Optimal Vibration Research Articles

Study on the optimal vibration isolation design and effect of composite multilayer wave impeding block in unsaturated soil

Study on the optimal vibration isolation design and effect of composite multilayer wave impeding block in unsaturated soil

Autonomous and ultrasonically assisted drilling in a range of rocks and ice

Drilling in extreme environments may require reductions in weight-on-bit, applied torque, or energy use, without compromising rate-of-progress. This paper examines the use of ultrasonic vibration, directly superimposed onto an augering coring bit, to achieve this goal in aircrete, limestone, marble, tuff, and ice.Compared to traditional rotary drilling processes using the same tool, the ultrasonically assisted drilling processes demonstrated improved rate-of-progress (∼400%) in all materials studied. In aircrete and limestone, there were also modest but consistent reductions in torque power demand and, at optimum vibration amplitudes, total energy consumption (∼25%). The other materials gave more mixed results: ultrasonically assisted drill cycles in marble were energy intensive, those in tuff were unpredictable due to the inconsistencies in that material, and those in ice led to the failure of the tooth bonding.

Influence of mechanical vibration on composite phase change material based thermal management system for lithium-ion battery

Electric vehicles are inevitably affected by vibration when driving. However, the influence of vibration on the thermal field is neglected in most theoretical and experimental studies on battery thermal management systems (BTMS) in the current literature. Due to the addition of high thermal conductivity elements such as carbon nanoparticles and graphene into pure phase change material (PCM), the heat transfer properties of these composite phase change materials (CPCM) differ significantly from those of pure PCM. The present work focuses on the influence of mechanical vibration on the BTMS based on CPCM. A series of experiments are carried out for the BTMS based on pure paraffin and three CPCM with a mass fraction of expanded graphite or graphene from 0 to 20 % under the vibration amplitudes of 2–4 mm and frequencies of 10–30 Hz. The results show that the small vibration amplitude is beneficial to strengthening the heat transfer of CPCM and lowering the battery's operating temperature. Besides, the mechanical vibration can accelerate the dispersion and collision of the high thermal conductivity particles in CPCM, thus improving the heat dissipation efficiency of the BTMS. It can significantly prolong the latent heat utilization time of the CPCM and then extend the period when the battery pack is in the suitable working temperature range. However, the too high or too low vibration frequency is not conducive to enhancing heat transfer. The 20 Hz is found to be an optimal vibration frequency. And the vibration has the best cooling effect on the CPCM with 20 % expanded graphite among the three CPCMs considered in this study. Finally, the grey relational analysis is applied to investigate the combined effects of three factors. It is determined that the impact ranking from the largest to the smallest is vibration frequency, the composition of CPCM, and vibration amplitude.

Transfer matrix model and experimental validation for the integrated piezo longitudinal actuators

The housing and pre-compressed spring of the integrated piezo longitudinal actuator can protect the piezoelectric stack from shear stress and tensile stress. In this paper, the limitations of this actuator model in existing vibration control projects are pointed out. An electromechanical coupling dynamic model in the transfer matrix form is established for the longitudinal vibration of the integrated piezo longitudinal actuator. The model includes all parameters of the integrated piezo longitudinal actuator: force and velocity at both ends, material and structural parameters, voltage and current, which is suitable for any mechanical and electrical boundary conditions; The transfer matrix method has a simple structure and clear physical definition, which is convenient to be applied to the vibration control system. This model is verified by the finite element software and experiments. In the experimental verification, an electromechanical coupling dynamic experiment system of the integrated piezo longitudinal actuator is established. The accuracy of this model is verified by comparing the frequency domain dynamic response of various parameters in the simulation and experiments. The integrated piezo longitudinal actuator model provides a wide range of possibilities for model-based controller design, active and semi-active control, electric power estimation, and optimal vibration isolation performance estimation.

On the dynamic stability and efficiency of centrifugal pendulum vibration absorbers with rotating pendulums

The automotive industry uses centrifugal pendulum vibration absorbers (CPVAs) to reduce vibrations of the transmission system. These passive devices are made of several masses oscillating along a given path relative to a rotor. This work addresses a recent design of CPVA, in which the pendulums are allowed to rotate relatively to the rotor. The dynamic stability of this CPVA and the shifting of its operating point are investigated in this paper. These two aspects, crucial for an optimal vibration reduction, are assessed using an analytic dynamical model based on a perturbation method. The results obtained allow to propose new design guidelines. The validity of the model is confirmed through a comparison with a numerical resolution of the system’s dynamics.

