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1
Mohanty, Lipi, Yaowen Yang, and Swee Tjin. "Passively Conducted Vibration Sensing with Fiber Bragg Gratings." Applied Sciences 8, no. 9 (September 10, 2018): 1599. http://dx.doi.org/10.3390/app8091599.
Повний текст джерелаАнотація:
Measuring vibrations is a common method of monitoring the integrity of structures and heavy machinery, that are subject to dynamic loads. Strong vibrations for prolonged periods of time can be caused by various sources, such as trains, motors and heavy machinery. These strong vibrations should be identified and managed to ensure operational safety. This study proposes a flexible metal beam sensor with a fiber Bragg grating (FBG) mounted on the surface to measure the vibrational frequency. We present a sensor for measuring the vibrational frequencies on-site by placing the beam so that it makes physical contact with the vibrating body. The sensor has been tested in the range of 50–200 Hz. The sensing beam can detect the vibrations that are induced in other metallic bodies where there are metallic structures of low stiffness to conduct the vibration. The results show that the sensing beam is capable of detecting the frequency of forced vibrations from its periphery when placed in different orientations.
2
Lackner, James R., Ely Rabin, and Paul DiZio. "Fingertip Contact Suppresses the Destabilizing Influence of Leg Muscle Vibration." Journal of Neurophysiology 84, no. 5 (November 1, 2000): 2217–24. http://dx.doi.org/10.1152/jn.2000.84.5.2217.
Повний текст джерелаАнотація:
Touch of the hand with a stationary surface at nonmechanically supportive force levels (<1 N) greatly attenuates postural sway during quiet stance. We predicted such haptic contact would also suppress the postural destabilization caused by vibrating the right peroneus brevis and longus muscles of subjects standing heel-to-toe with eyes closed. In experiment 1, ten subjects were tested under four conditions: no-vibration, no-touch; no-vibration, touch; vibration, no-touch; and vibration, touch. A hand-held physiotherapy vibrator (120 Hz) was applied ∼5 cm above the malleolous to stimulate the peroneus longus and brevis tendons. Touch conditions involved contact of the right index finger with a laterally positioned surface (<1 N of force) at waist height. Vibration in the absence of finger contact greatly increased the mean sway amplitude of the center of pressure and of the head relative to the no-vibration, no-touch control condition ( P < 0.001). The touch, no-vibration and touch-vibration conditions were not significantly different ( P > 0.05) from each other and both had significantly less mean sway amplitude of head and of center of pressure than the other conditions ( P < 0.01). In experiment 2, eight subjects stood heel-to-toe under touch and no-touch conditions involving 40-s duration trials of peroneus tendon vibration at different duty cycles: 1-, 2-, 3-, and 4-son and off periods. The vibrator was attached to the subject's leg and remotely activated. In the no-touch conditions, subjects showed periodic postural disruptions contingent on the duty cycle and mirror image rebounds with the offset of vibration. In the touch conditions, subjects were much less disrupted and showed compensations occurring within 500 ms of vibration onset and mirror image rebounds with vibration offset. Subjects were able to suppress almost completely the destabilizing influence of the vibration in the 3- and 4-s duty cycle trials. These experiments show that haptic contact of the hand with a stable surface can suppress abnormal proprioceptive and motor signals in leg muscles.
3
Mo, Yue Ping, Hong Jin, Peng Fei Xu, Dong Liu Jiang, and Yun Jing Liu. "The Experimental Research of a Piezoelectric Linear Motor." Applied Mechanics and Materials 130-134 (October 2011): 621–24. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.621.
Повний текст джерелаАнотація:
The working principle and driven approach of a piezoelectric linear motor which uses axial stretching vibration of cascading piezoelectric elements is introduced. The prototype of that motor is designed and fabricated. It’s performance is also tested. The motor’s vibrator is a stick and moving object is a cylindrical ring which contacts with vibrating stick in the shape of cylindrical surface. The forward and backward movements of moving object are achieved by utilizing the axial stretching vibration of vibrating stick. The moving direction is altered by changed the frequency of driving signal. The structure of the motor is simple and the power supply is single sine phase. So that it is easy to be smaller. In addition, the thrust force is increased by cylindrical surface contact between moving object and vibrating stick so that it is easy to be practical also. This kind of piezoelectric linear motor is very suitable for precise positioning of objects, fine material handling, and vibration cutting tools.
