Effect Of External Vibration Research Articles

Methodology for choosing the optimal layout of multilayer printed circuit boards taking into account external mechanical influences

Formulation of the problem. radio-electronic modules on multilayer printed circuit boards (PCB) are characterized by an extremely complex design. When creating such modules, it is necessary to take into account, often extremely contradictory, requirements for the placement of components on the surface, taking into account thermal criteria, requirements for vibration strength and electromagnetic compatibility. Special-purpose radio equipment is often placed in blocks of a "cassette" design, which has a feature in fixing the PCB. Unlike conventional printed circuit boards, in this design, the PCB can only be fixed at the edges, so the placement of components, especially those with a large area, for example, such as microcircuits in BGA, QFP, QFN, PLCC packages, must be given great attention, as this affects mechanical strength and performance of the device. Purpose. Improving the efficiency of the design process of radio-electronic modules by rational placement of components on the PCB of a "cassette" design. Identification of areas with the highest mechanical stresses and deflections. Results. It was found that on the PCB of a "cassette" design, when it is fixed only around the perimeter, there are areas with increased deflections, where the installation of components with a large area is undesirable, since this leads to the destruction of the solder joint and the failure of the device. The board can be conditionally divided into nine areas with an aspect ratio of a/4 and b/4, where a, b are the length and width of the board. Experimentally, the most loaded areas of the MPP and areas that have the least impact on the component during external vibration were identified. Practical significance. A method for placing components on the PCB of a "cassette" design is proposed, which makes it possible to reduce the negative effects of external vibrations and static loads.

The Effects of External Vibration on Coordination Strategies of Multi-Muscles during Voluntary Isometric Torque Production

PURPOSE: To investigate the effect of muscle vibration on performance accuracy and multi-muscle coordination pattern during voluntary isometric knee extension torque production.METHODS: The subjects were tested under two conditions of external vibration frequencies (90 Hz vibration (VIB)&no-vibration (NVIB)) with three levels of torque magnitudes of 20% (MVT20), 40% (MVT40), and 60% of maximal voluntary torque (MVT60). The subjects were instructed to perform a submaximal isometric ramp task and matched the produced torque with the torque template shown in the screen as accurately as possible. External vibration was applied to the rectus femoris (RF).RESULTS: The performance error (RMSENORM) was reduced in 60% of MVT (MVT60) in both ramp and SS phases, and the iEMGAGO was significantly reduced by vibration under the same torque conditions in the SS phase. In addition, the muscle-mode (M-mode) composition was found to be different in the VIB and NVIB in the SS phase. We found that the VIB condition showed co-contraction M-modes and mixed M-modes. However, there was no significant difference in the ramp phase under all conditions.CONCLUSIONS: The neurophysiological changes due to muscle vibration may positively affect the task characteristics and steps that require accurate torque generation and provide information for the quantitative understanding of multi-muscle coordination of vibration.

Effect of external vibrations on Electro-Mechanical impedance signatures in damage detection

Piezoelectric Lead Zirconate Titanate (PZT) transducers have gained their application in Structural Health Monitoring (SHM). The surface bonded PZT patches are actuated by an external voltage under a specified frequency range and the Electro Mechanical Impedance (EMI) Signatures are captured which can be utilized to assess and monitor structural health. Generally, with the assumption of the structure is excited only by the PZT actuator the health of the structure is assessed and monitored. However, the changes in the EMI signatures due to external vibrations are not taken into account and interpretation will lead to wrong assessments. The current paper focuses on the study of external vibration with different excitation frequencies and amplitudes on EMI signatures of healthy and damaged beams. Finite element analysis is conducted on a cantilever aluminium flat and the conductance signatures are extracted and the influence of external vibrations on EMI signatures is analyzed and presented.

Numerical Comparison of Triangular and Sinusoidal External Vibration Effects on the 3D Porous Drying Process

Drying is one of the most energy-intensive industrial processes. One of the techniques aiming to reduce energy consumption is the vibration technique which is generally employed to intensify the heat and mass transfer process. In this respect, this paper presents a three-dimensional numerical model to study the external vibration effects on the drying process of a porous medium. The model is based on a comparison of heat and mass transfer phenomena that arise during vibrating drying of unsaturated porous medium for two cases: triangular and sinusoidal external vibrations. The three-dimensional unstructured Control Volume Finite Element Method (CVFEM) is employed to simulate the vibrating drying. Numerical results of the time evolution of temperature, liquid saturation, pressure, and water content are compared and analyzed for the two cases.

