Low Vibration Levels Research Articles

Studies Regarding the Influence on the Surface Roughness Material of the Cutting Regime during the Milling Processing

The aim of the present paper is to establish the optimal parameter values of the cutting regime of a milling process. The paper presents a study regarding the influence of the cutting parameters on the surface roughness of the material and also on the vibration generated by their combinations, during a processing by milling. The studies are made on samples made from S355 JR steel with a metal milling machine FUS 25, which is used also for the experiments. The samples dimensions are 210x150x16mm. For the experiments there was used a cylindrical - frontal milling tool, with 32mm diameter and 10 tooth. Basic parameters of milling processing of materials we have considered in this paper are: feed rate [mm/min]; cutting speed RPM [rot/min]; depth of cut [mm]. For each of this parameters three levels were envisaged. For a 100% accurate experiment results at least 27 experiments must be done. Using an L9orthogonal array, the number of experiments is reduced to nine and the accurate of the method is around 99.96%. The optimal process parameters values are obtained using Taguchi method considering three situations. In the first case the goal is to get only a fine roughness for the sample. The second studied case is focused on finding a low level for the vibration generated during the milling process. The aim of the last study is to find a fine roughness and also a low level of vibration for the process. The analysis of variance (ANOVA) is applied, in all cases, in order to estimate the error variance and to rank the process parameters according to their importance.

Influence of People Walking on Floor Performance due to Low Level Vibration

Abstract. Vibration in building is one of the important problems which need to consider, especially in designing the floor. Floor vibrations are generally caused by dynamic loads applied particularly by human activity especially walking. Although it is specified as low level amplitude, walking induced vibrations can cause discomfort to human occupants and alarming for a certain items of precision sensitive equipment. This paper investigates the vibration response on floor performance due to one, three and five of people walking. Laser Doppler Vibrometer was used to obtain vibration data when people are walking. Further analysis was carried out by using finite element software package ANSYS to simulate the floor under vibration inputs to obtain natural frequency and mode shapes of the floor structure. The vibration data was then analysed in ModalV analysis to generate the vibration response. Then, the results were checked against the vibration criteria level guideline as a crude tool comparison. As a result, the numbers of people walking were influenced the floor performance, which indicated five peoples walking show the highest response up to ISO level due to vibration compared with one people walking.

Validating pipe-in-pipe vibration software model to accurately determine ground-borne noise and vibration above construction tunnels

The London Crossrail project required that re-radiated noise from the construction of the tunnels should achieve exceptionally stringent criteria with respect to ground-borne noise and vibration. The challenge has been to implement robust vibration modelling for the movement of construction trains within the tunnel in order to derive noise levels within sensitive properties. The Pipe-in-Pipe (PiP) software model has been modified and refined empirically utilising the measurement of exceptionally low vibration levels emanating from the temporary underground construction railway track.

Study on the influence of fluid application parameters on tool vibration and cutting performance during turning of hardened steel

Recently the concept of hard turning has gained much attention in the metal cutting industry. In hard turning, multiple operations can be performed in single step, thereby it replaces the traditional process cycle. But it involves very large quantities of cutting fluid. Procurement, storage and disposal of cutting fluid involve expenses and environmental problem. Pure dry turning is a solution to this problem as it does not require any cutting fluid at all. But pure dry turning requires ultra hard cutting tools and extremely rigid machine tools, and also it is difficult to implement in the existing shop floor as the machine tool may not be rigid enough to support hard turning. In this context, turning with minimal fluid application is a viable alternative wherein, extremely small quantities of cutting fluid are introduced at critical contact zones as high velocity pulsing slugs, so that for all practical purposes it resembles pure dry turning and at the same time free from all the problems related to large scale use of cutting fluid as in conventional wet turning. In this study, fluid application parameters that characterize the minimal fluid application scheme were optimized and its effect on cutting performance and tool vibration was studied. From the results, it was observed that minimal fluid application in the optimized mode brought forth low vibration levels and better cutting performance.

