Vibration and Impact Transmission for each Variable of Woodpile Metamaterial

In International Standard 10819 (1996), the requirements for a glove to be considered an anti-vibration glove are determined by the transmission of vibration to the palm of the hand. The transmission of vibration to a finger is very different from the transmission of vibration to the palm, but there are currently no requirements to measure the transmission of vibration through gloves to the fingers. This study investigated the effects of material dynamic properties on the transmission of vibration to the palm of the hand and to the fingers. Two materials (foam material from one anti-vibration glove and gel material from another anti-vibration glove) were investigated. Subjects placed their palms or index fingers on the material and pushed down with a force of 10 N while the transmission of random vibration was measured over the frequency range 5 to 500 Hz. At frequencies greater than 20 Hz, both materials attenuated vibration to the palm of the hand but amplified vibration to the finger. The study shows that the materials in gloves can both attenuate and amplify the transmission of vibration, depending on the material, the frequency of vibration, and the location on the hand (palm or finger).

During buzz pollination, bees use their indirect flight muscles to produce vibrations that are transmitted to the flowers and result in pollen release. Although buzz pollination has been known for >100 years, we are still in the early stages of understanding how bee and floral characteristics affect the production and transmission of floral vibrations. Here, we analysed floral vibrations produced by four closely related bumblebee taxa (Bombus spp.) on two buzz-pollinated plants species (Solanum spp.). We measured floral vibrations transmitted to the flower to establish the extent to which the mechanical properties of floral vibrations depend on bee and plant characteristics. By comparing four bee taxa visiting the same plant species, we found that peak acceleration, root mean-squared acceleration (RMS) and frequency vary between bee taxa, but that neither bee size (intertegular distance) nor flower biomass (dry mass) affects peak acceleration, RMS or frequency. A comparison of floral vibrations of two bee taxa visiting flowers of two plant species showed that, while bee species affects peak acceleration, RMS and frequency, plant species only affects acceleration (peak acceleration and RMS), not frequency. When accounting for differences in the transmission of vibrations across the two types of flower, using a species-specific 'coupling factor', we found that RMS acceleration and peak displacement do not differ between plant species. This suggests that bees produce the same initial acceleration in different plants but that transmission of these vibrations through the flower is affected by floral characteristics.

The transmission of vertical vibration through seats: Influence of the characteristics of the human body

The paper represents research aimed at assessing elastic and dissipation properties of enclosures on excitation and transmission of vibration in electronic packages. Once bearing parts of electronic packages, in particular printed circuit boards, receive resonant oscillations, the dynamic forces increase manifold so that they cause breakages of parts and components. In the paper, three basic problems are in objective for enclosed electronic packages forced by vibration: finding natural frequencies of printed circuit boards using estimation and test methods; assessing enclosure case design on vibration transmission to printed circuit boards installed inside; developing methods and means to reduce transmission and excitation of vibration inside the enclosure case.

This paper aims to review researchers’ concerns over time (from the 1980s to the present) regarding the transmission of mechanical vibrations in the workplace to the limbs, with a preponderant focus on the hand–arm system and some of the effects over time. These concerns are strictly approached from the point of view of their effects on different races, types of jobs, and forms of tools handled in the workplace. In this regard, when we refer to unwanted vibrations (harmful to a person) in the industrial environment, these are vibrations that can produce harmful effects on an individual’s health, leading to occupational diseases such as white finger syndrome. Some of the terms specific to the studies reviewed, such as vibration perception and biodynamic force, among others, are explained in this paper as needed. Studies in the field have shown that vibrations are transmitted differently when the arm is bent at the elbow joint compared to when it is outstretched; also, the transmission of vibrations is influenced by other factors, such as the temperature of the working environment, the gender and age of the person who is using the vibrating devices, and last but not least, the time of their use and the frequency. The conclusions presented by the specialized literature often refer to existing standards, in particular SR EN ISO 5349/2003. Finally, in this paper, conclusions are drawn regarding how to analyze the transmission of vibrations over time, and some recommendations are given for avoiding or minimizing them, which can be added to the already-existing standards.