4
Soom, Andres, and Jern-Wen Chen. "Simulation of Random Surface Roughness-Induced Contact Vibrations at Hertzian Contacts During Steady Sliding." Journal of Tribology 108, no. 1 (January 1, 1986): 123–27. http://dx.doi.org/10.1115/1.3261131.
Повний текст джерелаАнотація:
Random normal contact vibrations, excited by surface irregularities swept through the contact region of Hertzian contacts during sliding, are studied using digital simulation techniques. The input disturbances are modeled as random time processes with specified spectral content in the spatial wavenumber and frequency domains. The Hertzian contact stiffness is modeled directly or through a bilinear approximation. The contact vibration spectra and resulting mean square contact loading are obtained from the simulations. A comparison with previous measurements shows good agreement between the simulation and experimental results.
5
Wi, Daehan, and Angela A. Sodemann. "Exploring User Perception Challenges in Vibrotactile Haptic Display Using Resonant Microbeams under Contact with Skin." Multimodal Technologies and Interaction 3, no. 2 (May 28, 2019): 38. http://dx.doi.org/10.3390/mti3020038.
Повний текст джерелаАнотація:
Resonant vibrotactile microbeams use the concept of resonance to excite the vibration of cantilever beams, which correspond to pixels of an image. The primary benefit of this type of tactile display is its potential for high resolution. This paper presents the concept of the proposed system and human skin contact experiments to explore user perception challenges related to beam vibration during skin contact. The human skin contact experiments can be described in five phases: dried skin contact to metal beam tips, wet and soaped skin contact to metal beam tips, skin contact with a constraint, normal force measurement, and skin contact to the tips of silicone rubber beams attached to metal beam tips. Experimental results are analyzed to determine in what cases of skin contact the beams stop vibrating. It is found that the addition of silicone rubber beams allows the primary metal beams to continue vibrating while in contact with skin. Thus, the vibration response of a metal beam with silicone rubber beams is investigated for the better understanding of the effect of silicone rubber beams on the metal beam vibration.
6
Xu, Shaoyi, Fangfang Xing, Ruilin Wang, Wei Li, Yuqiao Wang, and Xianghui Wang. "Vibration sensor for the health monitoring of the large rotating machinery: review and outlook." Sensor Review 38, no. 1 (January 15, 2018): 44–64. http://dx.doi.org/10.1108/sr-03-2017-0049.
Повний текст джерелаАнотація:
Purpose At present, one of the key equipment in pillar industries is a large rotating machinery. Conducting regular health monitoring is important for ensuring safe operation of the large rotating machinery. Because vibrations sensors play an important role in the workings of the rotating machinery, measuring its vibration signal is an important task in health monitoring. This paper aims to present these. Design/methodology/approach In this work, the contact vibration sensor and the non-contact vibration sensor have been discussed. These sensors consist of two types: the electric vibration sensor and the optical fiber vibration sensor. Their applications in the large rotating machinery for the purpose of health monitoring are summarized, and their advantages and disadvantages are also presented. Findings Compared with the electric vibration sensor, the optical fiber vibration sensor of large rotating machinery has unique advantages in health monitoring, such as provision of immunity against electromagnetic interference, requirement of less insulation and provision of long-distance signal transmission. Originality/value Both contact vibration sensor and non-contact vibration sensor have been discussed. Among them, the electric vibration sensor and the optical fiber vibration sensor are compared. Future research direction of the vibration sensors is presented.
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Ometron Ltd. "Non-contact vibration measurement." NDT & E International 24, no. 1 (February 1991): 60. http://dx.doi.org/10.1016/0963-8695(91)90811-g.
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Popp, Karl, Lars Panning, and Walter Sextro. "Vibration Damping by Friction Forces: Theory and Applications." Journal of Vibration and Control 9, no. 3-4 (March 2003): 419–48. http://dx.doi.org/10.1177/107754603030780.
Повний текст джерелаАнотація:
In this paper, we deal with the vibrational behavior of mechanical structures interconnected by contacts with friction. The focus is set on the utilization of friction forces that are generated in the contact interfaces with the objective to increase damping and to reduce vibration amplitudes in order to prevent structures from failures owing to high resonance stresses. We present a comparison and classification of different contact models that are most commonly used, including the derivation of a three-dimensional contact model under consideration of rough surfaces. We give different solution methods for problems with non-linear friction elements. The effectiveness of friction damping devices is pointed out by a single-degree-of-freedom friction oscillator, beam-like structures with frictional interfaces and different underplatform dampers in turbo-machinery applications. It can be shown that in many practical applications friction damping devices provide a remarkable decrease of vibration amplitudes.
