Vibration Acceleration Amplitude Research Articles

Effects of Frequency and Acceleration Amplitude on Osteoblast Mechanical Vibration Responses: A Finite Element Study.

Bone cells are deformed according to mechanical stimulation they receive and their mechanical characteristics. However, how osteoblasts are affected by mechanical vibration frequency and acceleration amplitude remains unclear. By developing 3D osteoblast finite element (FE) models, this study investigated the effect of cell shapes on vibration characteristics and effect of acceleration (vibration intensity) on vibrational responses of cultured osteoblasts. Firstly, the developed FE models predicted natural frequencies of osteoblasts within 6.85–48.69 Hz. Then, three different levels of acceleration of base excitation were selected (0.5, 1, and 2 g) to simulate vibrational responses, and acceleration of base excitation was found to have no influence on natural frequencies of osteoblasts. However, vibration response values of displacement, stress, and strain increased with the increase of acceleration. Finally, stress and stress distributions of osteoblast models under 0.5 g acceleration in Z-direction were investigated further. It was revealed that resonance frequencies can be a monotonic function of cell height or bottom area when cell volumes and material properties were assumed as constants. These findings will be useful in understanding how forces are transferred and influence osteoblast mechanical responses during vibrations and in providing guidance for cell culture and external vibration loading in experimental and clinical osteogenesis studies.

Experimental Investigation and Determination of Abrasive Granularity Change Impact to Technology Head Vibration Generating during AWJ Technology Steel Cutting

The paper describes abrasive kind and granularity change impact to technology head vibration generating during cutting of seven selected investigated kinds of steel by means of AWJ technology. The investigation of abrasive granularity impact is carried out for three speeds of the technology head shift. A set of 3D comparative graphs of vibration parameter relations for seven analyzed kinds of steel from graphical records of vibration acceleration amplitude to frequency relation was created. On the base of the comparative graphs a discussion about results is generated and conclusions are defined. The work presents a thematically integrated part of a dissertation results and completes a group of recent knowledge focused on production systems working state diagnostics with the water jet technology.

Vibration and Experimental Comparison of Machining Process

Abrasive water jet technology is among the unconventional ways of machining. In today's modern and progressive era is often used for cutting and machining of various types of materials because of lower costs and environmental impact, as the cutting tool is water, in our case, with the addition of abrasives. Objective of the measurements was to evaluate the impact of vibration on the technological head in abrasive water jet technology in changing the selected technological parameters and the flow rate of technological head. In the given experiment, the used material - steel Hardox 500 with a thickness of 10 mm. The effort was to investigate the effects of changes in the speed rate of technological head (by speeds - 40, 200, 400 mm / min) on the size of the vibration acceleration amplitude and its frequency. Based on the measured values ​​of vibration to the technological head create the database and from it is evaluated the data in selected softwares (LabVIEW, SignalExpress and Microsoft Excel). Findings and conclusions are formulated on the basis of graphical dependencies, envelopes frequency spectra and comparison chart of envelopes.

Novel linear impact-resonant actuator for mobile applications

In this study, a novel linear impact-resonant actuator was proposed for mobile device applications. The most significant issue in mobile haptic actuators is the ability to provide various vibrotactile and alert functions despite their size and power consumption limitations. This study aimed to achieve fast and strong impact vibrations over a wide frequency range, including the resonant frequency, which decoupled the intensity and frequency of the vibration to achieve both fruitful vibrotactile feedback and strong alarming vibration. To accomplish this, a new mechanism was proposed that can amplify the impact force at the end of the stroke and increase the speed of the response. The magnetic flux path was optimized using an equivalent magnetic circuit model to maximize the electromagnetic force. The performance of a prototype actuator (11mm×9mm×3.2mm) was evaluated in terms of the response time and vibration acceleration amplitude under an input power of 0.3W. The experimental results clearly showed that the proposed actuator could create a vibration acceleration that was greater than 2g over a frequency range of 1–210Hz with a fast response of 4ms and extremely short residual vibration. In addition, a stronger impact force of around 3g could be generated near the resonant frequency of 190Hz.

G1001003 基礎励振を受ける自立型構造物の滑りを考慮したロッキング運動に関する基礎検討

Behavior of the self-standing structure on the ground under sinusoidal excitation in horizontal direction is investigated. The nonlinearities of rocking motion and sliding motion and the impact between base and structure are considered to examine this behavior. The analytical model is composed of a rigid block for simplification. The relationship between the amplitude of vibration acceleration and the excitation frequency is investigated, in addition to that between the amplitude of vibration acceleration and friction coefficient. It is found that the maximum rocking angle depends on frequency of input wave, and the maximum sliding displacement becomes large when the input wave has large acceleration in a long period region. In addition the rocking angle tends to decrease due to occurrence of sliding motion. Therefore, it is said that rocking and sliding motion should be suppressed simultaneously.

