Unwanted Vibrations Research Articles

A review on fabrication and in vivo applications of piezoelectric nanocomposites for energy harvesting

BackgroundEnergy-based piezoelectric nanocomposites have received a great deal of attention due to their wide range of applications in electronics, sensors, actuators, and tissue engineering. Polymeric piezoelectric nanocomposites have good mechanical flexibility, lower manufacturing cost, suitable output voltage, and fast processing compared to ceramic based composites. MethodsIn this paper a comprehensive review is conducted on the polymer-based nanocomposites that exhibit the piezoelectric effect. The most important fabrication strategies for piezoelectric polymer nanocomposites and the in vivo applications of these materials are investigated in this paper. The challenges/limitations associated with synthesis and preparation techniques of these materials are mentioned. Finally, a road map for future studies is provided. Significant findingsIt was found that piezoelectric nanocomposites are characterized with greater functionality for harvesting energy from unwanted mechanical vibration sources and in vivo movements. In general, commercialization and market growth of piezoelectric nanocomposites are highly related to two important factors, including enhancement in energy performance of related systems to match with the need and cost decrease to compete with traditional piezo-ceramics. As a result, it can be concluded that the electrospun piezoelectric nanocomposites are appropriate candidates for in vivo applications due to their high surface-to-volume ratio, sufficient porosity, high electrical properties, and biocompatibility.

Special Issue on the Application of Active Noise and Vibration Control

Active noise and vibration control aims at attenuating unwanted sound or vibration by automatically generating an anti-sound or vibration [...]

Stochastic propeller force and moment reconstruction at a shaft end based on an improved Kalman filter

Measuring the unsteady hydrodynamic excitation of a marine propeller at a shaft end accurately from multiple directions is crucial for minimizing the unwanted vibration and noise of ships. Due to the synchronous loading of high static thrust and torque, an innovative piezoelectric multicomponent balance embedded into a hollow shaft end is designed. However, complex coupling between the balance and shaft structure is formed. This leads to crosstalk disturbance and a modal dynamic amplification effect on all measuring channels. To overcome this, an improved Kalman filter algorithm based on the subspace modal identification (SMI) method is established, thus allowing us to reconstruct and locate equivalent unsteady excitations accurately in multiple directions with response-only networks. The effectiveness of proposed framework is test on a simulated nonrotating shaft end system with twelve force and three acceleration response channels. The selection of the smoothing delay parameter and whether crosstalk is considered are two main factors that influence the reconstruction accuracy.

Bottomhole-Assembly Dynamics Software Helps Mitigate Twistoffs While Drilling

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 202174, “Mitigating Twistoffs While Drilling With the Help of Bottomhole-Assembly Dynamics Software,” by Mario A. Rivas, SPE, Andres A. Ramirez, and Bader S. Al‑Zahrani, SPE, Saudi Aramco, et al. The paper has not been peer reviewed. _ A major challenge during drilling operations is the occurrence of twistoffs on bottomhole assembly (BHA) components. To overcome this challenge, a study was performed of twistoffs experienced on BHA components. Based on the findings, drilling operations and recommendations were provided to reduce or eliminate twistoffs related to suboptimal drilling parameters. This analysis will help drilling engineers and personnel foresee vibration dysfunctions and act accordingly with the use of BHA dynamics software to optimize drilling parameters before and during drilling. Twistoffs Caused by Drillstring Vibrations Field experience has shown that unwanted drillstring vibrations lead to failures, especially stick/slip (torsional vibrations) that occurs approximately 50% of the time during drilling. Three main types of vibrations can be distinguished: torsional (stick/slip oscillations), axial (bit bouncing), and lateral (whirling motion caused by an imbalanced drillstring). These three types of vibration can occur at any time during drilling. Induced axial vibrations at the bit can lead to lateral vibrations in the drillstring and BHA, and axial and torsional vibrations can be observed at surface. Sometimes the severe axial vibrations close to the bit may not be observed at surface, which may lead to a potential twistoff if drilling parameters are not changed and optimized. Additionally, fatigue failure is intensified with high vibrational loads, specifically at curved well trajectories or in buckled drillstring sections as shown in Fig. 1, where high bending stresses occur. The most critical fatigue damage will happen when the drillstring is in resonance with one of its natural frequencies, resulting in twistoff events at a much lower drillstring component yield strength. The objective of the study described in the complete paper is to pursue an integrated approach considering the use of vibration-analysis software in the design of a BHA to identify safe operating windows for rotary speed and weight on bit (WOB) to prevent buckling and analyze fatigue. BHA Dynamics Resonance occurs when the rotary speed is very close to one of the natural frequencies for torsional vibration (the primary cause of failure), and WOB natural frequency for flexural vibrations of the BHA. When the frequency of any excitation is one of the natural drillstring frequencies, then the drillstring will resonate and vibration levels will be highest. With very high amplitudes, vibrations will accelerate drillstring and BHA fatigue. To estimate the critical rotary speed (resonance frequency), the BHA can be simulated using available BHA dynamics and vibration software. This software can analyze downhole vibrations; its simulations have matched several cases very closely to what the operator has experienced. Three different examples were analyzed and presented in the complete paper. The software uses nonlinear vibration theory to determine drillstring-resonance frequencies.