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Bryja, Danuta, and Adam Popiołek. "Vibrations of the overhead catenary caused by the passage of a high-speed train through the track stiffness discontinuity." Transportation Overview - Przeglad Komunikacyjny 2018, no. 6 (June 1, 2018): 21–31. http://dx.doi.org/10.35117/a_eng_18_06_03.
Повний текст джерелаАнотація:
The paper presents the methodology for simulating vibrations of the railway catenary, caused by the passage of the train through the track stiffness discontinuity. The concept of the simulation algorithm takes into account the dynamic interaction between pantographs and the overhead contact wire as well as nonlinearity resulting from the specificity of the droppers behaviour, which do not carry compression - they only carry tensile forces. The coupling of track and rail vehicles vibrations is also included. According to physics, the effect of vibrations of the catenary carried by pantographs on the railway vehicle was not taken into account, which allowed to divide the simulation algorithm into two stages and develop two computer programs with a defined hierarchy of operation. In the first stage of the simulation, the time-histories of vibrations and vibration velocities of those train cars, on which the pantographs are mounted, are calculated. In the second stage, the previously calculated time-histories are set as the input data and the vibration characteristics of the catenary and contact force between pantograph and the contact wire are calculated. The paper presents examples of vibration simulations of a rail vehicle observed in real time at the theoretical point of the pantograph base. The results of the second stage of the simulation were also shown: selected vibration time-histories of the pantograph and the five-span section of the catenary, and oscillations of the contact force between pantograph and the contact wire. The impact of the track stiffness discontinuity on catenary vibration was assessed.
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Murthy, Perunalla PBGSN, Ch Srinivasa Rao, and K. Venkata Rao. "Tool and work piece vibrations measurement - a review." Independent Journal of Management & Production 9, no. 4 (December 1, 2018): 1254. http://dx.doi.org/10.14807/ijmp.v9i4.801.
Повний текст джерелаАнотація:
Tool condition monitoring is one of the important aspects in machining process to improve tool life. It comprises three important steps namely machining data acquisition, data analysis and decision making. Vibration in metal cutting has direct impact on the tool life as well as surface roughness. The present study focused on measurement of vibration during the machining process. Data acquisition is made by using various types of sensors. A wide variety of technologies like contact and non contact sensors have been used for real time data acquisition of tool or work piece vibrations. Research works carried out by many authors is highlighted in measurement of cutting tool and machine tool vibrations using different sensors. Influence of various input parameters like tool geometry, feed, speed and depth of cut on the magnitude of vibrations is discussed. Influence of vibration on surface roughness, tool life and power consumption is reviewed. Three dimensional vibration measurement with single Laser Doppler Vibrometer is also covered for precise analysis of vibration.
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Sobolev, Vladimir I., and Tatiana N. Chernigovskaya. "Research into the dynamics of radio telescope foundationsusing laser vibration measuring equipment." Journal «Izvestiya vuzov. Investitsiyi. Stroyitelstvo. Nedvizhimost» 10, no. 3 (2020): 420–27. http://dx.doi.org/10.21285/2227-2917-2020-3-420-427.
Повний текст джерелаАнотація:
This study presents a technology for determining the dynamic parameters of the foundation structures of radio telescopes by a non-contact method based on the use of laser vibration measuring equipment. The main results of a dynamic process analysis are described. The research was carried out in the form of microdynamic tests of foundation structures with the determination of natural oscillation periods based on lower vibrational forms. Measurements of natural vibrations of radio telescope foundations under applied shock were performed, followed by spectral mapping of vibrational processes. The tests were carried out using a tachometric laser vibrometer RSV-150 included in the register of vibration measuring equipment in Russia. Spectral mappings were obtained using Fourier transforms implemented in software packages of the hardware developers. The dynamic features of radio tele-scope foundations are formalized in the form of spectral maps of the initial records of vibrational proc-esses. The method of microdynamic tests using a vibration meter is presented, along with the principles of its operation and the sequence of numerical processing of records of dynamic processes imple-mented on a personal computer using frequency displays of natural vibrations of structures. The values of natural vibration frequencies obtained as a result of measurements confirmed the rigidity and integ-rity of foundation piles. Pronounced solitary peaks of natural vibration frequencies point to the form of natural vibrations of structures as single-mass systems with the absence of deformational forms of vi-brations in the foundation body.
