Influence Of Mechanical Vibrations Research Articles

Experimental study on condensing flow and heat transfer characteristics in minichannels under mechanical vibration conditions

Minichannel heat exchangers are often used in the condensers of vehicle air conditioners, and vibration is inevitable in vehicle driving. However, the influence of mechanical vibration on the characteristics of minichannel condensing flow and heat transfer has been rarely studied. Therefore, the experimental study of condensing flow and heat transfer in minichannels under mechanical vibration was carried out in this paper. With R134a as the working medium, the condensation heat transfer coefficient, frictional pressure drop and flow pattern images were measured in the saturation temperature of 40 °C, mass flux density of 200 kg/(m2·s), vapor quality range of 0–1, vibration frequency of 15–50 Hz and amplitude of 0–2.4 mm. For annular flow, intermittent flow and bubble flow, the vibration can enhance the wave of gas-liquid interface, and promote the breakup of long bubbles and the polymerization of small bubbles. Vibration enhances heat transfer in most cases, but weakens heat transfer in some specific cases. The frictional pressure drops under vibration conditions are greater than those under static conditions, which indicates that the influence mechanism of vibration on heat transfer and pressure drop is different. This paper attempts to analyze the complex mechanism of vibration affecting minichannel condensing heat transfer and pressure drop, which provides theoretical support for further study of condenser optimization design under vibration conditions.

Expression of Concern for article entitled “Influence of mechanical vibration on composite phase change material based thermal management system for lithium-ion battery”

Expression of Concern for article entitled “Influence of mechanical vibration on composite phase change material based thermal management system for lithium-ion battery”

Experimental study on binary solids drying in a vibro-fluidized bed

Vibro-fluidized beds can improve the solids drying characteristics by enhancing the gas–solid contacting. In this study, experiments in a pseudo-2D vibro-fluidized bed setup are performed in order to better understand this improved drying behavior of binary solids mixtures. A coupled particle image velocimetry-infrared thermography technique is applied. Furthermore, a machine learning algorithm is used to characterize the bed segregation and mixing dynamics under the influence of mechanical vibration. Significant changes in bed hydrodynamics and various impacts on segregation and mixing characteristics were observed for vibrational oscillations corresponding to low values of acceleration compared to gravitational acceleration. Larger vibration accelerations result in significantly increased solids mixing compared to a non-vibrating gas-fluidized bed due to enhanced meso-scale particle agitation.

Numerical simulation study of the effect of mechanical vibration on heat transfer in a six-fin latent heat thermal energy storage unit

The optimization of heat transfer in latent heat thermal energy storage units (LHTES) has received a lot of research during the past decade, and the use of fins to enhance heat transfer in phase change materials (PCM) is one of the efficient ways. However, the existing studies do not consider the influence of mechanical vibration which widely exists in LHTES. To fill the research gap in this important topic, a horizontal shell-and-tube six-fin latent heat thermal energy storage unit is investigated in this study, and the effects of mechanical vibration are investigated by numerically simulating the PCM charging process in LHTES using the Enthalpy-porosity technique. In this paper, the charging rate of PCM, variation of key parameters such as Nusselt number, temperature and liquid fraction are analyzed in detail under vibration conditions. And the following conclusions can be obtained. (1) Mechanical vibration can significantly increase the charging rate of PCM, under the condition of vibration amplitude of 10mm and frequency of 1Hz (the melting time of PCM is reduced by 46.6%). (2) The enhancement effect of mechanical vibration on the melting rate of PCM increases with the increase of amplitude and frequency, but the enhancement efficiency keeps decreasing. These observations result from that the mechanical vibration changes the velocity of the liquid PCM, so the forced convective heat transfer of the PCM is significantly enhanced. Furthermore, the melting process of PCM is sensitively affected by increasing the amplitude than by increasing the frequency. Increasing the amplitude or frequency alone (amplitude from 10mm to 40mm; frequency from 1Hz to 4Hz) can reduce the total melting time of PCM by 75% and 68.7%, respectively.

Research on the Influence of Mechanical Vibration on Radio Wave Propagation

Research on the Influence of Mechanical Vibration on Radio Wave Propagation

Effect of mechanical vibration on phase change material based thermal management module of a lithium-ion battery at high ambient temperature

Phase change material (PCM) based thermal management is regarded as a promising method for cooling power systems of lithium-ion battery electric vehicles. The battery thermal management modules of electric vehicles usually work under vibration conditions and it has been widely recognized that mechanical vibration can enhance heat transfer. However, the knowledge on effects of mechanical vibration on PCM-based lithium-ion battery thermal management systems is still sparse. To bridge the knowledge gap, the effect of mechanical vibration on a PCM-based lithium-ion battery thermal management module with a high environment temperature is investigated comprehensively for the first time. A variety of parameters, such as PCM thickness, vibration amplitude and vibration frequency, are discussed in detail. Some new findings are reported: (1) mechanical vibration has a significant influence on the PCM-based lithium-ion battery thermal management module, especially for a PCM layer with a moderate thickness; (2) when the vibration amplitude increases over a certain high value, the influence of mechanical vibration becomes nearly insensitive to the variation of vibration amplitude; (3) the thermal performance does not depend on vibration frequency monotonically. The research can provide guidance for the design of thermal management modules of electric vehicles.

