Different Types Of Vibrations Research Articles

A Screw Approach to Vibration Analysis of Beam Structures With Nonstandard Conditions

Abstract A major advantage of the screw theory is that translations and rotations are treated simultaneously, which can provide greater insight into the vibration phenomena, such as vibration centers and axes. The present study describes how these concepts are extended into beam theory. The stiffness matrix of a beam was derived by incorporating different types of vibrations, such as extension, compression, torsion, and bending, at the same time, which was then used to obtain the equations of motion, including nonstandard forms of boundary conditions. We then presented an analytical method to solve these equations by focusing on two distinct examples, namely the cantilever and robot link. In the first numerical example, the mode shapes of the beam could be regarded as rotations about the vibration centers or axes of the rigid bodies in a discrete system. In the second example, the analytical solutions of mode shapes and natural frequencies of a robot link, for which the revolute joints at both sides are not parallel, were presented to demonstrate the utility of the screw theory. We demonstrated that the screw approach could accurately describe the vibrations of both discrete and continuous systems and that the geometric meaning of the vibration modes of discrete systems can be extended into continuous systems.

A Pre-Post Study on the Cardiorespiratory Response to Different Protocols of Exposure on a Vibratory Platform in Young Healthy Individuals.

This study aimed to investigate the acute specific physiological effects of 15 min of whole-body vibration (WBV) exposure at six different types of vibrations on cardiorespiratory function in 26 healthy young subjects (sex ratio, 1:1; mean age, 20.73 years). The protocols included six variants of a combination of mechanical stimuli with different frequencies (15, 25, and 35 Hz) and direction of stimuli (vertical or diagonal). The investigated cardiorespiratory parameters were heart rate (HR), arterial oxygen saturation (SaO2), respiratory rate (RR), and spirometric indicators: tidal volume (TV), vital capacity (VC), forced vital capacity (FVC), forced expiratory volume at 1 s (FEV1), and maximum voluntary ventilation for 12 s (MVV). The data series were statistically processed by using descriptive and inferential statistical methods: the Shapiro–Wilk test, the two-way ANOVA with repeated measures, and post hoc analysis. We obtained significantly higher values for HR, TV, VC, FVC, FEV1, and MVV after the WBV exposure. These parameters are significantly influenced by both the frequency and direction of stimuli, and certain protocols of WBV are noticeable for their distinct effects. Our results offer a new perspective on the possibility of using preferential variants of vibratory stimulation to obtain maximum cardiorespiratory physiological effects.

How and why do bees buzz? Implications for buzz pollination.

Buzz pollination encompasses the evolutionary convergence of specialized floral morphologies and pollinator behaviour in which bees use vibrations (floral buzzes) to remove pollen. Floral buzzes are one of several types of vibrations produced by bees using their thoracic muscles. Here I review how bees can produce these different types of vibrations and discuss the implications of this mechanistic understanding for buzz pollination. I propose that bee buzzes can be categorized according to their mode of production and deployment into: (i) thermogenic, which generate heat with little mechanical vibration; (ii) flight buzzes which, combined with wing deployment and thoracic vibration, power flight; and (iii) non-flight buzzes in which the thorax vibrates but the wings remain mostly folded, and include floral, defence, mating, communication, and nest-building buzzes. I hypothesize that the characteristics of non-flight buzzes, including floral buzzes, can be modulated by bees via modification of the biomechanical properties of the thorax through activity of auxiliary muscles, changing the rate of activation of the indirect flight muscles, and modifying flower handling behaviours. Thus, bees should be able to fine-tune mechanical properties of their floral vibrations, including frequency and amplitude, depending on flower characteristics and pollen availability to optimize energy use and pollen collection.