Fluid inerter for optimal vibration control of floating offshore wind turbine towers

This paper proposes the use of a tuned mass damper fluid-inerter (TMDFI) for vibration control of spar-type floating offshore wind turbine towers. The use of an inerter in parallel with the spring and damper of a tuned mass damper (TMD) is a relatively new concept. The ideal inerter has a mass amplification effect on the classical TMD leading to greater vibration control capabilities. Previous work by the authors has shown that inerter based TMDs have great potential in vibration control of floating offshore wind turbines where enhanced vibration mitigation can be achieved using a relatively lighter device than classical TMDs. However, this previous work was based on the assumption of an ideal inerter that assumes the use of a mechanical flywheel type inerter. Mechanical inerters have some inherent disadvantages due to their complexity in design and high cost of maintenance. The use of a fluid inerter can alleviate these disadvantages as its design is rather simple and it comes with very low maintenance. Such devices have been proposed and investigated in the literature, however, their applicability in vibration control of floating wind turbines has not been investigated by researchers. The optimal design of a TMDFI is presented in this paper. It has been shown that optimization of a TMDFI is a six-dimensional non-linear optimization problem whose solution hyperplane contains multiple local minima. A systematic way has been developed in this paper, avoiding the use of metaheuristic search techniques, to optimize the damper while providing greater insight into the damper properties that offers a set of guidance to the designer. Numerical results demonstrate impressive vibration control capabilities of this new device under various stochastic wind-wave loads. It has been shown that the fluid-inerter performs as well as the ideal mechanical inerter. The considerable advantages of a TMDFI over the classical TMD demonstrated in this paper makes it an exciting candidate for vibration control.

Numerical Investigation of the Effect of Uniform Cutout on Performance of Ultrasonic Horn for Machining Nomex Honeycomb Core Material

Ultrasonic horn is utilized in order to enhance the amplitude of vibration transmitted by the transducer in an ultrasonic machining system. It plays a vital role in vibration amplification to a magnitude suitable for efficient machining of materials. Ultrasonic machining system has to operate at a frequency of at least . Therefore, horn may be subjected to high magnitude of stresses leading to failure. Mechanical horn is designed to get optimum vibration amplification while keeping stresses in acceptable limits. In this research an ultrasonic compound horn was designed with through cutout of uniform diameter. The performance of ultrasonic horn was observed by varying the cutout diameter by modelling horns of four different materials: titanium, aluminum, steel and stainless steel respectively. Modal analysis was performed for computing modal frequencies in the axial direction, whereas harmonic analysis was carried out in order to determine vibration amplitude, stresses and factor of safety. The effect of varying frequency ratio on vibration magnification, stresses, and factor of safety were also investigated. The axial modal frequency was observed to increase, whereas amplitude of vibration and stresses were observed to decrease by increasing the cutout size. Titanium was found to be the most suitable material for ultrasonic horns, because it provided up to 159.4 % more amplitude of vibration and 3 times higher safety factor thus operating life as compared to other materials.

Optimal vibration isolation and alignment over non-rigid bases with the CRO-SL ensemble

This work proposes the design of both Single-Input–Single-Output (SISO) and Multiple-Input–Multiple-Output (MIMO) isolation controllers, when the interaction between the isolator system and the base structure is considered. The problem to be addressed is based on the reduction of the vibration of every platform, and also on the alignment between the different isolators. Both techniques, SISO and MIMO, are optimally tuned by the recently-proposed Coral Reefs Optimisation with Substrate Layers (CRO-SL), a multi-method ensemble evolutionary approach. In the proposed design, the stability of both systems (the isolators and the supporting structure) is verified. Also, the importance of considering the supporting structure dynamic is shown, by comparing the results with those obtained when the base structure is assumed to be rigid and infinitely heavy. This work shows considerable and not obvious improvements when the interaction between the isolator system and the base frame is considered. Numerical examples are included to illustrate the significant differences between using SISO and MIMO cases, and to motivate the use of CRO-SL. In addition, a real application example is analysed based on experimental data. Verified practical guidelines to be followed in experimental tests are finally shown.

