Vibration Reduction Capability Research Articles

Optimizing Piezoelectric Material Location and Size for Multiple-Mode Vibration Reduction of Turbomachinery Blades

Abstract Modern turbomachinery blades have extremely low inherent damping, which can lead to high transient vibrations and failure through high-cycle fatigue. Smart materials enable vibration reduction while meeting strict blade requirements such as weight and aerodynamic efficiency. In particular, piezoelectric-based vibration reduction offers the potential to reduce vibration semi-actively while simultaneously harvesting sufficient energy to power the implementation. The placement and the size of the piezoelectric material is critical to the vibration reduction capabilities of the system. Furthermore, the implementation should target multiple vibration modes. This study develops a procedure to optimize electromechanical coupling across multiple vibration modes for a representative turbomachinery blade with surface-mounted piezoelectric patches. Experimental validation demonstrates good coupling across three targeted modes with a single piezoelectric patch. Placing the piezoelectric material in regions of high signed strain energy for all targeted modes enables vibration reduction across all of the targeted modes.

Development of tuned particle impact damper for reduction of transient railway vibrations

Herein, a tuned particle impact damper to reduce rail rolling noise is proposed, and its vibration reduction capability is investigated experimentally. The proposed damper was designed for easy attachment to a rail and possessed the combined characteristics of a tuned dynamic absorber and an impact damper. The vibration behaviour of the damper-attached rail was investigated using an actual UIC60 rail specimen. The measured vibration reduction performance was verified by simulation of the collision behaviours. The proposed damper exhibited excellent vibration reduction capability at a specific frequency band with additional damping in the broadband frequency range owing to partially inelastic particle impacts. A modal analysis of the tuned particle impact damper illustrated the mechanism of vibration reduction via the modal response of the proposed damper on the rail specimen. The interaction of the rail transverse vibration with the attached damper was analysed. The vibration reduction performances were investigated based on the damping coefficient predicted from both the least-squares and Prony’s methods. The damping capability was identified to investigate the effects of excitation force, coefficient of restitution, mass ratio, clearance, and clamping force. Based on applying impact damping on railway tracks, the proposed tuned particle impact damper showed excellent damping capability in reducing transient vibrations, which is essential for minimising rolling noise from passing trains.

Integration of an omnidirectional self-powering component to an MRE isolator towards a smart passive isolation system

Base isolator is one of the most adopted and effective means of mitigating unwanted and harmful vibrations to protect buildings and other key civil infrastructure from seismic events. For this reason, the base isolation technology has advanced greatly in recent years, especially the magnetorheological elastomer (MRE) isolator. However, the operation of such an MRE isolator needs external power supply to be activated, which may fail due to the power outage caused by the seismic movement. To this end, this work developed an MRE base isolation system with self-powering capability. This characteristic enables the isolation system self-sufficient without relying on external power. The self-powering component is an innovative omnidirectional element and can collect vibration energy from all horizontal directions. In addition, the self-powered isolation system performs rate-dependent softening behaviour which overcomes the conflicting requirements that the stiffness is required to be hard during daily operation but soft when the earthquake happens. For this reason, this new isolation system has been built and tested, including its MRE isolator and self-powering components. Its vibration reduction capability for building is also investigated on a scaled building. The theoretical analysis and verification is also performed and the conclusions coincide with the experimental results. The experimental and simulation results demonstrate that this new isolation system is capable of generating electricity which is sufficient to power itself when it is subjected to ground motions, and that it shows a high effectiveness in reducing the floor accelerations and the relative displacement.

Biodynamic Modelling of Hand for Glove Transmissibility Prediction using Artificial Neural Networks

Prediction of glove transmissibility to the hand plays an important role in order to improve its vibration reduction capability. This study presents a non-parametric biodynamic modelling of the hand based on artificial neural networks (ANNs) model for predicting the apparent mass in order to estimate the transmissibility of a glove to the hand. An experimental investigation was carried out to obtain the input-output vibration data using five subjects. Then, an ANNs model was used to map between the input and the output with its weight and bias parameters optimized using chaos-enhanced stochastic fractal search (CFS) algorithm. The results indicate that the developed ANNs hand model capable to predict the apparent mass of the human hand with an average accuracy of 97.67%.