Vibration suppression during input tracking of a flexible manipulator using a hybrid controller

The aim of this paper is to investigate the performance of the hybrid controller for end-point vibration suppression of a flexible manipulator, while it is tracking a desired input profile. Due to large structural vibrations, precise control of flexible manipulators is a challenging task. A hybrid controller is used to track large movements of flexible robotic manipulators, which is a combination of inverse dynamics feedforward control, command shaping and linear state feedback control. The case study of a single-link flexible manipulator is considered, where the manipulator is controlled under open-loop as well as closed-loop control scheme. In the open-loop control scheme, the aim is to test the effectiveness of the command shaper in reducing the vibration levels. Moreover, the effect of payload variations on the performance of command shapers and the importance of more robust shapers is demonstrated in this work. Under the closed-loop control scheme, the control objective is to track the large-hub angle trajectory, while maintaining low vibration levels. In comparison to collocated PD control, being reported in the literature, large reductions in tip acceleration levels as well as input torque magnitudes are observed with the proposed hybrid controller.

Floor Dynamic Assessment on Laboratory due to Ground Borne Vibrations Using ModalV Analysis from Passing Vehicles

High-tech development on laboratory with high resolution and sensitive device is increased nowadays. This equipment requires very sensitive location to accommodate in a special room, because it may cause improper functioning for a certain devise which required low level of vibration. Due to this problem, the aim of this study are to perform the structural response on two story laboratory subjected to ground vibration input due to traffics and to assess the level of vibration at the floor. The vibrations input are measured by using portable equipment called Laser Doppler Vibrometer. The field measurement is done at the laboratory Block E, Faculty of Mechanical and Manufacturing Engineering at Universiti Tun Hussein Onn Malaysia (UTHM). Finite element ANSYS software is fully utilized to model the building structure and perform analysis in order to determine structural modal and transient analysis for the building. Time history response from ANSYS post-processing is transferred into ModalV analysis in MATLAB software in order to evaluate the vibration criteria level of the floor according to specific overseas guideline. It was found that the vibration response on the middle slab of the first floor at level Vibration Criteria, VC-A or maximum particle velocity level at 50μm/s. Vibration Criteria (VC) curve analysis on floor slab indicated the highest vibration will occur at the middle of floor slab and the lowest vibration will occur at the edge of slab which near the column and below VC-E level for ground floor slab.

Design and Experimentation of Piezoelectric Crystal Sensor Array for Grain Cleaning Loss

In order to improve the accuracy and reliability for detection of grains cleaning loss, a piezoelectric crystal sensor array was proposed in full width of distribution to realize the online multipoints detection. The dynamic model for grain collision sensor array was evaluated by the method of experimental model analysis. The distribution of low-level vibration and deformation was tested for the sensitive elements of detection array using dynamic signal tester. The location and quantity of the piezoelectric crystal units were determined. The simulation was done based on the software ANSYS for the impacts of grains on the sensitive elements. A quantitative analysis was developed to correct the positions of the piezoelectric crystal units and the construction was adjusted according to the deformation contours. The exact positions were quantitatively analyzed and corrected based on the numerical results for the deformation placement, which was used for optimizing the array construction. Then, the grain impact experiment was established on the test bench. The results showed that the performance was stable for the piezoelectric sensor array, and output signal amplitude was about 2.5 V, with uniform sensitivity in the whole range. The present array sensor helps to provide a technical foundation for detection of grain cleaning loss.

Does low-level mechanical vibration improve BMD in the elderly?

Does low-level mechanical vibration improve BMD in the elderly?