Influence of mechanical vibration on composite phase change material based thermal management system for lithium-ion battery

Electric vehicles are inevitably affected by vibration when driving. However, the influence of vibration on the thermal field is neglected in most theoretical and experimental studies on battery thermal management systems (BTMS) in the current literature. Due to the addition of high thermal conductivity elements such as carbon nanoparticles and graphene into pure phase change material (PCM), the heat transfer properties of these composite phase change materials (CPCM) differ significantly from those of pure PCM. The present work focuses on the influence of mechanical vibration on the BTMS based on CPCM. A series of experiments are carried out for the BTMS based on pure paraffin and three CPCM with a mass fraction of expanded graphite or graphene from 0 to 20 % under the vibration amplitudes of 2–4 mm and frequencies of 10–30 Hz. The results show that the small vibration amplitude is beneficial to strengthening the heat transfer of CPCM and lowering the battery's operating temperature. Besides, the mechanical vibration can accelerate the dispersion and collision of the high thermal conductivity particles in CPCM, thus improving the heat dissipation efficiency of the BTMS. It can significantly prolong the latent heat utilization time of the CPCM and then extend the period when the battery pack is in the suitable working temperature range. However, the too high or too low vibration frequency is not conducive to enhancing heat transfer. The 20 Hz is found to be an optimal vibration frequency. And the vibration has the best cooling effect on the CPCM with 20 % expanded graphite among the three CPCMs considered in this study. Finally, the grey relational analysis is applied to investigate the combined effects of three factors. It is determined that the impact ranking from the largest to the smallest is vibration frequency, the composition of CPCM, and vibration amplitude.

Thermal stability measurement of terminal face relative pose for complex structure based on coordinate measuring machine

Abstract The coordinate measuring machine has high measurement accuracy, but it is only suitable for the precise measurement of the geometric size of the component in the normal temperature environment, and some complex structures need to assess the stability of the terminal face relative pose in the high and low temperature environment. In order to apply the high-precision measurement of the coordinate measuring machine to the thermal stability evaluation of the relative pose of the terminal face of complex structures, an extended temperature control method based on the coordinate measuring machine is proposed. The method realizes the loading control of the temperature environment of the specimen by the mobile temperature control module and the temperature control medium circulation module. The flexible connection mode is used between the temperature control module and the temperature control medium circulation module to reduce the influence of mechanical vibration on the measurement accuracy. The mixing fan and the temperature control medium dryer are installed in the pipeline to avoid frosting and dewing in the temperature control box and ensure the uniform distribution of the temperature field, so as to realize the accurate measurement of the relative pose of the terminal face of the complex structure under the high and low temperature environment by the coordinate measuring machine. The method is applied to the thermal stability test of the relative pose of the end face of a joint component, and the test results are good, which provides a new idea for the extended application of coordinate measuring machines.

Power Consumption Simulation of Servo Motors Focusing on the Influence of Mechanical Vibration on Motor Efficiency

This paper presents a simulation method for the power consumption of servo motors, focusing on the influence of vibrations on the motor efficiency. An apparatus consisting of two servo motors connected through a coupling was specifically designed for this study. The efficiency of the servo motor was experimentally investigated for several torque vibration levels imposed through the selection of the control parameters, and the torque vibration level was quantified through the standard deviation of the torque signal. The efficiency map characteristics for each torque oscillating level were determined. A numerical model of the apparatus clarifying the dependency of the coupling characteristics on the oscillating torque was developed, and the torque oscillation of the system was simulated. A model based on the measured motor efficiency maps and the torque oscillation level was developed to simulate the motor efficiency under several torque vibrating conditions. Finally, the power consumption of the motor was simulated based on the simulated efficiency and mechanical power. A balance of input, output, and loss powers was presented, and the experimental measurements were compared with the simulation results. The power consumption of the motor increased when the torque oscillated owing to vibrations, and the loss of power due to both oscillations and the loss of motor efficiency was quantified.