Numerical Comparison of Triangular and Sinusoidal External Vibration Effects on the 3D Porous Drying Process

Numerical Comparison of Triangular and Sinusoidal External Vibration Effects on the 3D Porous Drying Process

PHYSICAL NATURE OF OCCURRENCE OF LOCAL DEFECTS OF PRODUCTS AND THEIR INFLUENCE ON QUALITY OF FUNCTIONING OF MECHANICAL COMPONENTS

The paper is devoted to the consideration of the main reasons for the failure of various kinds of electromechanical instrument assemblies, caused by the occurrence of local defects in the material of the critical parts. The physical nature of the appearance of such defects, which is caused by discrete inclusions in the materials of parts, is disclosed. The origin of local defects largely affects the appearance of external vibration effects and dynamic processes in the nodes of the mechanisms of the devices and their further functioning and quality of work. A mathematical form of accounting for local defects when creating a mathematical model for describing a node of a mechanical system using Fourier analysis is given. The possible directions of development of local defects in the nodes of the system and the consequences of them are shown, and attention is also focused on the proposed methods for eliminating these defects in the manufacture of parts.

Experimental investigation on partially filled liquid pools under combined thermal and vibrational loads

The seismic excitation affects the performance of a heat exchanger submerged in a water pool. Hence, the potential effect of external vibrations on a boiling and heat transfer system is investigated in this work. The effect of horizontal vibration on heat transfer performance of a submerged heater rod has been experimentally investigated under atmospheric pressure conditions. The experimental results show that the heat transfer is enhanced by 15% with vibration in single-phase convection. Heat transfer in subcooled boiling is significantly affected by higher mode excitation frequencies. However, there is no significant influence of excitation frequency on heat transfer in the saturated boiling regime. The effect of circumferential wall temperature around the heater is investigated and a maximum temperature difference of 6.3% has been found between the top and bottom heater surface. Thermal stratification of pool water is also studied without and with external vibration. The vertical temperature difference between zone 1 and zone 2, (i.e. thermal stratification) is suppressed by 80% at excitation frequency of 6.35 Hz.

Immediate Effects of External Vibration vs Placebo on Vocal Function Therapy in Singers

External vibration therapy (EVT) has been widely used in chronic pain conditions, musculoskeletal rehabilitation, and athletic training. Vibration therapy has been suggested to enhance vocal performance and has been popularized in social media. However, there is no evidence to support its effect on vocal function. To evaluate the immediate effects of EVT in trained singers using acoustic and self-assessment parameters. Prospective, randomized, placebo-controlled interventional study at St Michael's Hospital Voice Clinic, affiliated with the University of Toronto. Data collection and analysis were performed by investigators who were blinded to the group assignment of the participants. Study participants were randomized to EVT or a placebo (control) group. The study dates were September 2015 to December 2016. Participants attended the voice laboratory at St Michael's Hospital, where a standardized data collection protocol was performed, including acoustic parameters, voice range profile, and soft voice tasks, followed by subjective rating of vocal effort or discomfort. The EVT group underwent EVT to 5 neck sites bilaterally. The placebo group underwent the same protocol with a modified device. After the intervention, the participants repeated the standardized data collection. The primary outcome in this study was acoustic analysis (jitter, shimmer, and pitch range) compared before and after treatment. In addition, secondary outcomes included perceived effort or discomfort evaluated by participants after 4 voice tasks proposed to investigate more subtle voice properties. Within and between groups, data sets were statistically analyzed for potential treatment effect. Among 27 participants (age range, 18-50 years; all female), 14 were randomized to the intervention group and 13 to the placebo group. Comparison of the treatment effect on the vowel token acoustic parameters evaluated showed that, after EVT, participants had a more cohesive change with a restricted 95% CI compared with placebo. The mean change in fundamental frequency after intervention was 5.00 Hz in both groups but the 95% CI was much wider after placebo (-30.30 to 19.20) than after EVT (-18.10 to 7.50). After EVT, the effect size was notable in the vowel (0.83) and SVT3 (0.79) task. In this study, EVT demonstrated a more predictable change in acoustic metrics compared with the placebo treatment. Effort ratings for 6 voice tasks evaluated in this study were not found to be different after EVT compared with the placebo treatment. clinicaltrials.gov Identifier: NCT02083341.

Characterization of natural and recoil-induced vibration of an AR-15 rifle at the cheekbone-stock interface

Effects of sound pressure and shock on hearing loss have been widely studied. Studies involving direct assessment of sound pressure levels and influencing variables related to rifle discharge, especially with respect to standard military small arms have mostly focused on the effects of external pressure on hearing. Other studies have characterized physiological effects of external vibration on animals and humans. Shock phenomena and high-pressure waves have been linked to effects from gradual changes in tissue thickness to traumatic brain injury and other central nervous system maladies. Rifle shooters, including soldiers, law enforcement officers, and hunters, typically shoulder rifle-type firearms in a way that puts the buttstock in direct contact with the cheekbone, known as the “cheek weld.” This work experimentally characterizes the vibrations experienced by the shooter at the cheek/buttstock interface, and discusses expected physiological and acoustical effects as a result of conduction into the skull.