Technological Head Tilt Angle Influence Analysis to Generation of Vibration during Ceramics Material Machining by Means of AWJ Technology

The thesis deals with a manufacturing system water jet technological head tilt angle influence analysis. The search is performed for two tilt angles and three speeds of the technological head shift. Frequency envelope comparative graphs are created for the head tilt angles 45o and 90o and for each of three speeds using graphical records which show vibration acceleration amplitude relation to its frequency. For each of the tilt angles summary comparative frequency envelope graphs in all analyzed speeds are created, too. On the base of the comparative frequency envelope graphs a discussion focused on results and formulated conclusion are performed. The paper presents a thematically integrated part of previous research and complements recent knowledge on technological and material parameter impact to water jet technology manufacturing system vibration generation.

Diagnostic and Experimental Valuation on Progressive Machining Unit

The main effort of each technological process is not only to reduce the costs, but also to reduce the impact on the environment. The technology of abrasive water jet is one of the methods of division and cutting materials with the lowest impact on the environment, since water is the cutting tool, in our case with the addition of an abrasive. The aim of the measurement was the observation (examination) and evaluation of the vibration impact on the technological head in the technology of abrasive water jet when changing the selected technological parameters, namely the feed rate of the technological head. The experiments were carried out on one kind of material - steel HARDOX 500 with a thickness of 10 mm. The impact of the change of the technological head’s feed rate (100, 50, mm/min) on the size of the vibration acceleration amplitude and its frequency were examined. A database was created from the measured vibration values on the technological head and from that database the data was evaluated in selected softwares (LabVIEW, SignalExpress a Microsoft Excel). Graphical dependencies, frequency spectra covers and covers comparison graph were created from which new findings and conclusions were formulated.

Analysis of Technological Head Working Pressure, Tilt Angle and Shift Impact to its Vibrations Using AWJ Technology

The paper deals with an experimental analysis of a technological head tilt angle impact to vibration generation. The search of the technological head tilt influence is performed for three technological head shift speeds and for three abrasive water medium pressure values. From graphic records showing relation of vibration acceleration amplitude to its frequency, a group of 9 comparative frequency envelope graphs for two tilt angles and three technological medium analyzed pressures for each of three speeds of the head shift is created. On the base of the frequency envelope comparative graphs a discussion and formulated conclusion are stated. The paper presents a thematically integrated part of the thesis and complements recent knowledge on water jet technology manufacturing system working condition diagnosis.

Establishment of Process Capability of Machine Centre Driling Using Multiple Regression Analysis

Assessment of process capability enables manufacturers to determine if a process produces products that meet customers expectation. Process capability can be beneficial in the long run in producing quality parts with minimum reject and optimum manufacturing cost. This paper proposes a procedure to assess process capability of a machining centers in drilling process using statistical analysis of machining parameters and machine rigidity. Experimental method used mild steel plate as work piece and carbide indexable cutting insert on drill of diameter 20mm. Cutting parameters such as cutting speed and feed rate were varied according to different cutting parameter level while wear in peripheral insert was inspected before and after each test run start. Machine rigidity in terms of vibration acceleration amplitude in x-, y-, and z-axis were measured and analyzed. Process capability index, Cpk of drilled hole accuracy was calculated. A regression model based on this experiment was established for predicting the process capability of machine tool in drilling operation. The established regression model is proven to have high accuracy, which is more than 80%. The validation test was carried out on a different machine tool with the same cutting conditions to check if different machine was adaptable to the regression model. This finding provides useful guidelines for machning operator to predict the process capability of the machine tool in the drilling process.

Determination of Parameters of Surface Acoustic Wave Vibration Sensors with the Help of Gravitational Field

The structure of probes for measurement of mechanical vibrations bases on three basic types of vibration sensors: seismometers, geophones, accelerometers [1 4]. A measuring sensor should remain in a rigid contact with the substrate. It transforms substrate vibrations into an output electric signal proportional to the vibration parameters. For harmonic vibrations the substrate displacement is determined by the following relation: Y (t) = D sinωt. The vibration parameters are as follows: the vibration frequency ω and one of the amplitudes: the displacement amplitude D, the vibration velocity amplitude [(dY (t)/dt) = Dω cosωt] or the vibration acceleration amplitude [(dY (t)/dt) = −Dω sinωt]. The output signal from a seismometer and a geophone is approximately proportional to the enforced vibration velocity, where the output signal from an accelerometer is approximately proportional to the enforced vibration acceleration.