A New Insight to Vibration Characteristics of Spans under Random Moving Load: Case Study of 38 Bridges in Ho Chi Minh City, Vietnam

We propose a novel representative power spectrum density as a specific characteristic for showing responses of spans during a long operational period. The idea behind this method is to use the representative power spectrum density as a powerful tool to evaluate the stiffness decline of spans during their operation period. In addition, a new measurement method has been introduced to replace the traditional method of monitoring the health conditions of bridges through a periodic measurement technique. This helps to reduce costs when carrying out testing bridges. Besides, the proposed approach can be widely applied not only in Vietnam but also in many other underprivileged countries around the world. Obtained results show that, during the operational process of spans, there is not only a pure vibration evaluation such as bending vibration and torsion vibration tests but also a combination of various vibration types including bending-torsion vibration or high-level vibrations like first-mode bending and first-mode torsion. Depending on each type of structure and material properties, different types of vibrations will appear more or less during the operational process of spans under a random moving load. Furthermore, the representative power spectrum density is also suitable for evaluating and determining many different fundamental vibrations through the same measurement time as well as various measurement times.

Coupled dynamic analysis of a heavily-loaded propulsion shafting system with continuous bearing-shaft friction

This paper studies the friction-induced instability and nonlinear dynamics of a heavily-loaded slow speed propulsion shafting subjected to the uninterrupted contact between the shaft and the water-lubricated rubber bearing. A high-dimensional analytical model is developed to take into consideration the intrinsic interactions among the torsional and lateral vibrations of the continuous shaft, bearing vibrations and the friction nonlinearity. The exponential friction model derived from experimental data is adopted to qualitatively represent the velocity-dependent behaviours of friction for water-lubricated rubber bearings. A stability analysis based on the complex eigenvalue calculations of the linearised system is performed to estimate the effects of parameter variations on instabilities. Two potential instabilities concerning the self-excited whirl motions and stick-slip torsional motions are identified. Corresponding transient dynamics are then numerically studied to explore the roles of different types of vibrations on nonlinear behaviours. The results reveal that the velocity-weakening and discontinuity effects of nonlinear friction may induce the occurrence of limit-cycle type self-excited vibrations for both instabilities. Additionally, the effects of cross-coupling and the kinematic coupling at the bearing-shaft interface on the dynamic interaction among different vibration modes are also highlighted.

Complementary vibrational spectroscopy

Vibrational spectroscopy, comprised of infrared absorption and Raman scattering spectroscopy, is widely used for label-free optical sensing and imaging in various scientific and industrial fields. The two molecular spectroscopy methods are sensitive to different types of vibrations and provide complementary vibrational spectra, but obtaining complete vibrational information with a single spectroscopic device is challenging due to the large wavelength discrepancy between the two methods. Here, we demonstrate simultaneous infrared absorption and Raman scattering spectroscopy that allows us to measure the complete broadband vibrational spectra in the molecular fingerprint region with a single instrument based on an ultrashort pulsed laser. The system is based on dual-modal Fourier-transform spectroscopy enabled by efficient use of nonlinear optical effects. Our proof-of-concept experiment demonstrates rapid, broadband and high spectral resolution measurements of complementary spectra of organic liquids for precise and accurate molecular analysis.

Dynamic properties of single and multi-bolted composite joints at different bolt-loads and elevated temperature

ABSTRACT Bolted composite joints are one of the most common joining methods used in aerospace industry for joining of parts and sub-assemblies, where there is a need to transfer high load with consistency and easy to assemble/ dissemble of parts for maintenance. Bolted connection undergoes different types of vibrations during their service life, that make the pre-load on bolted joints to decrease and call for increase in dynamic loading and failure. Regular checking and tightening of bolted joints become a crucial and expensive activity to maintain the structure to perform efficiently. The natural frequency is one of the most important factors of vibration of structure that depends on the geometry and material properties of the structure. In this paper, the effect of pre-load and temperature on the natural frequency of single bolted and double-bolted joints is investigated experimentally and numerically.