Improvement of quality of details at round grinding in the conditions of a floating workshop

The results of laboratory studies of the grinding processing process are given taking into account the evaluation of the quality of the surfaces of the shafts with disturbing vibrational influences on the equipment of external forces that are the consequence of sea waves, as well as the neighboring operating equipment in a floating workshop. To determine the influence of external influences on the quality of processing during grinding, an experimental stand was used, including a cylindrical grinding machine with a complex of test equipment, as well as a compressor placed at a different distance from the machine, creating external vibration effects simulating external disturbances through the surface Floor and foundation on the machine bed, corresponding to the effects of the external environment and the operating neighboring equipment. The dependences of the frequency of mechanical oscillations (in the measuring zones-the base-bed and the machine table guides in the transverse and vertical directions) are obtained, the amplitude of the vibro-displacement in these zones from the conditions of the circular grinding machine and sea-wave levels. The changes in the error in the shape of the machined parts, the roughness of the machined surface, the waviness of the roll neck surfaces according to the basic and achieved variants are determined taking into account the use of new designs of effective vibration isolating supports and devices.

Improvement of reference base in the field of metrological assurance of thread joints

We consider the main and essential legislative and applicative issues of metrological assurance of thread joints in the Russian Federation and international practice. Basic limitations of the existing measuring methods of the main thread gage parameter - the pitch diameter of thread - are represented. We give the description of the first echelon state working calibration standard for linear unit, placed in service in D.I. Mendeleyev Institute for Metrology (VNIIM), including the general field of applications and metrological characteristics according to the state verification schedule. The possibilities of etalon application in the field of measurements of thread gages parameters are shown. Technical solutions for reducing the components of uncertainty of measurements of the pitch diameter using the etalon are described: temperature stability; reducing of external vibration effects on measuring procedure; developing of the special software for minimizing human factor and increasing automation level of the measuring procedure. The solutions described have enabled to achieve expanded uncertainty value about 0.7-1.0 microns. As a result, we also propose further ways for development and improvement of the system of metrology assurance in the field of thread joints.

S1110401 玉軸受の寿命に及ぼす外部振動の影響

Boll bearing life can be calculated by using bearing life equation. There are a number of factors involved in the equation but the equation does not include the effect of external vibration to the bearing. Nowadays, the effect of external vibration is included in the load factor which is normally determined by previous experiences. To evaluate the effect of external vibration towards bearing life, a proper experimental apparatus that can constantly apply external vibration to the test bearing during bearing life test is designed and created. The result is studied and discussed.

小口径ジャーナルすべり軸受における安定化流量の実験的検討

The effects of temperature distribution and external vibration on stabilized supply flow rate of small bore journal sliding bearing were experimentally investigated. Journal sliding bearings are used widely in many rotational machineries such as engine, turbine, HDD etc.. However, journal sliding bearings generate oilwhip under high speed operation. In order to solve this problem, Hashimoto suggested a stabilization method for suppressing oilwhip by using starved lubrication in which supply oil rate is reduced. However, the starved lubrication have the risks of sudden rising of temperature and regenerating oilwhip caused by external vibrations. In this study, the temperature distribution around the axis and the effect of the external vibrations was investigated to make clear the behaivior of the oil. The temperature distributions were measured with thermocouples and cavitations generating in the bearing clearance were visualized by using a high-speed camera. In addition, the vibration test was carried out with an impulse hammer and an acceleration sensor. The area was observe for the temperature to increase rapidly from the results of reducing supply of flow rate. In addition, in the case of increasing supply frow rate, the difference between the maximum temperature and minimum temperature in the bearing is reduced gradually. Moreover, the oil whip was occurred by the external vibration. It was found that both risks were possible to avoid by adjusting the supply flow rate adequately.

Two-dimensional modeling of the effects of external vibration on the PZT impedancesignature

The electromechanical impedance (EMI) technique using piezoelectric ceramic leadzirconate titanate (PZT) transducers has been increasingly applied to structural healthmonitoring (SHM) of aerospace, civil and mechanical structures. The PZT transducers areusually surface bonded to or embedded in a structure and subjected to actuation so as tointerrogate the structure at the desired frequency range. The interrogation results inelectromechanical admittance (inverse of EMI) signatures which can be used to estimatethe structural health or integrity according to the changes of the signatures. In the existingEMI method, the vibration of the structure caused by the external excitations has beenconsidered only for the one-dimensional scenario. This paper develops a two-dimensionalEMI model to account for the effect of external excitation on the PZT admittancesignature. An application is illustrated with modeling of a cantilevered Kirchhoffplate interrogated by a single surface-bonded PZT transducer. Experiments andnumerical simulations are also carried out to verify the theoretical model. Finally,the effects of external excitation on PZT impedance signatures are discussed.