A Novel Model for Evaluating the Operation Performance Status of Rolling Bearings Based on Hierarchical Maximum Entropy Bayesian Method

Information such as probability distribution, performance degradation trajectory, and performance reliability function varies with the service status of rolling bearings, which is difficult to analyze and evaluate using traditional reliability theory. Adding equipment operation status to evaluate the bearing operation performance status has become the focus of current research to ensure the effective maintenance of the system, reduce faults, and improve quality under the condition of traditional probability statistics. So, a mathematical model is established by proposing the hierarchical maximum entropy Bayesian method (HMEBM), which is used to evaluate the operation performance status of rolling bearings. When calculating the posterior probability density function (PPDF), the similarities between time series regarded as a weighting coefficient are calculated using overlapping area method, membership degree method, Hamming approach degree method, Euclidean approach degree method, and cardinal approach degree method. The experiment investigation shows that the variation degree of the optimal vibration performance status can be calculated more accurately for each time series relative to the intrinsic series.

Vibration simulation and experiment of three open-center shape olive trees

Appropriate vibration parameters can improve the efficiency of vibration harvesting, so the selection of vibration harvesting parameters is very important. In this paper, the stress of olive fruit is analyzed, and the vibration of olive tree is tested and simulated. Design-Expert 12.0 is used for experimental design, The diameter, height and angle of main branches were selected as the test factors, and the optimal vibration frequency and force were selected as the evaluation indexes. determines the optimal vibration frequency through modal analysis; the optimum vibration force is determined by harmonic response analysis and test. The quadratic polynomial response regression model of optimal vibration frequency and optimal vibration force is obtained. The research results can provide reference for the design of Vibrating harvester.

Analysis of double-layer vibration isolation characteristics of ship power equipment

The vibration isolation device of ship power equipment is the key equipment to protect it from damage, and its performance determines whether the ship can sail safely. To address the problem that it is difficult to achieve the optimal vibration isolation performance of ship’s double-layer vibration isolation, this paper establishes a vibration transmission theory model of ship’s power equipment double-layer vibration isolation system, derives the vibration displacement transmission rate formula based on the model, and studies the influence law of the stiffness ratio of the lower and upper layers of vibration isolation devices, the mass ratio of the intermediate raft frame to the power equipment and the damping of the upper and lower layers of vibration isolation devices on the vibration transmission. The results show that reducing the stiffness ratio of upper and lower layer vibration isolators and increasing the mass ratio of intermediate raft frame and power equipment can reduce the two resonant frequencies and narrow the interval between the two resonant frequencies, and increasing the damping of upper and lower layer vibration isolators can reduce the vibration peak at the two resonant frequencies, but the vibration isolation effect in the high frequency band becomes worse. It provides a theoretical basis for the design optimization of the double-layer vibration isolation system for ship's power equipment.

Free vibration of a taut cable with a parallel-connected viscous mass damper and a grounded cross-tie

Recent studies have shown that the combination of external dampers and cross-ties can overcome their respective deficiencies while retaining their respective merits. Inspired by the advantages of a viscous damper (VD) and a cross-tie on a single stay cable, the coupled damping effect of a parallel-connected viscous mass damper (PVMD) and a grounded cross-tie on a single stay cable is investigated in this paper. The complex wave number equations of the cable–PVMD–cross-tie system are first formulated through the complex modal analysis. Subsequently, the asymptotic and iterative complex wave numbers are compared to evaluate the applicability of the asymptotic and iterative solutions. Furthermore, parametric studies are carried out to investigate the effects of the stiffness coefficients and the installation positions of the cross-tie on the first supplemental modal damping ratio and frequency of the cable. Finally, the installation positions of the cross-tie are optimized to achieve the optimal vibration control of the cable with the PVMD and the cross-tie.

Utilize mechanical vibration energy for fast thermal responsive PCMs-based energy storage systems: Prototype research by numerical simulation

