Passive stand-off layer (PSOL) and slotted stand-off layer (SSOL) damping treatments are presently being implemented in many commercial and defense designs. In a PSOL damping treatment, a stand-off or spacer layer is added to a conventional passive constrained layer damping treatment. In an SSOL damping treatment, slots are included in the stand-off layer. A set of experiments using PSOL and SSOL beams in which the geometric properties of the stand-off layer were varied was conducted to analyze the contribution of the stand-off layer to the overall system damping. This set of experiments measured the frequency response functions for a series of beams in which the total slotted area of the stand-off layer was held constant while the number of slots in the stand-off layer was increased for a constant stand-off layer material.
Finite element analysis models were developed in ANSYS to compare the predicted frequency response functions with the experimentally measured frequency response functions for the beams treated with PSOL and SSOL damping treatments. In these beams, the bonding layers used to fabricate these treatments were found to have a measurable and significant effect on the frequency response of the structure. The finite element model presented here thus included an epoxy layer between the base beam and the stand-off layer, a contact cement layer between the stand-off layer and the viscoelastic layer, and a method for modelling delamination.
Passive stand-off layer and slotted stand-off layer damping treatments are presently being implemented in many commercial and defense designs. In a passive stand-off layer damping treatment, a stand-off or spacer layer is added to a conventional passive constrained layer damping treatment. Additionally, this stand-off layer can be slotted in order to reduce the bending rigidity and total mass of the damping treatment. A preliminary analytical model has being developed for a slotted stand-off layer damping treatment applied to a beam. This mathematical model is based on Euler-Bernoulli beam theory, and may be able to provide an analytical solution of the frequency response for a beam treated with slotted stand- off layer damping.
Passive stand-off layer (PSOL) damping treatments are presently being implemented in many aerospace and defense designs. In a PSOL damping treatment, a stand-off or spacer layer is added to a conventional passive constrained layer (PCL) damping treatment. The addition of this stand-off layer increases the distance of the viscoelastic and constraining layers from the neutral axis of the vibrating structure. This is thought to enhance the damping by increasing the shear angle of the viscoelastic layer. In this experimental study, a PSOL damping treatment was applied to an Euler-Bernoulli beam. The frequency response of the treated PSOL beam was then compared with a conventionally treated PCL beam of similar dimensions and materials. Previous theoretical studies indicated that PSOL treatments provided greater damping than similarly sized conventional PCL treatments. This study verified experimentally that the beam treated with PSOL had greater damping of the first four modes than a similarly sized beam treated with PCL.
Passive constrained layer (PCL) damping treatments have been shown to be a very effective and reliable method for the damping of structures and have been implemented successfully in many commercial and defense designs for the aerospace and automotive industries. A conventional passive constrained layer damping treatment consists of a viscoelastic layer sandwiched between the vibrating structure and a cover layer. In a passive stand-off layer (PSOL) damping treatment, a stand-off or spacer layer is added to a conventional passive constrained layer damping treatment between the vibrating structure and the viscoelastic layer. The addition of this stand-off layer increases the distance of the viscoelastic and constraining layers from the neutral axis of the vibrating structure. This is thought to enhance damping by increasing the shear angle of the viscoelastic layer. To investigate how the bending and shearing rigidities of the stand-off layer (SOL) affect the damping performance, an analytical model has been developed for a PSOL damping treatment applied to an Euler-Bernoulli beam. In this paper, the equations of motion are derived and solved. The resulting simulations of the frequency response are then discussed.
A variational formulation of active constrained layer (ACL) damping treatments has indicated that the power dissipated through the active damping is the product of the electric field and the axial velocity of the piezoelectric constraining layer at the boundaries. This feature, unique to this formulation, suggests that a self-sensing and actuating piezoelectric constraining layer using rate of strain feedback may be an appropriate method of dissipating vibration energy with less instability, since the sensor and actuator are truly collocated. A partial ACL damping treatment design for an Euler-Bernoulli beam using a self-sensing actuator (SSA) as the active layer has been developed. The open loop transfer functions of the treated beam given by the SSA rate of strain circuit show great similarity to transfer functions taken from a reference sensor laminated directly to the beam. It has been shown experimentally that this beam treatment significantly increased the damping coefficient of the first mode in closed loop.
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