Feedforward Control Based on Neural Networks for Hard Disk Drives

We present a novel feedforward control based on neural networks to attenuate the effect of external vibrations on the positioning accuracy of hard disk drives. The neural network compensator, which is an add-on function on top of nominal feedback control, uses the accelerometer signals obtained from a sensor to detect external vibrations. Our feedforward control can be regarded as a nonlinear finite impulse response (FIR) that corresponds to linear FIR when the basis function of the neural network is linear. By neural network learning, the tracking performance of hard disk drives can be improved with no information on disturbance dynamics or sensor model. We have analyzed the stability of the proposed scheme by the Lyapunov criterion. Here, we give simulation results to demonstrate that our control scheme can eliminate the effect of external disturbances on positioning accuracy.

Feedforward control based on neural networks for disturbance rejection in hard disk drives

A feedforward control based on neural networks to attenuate the effect of external vibrations on the positioning accuracy of hard disk drives (HDDs) is presented. The adaptive neural network compensator utilises accelerometer signals to detect external vibrations. No information on the plant, sensor and disturbance dynamics is needed in the design of the adaptive neural network compensator. The stability of the proposed scheme is analysed by the Lyapunov criterion. Experimental results show that the tracking performance of HDDs can be improved significantly by using the feedforward controller when compared with the case without compensation.

Neural network compensation control for mechanical systems with disturbances

Two novel compensation schemes based on accelerometer measurements to attenuate the effect of external vibrations on mechanical systems are proposed in this paper. The first compensation algorithm exploits the neural network as the feedback-feedforward compensator whereas the second is the neural network feedforward compensator. Each compensation strategy includes a feedback controller and a neural network compensator with the help of a sensor to detect external vibrations. The feedback controller is employed to guarantee the stability of the mechanical systems, while the neural network is used to provide the required compensation input for trajectory tracking. Dynamics knowledge of the plant, disturbances and the sensor is not required. The stability of the proposed schemes is analyzed by the Lyapunov criterion. Simulation results show that the proposed controllers perform well for a hard disk drive system and a two-link manipulator.

The Role of Nitric Oxide in Skin Blood Flow Increases Due to Vibration in Healthy Adults and Adults with Type 2 Diabetes

We recently demonstrated concomitant increases in skin blood flow and nitric oxide (NO) production in young healthy adults in response to externally applied vibration of the forearm. Research has shown that adults with type 2 diabetes exhibit depressed NO production and vascular responses to NO. We hypothesized that subjects with type 2 diabetes would display lower than normal increases in skin blood flow to externally applied vibration. Therefore, the purpose of this study was to compare 20 male and female, age- and body mass index-matched normal adults and adults with type 2 diabetes in terms of the effects of external vibration of the forearm on skin blood flow and the rate of NO production. Skin blood flow and NO production were measured before vibration, immediately after 5 min of vibration, and 5 min after vibration ceased. Although externally applied vibration significantly increased skin blood flow for both groups (P = 0.0001), those with diabetes had significantly lower (223%; P = 0.003) skin blood flows compared to the healthy older adults (461%). The rate of NO production, expressed as microM NO . flux, also increased significantly in both groups after vibration (healthy group, 374%; diabetes group, 236%) and remained significantly elevated (healthy group, 258%; diabetes group, 177%) for at least 5 min; however, the difference between groups was not significant (P = 0.12). These findings suggest that subjects with diabetes exhibit a lower skin blood flow and lower NO response to externally applied vibration than matched normal subjects.

The modelling of roundness in cylindrical plunge grinding to incorporate wave shift and external vibration effects

An elastic model has been developed which predicts the roundness profiles generated in cylindrical plunge grinding. The model considers two sources of error, which are run-out of the grinding wheel and an external vibration. Comparisons are made with experimental measurements, in which wheel run-out and an external vibration are imposed. Explanations are given for the differences. In particular, the model shows that roundness profiles are sensitive to small changes in conditions, such as wheel and workpiece speeds. In addition, the model clearly illustrates the difficulty in trying to assess the sources of errors from the shape of the roundness profile when more than one source of error is present.

Surface response functions for a thin-film between fluids with infinite boundaries and for a fluid-fluid interface between finite boundaries

Measuring the surface response function of a fluid allows us to ascertain many of its properties. Simplified surface response functions are presented for several interface conditions, including (a) a thin-film between two fluids of infinite extent, (b) the newly derived fluid-fluid interface between finite boundaries, and (c) the traditional fluid-fluid interface between infinite boundaries. The finite-boundary derivation indicates that wall effects are very short range. This portends that the effects of external vibrations, which traditionally make this measurement challenging, can be mitigated by scattering from thin fluid layers.