Dynamic properties of bolted joints in laminated composites evaluated using flexural wave propagation

In this study, a method to evaluate the dynamic properties of bolted joints in laminated composites is proposed. The propagation of flexural waves through the joint was used to identify the joint stiffness. Experiments were performed by using carbon fiber/epoxy specimens. The specimens were fastened by a single-lap bolted joint. Vibration responses were measured for specimens fastened using different clamping forces. The dynamic properties of the joint were evaluated using translational and rotational complex joint stiffnesses. The predicted effects of the joint on the system vibration properties were compared to the measurements. A numerical method was proposed to calculate the dynamic properties. The stiffness and loss factor were derived to find the effects of the clamping forces. The evaluated stiffness was close to the predicted static stiffness. The joint loss factor was larger than that of the composite itself. With the increasing clamping forces, the stiffness increased and the loss factor decreased. The proposed method allows non-destructive continuous monitoring of a clamped part with additional information about the vibration reduction capability.

Further Improvements in the SNUF Blade Design by Numerical Design Optimization Framework

This paper focused on improving a small-scaled helicopter rotor blade prototype with a flap-driving mechanism termed the Seoul National University Flap (SNUF). The design of the SNUF included realizing vibratory load reduction. First, a multibody structural dynamics analysis was performed to determine the influence of the flap dimension and location within the rotor blade with respect to hub vibratory load reduction. This process was followed by selecting a specific blade configuration that maximized vibration reduction capability. Following this, a numerical optimization technique was applied to improve the cross sectional design of the SNUF blade. The design optimization procedure obtained improved blade sectional design with decreased first torsional frequency and reduced blade weight, and it satisfied sufficient structural integrity. Three-dimensional nonlinear static structural analysis also was performed for the optimized SNUF design. The von Mises stress distribution on the blade and components was predicted by considering external aerodynamic loads, centrifugal loads because of rotation, and contact among the internal components. Future studies will include fabricating the prototype blade on the basis of the optimized design and performing a whirl tower test.

Structural control with tuned inertial mass electromagnetic transducers

Summary This paper investigates the validity of the tuned inertial mass electromagnetic transducer (TIMET) applied to building structures subjected to seismic motions. The TIMET is a device inspired by two innovative structural control devices proposed recently, that is, tuned viscous mass damper and electromagnetic transducer. The TIMET consists of a spring, an inertial mass produced by a ball screw mechanism, and an electromagnetic transducer part composed of a motor and an electrical circuit. The stiffness of the spring is tuned such that the inertial mass resonates with the vibrating building. This makes the motor installed in parallel with the inertial mass run up in an efficient way, and the vibration energy is converted to electrical energy effectively. As a result, vibration of the building decays fast and electrical energy is stored. This generated energy that is reusable for the self-powered control systems, structural health monitoring, emergency power source, and so on. In this paper, through numerical simulation studies employing the scaled three-story building model proposed for benchmark studies, the vibration reduction and energy harvesting capabilities of the TIMET is explored and the application potentiality to civil structures is discussed.

Optimization design and experimental verification of track nonlinear energy sink for vibration control under seismic excitation

Nonlinear energy sinks (NES) are efficient vibration control devices, which have been studied and applied in mechanical, automobile, and aerospace engineering. However, there are few applications in civil engineering. A new type of NES, which is termed as track NES, is proposed in this paper. The optimal mass ratio and track shape expression of NES were determined based on a preliminary optimization design process. To verify its vibration control effects on building structures, a series of shake table tests were conducted on a five-story steel frame. Tracks of the NES were installed at the roof of the frame with rigid connections and the mass of the NES was constrained to slide along the track by using wheels. Five earthquake waves with different frequency spectrums were selected to excite the frame coupled with NES under minor, moderate, and major levels. Accelerations and displacements on each story of the frame were measured, recorded, and evaluated. The experimental results demonstrate that with small mass ratio (2%) of main structure, NES has good performance in reducing the dynamic responses of the frame under seismic excitations. The reduction ratio for peak response is up to 50%, while for root mean square response is up to 80%. NES also exhibits wide-band frequency vibration controlling attributes, and the responses of the frame are reduced in multiple vibration modes. In addition, the vibration reduction capability of the NES with steel wheels and that with rubber wheels are compared, and it is verified that different damping of NES makes a difference to the vibration control effects. The displacement reduction performance is not sensitive to the damping factor of the NES, but acceleration response is highly affected by the damping feature of the NES.