For commercialisation of PCMs (liquid-solid phase change materials) based energy storage systems, the biggest challenge is to improve the thermal responsive rate of PCMs. In the present authors’ latest study, it is found mechanical vibration may be utilized to address the challenge as most engineering systems work under vibration conditions. However, to utilize mechanical vibration more efficiently, it is critical to accelerate melting speed of solid PCMs in the beginning of charging processes. In the present study, a fin is introduced for the purpose. Here comprehensive numerical simulation is conducted to reveal the effectiveness of the new combination of a fin and mechanical vibration. So far there is no open research on feasibility of this new combination. The present work bridges the gap. The present research shows the integration of a fin and mechanical vibration can provide an effective way to maintain a sustainable high thermal responsive rate for PCMs during charging processes. The fin and mechanical vibration are complementary: the fin can improve thermal responsive rate of PCMs significantly in the early period of the charging process but its influence will become weak; on the contrary, the enhancement effect of mechanical vibration is slight in the beginning but later will become strong. The effects of vibration frequency, vibration amplitude and fin length are investigated numerically. It is found a low/moderate vibration frequency can accelerate charging processes more effectively and the optimal vibration frequency range is around 0–200. And there is also an optimal range for fin length. If the ratio of fin length to side length of the cubic tank is more than 3/4, the benefit by introducing a fin will become slight, which indicates the length of fin is not the longer the better. The present work proposes a new way to develop commercial PCMs-based energy storage systems. The findings can serve as guides for realistic engineering applications.

Approximation Optimal Vibration Control with Applications to Jacket Offshore Platforms with Nonlinear Dynamic Characteristics

Approximation Optimal Vibration Control with Applications to Jacket Offshore Platforms with Nonlinear Dynamic Characteristics

Performance evaluation and design criterion of a nonlinear energy sink

In the evaluation of the vibration mitigation effect of a nonlinear energy sink (NES), the selection of performance measures is important for the optimal design. This paper aims to propose new reasonable performance measures and new design criteria of the NES in harmonic excitation. To broaden the application range of the slow invariant manifold, coordinate correction is carried out for the square root model of the bistable NES. Two existing performance measures (the displacement amplitude of the main system and the energy dissipation rate of the NES) and two new performance measures (the mechanical energy and the input energy of the main system) are compared. The optimal geometric configuration and response form of the NES are found in different excitation conditions. The results show that the energy dissipation rate of the NES is not competent to evaluate the performance of the NES in harmonic excitation, while the two new performance measures show competence. By adjusting the geometry parameter, the nonlinear vibration absorber with positive linear stiffness and the bistable NES show optimal vibration mitigation effect in small and large excitation amplitudes, respectively. Unusually, the optimal response form is the periodic response rather than the strongly modulated response. In summary, the proposed performance measures and design criteria will contribute to the design of NESs.

Optimization approach to suppression of vibrations: For axially moving webs in a fluid flow

A web (continuum) traveling in a flow of ideal fluid between two fixed supports with a constant velocity and performing transverse vibrations is considered by modeling the web as an isotropic type elastic panel. The fluid flow is considered as a potential flow. The web transverse vibration process is analyzed taking into account both material elasticity and the fluid-structure interaction between the traveling material and the surrounding flowing fluid. It is supposed that the actuator system is used for suppression of occurring transverse vibrations. An optimization approach based on the modern control theory and calculus of variations is proposed for determining the optimal suppressive actions at a given time interval. The quality of suppression vibration process is evaluated by means of the functional depending on displacements and velocities at the terminal time. The example (carried out in an analytical way) illustrating all basic stages of finding of optimal vibration suppression is presented.

Vibro-Tactile Stimulation as a Non-Invasive Neuromodulation Therapy for Cervical Dystonia: A Case Study.

Cervical dystonia (CD) is a type of focal dystonia that is characterized by involuntary neck postures. The underlying neurophysiology mechanism of CD is unknown, but there is increasing empirical evidence that motor deficits of CD are associated with somatosensory and proprioceptive deficits in the upper limb area. Vibro-tactile stimulation (VTS) is a non-invasive somatosensory stimulation approach where afferent signals from the vibrated muscle and tactile mechanoreceptors modulate cortical activity. Previous studies have shown that VTS could be an effective neuromodulation therapy for treating laryngeal dystonia. This proof-of-concept study examined the effect of VTS on alleviating the involuntary cervical muscle contractions in a female participant with intermittent torticollis. VTS was applied sequentially on four neck positions: bilateral trapezius (TRP) and bilateral sternocleidomastoid (SCM). Each VTS site was vibrated continuously for six minutes. The kinematics and underlying neck muscle activities during dystonic neck movements were examined with acceleration and surface electromyography (sEMG). To quantify the efficacy of VTS, two acceleration features and one sEMG feature were derived: (1) number of acceleration peaks per minute; (2) peak amplitude of acceleration (PAA); (3) change in power of sEMG after VTS. The frequency of intermittent dystonic neck movements decreased by 60% after VTS. In addition, PAA during dystonic episodes was drastically reduced after VTS when compared to baseline. Third, the effectiveness of VTS in alleviating dystonic muscle spasms depended on the site of vibration. For this participant, the left trapezius muscle was shown as the optimal vibration site reducing sEMG signal power by 15% across all recorded muscles. This case study offered preliminary insight into the assumed effectiveness of neck muscle VTS as a treatment for CD. Our participant experienced pain relief after VTS with measured improvements reflected by electrophysiological and kinematic data. A systematic study with a larger sample size is required in the future to validate the effectiveness of VTS for treating symptoms in CD.