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Gaul, L., and J. Becker. "Reduction of Structural Vibrations by Passive and Semiactively Controlled Friction Dampers." Shock and Vibration 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/870564.
Повний текст джерелаАнотація:
Reduction of structural vibrations is of major interest in mechanical engineering for lowering sound emission of vibrating structures, improving accuracy of machines, and increasing structure durability. Besides optimization of the mechanical design or various types of passive damping treatments, active structural vibration control concepts are efficient means to reduce unwanted vibrations. In this contribution, two different semiactive control concepts for vibration reduction are proposed that adapt to the normal force of attached friction dampers. Thereby, semiactive control concepts generally possess the advantage over active control in that the closed loop is intrinsically stable and that less energy is required for the actuation than in active control. In the chosen experimental implementation, a piezoelectric stack actuator is used to apply adjustable normal forces between a structure and an attached friction damper. Simulation and experimental results of a benchmark structure with passive and semiactively controlled friction dampers are compared for stationary narrowband excitation. For simulations of the control performance, transient simulations must be employed to predict the achieved vibration damping. It is well known that transient simulation of systems with friction and normal contact requires excessive computational power due to the nonlinear constitutive laws and the high contact stiffnesses involved. However, commercial finite-element codes do not allow simulating feedback control in a general way. As a remedy, a special simulation framework is developed which allows efficiently modeling interfaces with friction and normal contact by appropriate constitutive laws which are implemented by contact elements in a finite-element model. Furthermore, special model reduction techniques using a substructuring approach are employed for faster simulation.
13
Ghasemloonia, Ahmad, D. Geoff Rideout, Stephen D. Butt, and Ali Hajnayeb. "Elastodynamic and finite element vibration analysis of a drillstring with a downhole vibration generator tool and a shock sub." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 8 (July 24, 2014): 1361–84. http://dx.doi.org/10.1177/0954406214543491.
Повний текст джерелаАнотація:
Applying high-frequency axial oscillation into an oilwell drillstring in the “bottom-hole assembly” (BHA) has the potential to enhance drilling efficiency in extended reach wells. Downhole vibration generator tools such as agitators reduce the drillstring–wellbore friction and enhance the rate of penetration. However, introducing controlled vibrations into the drillstring can result in undesired vibration waves propagating along the drillstring, leading to inefficient drilling and catastrophic fatigue failure of the BHA components, “measurement-while-drilling” tools, and mud motors. A dynamic model of the entire drillstring, including vibration generators and shock subs, is required to study the effect of vibration generators on the complex nonlinear coupled axial-lateral dynamics of a drillstring inside a wellbore, to study the effect of vibration tools on the developed cutting force at the bit, and to facilitate simulation-based design of shock subs. A dynamic finite element model (FEM) and an analytical elastodynamic model, both including the vibration generator tool and a shock sub, have been developed. The “Bypassing PDEs” method was implemented on the Lagrangian of the system to develop the analytical equations. A multi-mode expanded Galerkin’s approximation, in conjunction with a multi-span BHA and Hertzian contact assumption, allowed analysis of multiple BHA contact points and, thus, more realistic estimates of drilling rotary speeds that can cause excessive vibration. The models also include torque, mud damping, spatially varying axial force, geometric nonlinearity, and axial stiffening. While the analytical model has fast running time and symbolic solution, the FEM model enables easy reconfiguration and future extensions of model geometry, interactions, and modified BHA configurations. There is agreement between the analytical and FEM simulation results for the vibration suppression ability of the shock sub, dynamic amplification of the vibrating tool force, critical rotary speeds, axial force along the drillstring, axial and lateral displacements, and the contact locations and severity.
14
Liu, Jing, Linfeng Wang, Zhifeng Shi, Wennian Yu, and Huifang Xiao. "A comparison investigation of the contact models for contact and vibration features of cylindrical roller bearings." Engineering Computations 36, no. 5 (June 10, 2019): 1656–75. http://dx.doi.org/10.1108/ec-11-2018-0516.
