Strategies for using cellular automata to locate constrained layer damping on vibrating structures

Abstract

It is often hard to optimise constrained layer damping (CLD) for structures more complicated than simple beams and plates as its performance depends on its location, the shape of the applied patch, the mode shapes of the structure and the material properties. This paper considers the use of cellular automata (CA) in conjunction with finite element analysis to obtain an efficient coverage of CLD on structures. The effectiveness of several different sets of local rules governing the CA are compared against each other for a structure with known optimum coverage -namely a plate. The algorithm which attempts to replicate most closely known optimal configurations is considered the most successful. This algorithm is then used to generate an efficient CLD treatment that targets several modes of a curved composite panel. To validate the modelling approaches used, results are also presented of a comparison between theoretical and experimentally obtained modal properties of the damped curved panel.

A novel viscoelastic damping treatment for honeycomb sandwich structures

“…The present finite element model was benchmarked against the work by Chia et al [16], in which they predicted a loss factor ratio per unit mass of 1.3477 (see Table 2 in [16]) for one CLD configuration (see Fig.7 in [16]). The same configuration modelled in this study predicted a loss factor ratio per unit mass of 1.3454.…”

“…The viscoelastic material density was approximately a third of the aluminium density, its modulus 70 000 times lower than aluminium, and had a material loss factor 200 times higher than aluminium. These values sits within the normal range of viscoelastic polymer material properties [16]. Material-dependant damping (ANSYS command MP, DMPR) was adopted to describe the damping ratio of each material.…”

“…More accurate estimation techniques such as the Modified Modal Strain Energy method [26] would add complexity without necessarily aiding comparison between the different devices presented in this study. A similar approach was adopted by Chia et al [16]. Douglas and Yang [27] formulated the frequencydependant complex shear modulus of the viscoelastic core of a constrained layer damper as…”

“…The contact interaction between solid and shell elements required to overlap the contact surfaces in order to ensure the nodes to be coincident at the interface. The degrees of freedom of these nodes were then coupled using the ANSYS command CPINTF in order to enforce compatibility at the interface, similar to the approach adopted by Chia et al [16]. The enhanced strain formulation was used to overcome shear locking in this bending-dominated problem.…”

“…They proposed an optimised solution for the position of CLD on simply supported plates thanks to a topographical optimisation method. The cellular automaton method is particularly well suited to this problem, and has been implemented by Chia et al [16], [17] to identify optimal weight-efficient CLD configurations for plates with free boundary conditions using the loss factor as objective function. Kim also used a topology optimisation in order to find the best configuration of CLD on a fully clamped and cantilevered plate [18] that give the highest modal loss factor for a minimal increase in mass.…”