The transmission of longitudinal vibration in the hand-arm system of five subjects was investigated. Altogether 405 individual tests were made. Vibration was measured with an accelerometer (weight 0.4 g) fixed in turn to the wrist, the elbow, and the upper arm by means of a supporting device (weight 34 g). A handle with strain gauges attached was used to study the effect of compression force (10, 20 and 40 N) and constant acceleration (1, 3 and 10 g) on the transmission of vibration at frequencies from 20 to 630 Hz. In the curves recorded, sharp dips appeared which were evidently caused by resonances from the soft tissues of the hand. However in the hand-arm system no common resonance frequency was observed that would harmfully affect the health of workers. Vibration in the hand-arm system was attenuated at an average of 3 dB per octave at the frequencies between 20 and 100 Hz. Between 100 and 630 Hz the attenuation was about 6 dB per octave in the wrist and 10 dB per octave in the elbow and upper arm. At the frequency of 630 Hz the attenuation was hence about 35 dB in the wrist and about 45 DB in the elbow. The attenuation of vibration in the elbow joint was 2 to 4 dB at all frequencies. The hand-arm system appears to be linear at the acceleration range considered; the increase in handle vibration by, e.g., 10 dB also increased vibration in the hand by 10 dB. When the grip strength was increased fourfold, i.e., 12 dB, vibration increased only 3 to 5 dB in the hand-arm system. Thus changing the weight of a vibrating tool does not reduce vibration enough. Therefore attempts to reduce vibration should concentrate on the mechanical parts of the engines.

This paper presents a quantitative investigation on the level of vibration force and power flow transmission between linearly coupled nonlinear oscillators. Both analytical and numerical methods are employed for systematic examinations of the vibration transmission associated with hardening, softening and double-well potential stiffness nonlinearities in the oscillators. The method of averaging is employed to obtain analytical formulations of the steady-state frequency-response relationship. Time-averaged power flow variables are formulated and used to quantify vibration input, dissipation and transmission levels associated with both periodic and chaotic responses. It is shown that the stiffness nonlinearities have significant effects on vibration transmission levels near resonance frequencies and in the low-frequency range. It is also shown that when both oscillators are of double-well potential stiffness, the system may exhibit chaotic motions with higher levels of vibration transmission between the oscillators as compared to the corresponding first-order analytical approximations, because of large super-harmonic components in the response. It is found that there may be multiple possible levels of vibration transmission due to co-existing periodic or chaotic responses. It is shown that when comparing the vibration transmission levels of the co-existing stable responses, the use of time-averaged transmitted power and force transmissibility may lead to different evaluation outcomes. These findings provide a better understanding of the effects of stiffness nonlinearities on the vibration transmission which may be maximized or suppressed based on specific design objectives for enhanced dynamic performance.

Vibration transmission and power flow of laminated composite plates with inerter-based suppression configurations

Whole body vibration (WBV) transmission to vehicle occupants is a function of both vibration characteristics and human posture/movement. The majority of earlier studies investigating biomechanical responses to WBV have considered only a static posture. However, vibration transmission can be affected by dynamic movements when reaching in vehicle and may be transmitted in three-dimension (3D). This study investigates vibration transmission to the upper extremities with changes in posture/movement along the intended reach trajectory under selected sinusoidal WBV conditions. In biodynamic WBV experiments, 21 subjects performed a reaching task to targets located in the right hemisphere under vibration exposure. Intermediate targets were also placed in the expected trajectories of hand movements. 3D biodynamic responses are characterised as a function of upper body posture. This study establishes the empirical database necessary to support a biodynamic model taking into consideration human activity to predict reaching performance under WBV exposure.

The transmission modes of multiple rotating parts on the combine harvester are complex and diverse, and the excitation vibrations are coupled with each other, which makes it difficult to dynamically balance the parallel rotating bodies on-site. In order to obtain the influence of the multicylinder transmission system on the vibration response and transmission characteristics of the whole machine providing an experimental basis for the overall balance of the multicylinder system, this paper tested and analyzed the vibration response and shaft vibration state of the system under different transmission modes. On this basis, the influence of chain drive and different transmission modes on the vibration characteristics of the multicylinder was analyzed. Through the tests of the vibration response of the multicylinder frame, the main transfer path of the vibration of each excitation source was analyzed. The results showed that the transmission chain and transmission mode would affect the stiffness, damping, and vibration response of the cylinder fundamental frequency of the chain transmission system on both sides of the multicylinder. The contribution rate of different transmission modes and rotation speeds to the vibration at the fundamental frequency of the multicylinder was 5%∼30%, which would also cause the deflection angle of the roller axis track to change from 1° to 5°. The frame was the main path of vibration transmission of bilateral chain drive of the multicylinder system, and the vibration transmission efficiency of the frame under different frequencies can reach more than 80%. In addition, the vibration response of each cylinder would also be transmitted to each bearing seat position of the multicylinder through the frame.