Influence of geometric parameters and material properties of the reinforcing core on the modal properties of vibrating beam structures

The beam structures are considered as fundamental structural elements that are widely used in mechanical and building structures. One of the important tasks in the structural design of beam structures should be the ability to prevent or reduce the level of unwanted vibrations. It is obvious that the dynamic properties of beam structures depend on their shape structure, i.e. from their geometric parameters and material properties. Usually, the beam structures have constant cross-section and made of homogeneous material. However, these structures in many cases do not have the required dynamic properties. The design and analysis of the beam structures that will allow its spatial properties (mass and stiffness) to be redistributed using the sliding core inserted into the beam structure is investigated in this paper.

Fault Diagnosis of Two Rotor System

Abstract: Misalignment and unbalance are the most probably common cause of machine vibration. Vibration monitoring is a useful technique for application to rotating machinery and provides valuable information regarding symptoms of machinery failure which may avoid costly breakdown. Understanding and practicing the fundamentals of rotating shaft parameter is the firststep in reducing unwanted vibration. Experimental studies were performed on two rotor dynamic test apparatus to predict the vibration spectrum for different faults. The experimental test rig was designed and tested for misalignment and unbalance condition. The rotor shaft accelerations were measured at 1000 rpm speed using four channel vibration FFT (Fast Fourier Transform) analyzer. The experimental frequency spectra were obtained for misalignment and unbalanced condition leading to reliable diagnostic information.

Powertrain Modal Analysis for Defining the Requirements for a Vehicle Drivability Study

The powertrain of a car plays a major role in establishing the vehicle’s offered comfort due to vibrations because it is the heaviest single component installed on the chassis; therefore, when oscillating, it transmits considerable forces to the chassis, inducing unwanted vibrations. For this reason, it is important to identify some associated properties with the powertrain suspension system that describe the performance of its rigid body dynamics. In this way, we could place constraints and requirements on these quantities in order to exclude all the configurations that cause intolerable levels of vibrations, and include all the others in the analysis for further evaluation. The definition of these requirements is critical: a poor setting of requirements excludes potentially good powertrain suspension setups and includes those ones with a drivability index that is too poor. In this paper, we identify a set of quantities that show correlation with the vibration performance of the powertrain setup. A method for testing the specificity of the requirements is also shown in order to evaluate which requirements perform best when it comes to filtering engine suspension setups that provide an acceptable level of vibrations.

Novel Genetic Algorithm with Parameter Exchanger (GAPE) for identification of flexible manipulator system

As technology advances, more applications require lighter, more flexible and less bulky structures. Thus, flexible manipulator has been favoured in robotics and mechanical systems. This paper presents the modeling of single-link flexible manipulator system using an intelligent optimizer, Genetic Algorithm with Parameter Exchanger (GAPE). In this highly complex system where unwanted vibrations occur during operation, GAPE was developed to accurately model this system. A single-link flexible manipulator experimental setup was initially developed. Hub angle and end-point acceleration experimental data was collected and fed to the system identification method. After that, identification was carried out by applying the proposed novel GAPE through a linear auto regressive with exogenous (ARX) model structure as compared to a standard Genetic Algorithm (GA). Algorithms was then validated based on the reducing value of mean-squared error (MSE) and correlations test. From the results, the advantages of the ‘parameter exchanger’ was confirmed where GAPE achieved the smallest MSE value of 2.9567 × 10−5 and 6.4614 × 10−6 for end-point acceleration and hub angle modelling, respectively. Good correlation values was also achieved by both models which indicating within 95% confidence interval. In the future, validated model will serve as a platform for implementation of active vibration control of flexible manipulator systems.