Manufacture and Characterisation of Piezoelectric Broadband Energy Harvesters Based on Asymmetric Bistable Cantilever Laminates

In this paper a bistable asymmetric laminate is manufactured and coupled to a ferroelectric material for potential energy harvesting applications. A cantilever configuration is explored and the harvester response as a function of vibration frequency, vibration level and electrical load resistance examined. The harvester is characterised at low and high vibration levels where the device exhibits either single well oscillations (at low vibration amplitude) or snap-through events (at high vibration amplitude). As the vibration levels increase and the device approaches snap-through it exhibits ‘softening’ where the peak power moves to lower frequencies with differences in power levels during up-sweep and down-sweep of frequencies. Examination of the frequency dependence of power for a range of load resistances indicates a broadening of the harvester performance at higher vibration levels and during snap-through.

A review of studies on low-level vibrations as a source of electric power generation

Abstract. Recent advances in low power VLSI design, with a low duty cycle has been able to resolve wireless sensor problems. In addition, researchers are looking to generate electrical energy from vibrations. The present paper discusses the low level vibration sources and their use in piezoelectric circuit for the production of electrical energy. The simulation results show that this scheme can convert low-level vibrations in nature, home environment, workplace, etc. into electrical energy.

Nonlinear M-shaped broadband piezoelectric energy harvester for very low base accelerations: primary and secondary resonances

It has been well demonstrated over the past few years that vibration energy harvesters with intentionally designed nonlinear stiffness components can be used for frequency bandwidth enhancement under harmonic excitation for sufficiently high vibration amplitudes. In order to overcome the need for high excitation intensities that are required to exploit nonlinear dynamic phenomena, we have developed an M-shaped piezoelectric energy harvester configuration that can exhibit a nonlinear frequency response under very low vibration levels. This configuration is made from a continuous bent spring steel with piezoelectric laminates and a proof mass but no magnetic components. Careful design of this nonlinear architecture that minimizes piezoelectric softening further enables the possibility of achieving the jump phenomenon in hardening at few milli-g base acceleration levels. In the present work, such a design is explored for both primary and secondary resonance excitations at different vibration levels and load resistance values. Following the primary resonance excitation case that offers a 660% increase in the half-power bandwidth as compared to the linear system at a root-mean-square excitation level as low as 0.04g, secondary resonance behavior is investigated with a focus on 1:2 and 1:3 superharmonic resonance neighborhoods. A multi-term harmonic balance formulation is employed for a computationally effective yet high-fidelity analysis of this high-quality-factor system with quadratic and cubic nonlinearities. In addition to primary resonance and secondary (superharmonic) resonance cases, multi-harmonic excitation is modeled and experimentally validated.

Development of a cost-effective and flexible vibration DAQ system for long-term continuous structural health monitoring

In the structural health monitoring (SHM) field, long-term continuous vibration-based monitoring is becoming increasingly popular as this could keep track of the health status of structures during their service lives. However, implementing such a system is not always feasible due to on-going conflicts between budget constraints and the need of sophisticated systems to monitor real-world structures under their demanding in-service conditions. To address this problem, this paper presents a comprehensive development of a cost-effective and flexible vibration DAQ system for long-term continuous SHM of a newly constructed institutional complex with a special focus on the main building. First, selections of sensor type and sensor positions are scrutinized to overcome adversities such as low-frequency and low-level vibration measurements. In order to economically tackle the sparse measurement problem, a cost-optimized Ethernet-based peripheral DAQ model is first adopted to form the system skeleton. A combination of a high-resolution timing coordination method based on the TCP/IP command communication medium and a periodic system resynchronization strategy is then proposed to synchronize data from multiple distributed DAQ units. The results of both experimental evaluations and experimental–numerical verifications show that the proposed DAQ system in general and the data synchronization solution in particular work well and they can provide a promising cost-effective and flexible alternative for use in real-world SHM projects. Finally, the paper demonstrates simple but effective ways to make use of the developed monitoring system for long-term continuous structural health evaluation as well as to use the instrumented building herein as a multi-purpose benchmark structure for studying not only practical SHM problems but also synchronization related issues.