Incorporating piezoelectric energy harvester in tunable vibration absorber for application in multi-modal vibration reduction of a platform structure

Tunable vibration absorber is an effective device to reduce the vibration of structure subjected to harmonic excitation. The vibration energy is transferred mostly to the absorber when the natural frequency of the absorber is tuned to the excitation frequency. In this study, a piezoelectric (PZT) transducer was incorporated into the absorber in order to harvest the vibration energy and still alleviate the vibration of a platform structure. The tuning in dynamic characteristics of the absorber was facilitated by controlling its tip mass. The design formulation of the absorber was presented with a single degree-of-freedom (SDOF) model having the equivalent parameters. In the meantime, an optimal electric load resistor was determined to maximize the power output from the PZT transducer. The experimental measurement validated the SDOF model with good accuracy both in the vibration response and the output electric voltage. Finally, the absorber was installed on a platform structure to investigate its vibration reduction and energy harvesting capability for the external disturbance frequency covering certain frequency span. With three resonance modes of the platform studied, the absorber was able to reduce more than 80% of its original vibration and harvest several folds of electric power comparing with the untuned absorber. Although the performance in vibration reduction was slightly influenced (<6%), the great increase in the electric energy harvested revealed the absorber design a good potential toward self-powered sensor or actuator applications.

A seat suspension with a rotary magnetorheological damper for heavy duty vehicles

This paper presents the development of an innovative seat suspension working with a rotary magnetorheological (MR) fluid damper. Compared with a conventional linear MR damper, the well-designed rotary MR damper possesses several advantages such as usage reduction of magnetorheological fluid, low sealing requirements and lower costs. This research starts with the introduction of the seat suspension structure and the damper design, followed by the property test of the seat suspension using an MTS machine. The field-dependent property, amplitude-dependent performance, and the frequency-dependent performance of the new seat suspension are measured and evaluated. This research puts emphasis on the evaluation of the vibration reduction capability of the rotary MR damper by using both simulation and experimental methods. Fuzzy logic is chosen to control the rotary MR damper in real time and two different input signals are considered as vibration excitations. The experimental results show that the rotary MR damper under fuzzy logic control is effective in reducing the vibrations.

Boundary control of harmonic disturbances on flexible cantilever beams using piezoelectric patch actuators

This work addresses the control of vibrations in flexible structures caused by external harmonic disturbances using a boundary control method. The research is motivated by practical systems where beam-like structures require vibration suppression to prevent fatigue and system damage, or to increase efficiency. Importantly, this paper addresses a practical constraint of the actuation points being at the boundaries only. The method presented here is an open-loop control scheme which requires knowledge of the harmonic disturbance and a model of the flexible system. The controller uses the model, developed using the Rayleigh–Ritz method, to predict the reaction of the beam to the known input disturbance and compute an optimized control input which reduces the steady state vibration in the system. By properly choosing the cost function, the controller can be used to reduce the total vibration or to reduce the vibration in certain spatial locations. The method's vibration reduction capabilities are studied over a range of frequencies; data collected from experiments on a physical beam model is used to validate the predicted behavior of the system.

Zero-phase velocity tracking of vibratory systems

The focus of this paper is on the development of an input shaper/time-delay filter that permits the precise tracking of a ramp input, while eliminating residual vibrations. Zero phase error velocity tracking is often required in applications where moving parts have to be mated, such as manufacturing lines with high production output. A closed form solution to a pre-filtering technique is presented which achieves the desired characteristics. The performance of this technique is compared with other input shaper designs in current literature, and is shown to achieve smaller settling time and maintain zero steady state phase error without a priori knowledge of the initiation and termination of ramp profiles. The technique is then physically applied to a rotary pendulum to demonstrate the consistency of its ramp tracking and vibration reduction capabilities.