Numerical and Experimental Researches of 1:10 Tank Car Longitudinal Vibration with Fluid Sloshing

A 1:10 tank-car 2D fluid simulation model based on the computational fluid dynamics is established, and exchange the data with tank-car vibration model while simulating. In the paper, the 2 dimension fluid-structure coupling tank-car which owns two DOF is simulated, and the affect of fluid sloshing to tank-car longitudinal vibration is analyzed through the coupled vibration experiment. In the simulation and experiment, fluid sloshing increased the tanker longitudinal vibration acceleration amplitude and slowed response time is obtained through analyzing the difference between the different volume of fluid and the relevant solid without sloshing, and the difference of longitudinal vibration between full tank and non-full tank is significant.

G051056 振動する液面上に保持された液滴の保持位置と液面波形の関係([G051-05]流体工学部門,一般セッション : 液膜・液滴)

It is known that a droplet is held on the vertically vibrating pool of the same kind of liquid. When the frequency of oscillation is at the resonance of the apparatus, the droplet is found to a certain position on the pool regardless of the initial dropped position. In this case, the lifetime of a droplet is as long as several hours, perhaps because of the larger amplitude of vibration acceleration than the gravity as previously reported. Then we investigated waveform at the resonance frequency to clarify the relationship with the position where the droplet is retained. The amplitude, phase, and average displacement of the surface of oscillating pool were measured by a laser displacement meter and FFT analyzer. The average displacement is relevant to the position of a droplet, while the amplitude and phase are not; in the distribution where the regression plane of the average displacement is subtract, its minimum position is almost the same as the retained droplet.

Experimental verification of the frequency spectrum of unwears and wears guidance tube on the technological head vibrations creation in the production system with AWJ technology

The solution and evaluation of the production system (PS) operation with water jet technology was addressed in more works. It is appropriate to complement this knowledge from works focused on investigation of the other factors effect which affecting the emergence and spread of technological head vibrations, affecting reliability, durability, economic efficiency and operation safe of PS with water jet technology. The article presents experimental investigation results of the vibration acceleration frequency spectrums during cutting steel by unwear and wear rectifying tube with water jet technology. The vibrations size was assessed by two basic vibrations parameters - vibrations frequency and vibration acceleration amplitude.

Effect of radial depth on vibration and surface roughness during face milling of austenitic stainless steel

This paper studies the influence of radial depth on vibration, chip formation and surface roughness during face milling of AISI304 austenitic stainless steel with indexable cemented carbide milling cutters. The amplitude of vibration acceleration increased with the increasing radial depth up to 80 mm. And the domain vibration frequency varied with the radial depth. In this paper, three types of chips were found: C shape, long shape and spiral shape. The minimum surface roughness value occurred when the radial depth equalled 40 mm in the experiment. Irregular changes of chip curl radius and chip thickness could be attributed to different numbers of alternately engaged teeth when the feed and speed were fixed. Surface roughness is related to forced vibration and chip formation. Radial depth with different numbers of alternately engaged teeth could significantly influence the forced vibration, chip formation, and surface roughness.

A Study on the Vision-Based Flexible Vibratory Feeding System

This paper describes a vision-based flexible vibratory feeding system (VBFVFS) for agile manufacturing, which mainly consists of a decupled vibratory feeder, a machine vision system, displacement sensors, power amplifiers and a computer system. Its major feeding parameters such as the vibration angle, frequency, acceleration amplitude, and phase difference all can be easily adjusted online by software means. Consequently, the system not only can feed a wide range of parts without any retooling of the feeder, but also can feed various parts made of different material in a way close to the optimal state. The VBFVFS also has intelligence. It can find out the natural frequencies of the decoupled vibratory feeder by means of automatic frequency response analysis and hence determine the best frequency for the driving signals. It can also find out any parts jamming and eliminate it by making the parts move in reverse directions. Prototypes of the decoupled vibratory feeder have been successfully developed. Experimental investigation is carried out based on the prototypes and the results agree well with the simulation results. Moreover low-cost vision technique is also discussed for the commercialization of the vision-based flexible vibratory feeding system.

Prediction of vibration amplitude from machining parameters by response surface methodology in end milling

Decreasing vibration amplitude during end milling process reduces tool wear and improves surface finish. Mathematical model has been developed to predict the acceleration amplitude of vibration in terms of machining parameters such as helix angle of cutting tool, spindle speed, feed rate, and axial and radial depth of cut. Central composite rotatable second-order response surface methodology was employed to create a mathematical model, and the adequacy of the model was verified using analysis of variance. The experiments were conducted on aluminum Al 6063 by high-speed steel end mill cutter, and acceleration amplitude was measured using FFT analyzer. The direct and interaction effect of the machining parameter with vibration amplitude were analyzed, which helped to select process parameter in order to reduce vibration, which ensures quality of milling.