Vibration control of floating offshore wind turbine using semi-active liquid column gas damper

Floating offshore wind turbines (FOWTs) are becoming an essential instrument for energy generation worldwide. Specific environmental conditions at sea have led to unwanted vibrations and excessive displacement in floating wind turbines, which reduce the performance of these systems. This study aimed to evaluate the effect of semi active liquid column gas damper (SALCGD) on controlling the vibrations of a FOWT under different loads with wave and wind. Variable hydraulic head loss coefficient and variable frequency were used in this study, as well as DBG, VBG, and Bang-Bang algorithms. An analytical model was developed to analyze the dynamic response of the joint wind turbine and damper system, and a time history analysis was performed in the SIMULINK/MATLAB simulation environment. The results indicated that the SALCGD could reduce the displacement response of the pitch degree of freedom in platform in both semi-activation methods. In addition, the performance of each control algorithm varied according to the loading conditions. The effect of SALCGD and TLCGD (tuned liquid column gas damper) was compared in controlling the vibrations of the wind turbine system. According to the results, the superiority of using a semi-active damper was revealed in control.

Suppressing vibration of structures using nonlinear single unit impact dampers via Taguchi method

This paper investigates a vibratory system that employs Hertzian contact theory in terms of free vibration. Nonlinear impact dampers are created by using a spring, mass, and viscous damper model. The model is simulated in MATLAB software using the DAS method as a proper simulation framework. The Taguchi method is used to examine the efficacy of impact dampers for controlling structural vibrations of the structure. It is demonstrated that the optimal factors obtained can effectively suppress the structure’s unwanted vibrations. The analysis of variance is also used to indicate the most influential factor of dampers to demonstrate their ability to quench vibrations.

Attenuation of magnetomechanical hysteresis effect by excessively annealing Fe-16Cr-2.5 ∼ 3.5Mo damping alloys

Ferromagnetic Fe-Cr alloys can be used to reduce unwanted noise and vibrations because of their high damping capacity which is attributed to the irreversible magnetic domain-wall movement. However, excessive annealing usually causes an obvious drop of damping capacity of the alloys. In the present study, the magnetomechanical hysteresis effect (MMHE) is investigated by measuring magnetostriction coefficients of the annealed Fe-16Cr-2.5 ∼ 3.5Mo alloys. It is found that the annealing more than 1 h at 900℃ causes the attenuation of MMHE. The higher Mo concentration restrains the MMHE attenuation and the damping decline due to the MMHE attenuation. The research could help us to better understand the alloying role in the damping mechanism of Fe-Cr based alloys.

Active Air-borne noise suppression for pipe break early warning in smart water networks

Acoustic alarm systems using IoT (internet of things) smart sensors (e.g. accelerometers) for leak detection in water networks are rapidly gaining popularity. One of the issues for such systems is the false alarms which often occur as a result of signal contamination by environmental noise, especially by air-borne noise resulting in additional vibration. This research proposes a dual-sensor concept for active air-borne noise suppression in accelerometer signals that are excited by both fluid-borne noise (including the leak signal) and air-borne environmental noise. In the proposed arrangement, a microphone adjacent to the measurement station is used to measure the air-borne noise simultaneously to the accelerometer mounted to the pipe. Three methods have been applied in this paper: 1) using the non-coherent output power (NCOP) between the accelerometer and microphone signals; 2) using a Wiener filter; and 3) using adaptive least mean square (LMS) filters together with adaptive infinite impulse response (IIR) filters. Field tests have been carried out on a cast iron water main embedded in a water distribution system. A speaker was used to generate air-borne noise around the measurement station and to excite unwanted vibrations in the pipe. The results show that all three methods can effectively suppress air-borne noise from the accelerometer signals mounted to the pipe. A noise reduction of 30 dB can be achieved using the NCOP in the frequency domain or using the Wiener filter in the time domain. The adaptive filters are relatively less effective and the effectiveness reduces with the increase in bandwidth of the air-borne noise. However, the adaptive filters have the potential to be applied online for real-time processing.