Повний текст джерелаАнотація:
Purpose The purpose of this study is to investigate the contact models for contact and vibration features of cylindrical roller bearings (CRBs). CRBs are important parts of rotating machinery. The contact deformation between the roller and the raceway is an essential research topic for the CRBs. The contact deformation between the roller and the raceway can greatly affect vibration characteristics and fatigue life of the CRBs. In this investigation, six different methods are adopted to calculate the contact deformation, contact area width and contact stress between the roller and raceways of a CRB. Design/methodology/approach In this paper, the contact deformations and the contact stiffnesses between the roller and the raceway of a CRB obtained by various well-known empirical methods (Lundberg’s, Palmgren’s, Houpert’s, Cheng’s and Hertzian methods) are directly compared with those by the finite element (FE) method. A two degree-of-freedom (2 DOF) dynamic model of the CRB is applied to investigate the effects of the contact stiffness obtained by different line contact deformation calculation methods on the vibration characteristics, such as the root mean square (RMS), the peak to peak (PTP), the crest factor and the kurtosis of the displacement, velocity and acceleration of the inner raceway. Findings The computational results show that different calculation methods for the contact deformations between rollers and raceways have significant effects on the vibrations of the CRB. It is found that that the differences of computational results obtained by Palmgren’s and Lundberg’s models with respect to the FE method are smaller than those by the other three methods, i.e. Houpert’s, Cheng’s and Hertzain models. The amplitude and peak frequency of the frequency response functions from Palmgren’s method are much more similar to those from the finite element method. The above results indicate that Palmgren’s method is a better calculation method for predicting the contact deformations and dynamics of the CRBs. Originality/value This work adopts six different methods to calculate the contact deformation, contact area width and contact stress between the roller and raceways of a CRB. Moreover, a vibration model of a CRB is used to investigate the effect of contact stiffness obtained by the above methods on the vibrations of the CRB. The works can give some guidance for the accurate analytical method for calculating the contact deformations between rollers and raceways and the vibrations of the CRB.
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Wang, Yan Qing, Sen Wen Xue, Xiao Bo Huang, and Wei Du. "Vibrations of Axially Moving Vertical Rectangular Plates in Contact with Fluid." International Journal of Structural Stability and Dynamics 16, no. 02 (February 25, 2016): 1450092. http://dx.doi.org/10.1142/s0219455414500928.
Повний текст джерелаАнотація:
The vibration characteristics of an axially moving vertical plate immersed in fluid and subjected to a pretension are investigated, with a special consideration to natural frequencies, complex mode functions and critical speeds of the system. The classical thin plate theory is adopted for the formulation of the governing equation of motion of the vibrating plates. The effects of free surface waves, compressibility and viscidity of the fluid are neglected in the analysis. The velocity potential and Bernoulli’s equation are used to describe the fluid pressure acting on the moving plate. The effect of fluid on the vibrations of the plate may be regarded as equivalent to an added mass on the plate. The formulation of added mass is obtained from kinematic boundary conditions of the plate–fluid interfaces. The effects of some system parameters such as the moving speed, stiffness ratios, location and aspect ratios of the plate and the fluid-plate density ratios on the above-mentioned vibration characteristics of the plate–fluid system are investigated in detail. Various different boundary conditions are considered in the study.
16
Zhang, Rong Hai, Ning Yuan Zhu, and Gai Pin Cai. "Surface Effect Mechanism Analysis for Vibrational Rotary Forging." Advanced Materials Research 314-316 (August 2011): 753–58. http://dx.doi.org/10.4028/www.scientific.net/amr.314-316.753.
Повний текст джерелаАнотація:
As a contact of vibrational rotary forging is highly nonlinear, the contact area and boundary between rotary toolhead and workpiece had more accurate calculation, made the contact boundary more tally with the actual situation. For a surface effect is of complexity for vibrational rotary forging, a vibrational rotary forging visco-elasticity plasticity model was built, and the visco-elasticity spatial matrix and the visco-plasticity spatial matrix were derived by the generalized Hooke's law in elasticity theory and the increase theory in mechanics of plasticity, then by the finite element founction of MATLAB for the surface effect analyzed during the vibrational rotary forging deformation, it is shown as blow: the surface effect should be appeared with high frequency vibration or low frequency vibration, but there are some conditions for surface effect produced during plastic process, and then the hypothesis that the friction vector is reversal of deformation load, and it is benefit to deformation process during the part of time in vibration period is validated.