Influence of Mechanical Vibration on Optical Fire Alarm System and Its Improvement Measures

Influence of Mechanical Vibration on Optical Fire Alarm System and Its Improvement Measures

Comparison between the influence of mechanical vibration and junction temperature rise originated bond wires detachment on the characteristics of IGBT module

As the main device in a power system, the IGBT module works in the frequent power cycle for a long time, resulting to the fluctuation of junction temperature and heavy mechanical stress loading. These two factors threaten the reliability of bond wires and the IGBT module significantly. This study aimed at improving the reliability of the semiconductor device. IGBT dual bridge module was used as the primary research object, establishing the relationship between the bond wires detachment and resistance. MATLAB was used for mathematical analysis to determine the quantitative influence of the two conditions on several static characteristics of the IGBT module. Our study provides more samples and references to monitoring the IGBT bond wires and demonstrates the difference and similarity of these two factors.

Discharge of a granular silo under mechanical vibrations

In this paper, we study the flow rate of model granular material in a silo under the influence of mechanical vibrations. Experimental measurements and discrete element simulations (DEM) are performed in a quasi-2D silo. The influence on the flow rate of the opening size and the vibration applied on the entire silo is studied. Two distinct regimes are evidenced, governed by the Froude numberFrand the relative frequency Ω. In the first regime, a decreased flow rate is observed when increasing the vibration intensity. This behavior is explained by the presence of reorganizations induced by the vibration, leading to a more homogeneous but also slower flow. In the second regime, an increased flow rate is evidenced when increasing the vibration intensity. We find this behavior comes from the intermittent nature of the flow, where the flow rate is directly controlled by the propagation of shock waves all along the silo.

Influence of mechanical vibration on characteristics of plane tactile sensing

Influence of mechanical vibration on characteristics of plane tactile sensing

Влияние механической вибрации на оптические свойства инфракрасных световодов состава AgCl-AgBr

The influence of mechanical vibrations on the optical transmission of infrared fibers of AgCl0.25Br0.75 and AgCl0.5Br0.5 within 30 hours was investigated. It was demonstrated, that vibration effects on the fibers leads to decrease of their transmittance. The selective character of infrared fiber transmission in wavelength ranges 2.0–4.0 μm and 6.0–9.0 μm was found.

Influence of the vibrations in the interfacial layer on the wettability of adhesized material interfacial formations in systems with d- and f-elements

The effect of local vibration at interfacial layer of a heterogeneous liquid system on the wettability of the material of interfacial formations based on the salt of the d- or f-element of di-(2-ethylhexyl)phosphoric acid adhered to glass has been investigated. It is shown that in the field of mechanical vibrations one can obtain a material with a given value of the wetting angle, which has hydrophobic properties. It is established that the influence of mechanical vibrations is due to changes in the hydrodynamic situation in the transition region and is the result of complex interactions mainly hydrodynamic and coagulation processes in the interfacial layer of the di-(2-ethylhexyl)phosphoric acid - solvent system / water solution of the d- or f-element salt. The dependence of the wettability of the material of interfacial formations adhered to glass on the parameters of the force field (vibration frequency, amplitude), the design features of the experimental setup, and the composition of the system is shown.

Influence of Vibrations in the Interfacial Layer on the Wettability of an Adhered Material of Interfacial Formations in Systems with d and f Elements

The effect of local vibration in an interfacial layer of a heterogeneous liquid system on the wettability of the material of interfacial formations based on a d- or f-metal di-(2-ethylhexyl)phosphate salt adhered to glass has been studied. It has been demonstrated that, in the field of mechanical vibrations, one can obtain a hydrophobic material with a desired wetting angle value. It has been established that the influence of mechanical vibrations is caused by changes in the hydrodynamic situation in the transition region and is a result of complex interplay mainly between hydrodynamic and coagulation processes in the interfacial layer of the di-(2-ethylhexyl)phosphoric acid–solvent/aqueous solution of a d- or f-metal salt system. The wettability of the material of interfacial formations adhered to glass turns out to depend on the parameters of the force field (vibration frequency and amplitude), the design features of the experimental setup, and the composition of the system.