In this work, we present a series of hammering tests on full-scale unit-plate ballastless tracks used for long-span bridges. There is no denying that it is a new attempt to pave ballastless tracks on high-speed railway long-span bridges; the related issues deserve to be studied, and especially the vibration characteristics. Hence, the vibration characteristics and transmission rules of the ballastless track with geotextile or rubber isolation layers are explored, and the vibration reduction effect of the rubber isolation layer is analyzed. The main conclusions are as follows: the isolation layers change vibration modes and transmission characteristics of ballastless tracks; the introduction of the rubber isolation layer makes the excited vibration frequency range of the ballastless track concentrated; and the vibrations of the ballastless track with the rubber isolation layers are stable. Moreover, the rubber isolation layer has an obvious attenuation effect on vibration transmission in ballastless track structures. When the vibration is transmitted from the rail to the bridge deck, the vibration level differences of the ballastless track with rubber isolation layers are 20 dB larger than that of the ballastless track with the geotextile isolation layers. The vibration attenuation rate of the rubber isolation layer is about ten times larger than that of geotextile isolation layer.

The use of dental hand pieces endanger dentists to vibration exposure as they are subjected to very high amplitude and vibration frequency. This paper has envisaged a comparative analysis of vibration amplitudes and transmissibility during idling and drilling with micro motor (MM) and air-turbine (AT) hand pieces. The study aims to identify the mean difference in vibration amplitudes during idling, explore different grasp forces while drilling with irrigant injection by the dentist, and various vibration transmission of these hand pieces. The study utilized 22 separate frequency resonances on two new and eight used MMs and two new and eight used ATs of different brands by observing the investigator at 16 different dentist clinics. The study adopted a descriptive research design with non–probability sampling techniques for selecting dentists and hand pieces. Statistical methods like Levene Test of Homogeneity, Welch ANOVA, independent t-test, and Games–Howell test were utilized with SPSS version 22 and MS-Excel. The results reveal that vibration amplitudes and vibration transmissibility when measured at position 2 are higher than in another position 1. Vibrations during idling for used MMs are more than AT hand pieces, and the used MM (MUD) and used AT (AUA) hand pieces differ due to their obsolescence and over-usage. Vibration amplitudes increase every time with the tightening of grasping of the hand piece. Vibration amplitudes for each grasping style of MM hand piece differ from all other grasping styles of AT hand pieces. Routine exposure to consistent vibrations has ill physical, mental, and psychological effects on dentists. The used hand pieces more hazardous as compared to newer ones. The study suggests that these hand pieces must be replaced periodically, sufficient to break between two operations, especially after every hand piece usage. Hence, the present research work can be further extended by creating some control groups among dentists and then studying the vibration amplitude exposure of various dental hand pieces and subsequent transmissibility to their body parts.

Transmissibility and waveform purity of whole-body vibrations in older adults

A method for the control of the transmission of bending vibrations in beams is described. A composite beam (a structural insert) is inserted into a part of the structure to affect the transmission there. The insert comprises two elastic face plates and a central core of tunable fluid such as an electrorheological (ER) or magnetorheological (MR) fluid. By adjusting the applied electric or magnetic field the theological properties of the fluid can be controlled and so can the vibration transmission properties of the insert. Theoretical results concerning the transmission of vibrations in beam-like structures are reviewed. Numerical results are presented for the transmission through ER and MR fluid filled inserts, with experimental results for an ER case. The transmission is seen to show a pass/stopband structure with the stopbands being tunable.

The present work exposes an alternative system for detecting vibrations generated by impact on concrete and mortar sheets. In order to carry out the tests it is necessary to implement a system of measurement different than the one proposed by the current UNE EN 140-7. This system consists of an amplifier and a striking device that is also able to measure the deformation of the material once the impact has been produced. This system is able to detect variations in transmission of vibration at the same frequency between the various building materials employed, after establishing a relationship between the theoretical predictions and the experimental results. Thus, this system could be used as a vibration detection system and as an alternative method of standardization of materials against their acoustic characteristics.