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Zhang, Jianjun, Qibo Ni, Jing Wang, and Feng Guo. "Transient thermal elastohydrodynamic lubrication of point contacts subjected to normal vibration." Industrial Lubrication and Tribology 68, no. 5 (August 8, 2016): 536–47. http://dx.doi.org/10.1108/ilt-06-2015-0085.
Повний текст джерелаАнотація:
Purpose Vibration exists widely in all machineries working under high speed. The unpredictability of vibration and the change of the relative surface speed may result in difficulties in the elastohydrodynamic lubrication (EHL) analysis. By far, few studies on EHL relating to vibration have been published. The purpose of the present study is to investigate the effect of the vertical vibrations and the influence of temperature on the thermal EHL contacts. Design/methodology/approach The lubricant was assumed to be Newtonian fluid. The time-dependent numerical solutions were achieved instant after instant in each period of the vibration. At each instant, the pressure field was solved with a multi-level technique, the surface deformation was solved with a multi-level multi-integration method and the temperature filed was solved with a finite different scheme through a sweeping progress. The periodic error was checked at each end of the vibration period until the responses of pressure, film thickness and temperature were all periodic functions with the frequency of the roller’s vibrations. Findings The results reveal that normal vibration produces little drastic change of pressure, film thickness and temperature in EHL. Under some conditions, the vibrations of the roller can produce transient dimples within the contact conjunction. It is also showed that the lubrication in the same sliding is better than the opposite sliding. Research limitations/implications For the unpredictability of vibration, it is not easy to do the experiment to realize a real comparison with numerical results. The reach does not show any verification and consider the effect of non-Newtonian fluid. Originality/value The effect of the vertical vibrations on the thermal EHL point contact hast been studied. The effects of both the amplitude and the frequency on the predicted load-carrying capacity, minimum film thickness, center pressure and center temperature and the coefficient of friction were investigated. The role of the thermal effect was given.
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Kim, Hyung Kyu, Ju Sun Song, Young Ho Lee, Youn Ho Jung, and Jae Hoon Kim. "Prediction of Slip Displacement in Nuclear Fuel Fretting Wear." Key Engineering Materials 297-300 (November 2005): 1365–70. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.1365.
Повний текст джерелаАнотація:
Slipping characteristic on the contacts between the tubes and the supports is investigated to study the fretting wear of a vibratory tube. Tests were carried out to simulate the vibration of the fuel rods supported by the springs and dimples. A tube was forced to vibrate with 30Hz. The supporting condition was varied artificially: positive contact force or gap existence. During the tube vibration, amplitudes were measured continuously in the vicinity of the supports. Simple equations were derived to evaluate the slip displacement on the contacts. As a result, it was found that the supporting condition affected the vibration characteristic near the contacts. In the positive contact condition, the phase difference of the vibration signals at both sides of the contact was 180 degrees. It is altered in the gap condition and the higher frequency components than 30Hz appeared. The severer wear in the case of the gap existence is discussed with the evaluated slip distance per cycle.
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Matsuki, Kaoru. "Vibration-type contact detection sensor." Journal of the Acoustical Society of America 114, no. 4 (2003): 1713. http://dx.doi.org/10.1121/1.1627515.
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Alphin, M. S., J. Paul Chandra Kumar, and B. Jain A. R. Tony. "Biomechanical Response of the Human Foot Model Exposed to Vibrations: A Finite Element Analysis." Journal of Biomaterials and Tissue Engineering 11, no. 11 (November 1, 2021): 2097–108. http://dx.doi.org/10.1166/jbt.2021.2748.