Vibration Control of Functionally Graded Panels using Parallel Resonators

Functionally graded materials (FGM) are often an integral part these days in many engineering applications, such as, nuclear structural components, spacecraft and marine structures, thermal barrier coatings used for military applications, etc. These structures are also susceptible to dynamic loads varying from harmonic to impulse type of loadings which are in the form of rotating engines, sudden blasts and others. These loadings often pose serious threats to the structural systems by inflicting fatigue damages or by driving the system in tune with its resonating frequency that eventually lead to the complete collapse of the structure. Therefore, a vibration control strategy needs to be devised to protect these structures from unwanted vibrations due to the external loading. A passive vibration control strategy is proposed in the present research work to control the vibration response of a flat panel made of functionally graded material. At first, the FG plate is numerically modelled using the finite element (FE) method to calculate its response due to a point harmonic force. Ceramic (Alumina) is used for the top part of the FG plate while the bottom is made of metal (Aluminium) and the material property is smoothly varied from ceramic to metal using the power law distribution. Then, several resonators consisting of spring-mass system and parallel to each other are attached to both sides of the panel to isolate the response in the resonating frequency ranges. The FE model for the FG plate with resonator is developed and the controlled vibration response is obtained. The controlled response indicates that the resonators are efficient to produce band-gaps in the resonating frequency regime compared to the bare FG plate.

Small-Scale Dynamic Behavior of Embedded Beams Under Moving Force in Complex Environments

Forced and free dynamic responses of nanobeams resting on a three-parameter foundation subjected to a moving force in magneto-hygro-thermal conditions are investigated based on the nonlocal strain gradient theory. Also, a detailed parametric study is conducted to identify the impact of slender ratio, axial and distributed tangential loads on the vibration characteristics and dynamic phenomena of the small-scale system. Comparative studies with existing results in the literature are performed to ensure the accuracy of the presented model and solution approach. Analytical and numerical methods are implemented to detect the effects of foundation coefficients, environmental conditions, geometrical and scale parameters on the dynamic amplification factor, critical moving force velocity, cancellation, and maximum free response mechanisms of the system. The outcomes revealed that the critical moving force velocity is enhanced by ascending the slender ratio, elastic, and shear moduli of the foundation. It is found that when the damping factor is considered for the foundation, it is feasible to prevent the occurrence of the cancellation phenomenon. Also, it is concluded that by fine-tuning scale parameters and environmental conditions, unwanted vibration of the system can be suppressed. The attained results of this study can be helpful in the vibration control of nanoscale actuators, switches, and resonators.

엔진 마운트 최적 댐핑 제어와 MR 마운트에의 적용

Passenger ride comfort is an integral component of any road vehicle. Ride comport is impacted by vibration resulting from road roughness of low frequency, and also engine vibration of high frequency. The engine mount is an essential component, which acts as a vibration isolator from unwanted vibration. However, vibration isolation requires conflicting design criterion, such as high damping in low frequency range, and low damping in high frequency range. The purpose of this study was to develop a new optimal damping design method for engine mounts based on minimizing HSUB∞/SUB-norm. The damping minimizes HSUB∞/SUB-norm of displacement and force transmissibilities in the wide-frequency vehicle operating range. The proposed optimal damping control was applied to a Magnetorheological (MR) engine mount, to investigate the vibration isolation performance. The feasibility of the proposed method is verified, with some numerical simulation examples.