Ionization and high-order harmonic generation from highly vibrational [formula omitted

We point out the dependence of ionization probability and the high-order harmonics intensity on vibration levels of H2+. The ionization probability shows a maximum value at a certain level. Moreover, saturation in the high-order harmonic generation (HHG) spectra of a vibrating H2+ is also found from numerically solving the time-dependent Schrödinger equation. With some low vibration levels, the intensity of the HHG increases with respect to vibration levels but with higher ones, the harmonics intensity demonstrates a saturated value. The internuclear separation is based on to explain obtained results.

Numerical Study of Sub-Nozzle Flows for the Weft Transmission in an Air Jet Loom

The air jet loom is widely applied in the textile industry due to its high productivity, convenient controllability, high filling insertion rate, low noise and low vibration levels. High-Speed air jet weaves the weft yarn, and transports it through the weft passage. In the present study, a computational fluid dynamics method is applied to solve the incompressible Navier–Stokes equations with one-equation Spalart-Allmaras turbulence model. Which is used to solve the flow filed in a weft passage. The aim of this analysis is to determine the distribution of the flow velocity along the weft passage. Results revealed the strong relationship between air jet velocity and forces on the weft.).

DESIGN AND TESTING OF AUTOMOBILE EXHAUST SYSTEM

The aim of this paper is to provide deeper understanding of the dynamics of automobile exhaust system to provide a basis for the improved design & development of computationally inexpensive theoretical system model. Modeling, simulation & experimental investigation of a typical exhaust system are performed to gain such an understanding & to evaluate modeling ideas. These models incorporate adjustable flexibility in their connection to the exhaust pipes & a procedure is developed for automatic updating of these parameters to obtain better correlation with experimental results. The agreement between the simulation results of the updated models & experimental results is very good, which confirms the usability of these models. The main objective of this project is to design exhaust system and to compare its performance with an existing system available. The newly designed exhaust system shows lower back pressure which ultimately results better performance of the engine. Low vibration levels are critical to achievee in automobile exhaust system . It is therefore important design engineers to be able to predict, explain & assess the dynamics of various system design proposals during product development.

Frequency sensing of medical signals using low-voltage piezoelectric sensors

Piezoelectric sensors are used to pick up low level vibrations in automotive, biomedical and industrial fields and are subject to errors due to the input current and voltage noise of amplifiers, when connected with a large bias resistor. The noise levels, especially from the bias resistor, degrade the signal to noise ratio of the signal which leads to less reliable feature detection. We report the experimental investigation of a frequency sensing front-end in terms of its linearity, noise and gain in order to acquire medical signals at low frequencies and voltages, e.g. arterial pulse signal, Ballistocardiogram and heart sounds. An LC oscillator is used with a commercial phase locked loop for this purpose. We show that the noise levels in frequency sensing can be reduced by increasing the oscillation frequency, while maintaining 1% non-linearity. Overall, the readout runs at 5V and has a mean noise floor of 1.43μV/Hz and a non-linearity of 1% when subject to a sine wave between 20mV and 200mV peak to peak amplitude. The results of this work are expected to contribute towards low noise analog front end designs for piezoelectric sensors using frequency sensing as an alternate architecture.

Whole-body vibration and the risk of low back pain and sciatica: a systematic review and meta-analysis.