Повний текст джерелаАнотація:
Prolonged exposure to mechanical vibration has been associated with many musculoskeletal, vascular and sensorineural disorders of the foot from simple Plantar fasciitis and Achilles Tendonitis to complex ones as Tarsal tunnel syndrome (TTS) and Vibration white feet/toes. Foot-transmitted vibrations (FTV) are exposed to the occupants using vibrating equipment’s or standing on vibrating platforms. Prolonged exposure to foot-transmitted vibrations (FTV) can lead to syndromes like vibration white feet/toes may result in tingling sensation, blanching of the toes and even numbness in the feet and toes. A multi-layered two dimensional, plane strain finite element model is developed from the actual cross-section of the human foot to study the stresses and strains developed in the skin and soft tissues. The foot is assumed to be in contact with a steel plate, mimicking the interaction between the foot and the work platform. The skin and the subcutaneous tissue are considered as hyperelastic and viscoelastic. The effects of loading in the form of displacements and the frequency of sinusoidal vibration on a time-dependent stress/strain distribution at various depths in the subcutaneous tissue of the foot are investigated. The simulations indicate that lower frequency vibrations penetrate deep into the subcutaneous tissue while higher frequencies are concentrated in the outer skin layer. The present biomechanical model may serve as a valuable tool to study the response of foot of those who work on a vibrating platform.
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Tamer, Aykut, Andrea Zanoni, Alessandro Cocco, and Pierangelo Masarati. "A Generalized Index for the Assessment of Helicopter Pilot Vibration Exposure." Vibration 4, no. 1 (February 20, 2021): 133–50. http://dx.doi.org/10.3390/vibration4010012.
Повний текст джерелаАнотація:
Helicopters are known to exhibit higher vibratory levels compared to fixed-wing aircraft. The consequences of vibrations depend on the affected helicopter component or subject. Specifically, pilots are in contact with several parts of the helicopter; vibrations can spoil the pilot-vehicle interaction. To evaluate the effects of vibration exposure on pilots, comfort levels resulting from whole-body vibration are computed. However, specific body parts and organs, e.g., hands, feet, and eyes are also adversely affected, with undesirable effects on piloting quality. Therefore, a detailed assessment is necessary for a more accurate estimation of pilot vibration exposure when comparing different configurations, tracking changes during design, and determining the safety of the flight envelope. A generalized assessment is presented by considering vibrations at the seat surface, hand-grip of controls, eyes, and feet. The suggested vibration measure includes comfort, handling, feet-contact, and vision in a single formulation. It is illustrated by coupling a high-fidelity biodynamic model of the pilot to a helicopter aeroservoelastic model in a comprehensive simulation environment. Using appropriate modeling techniques, vibration exposure of helicopter pilots could be evaluated during all stages of design, to achieve a more comfortable and safer flying environment.
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Meng, Wenjun, and Yao Wang. "Comprehensive analyses of the elasto-plastic oblique contact-impact with vibration response." Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 233, no. 2 (October 3, 2018): 441–54. http://dx.doi.org/10.1177/1464419318801732.
Повний текст джерелаАнотація:
Contact-impact between different surfaces is a ubiquitous phenomenon especially in the mechanical systems. Previous work of authors indicated that the effect of longitudinal and/or transverse vibration response during the motion and dynamic modeling cannot be neglected for the elasto-plastic contact-impact events. In this study, further analyses were performed to characterize the contribution of longitudinal and transverse vibration responses during the elasto-plastic oblique contact-impact, and the formula to calculate the influence factor of vibration, ξ, was proposed based on the contact force with different vibrations during the impact. The momentum theorem and assumed mode method were used to develop the equations of motion of a flexible bar with a solid flat surface. Simulation results were compared with experimental results reported in the literature to verify the accuracy of the established model. The tangential and normal velocities of the contact point after the impact were compared with the simulations for different vibration cases, and the comparison between the simulations and the experimental results had yield encourage results. For different elasto-plastic materials, three critical initial impact angles had been found from the simulation to determine whether the flexible bar slides or sticks the flat surface. Although considering the effect of vibration response during the motion and dynamic modeling is very significant, increasing the number of shape functions did not effect the result significantly. The longitudinal and transverse vibration responses were found to effect the normal and tangential velocities of the contact point after the impact, respectively. Moreover, it had been shown that for the oblique contact-impact with sliding, considering the response of longitudinal and transverse vibration at the same time is more reasonable than other cases, which also reveals that, in this case, there is a good agreement between the simulation and experimental results. Besides, the mathematical expression on the influence factor of vibration depending on the initial velocity also had been obtained by a numerical analysis. This work can provide useful insights for dynamic modeling of complex multi-body systems during the contact-impact.
