Investigation of stability in internal turning using a boring bar with a passive constrained layer damping

The vibrations produced in a boring tool in internal turning deteriorate the machined surface quality and reduce the tool life, which results in a massive noise during the machining. Therefore, unwanted vibrations are necessary to be eliminated by improving the boring bar's dynamic stiffness and damping capacity. This paper investigates a passive constrained layer damping (CLD) boring bar with a hybrid damping layer to study the internal turning system's stability. Initially, the dynamic models of the conventional and CLD tools are thoroughly studied using Euler-Bernoulli beam theory (EBT) and validated them with finite element modelling (FEM). The frequency response functions (FRFs) obtained from the impact hammer tests are used to estimate the modal parameters. With modal parameters, the semi-analytical stability lobe diagrams (SLDs) are plotted for the boring system with the conventional and CLD boring bar. Tool-tip responses for various cutting conditions are simulated numerically to validate and to study stability. The cutting experiments with traditional and CLD boring bar are conducted for stability analysis and compared tool-tip responses with numerical results. It is observed that both the numerical and experimental results agree with the selected cutting conditions from SLDs. It is also observed that the CLD boring bar with a hybrid damping layer reduced the vibration displacements by five times compared to the conventional one.

Hybrid Control of Rotating Beams Using Pattern Search Based Optimization Technique

Rotating beams are quite common in rotating machinery e.g. fans of compressors in an airplane. This paper presents the experimental, hybrid, structural vibration control of flexible structures to enhance the vibration behavior of rotating beams. Smart materials have been used as sensors as well as actuators. Passive constrained layer damping (PCLD) treatment is combined with stressed layer damping technique to enhance the damping characteristics of the flexible beam. To further enhance the damping parameters, a closed form robust feedback controller is applied to reduce the broadband structural vibrations of the rotating beam. The feed forward controller is designed by combing with the feedback controller using a pattern search based optimization technique. The hybrid controller enhances the performance of the closed loop system. Experiments have been conducted to validate the effectiveness of the presented technique.

A reduced passive constrained layer damping finite element model based on the modified improved reduced system method

This paper proposed a new reduced passive constrained layer damping finite element model. The passive constrained layer damping structure is a sort of sandwich plate made up of a viscoelastic core sandwiched between two elastic faces. The model is built by combining the first shear deformation theory with the Golla-Hughes-McTavish model that takes the frequency dependence of the viscoelastic material property into consideration. Due to the Golla-Hughes-McTavish model, the stiffness, damping and mass matrices are at least doubled, which requires a large amount of calculation. Then, a modified improved reduced system method is proposed to reduce the order of the model. Finally, the proposed reduced model is compared to the Guyan reduction, the mode truncation and the improved reduced system models by two numerical examples. It demonstrates that the proposed modified improved reduced system method is obviously superior to the other three classical methods and the presented passive constrained layer damping model with the Golla-Hughes-McTavish model is an effective and accurate sandwich model, which can be applied to the finite element software.

Free Vibration and Damping of Rotating Composite Shaft with a Constrained Layer Damping

The free vibration and damping characteristics of rotating shaft with passive constrained layer damping (CLD) are studied. The shaft is made of fiber reinforced composite materials. A composite beam theory taking into account transverse shear deformation is employed to model the composite shaft and constraining layer. The equations of motion of composite rotating shaft with CLD are derived by using Hamilton’s principle. The general Galerkin method is applied to obtain the approximate solution of the rotating CLD composite shaft. Numerical results for the rotating CLD composite shaft with simply supported boundary condition are presented; the effects of thickness of constraining layer and viscoelastic damping layers, lamination angle, and rotating speed on the natural frequencies and modal dampings are discussed.

Damping Analysis of Multilayer Passive Constrained Layer Damping on Cylindrical Shell Using Transfer Function Method

Based on the Donnell assumptions and linear viscoelastic theory, the constitutive relations for the multilayer passive constrained layer damping (PCLD) cylindrical shell are described. In terms of energy, the motion equations and boundary conditions of the cylindrical shell with multilayer PCLD treatment are derived by the Hamilton principle. After trigonometric series expansion and Laplace transform, the state vector is introduced and the dynamic equation in state space is established. The transfer function method is used to solve the state equation. The dynamic performance including the natural frequency, the loss factor, and the frequency response of the multilayer PCLD cylindrical shell is obtained. The results show that with more layers, the more effective in suppressing vibration and noise, if the same amount of visco-elastic and constrained material is applied. It demonstrates a potential application of multilayer PCLD treatment in some critical structures, such as cabins of aircrafts, hulls of submarines, and bodies of rockets and missiles.