Dynamic analysis of slender rotor of vertically suspended centrifugal pumps due to various hydraulic design factors

If a rotor is excited at one of its natural frequencies, a resonance occurs. The resonance can lead to large amplitude oscillations and subsequently failures. Field experience proves that the excessive vibration of the rotor of centrifugal pumps shows itself in wear and fatigue failure of shafts, bearings, wear rings, seals and impellers. So, modal analysis of a pump rotor is of great concern to researchers, international standard organizations and industries. In this research, dynamic behavior of a nonlinear finite element model of slender rotor of vertically suspended centrifugal pumps is studied. The dynamic model of the rotor is discretized into an appropriate number of three-dimensional Timoshenko beam elements. In addition to the main nonlinear terms and particularly the geometric stiffening effect, the gyroscopic effect has been also taken into account. The full-order equations of the motion, which are obtained by the Lagrangian approach and the finite element method, are integrated into a computational plan. The ability of the recent nonlinear dynamic model, which is intended to furnish a basic model for further development of a more comprehensive model, is examined to track the coupling between different types of vibrations. The comprehensive modal analysis of the rotor due to various hydraulic design factors is presented.

Vibrational Durability Test Methodology for an EGR Cooler

EGR Cooler is one of the key automotive components which uses coolant to reduce exhaust gas high temperature while discharge through the air induction system. These automotive components are exposed to different types of vibrations from road such as simple sinusoidal, random excitations. This work presents vibration durability test methodology which is used for the EGR cooler of Heavy Duty Vehicle. Test set-up and test procedures are developed to assess durability performance of the EGR on the electrodynamic shaker. Sinus, random test profile and sinus on random profiles are compared to show effect of the EGR durability

On the Need to Take Into Account Vibrations when Designing the Elements of the Drill String

Uneven rotation of the bottom hole drill stem assembly (BHA) and the drill string is a source of torsion shocks that create high-frequency and high-amplitude vibration. A correlation between torsional and lateral vibrations is discovered. An analysis demonstrates that an increased vibration load on the drill string and the bottom hole drill stem assembly leads to a decrease in the mechanical on-bottom drilling rate and premature wear of equipment. A suitable selection of all the elements of BHA that takes into account the possibility that different types of vibrations may arise and an adjustment of the drilling parameters (bit load, rotational speed) together lead to an increase in the drilling rate, the reliability of the drilling equipment, and a decrease in the time needed to construct the well. Real-time monitoring for shocks, vibrations, and stick-slip will help to increase the precision of estimates of the state of downhole equipment.

Harmonic analysis of wrist mechanism of robot manipulator

Wrist mechanism is a part of robot manipulator which is used to provide the pitch and yaw motions to the end effectors for orienting the loads carried by the end effectors. The wrist mechanism is subjected to different types of vibrations because of the various working conditions. Due to these vibrations wrist mechanism experience higher deformations and stresses; this causes failure of wrist mechanism. It is important to study the dynamic behaviour of the wrist mechanism under different loads before adopting in the application. The structure of the wrist mechanism is modelled in the ANSYS Workbench software and analysed for harmonic loads. Proper boundary conditions, mesh and connections between links& pins are assigned to the wrist mechanism assembly. From the present work, peak deformations of links and pins are occurred at 569.83Hz. Further, the link are analysed with 3D composites those are carbon epoxy and E-glass epoxy. It is observed that carbon epoxy shows better stiffness than E-Glass epoxy and it has weight reduction of 13.76% compared with metals.

Development and Optimization of Vibration-Damped Tool Holders for High Length-to-Diameter Boring Operations

AbstractWhen the length-to-diameter ratio of a boring bar becomes too high, the vibration problem becomes excessive. This paper discusses the design and optimization of tuned mass dampers (TMDs) for vibration-damped boring bars. A typical TMD for a boring bar consists of a high-density mass, rubber elements, and viscous damping fluid. The TMD is mounted as close to the free end of the boring bar as possible for maximizing the damping effect. The different tuning strategies are related to the different types of vibrations that are observed in machining operations. It is shown that the classical tuning with minimized magnitude of the frequency response function will give the shortest settling time for free vibrations, while tuning for maximized negative real part of the frequency response function will give the highest resistance to regenerative chatter. For suppressing regenerative chatters, the internal damping in the material in the boring bar body is of minor importance for boring bars with TMDs, but of high importance for conventional undamped boring bars. The paper presents design solutions for TMDs in boring bars.