The aim of this systematic literature review was to evaluate the association between whole-body vibration (WBV) and low back pain (LBP) and sciatica with special attention given to exposure estimates. Moreover, the aim was to estimate the magnitude of such an association using meta-analysis and to compare our findings with previous reviews. The authors systematically searched the PubMed (National Library of Medicine, Bethesda), Nioshtic2 (National Institute for Occupational Safety and Health (NIOSH, Morgantown), and ScienceDirect (Elsevier, Amsterdam) databases for records up to December 31, 2013. Two of the authors independently assessed studies to determine their eligibility, validity, and possible risk of bias. The literature search gave a total of 306 references out of which 28 studies were reviewed and 20 were included in the meta-analysis. Exposure to WBV was associated with increased prevalence of LBP and sciatica [pooled odds ratio (OR) = 2.17, 95% confidence interval (CI) 1.61-2.91 and OR 1.92, 95% CI 1.38-2.67, respectively]. Workers exposed to high vibration levels had a pooled risk estimate of 1.5 for both outcomes when compared with workers exposed to low levels of vibration. The results also indicate that some publication bias could have occurred especially for sciatica. This review shows that there is scientific evidence that exposure to WBV increases the risk of LBP and sciatica.

A Scalable Nanogenerator Based on Self‐Poled Piezoelectric Polymer Nanowires with High Energy Conversion Efficiency

Nanogenerators based on piezoelectric materials convert ever-present mechanical vibrations into electrical power for energetically autonomous wireless and electronic devices. Nanowires of piezoelectric polymers are particularly attractive for harvesting mechanical energy in this way, as they are flexible, lightweight and sensitive to small vibrations. Previous studies have focused exclusively on nanowires grown by electrospinning, but this involves complex equipment, and high voltages of $\approx$ 10 kV that electrically pole the nanowires and thus render them piezoelectric. Here we demonstrate that nanowires of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) grown using a simple and cost-effective template-wetting technique, can be successfully exploited in nanogenerators without poling. A typical nanogenerator comprising $\approx$ 10$^{10}$ highly crystalline, self-poled, aligned nanowires spanning $\approx$ 2 cm$^2$ is shown to produce a peak output voltage of 3 V at 5.5 nA in response to low-level vibrations. The mechanical-to-electrical conversion efficiency of 11% exhibited by our template-grown nanowires is comparable with the best previously reported values. Our work therefore offers a scalable means of achieving high-performance nanogenerators for the next generation of self-powered electronics.

Charging and characterization of non-patterned organic micro electret arrays

This paper presents the charging and characterization of an organic micro electret array for vibration energy harvesting. Micro sized electrets with stable and high surface potential are essential for the long-term effectiveness of micro electrostatic power generators which harvest low-level vibration energy. In this study, a localized corona charging method to obtain micro sized electret areas on non-patterned macro sized dielectric thin film has been proposed to solve the problem of low charging efficiency and fast charge decay of micro sized electrets. This method involves using a shadow mask to transfer charge patterns and a triode corona charging configuration to facilitate charge penetration. Charging efficiency of 93.6% is achieved on an electret area of 100 µm × 100 µm, and 87% of its initial surface potential remains on the shrunken area of 50 µm × 50 µm after 240 days of storage. A technique combining SEM surface topography and non-contact measurement of the average surface potential has been developed to map the charge distribution on locally charged dielectric thin film and measure the surface potential on the micro sized charged area by incorporating the layout characteristic of a micro electret array.

Whole-body vibration exposure of haul truck drivers at a surface coal mine

Haul truck drivers at surface mines are exposed to whole-body vibration for extended periods. Thirty-two whole-body vibration measurements were gathered from haul trucks under a range of normal operating conditions. Measurements taken from 30 of the 32 trucks fell within the health guidance caution zone defined by ISO2631-1 for an 8 h daily exposure suggesting, according to ISO2631-1, that “caution with respect to potential health risks is indicated”. Maintained roadways were associated with substantially lower vibration amplitudes. Larger trucks were associated with lower vibration levels than small trucks. The descriptive nature of the research, and small sample size, prevents any strong conclusion regarding causal links. Further investigation of the variables associated with elevated vibration levels is justified. Relevance to industryThe operators of mining equipment such as haul trucks are exposed to whole-body vibration amplitudes which have potential to lead to long term health effects. Systematic whole-body vibration measurements taken at frequent intervals are required to provide an understanding of the causes of elevated vibration levels and hence determine appropriate control measures.