ДО ВИЗНАЧЕННЯ СТАНУ КОМПЛЕКСНИХ КОНТАКТНИХ З'ЄДНАНЬ ПРЕЦИЗІЙНИХ РОТОРНИХ СИСТЕМ

In this paper, the problem of determining the state of complex contact joints of precision rotary systems is investigated on an example of symmetrical structures with combined ball-bearing supports. The conformity of the axial rigidity of the ball bearings to the nominal value is diagnosed. The dynamical model of the node is considered and the functions of influence are defined. The materials of the article today are relevant, because in any prefabricated design, system parameters in the process of assembly may differ from the calculated values ​​and change in the process of operation. In order to predict the consequences of this, you need to know the reaction of the system to these changes. High-speed rotary systems, which are used in large quantities in engineering (for example, gyroscopes), in real conditions operate under the influence of mechanical vibrations, which greatly reduces the accuracy of the system. The nature of the vibrations of the rotor of the electric motor, which is caused by the vibration of the body, is characterized by rigid and damping characteristics of the system, constant and alternating components of the moment of the forces of resistance of rotor rotation in the supports, axial and radial oscillations of the centre of gravity and a number of other characteristics. An analytical study of the dynamics of such systems is a very difficult task, but the definition of sensitivity functions for this kind of compounds experimentally is still a much more complicated technological problem, so their characteristics should be obtained by different methods of identification. At the same time, in many cases it is virtually impossible to evaluate experimentally the influence of parameters on the behaviour of the system. Therefore, it is necessary to study and analyse the influence of changes in parameters on the properties of the system analytically, that is, according to the well-known mathematical model of the system. The main purpose of this work is to determine the conformity of the axial rigidity of the ball bearings to their nominal value. The dynamical model of the node is considered and the functions of influence of system parameters on qualitative indicators are determined. This allows us to conclude that the results obtained with respect to the parameters of the test node do not exceed the limits of permissible zones. That is, the node is suitable for subsequent assembly operations. Thus, controlling the ascending technical condition of products, it is possible to prevent sudden failures in the most important elements of rotary systems, that is all contributes to improving the quality and reliability of the operation of devices. The problem of determining the state of complex contact joints of precision rotary systems on the example of symmetrical structures with combined ball bearings is investigated. The conformity of the axial rigidity of the ball bearings to the nominal value is diagnostically verified. The dynamical model of the node is considered and the functions of influence are defined.

The influence of mechanical vibration on local and central balance control

Fall prevention has an indispensable role in enhancing life expectancy and quality of life among older adults. The first step to prevent falls is to devise reliable methods to identify individuals at high fall risk. The purpose of the current study was to assess alterations in local postural muscle and central sensory balance control mechanisms due to low-frequency externally applied vibration among elders at high fall risk, in comparison with healthy controls, as a potential tool for assessing fall risk. Three groups of participants were recruited: healthy young (n = 10; age = 23 ± 2 years), healthy elders (n = 10; age = 73 ± 3 years), and elders at high fall risk (n = 10; age = 84 ± 9 years). Eyes-open and eyes-closed upright standing balance performance was measured with no vibration, 30 Hz, and 40 Hz vibration of Gastrocnemius muscles. When vibratory stimulation was applied, changes in local-control performance manifested significant differences among the groups (p < 0.01). On average between conditions, we observed 97% and 92% less change among high fall risk participants when compared to healthy young and older adults, respectively. On the other hand, vibration-induced changes in the central-control performance were not significant between groups (p ≥ 0.19). Results suggest that local-control deficits are responsible for balance behavior alterations among elders at high fall risk and healthy individuals. This observation may be attributable to deterioration of short-latency reflexive loop in elders at high fall risk. On the other hand, we could not ascribe the balance alterations to problems related to central nervous system performance or long-latency responses.

Investigate the Influence of Mechanical Vibrations on the Hardness of Al5052 Weldments

Objectives: This paper presents the influence of vibratory Tungsten inert gas welding on the hardness of aluminum 5052- H32 alloy weldments are studied. Methods/Statistical Analysis: Hardness of Al5052-H32 is analyzed for different voltage inputs keeping other parameters like welding current, welding speed and gas flow rate constant. Findings: Hardness values are compared for the specimens prepared with vibrations and without vibrations. Hardness of Al5052-H32 specimens prepared at 160 V input voltage is more compared to the specimens prepared at 70 V, 230 V and without vibration. There is a decrease of hardness value is observed for specimens prepared at 230 V compared to the specimens prepared at without any vibrations.

Structures of Aluminum Base Alloys Solidified by Vibrations

As it is known the improving of the casting alloys properties supposes both finishing and modifying their structure. Dates from castings production specify that for structure improvement the metallurgical methods are more preferred than physical ones. The study analyzes the structural changes caused by melt vibration during crystallization of hypoeutectic and eutectic silumins and of the aluminum-copper alloy. The analysis of solidification conditions was achieved by recording cooling curves, and by the qualitative and quantitative examination of the obtained structures. The monitoring of the cooling intensity with or without mechanical vibrations was performed by calculate the global thermal transfer coefficient. It was followed in the same time the influence of mechanical vibrations on the casting alloys compactity. Global thermal transfer coefficient value increased 3.5 times.