Influence of Different Types of Vibrations on Technical Acceptance of a Mobile Game Aiming for Hedonic Satisfaction

Rapid increases in the smartphone gaming industry have made in-game usability increasingly important. However, industrial usability is still focused on performance although high performance is not necessarily a goal in actual games. Mobile gamers largely want to increase their hedonic satisfaction. So already established usability guidelines can fail in mobile gaming. Focusing on vibrations as a haptic feedback, this study analyzed the influences of intensity and length of vibrations on user perceptions based on the technology acceptance model aiming for hedonic satisfaction when mobile gaming. A smartphone game was modified to generate seven types of vibrations for a human factors experiment with 70 subjects and administered a questionnaire to measure their perceptions of the game influenced by the vibrations. The results show that including vibrations significantly increases the perceived ease of use, perceived usefulness, and cognitive concentration in the game. The stronger vibration intensity significantly improves user perceptions of the usefulness and cognitive concentration, whereas the length of vibration is not a critical factor as long as vibrations exist.

Different Types of Vibrations Interacting with Electronic Excitations in Phycoerythrin 545 and Fenna-Matthews-Olson Antenna Systems.

The interest in the phycoerythrin 545 (PE545) photosynthetic antenna system of marine algae and the Fenna-Matthews-Olson (FMO) complex of green sulfur bacteria has drastically increased since long-lived quantum coherences were reported for these complexes. For the PE545 complex, this phenomenon is clearly visible even at ambient temperatures, while for the FMO system it is more prominent at lower temperatures. The key to elucidate the role of the environment in these long-lived quantum effects is the spectral density. Here, we employ molecular dynamics simulations combined with quantum chemistry calculations to study the coupling between the biological environment and the vertical excitation energies of the bilin pigment molecules in PE545 and compare them to prior calculations on the FMO complex. It is found that the overall strength of the resulting spectral densities for the PE545 system is similar to the experiment-based counterpart but also to those in the FMO complex. Molecular analysis, however, reveals that the origin for the spectral densities in the low frequency range, which is most important for excitonic transitions, is entirely different. In the case of FMO, this part of the spectral density is due to environmental fluctuations, while, in case of PE545, it is essentially only due to internal modes of the bilin molecules. This finding sheds new light on possible explanations of the long-lived quantum coherences and that the reasons might actually be different in dissimilar systems.

Vibrations in Steel Strips: Effects on Flatness Measurement and Filtering

Vibrations are periodic or random motion from an equilibrium position. In the steel industry, vibrations are an undesirable phenomenon, as they waste energy and create unwanted noise. For example, vibrations affect steel strips during rolling and transportation, producing random or periodic vertical movements of the strips as they move forward along a roll path. The consequences of these vibrations are particularly harmful for 3D reconstruction and flatness measurement based on non-contact techniques. Vibrations corrupt the height profiles, causing an erroneous reconstruction of the 3D surface. The flatness measurement is also distorted because the estimated lengths of the strip fibers with vibrations are different. This paper analyzes how vibrations in steel strips affect flatness measurement, and proposes methods to remove or reduce these effects. The shape of steel strips is firstly modeled including the two most common flatness defects: wavy edges and center buckle. Then, different types of vibrations are added to the strip models, and their effects on the resulting flatness measurement are analyzed. The method proposed to reduce the effects of vibrations is a combination of a low-pass filter and geometric transformations. Finally, these methods are applied to data from real strips.