Nonlinear vibration isolator with adjustable restoring force

This paper presents a vertical quasi-zero stiffness (QZS) vibration isolator with a mechanism for adjusting restoring force. QZS vibration isolators have high initial stiffness and QZS around the static equilibrium position. This way, excessive deformation due to self-weight can be avoided while having enough vibration reduction capability to dynamic excitations. One of the main issues left for QZS vibration isolators is the difficulty in keeping the vibration reduction capability when the vibration isolated object is replaced. In such a case, adjustment of its restoring force becomes necessary in accordance with the self-weight of the newly placed vibration isolated object. This paper attempts to address this issue by proposing a mechanism that enables quick and easy adjustment of the restoring force of a QZS vibration isolator. The proposed mechanism consists of cranks and a screw jack. With the present mechanism, the restoring force provided by horizontally placed springs can be converted into the vertical restoring force of the vibration isolator. In the conversion, the vertical resisting force can be adjusted simply by applying and removing torque to the screw jack to change and hold the angle of inclined bars placed in the cranks. In this study, a prototype of a class of QZS vibration isolator having the proposed mechanism is produced. Shaking table tests are performed to demonstrate the efficacy of the present mechanism, where the produced prototype is subjected to various sinusoidal and earthquake ground motions. It is demonstrated through the shaking table tests that the produced prototype can reduce the response acceleration within the same tolerance even when the mass of the vibration isolated object is changed.

Research the Influence of Curved Shape on the Multilayer Bellows

As a cylindrical thin-walled container, multilayer bellows has greater bit shift compensation, vibration and noise reduction capabilities while the appropriate metal and viscoelastic damping materials are adopted. Finite element models are adopted to analyze the loss factor of multilayer bellows in ANSYS. The strain energy distribution of Multilayer bellows and viscoelsticity layer are given. According to the strain energy, the influence of structural parameters on the loss factor is studied. The results show that the loss factor can be improved by employing the curved shape with big wave height, small wall thickness, small wave pitch and diameter of bellows.

Synthesis and Mechanical Properties of Interconnected Carbon Nanofiber Network Reinforced Polydimethylsiloxane Composites

Carbon nanofiber (CNF) reinforced elastomer composites with light weight, sustainability of large deformation, chemical stability, corrosion and fatigue resistance, and vibration and noise reduction capability can have positive impact on a wide range of applications. However, this type of composite is still a under studied research area due to the difficulties in material handling and processing. To improve processing control and reproducibility for large scale engineering applications, cost effective carbon nanofibers (CNFs) in form of interconnected porous network structure were used as nanofillers. Processing, microstructure and mechanical properties of carbon nanofibers reinforced polydimethylsiloxane (PDMS) have been studied. Mechanical measurements on the composites show that the CNF-PDMS interfacial bonding can be until failure, interfacial debonding happens in the CNF-PDMS composites and the resulted permanent deformation stabilizes with increasing load-unload cycles with significant energy dissipation.

Vibration control and shock absorption techniques for Hi‐Tech manufacturing plants

SUMMARYThe Hi‐Tech industrial plant that houses manufacturing processes of high precision requires much more vibration‐proof and earthquake‐proof structures than conventional plants. Taiwan is densely populated in limited space so that the Hi‐Tech industry does not have too much leeway for locating the manufacturing plant at locations that are away from sources of vibration. Hence, strengthening the capacity of Hi‐Tech plant structures to resist vibration is of primary importance to Hi‐Tech industries. In this research, the TFT‐LCD plant structure is selected for improving its shock absorption capability by replacing the braces at soft floor of the structure with Viscous Damper (VD) and Velocity and Displacement Hydraulic Damper (VDHD). The reinforced structure is then subject to vibrations of various accelerations for analysing the dynamics and efficiency of vibration reduction. The results show that: (1) When subject to micro vibration, VD and VDHD that have similar capabilities in controlling displacement and responding to acceleration are more effective than Buckling Resistant Bracing, BRB; (2) When subject to medium vibration, VD, BRB and VDHD show tremendous improvements in controlling the momentum of story drift or slab acceleration. However, BRB shows buckling that may lead to permanent structural deformation whereas the overflow occurs in the Relief valve of VDHD causing the energy‐dissipating viscosity of VDHD from a VD‐like to BRB‐like behavior; (3) Under strong vibration, when the maximum force of a VD exceeds its design value, the VD has inferior capacity than BRB and VDHD in reducing acceleration. The VDHD always has smaller acceleration response than BRB because the former has damping effect under strong vibration. The results obtained in this research will obtain the suitability of VDHD in reducing vibration and confirm its superior vibration reduction capability. Copyright © 2010 John Wiley &amp; Sons, Ltd.