Active Fault-Tolerant Control for Discrete Vehicle Active Suspension Via Reduced-Order Observer

In this article, the fault-tolerant control (FTC) problem of vehicle active suspension is concerned in the discrete-time domain, in which the road disturbances and faults in actuator and measurement are considered. The main contribution consists of proposing an active physically realizable fault-tolerant controller based on a reduced-order observer, which makes up an optimal vibration control component and an event-triggered FTC component. More specifically, by discussing a discrete vehicle active suspension subject to road disturbances generated from the output of a designed exosystem, the optimal vibration control component is derived from maximum principle to offset the inevitable vibrations. Meanwhile, based on the real-time system output of vehicle suspension rather than residual error, a reduced-order observer is proposed to cover the physically unrealizable problem for the designed optimal vibration control component. After that, an event-triggered FTC component and an event-triggered restructured system output are designed to compensate the faults in actuator and measurement, respectively. Finally, extensive experiments are conduced to the control performance of vehicle active suspension under the proposed controller, and confirm its effectiveness and superiority over other control schemes.

Modeling of asphalt mixture-screed interaction: A nonlinear dynamic vibration model for improving paving density

Paving compaction has an important influence on the significant improvement of the asphalt mixture density during pavement construction, and the paving density is mainly affected by the paver response and material behavior. To improve the density of asphalt pavement, this paper proposes a nonlinear dynamic vibration system of the interaction between asphalt mixture and screed plate. Based on the harmonic balance principle, a multi-degree of freedom nonlinear system of the screed plate-asphalt mixture interaction was established. By considering material characteristics and energy absorption efficiency during paving compaction, a paving density tendency-vibration frequency theoretical model was applied to analyze the influence law of dynamic response of the asphalt-screed interaction on the material density. The analysis results indicated that 1) both the characteristics of the asphalt mixture and the vibration frequency of the screed affected the material density during the paving process; 2) the optimal vibration frequency was higher than the natural frequency, and further compaction with a lower vibration frequency can effectively improve the energy absorption efficiency; 3) for the screed in movement, only when the vibration frequency enters the resonance region of the high-density mixture can a better compaction effect be obtained. Finally, the nonlinear dynamic model was experimentally verified. The research results are beneficial for improving the paving density and the quality of asphalt pavement, providing a basis for the effective compaction of asphalt pavement.

Effect of vibratory mixing on the slump, compressive strength, and density of concrete with the different mix proportions

Mixing method plays a critical role in the properties of concrete. Vibratory mixing as a novel mixing method has its advantages in improving the properties of concrete. But the specific property of concrete is sensitive to the operation parameters of the vibratory mixing. This paper is motivated to study the effect vibration amplitude and acceleration on the concrete properties and to compare with the conventional mixing at four groups of mix proportions. The macroscopic performance was measured by slump test, compressive strength test, and density test, and the microscopic characteristics was analyzed by scanning electron microscope (SEM). The test results indicates that the slump, compressive strength, and density of the different concrete were both improved using vibratory mixing. Analysis of variance (ANOVA) results showed that vibration amplitude significantly influenced the compressive strengths. At optimum vibration parameters, the slump of M1, M2, M3, M4 was increased by 36%,15% 25%, 26%, separately; the compressive strength increased by 13%, 15%, 35%, 44%; the density was improved by 1.3%, 2%, 1.4%, 1.3%. Concrete with a low w/c ratio (0.33) requires more vibration energy. Moreover, fewer defects and denser structure were observed by vibratory mixing, which benefited to a higher bond strength. Under the same mix proportions, the slump shows a positive relationship with compressive strength by vibratory mixing. The low w/c ratio concrete has the higher change rate of compressive strength with the density.