Micropower Design of a Fully Autonomous Energy Harvesting Circuit for Arrays of Piezoelectric Transducers

This paper presents a self-powered energy harvesting circuit based on synchronous charge extraction with a single shared inductor for power conversion from arrays of independent piezoelectric transducers. The number of handled elements can be easily increased at the expense of few additional components and without affecting performance. The energy harvesting circuit was characterized with three 0.5 × 12.7 × 31.8 mm3 piezoelectric cantilevers subject to different types of vibrations. Throughout all operating conditions, the circuit was able to extract the maximum power independently from every transducer. Compared to passive energy harvesting interfaces, the output power is significantly higher, with worst-case increases ranging from +75% to +184%. The circuit starts up passively and is based on ultralow power active control, which consumes during operation at 3 V a fraction of the extra harvested power as low as 10 μW per source. As part of the best tradeoff between harvested and intrinsic power, an overall energy efficiency up to 74% was achieved.

Correcting vibration-induced performance degradation in enterprise servers

Server fan subsystems are power-hungry and generate vibrations, degrading the performance of data-intensive workloads and inflating the uptime electric bills of cost-sensitive datacenters. In this paper, we demonstrate a systematic server measurement methodology to isolate different types of vibrations and quantify their effect on hard disks. We introduce a thermal and cooling management policy that mitigates vibrational effects workload scheduling and fan control, and study the benefits of a hybrid storage array with solid-state drives (SSDs) that are impervious to vibrations. We achieve performance improvements of up to 73% and energy savings of up to 76% over the state of the art, while meeting thermal constraints and improving the system's resilience to both internal and external vibrations.

Lift force acting on the cylinder in viscous liquid under vibration

The averaged lift force acting on a solid in viscous liquid in case of translational or rotary vibrations of a cavity is experimentally investigated. Experiments are performed with a heavy cylinder; different types of vibrations, translational and rotational, are investigated. It is found that the vibrations excite the mean lift force which could provide the suspension of solid even in gravity field. The repulsion lift force acts on the body near the walls of the vibrating cavity. It is caused by the viscous hydrodynamic interaction of oscillating body with the wall and is significant at a distance comparable with the thickness of Stokes layer. The intensification of vibration results in the excitation of tangential lift force, which is caused by the brake of the symmetry of the body's oscillations with respect to the cavity wall. In case of rotary vibrations the lift force of high intensity manifests itself in the bulk of the cavity due to the interaction of body with the oscillating shear flow. The mean dynamics of the solid body in a cavity under the rotary vibrations is determined by the combined action of two averaged vibrational effects—levitation of the body in the oscillating shear flow and hydrodynamic interaction of the body with the wall. In case of translational vibrations the dynamics of the solid is mainly determined by interaction with the walls. The experiments demonstrate that the vibrations have strong mean effect on the bodies in liquid; they could be used for efficient control of solid inclusions in microgravity and must be taken into account in space experiments and technologies.

Monopole oscillations in light nuclei with a molecular dynamics approach

Collective monopole vibrations are studied in the framework of an antisymmetrized version of molecular dynamics as a function of the vibration amplitude. The giant monopole resonance energy in ${}^{40}Ca$ is sensitive to the incompressibility of the effective interaction, in good agreement with complete time-dependent Hartree-Fock calculations. The collective response of ${}^{12}C$, ${}^{16}O$ and ${}^{24}Mg$ is also studied. For these lighter nuclei that have an important contribution of an $\alpha$-clustered component, different frequencies are observed, corresponding to two different types of vibrations associated with breathing and moving of the underlying clusters. Possible connections with direct breakup into $\alpha$ clusters at high excitation energy are discussed.

Vibrations of shallow noncircular membranes with initial stresses

The basic relations for a geometrically nonlinear (quadratic approximation) theory of thin elastic membranes are obtained. The relations are used to develop a variational method for studying free vibrations of initially flat membranes bounded by a stationary piecewise-smooth contour. The membrane is deformed by uniform pressure. Numerical results are given for different types of vibrations of rectangular and elliptical shells.