by less than 23.5% compared to the original structure.

Constrained Layer Damping of Initially Stressed Composite Beams Using Finite Elements

Abstract: This paper presents the development of an efficient finite element model for the analysis of laminated composite beams treated by a constrained viscoelastic layer. The formulation presented includes the ability to model a structure about preloaded con- figurations. Since most of the damping ability is due to the shearing of the viscoelastic layer, the model is designed to represent this aspect accurately. An offset beam, shear- deformable element, which is specially suited for modeling such laminated beams is pre- sented. The viscoelastic layer is modeled by using two-dimensional plane finite elements which are compatible with the beam elements. In case of a structure with initial load, the final equations are linearized so that first increment of motion, the part due to the initial load is linear, and the second, the part due to the dynamic load is linearized. System damping and tip displacement are compared with existing approximate results and experi- mental data whenever possible. Results confirm that dynamic response is substantially im- proved by use of such damping treatments, and give some useful information regarding de- signing a structure for high damping using constrained damping treatments.

Comparison of Damping Augmentation Mechanisms with Position and Velocity Feedback in Active Constrained Layer Treatments

Abstract: In active constrained layer damping treatments there are two distinct physical mechanisms that contribute to vibration damping - increased passive damping due to increased shear in the viscoelastic material (VEM) layer, and damping due to transmission of active forces to the host structure. The present study demonstrates that the first mechanism is dominant when proportional feedback is used while the second mechanism is dominant when derivative feedback is used. In the case of proportional feedback, the shear in the VEM increases considerably so that the passive damping is significantly larger than that obtained for the zero-voltage case, but the active action is actually detrimental. In the case of velocity feedback, the shear strain levels in the VEM are virtually unchanged, and all of the damping augmentation is due to the active action. It is also seen that if position feedback is used, moderate values of VEM shear modulus that provide optimal passive damping, are best. On the other hand, if velocity...

Optimal Placement of Constrained-Layer Damping for Reduction of Interior Noise

Abstract: In this paper, an efficient constrained-layer damping layout optimization method in structural-acoustic systems is proposed. To simulate vibro-acoustic systems, a hybrid model that uses finite elements for structures and boundary elements for the cavity is developed. With a finite element formulation, the intrinsic nonlinearities of viscoelastic damping materials with respect to frequency and temperature are included using a fractional-derivative model. The resulting complex eigenvalue problem is solved using an iterative scheme. The optimal layout of the constrained viscoelastic layer damping on the structure is identified using a gradient-based numerical search algorithm. The sensitivity formulas are derived analytically for acoustic and structural responses. The optimal damping-layer layouts that minimize the added mass with minimum sound pressure level requirements are obtained for different temperatures.