Design and implementation of tuned viscoelastic dampers for vibration control in milling

Passive means of vibration attenuation have been employed successfully and efficiently in machining systems such as turning and milling. Traditional approach to controlling vibration in a milling system is to develop control mechanisms for cutting tools or machine spindles. However, due to the nature of milling operations where the cutting tools rotate at high speed, the passive vibration control methods find very limited application with the traditional approach. In order to utilise the potential of the passive vibration control methodology in milling applications, the milling operation should be viewed as a system comprising an elastic structure and operation parameters. Dynamics of this closed-loop system should improve with improvement in dynamics of any of the system components, especially within the elastic structure that comprises the cutting tool, the machine tool, the workholding system and the workpiece. Although the level of improvement will vary depending on which component of the elastic chain is targeted for this purpose. This paper presents the development and testing of tuned viscoelastic dampers (TVDs) for vibration control through their application on a workpiece in milling operations. This work targets workpiece held on a palletised workholding system for the control of unwanted vibration and thus deviates from the traditional approach where cutting tool and/or machine spindles are targeted for vibration control strategies. Palletised workholding systems, due to their compact design, offer an opportunity to design passive damping mechanisms that are easier to implement in the case of a milling system. The TVD developed through this research is based on a commercially available viscoelastic damping polymer. Advantage of such materials is their high damping performance over a wide range of excitation frequencies. The TVD design process has used a unique combination of analytical modelling with experimental FRF data. Modal impact testing showed that the application of the TVD reduced the amplitude of vibration acceleration by 20 dB for the target mode. Since the target mode corresponded to torsional vibration, the TVD was effective in two planar coordinates, i.e. X and Y. In addition, the TVD also significantly reduced the amplitude of a vibration mode far from the mode it was designed for. The system has been tested experimentally to demonstrate significant reduction in vibration amplitudes during a milling process. The milling tests with different combinations of cutting parameters show that multi-TVD approach is always valid regardless of the parameters being used. The only requirement for TVDs to function effectively is that the natural frequency of the system, for which the TVDs are designed, is excited during the milling process.

Vibration Control of Variable Rigidity Frame Structure by Magnetic Clutch

There are many studies on base isolation and seismic isolation of structures. In order to clarify experimentally, the efficiency of variable stiffness control that has been considered using numerical simulation, a variable stiffness structure using a clutch system was made. A simple on-off control with a clutch mechanism of a variable stiffness structure to the magnitudes of acceleration has been proposed. This control method was examined in the research.Using this method, when the vibration acceleration amplitude is large, the clutch is connected to the additional structure saving potential energy in the additional structure, and when the vibration acceleration amplitude decreases, the clutch is disconnected from the additional structure releasing the potential energy at once and attenuating the displacement amplitude of vibration, so that the vibration can be decreased effectively.

Effects of Amplitude and Frequency of Mechanical Vibration Stimulation on Cultured Osteoblasts

Mechanical stimulation to bones affects bone formation such as decrease of bone mass of astronauts under zero gravity, walking rehabilitation to bone fracture and fracture repair with ultrasound devices. Bone cells have been reported to sense and response to mechanical stimulation at cellular level morphologically and metabolically. In the view of mechanical vibrations, bone cells are deformed according to mechanical stimulation and their mechanical characteristics. In this study, sinusoidal inertia force was applied to cultured osteoblasts, which are a kind of bone cells, and effects of frequency and acceleration amplitude of mechanical vibration on the cells were investigated in respect of the cell proliferation, bone matrix generation and alkaline phosphatase (ALP) gene expression. The results to be obtained are as follows. The significant difference of cell density and bone mass generation between the non-vibrating and vibrating groups is found. ALP gene expression shows a peak to frequency at 50 Hz and the value of it is approximately 4.5 times as high as that of the non-vibrating group in the case of the acceleration amplitude of 0.5 G. ALP gene expression at 0.5 G is significantly larger than at 0, 0.125 or 0.25 G in the case of the frequency of 50 Hz.

Research on Semi-Active Control for Equivalent Conicity

It is important to reduce the amplitude of lateral vibration acceleration to improve ride comfort on train journeys. As a method for such a purpose, semi-active suspension has been proposed and substantially used. On the other hand, the longer distance of the train runs, the more severe wears are evident on wheel treads; an equivalent conicity becomes larger, which adversely affect the characteristics of vehicle dynamics. It is hence expected to improve ride comfort under vibrations by adequate semi-active control without depending on the equivalent conicity. A study under this research with a simulation model was made to the effect of the semi-active control for the equivalent conicity. We could verify that as the equivalent conicity becomes larger caused by more train runs, the lateral relativity velocity between a car body and a bogie became smaller ; a damping ratio by semi-active damper became smaller. As the result, it is conceivable that an impact accordingly decreases with the semi-active control.