Effect Of Gap Ratio On Flow Influenced Actions Of Two Circular Cylinders In Side-By-Side Arrangement

<p>In order to understand the flow characteristics over cylinders, the investigation is required on a particular structure where interaction of fluid and solid must be there. This phenomenon is quite common in many industrial applications like transmission cables, heat exchanger tubes, cooling towers etc. Flow influenced forces can cause unwanted vibration in the structure that may cause permanent damage to the structure. In this study, one particular set up has been chosen where circular cylinders have been placed in a flow field using side-by-side arrangement in a fluid domain and the effects of the flow influenced vibration have been observed by varying the gaps between two cylinders. The entire work has been done using a CFD software based on the finite element analysis. </p>

A Nonlinear Energy Sink Design to Attenuate the Torsional Oscillations of Lightly Loaded Gear Pairs

Nonlinear energy sinks (NES) have recently attracted significant interest for the suppression of unwanted vibrations in a variety of mechanical systems. The key advantage in employing this (vibration absorber) approach is the broadband nature of the interactions with a primary system for which vibration energy dissipation is required. Thus, the effectiveness of the NES is decoupled from the need of tuning to specific frequencies. Nevertheless, NES for rotational fluctuations of powertrains have received limited attention in the literature. In this work, a design for a rotational NES to mitigate speed fluctuations in gear trains is presented and tested experimentally. The development of the proposed system is underpinned by previous optimisation studies conducted by the authors, where a disk was utilised as an inerter NES. A set of beams couple the inerter with the wheel gear of a spur gear pair with a nonlinear restoring torque, which is designed to approach the desired essential nonlinearity within realistic practical tolerances. Static and dynamic identification is conducted to confirm the desired characteristics. Despite uncertainties in the prototype testing, the approach is found to reduce the speed fluctuations on the gear pair output shaft, with appropriate predictability established for the model and the design procedure.

An experimental study on the damping characteristics and tuning of the liquid column vibration absorber

This paper deals with an experimental investigation of the damping characteristics of the liquid column dynamic vibration absorber. The laboratory test rig of a single degree of freedom system integrated with a liquid column dynamic vibration absorber was designed and manufactured to study the efficiency of this type of dynamic absorbers. The system response has been measured and recorded by using a (DXL-345) accelerometer and data acquisition system. The effects of mass ratio, length ratio, and the opening ratio of the central orifice on the vibration reduction of the main structure in free vibration mode were evaluated. The results showed that the tuned liquid column vibration absorber has a good ability to reduce or eliminate unwanted vibration by the suitable selection of the combination of its design parameters. The maximum damping of the main system was achieved at the mass, length and orifice opening ratios equal to 7.7 %, 87% and 74% respectively.

Design and Fabrication of X-Y Gantry Mechanism using Python: A Review

Abstract: A crane is a machine that is primarily used to handle big weights in a variety of jobs. For instance, building work, shipbuilding, cargo transportation, and the cement industry may all benefit from this technology since it allows them to monitor and control their video processing systems using a PC. Cranes are frequently utilized in the industrial sector around the world to boost productivity and minimize personnel. Cranes are used to transport loads from one location to another. During this movement, there are typically unwanted vibrations and variations in the hoisted weight that must be managed. This paper gives a review of a new way for operating an overhead crane that uses a PC (Portable Computer), RF (Radio Frequency), and video processing approach to operate the crane from a certain distance. The crane movement is now controlled directly by the crane operator; nevertheless, due to the human inability to handle the crane efficiently, the crane speed is severely limited. This procedure allows a single employee to handle the crane from a greater distance by watching the location of each and every movement towards and away from the crane using a video processing technology and a radio frequency controlling system. The technology use computer vision to identify load location, which is then used to optimize crane operation. The intimation of the PC monitors reveals that the accident levels to become decline for handling the overhead crane even by operator, according to the technology for sustaining job.

Dynamic Response of the Inertial Platform of the Laser ELI-NP Magurele-Bucharest Facility

Previous studies on the vibrational behavior of the inertial platform installed at ELI-NP, in Magurele-Bucharest have reported eigenfrequencies in the domain in which excitations can occur from earthquakes which manifests itself periodically in this geographical area. The paper aimed to study the vibrational response that may occur, due to human activities or natural phenomena (earthquakes), at the inertial platform of the Laser + Gamma building within the ELI-NP complex. The large mass of the platform, 54,000 tons in full condition, must ensure that the experiments are carried out without being disturbed by unwanted vibrations. The laser and gamma beam must be very precisely positioned and the shocks and vibration from the external environment must be damped or absorbed. To realize this, the behavior of the inertial concrete platform at external excitations was studied based on a model with finite elements. The response to the forced vibrations of the platform and the possible behavior in case of an earthquake were obtained.