A feasibility study on smart base isolation systems using magneto-rheological elastomers

This study proposes a new smart base isolation system that employs Magneto-Rheological Elastomers (MREs), a class of smart materials whose elastic modulus or stiffness can be varied depending on the magnitude of an applied magnetic field. It also evaluates the dynamic performance of the MRE-based isolation system in reducing vibrations in structures subject to various seismic excitations. As controllable stiffness elements, MREs can increase the dynamic control bandwidth of the isolation system, improving its vibration reduction capability. To study the effectiveness of the MRE-based isolation system, this paper compares its dynamic performance in reducing vibration responses of a base-isolated single-story structure (i.e., 2DOF) with that of a conventional base-isolation system. Moreover, two control algorithms (linear quadratic regulator (LQR)-based control and state-switched control) are considered for regulating the stiffness of MREs. The simulation results show that the MRE-based isolation system outperformed the conventional system in suppressing the maximum base drift, acceleration, and displacement of the structure.

Design and aeroelastic analysis of active twist rotor blades incorporating single crystal macro fiber composite actuators

The advanced active twist rotor (AATR) blade incorporating single crystal macro fiber composite (single crystal MFC) actuators is designed and the aeroelastic analysis is performed. The AATR blade is designed based on an existing passive blade and the NASA/ARMY/MIT active twist rotor (ATR) prototype blade. The AATR blade is designed to satisfy all the requirements and the properties of the AATR blade are compared with those of the ATR prototype blade. The aeroelastic analysis of the designed AATR blade for the hover condition is conducted. In order to predict the vibration reduction capability, the twist actuation frequency response of the AATR blade is investigated by the numerical simulation. As a result, although lower input voltage is used, the AATR blade can achieve higher twist actuation that is sufficient to alleviate the helicopter vibration as compared with the ATR blades using the AFC and the standard MFC.

Suppression of motion-induced residual longitudinal vibration of an elastic rod by input shaping

Various input-shaping schemes such as the “zero-vibration” (ZV), “zero-vibration-and-derivative” (ZVD), “negative ZV” (NZV), and “negative ZVD” (NZVD) schemes have previously been proposed to suppress motion-induced residual vibration of lightly damped structures. In such schemes, the input command of the dynamical system in question is properly administered (i.e., shaped), so that the dominant induced vibration modes are annihilated through destructive interference. Here we are concerned with the effects of system payload on the vibration reduction capabilities of the aforementioned input-shaping schemes, especially when they are applied to continuous systems. By use of the simple structure of a linearly elastic rod as a specific example, it is demonstrated that both the minimum achievable residual vibration amplitude and the tolerance of detuning parameter errors of the input-shaping schemes are sensitive to the amount of payload on the system. It is therefore imperative to take the factor of system payload into account in the design of practical input shapers.

Energy Regenerative and Active Control of Electro Dynamic Vibration Damper

Active vibration control is introduced to an electrodynamic regenerative vibration damper. It is intended to improve vibration reduction capability using the regenerated energy. An electrodynamic actuator is used as an energy regenerative damper and active control actuator. This idea is applied to a moving mass type vibration absorber and vibration control is performed. In the case of energy regenerative control, a PWM step-up chopper is used to solve the dead zone problem. Active control signal is also controlled by other PWM chopper from the power supply. However, energy regenerative and active control mode can not operate at the same time. A new control law is introduced to switch control mode and to follow the ideal force. The ideal force is calculated using the LQ control theory. Experimental setup is mode to confirm the proposed technique and the damping capability is tested.