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GAWĘDZKI, Wacław, and Jerzy TARNOWSKI. "A STUDY OF THE INFLUENCE OF FRICTION FORCES ON THE TRANSMISSION OF SOIL VIBRATION ON GAS PIPELINES." Tribologia 272, no. 2 (April 30, 2017): 49–58. http://dx.doi.org/10.5604/01.3001.0010.6272.
Повний текст джерелаАнотація:
The article presents the influence of friction force values during the contact of a gas pipeline with sand pack on the transmission of soil vibrations on a tested pipe section. Field experiments were carried out on standard gas pipeline insulations subjected to dynamic interactions. The load sources comprised artificially generated soil vibrations with an impulsive character. Within the course of experiments, soil and pipe vibration acceleration signals were registered for different values of friction forces in its contact with the soil. The value of friction forces being a variable parameter during experiments were applied by the change of values of the tension static force of the gas pipeline section. The analysis of the registered soil and pipe vibration acceleration signals were conducted based on the time-domain signal decomposition method, Hilbert-Huang Transform (HHT). This method enables one to decompose the non-stationary vibration acceleration signal into narrowband components. For each component, a course of instantaneous values for frequency and amplitude was specified. The dependence of the pipe vibration acceleration amplitude on the pipe tensile force and friction force of the pipe in the contact with the soil was demonstrated.
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Hao, Wu, Chen Ping, Liu Yang, and Ma Tianshou. "Effect of Axial Vibration on Sliding Frictional Force between Shale and 45 Steel." Shock and Vibration 2018 (2018): 1–13. http://dx.doi.org/10.1155/2018/4179312.
Повний текст джерелаАнотація:
Activating drill string vibration is an effective means to mitigate the excessive drag encountered during drilling complex-structure wells. However, the Coulomb model cannot describe the sliding friction behavior between drill string and borehole rock with imposed axial vibrations. To solve this problem, a specially designed experimental setup was utilized to investigate the characteristics of axial vibrating-sliding coupling friction. The results indicate that when vibration velocity is greater than sliding velocity, axial vibration can significantly reduce friction force between contact surfaces. Its friction reduction mechanism embodies not only the changes of instantaneous friction force, but also friction coefficient. Meanwhile, a friction coupling model was established based on the Hertz contact theory and Dahl model. The corresponding computational program was developed in Matlab/Simulink environment. The calculation results are in good agreement with the experimental results, verifying the validity of the present method. Furthermore, to overcome the shortcoming of Dahl model, a dynamic friction coefficient model was proposed to evaluate the friction-reducing effect of axial vibration using dimensional analysis method. The model parameters under different lubrication conditions were retrieved through inverse calculation with experimental data. This method provides a new solution for evaluating the friction-reducing effect of hydraulic oscillator and optimizing its placement.
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Kupchenko, S. S., and D. P. Hess. "Mechanical Contact Frequency Response Measurements." Journal of Tribology 122, no. 4 (June 22, 2000): 828–33. http://dx.doi.org/10.1115/1.1314601.
Повний текст джерелаАнотація:
This paper presents friction frequency response measurements taken from a planar steel contact subjected to controlled random broadband normal vibration. Data are included from both dry and various lubricated contact conditions under different vibration input levels and different sliding velocities. Frequency response data for dry contacts are found to have nearly steady magnitude and negligible phase lag over a relatively wide range of frequencies. This suggests a coefficient of friction, independent of frequency but dependent on levels of normal acceleration and sliding velocity, may adequately define the dry contact frequency response. The frequency response data for lubricated contacts are mixed. For example, with MoS2 grease the frequency response may adequately be defined by a constant, as with dry conditions. However, frequency response data for contacts with pure mineral oils, mineral oils with additives, and lithium grease are found to be dependent on frequency. [S0742-4787(11)00101-9]
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Shi, Zhifeng, Jing Liu, and Shaojiang Dong. "A numerical study of the contact and vibration characteristics of a roller bearing with a surface crack." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 234, no. 4 (January 30, 2020): 549–63. http://dx.doi.org/10.1177/1464420720903075.
Повний текст джерелаАнотація:
Roller bearings are key parts in different machineries. As one of the major incipient failure models in the bearings, the surface crack will be enlarged to be a large spalling failure. Moreover, the abrupt changes in the contact characteristics caused by the crack zone would produce unacceptable impulses, which can affect the bearing vibrations. Thus, a study of the contact characteristics and vibrations of the bearings including the surface crack could be conducive for the incipient fault monitoring methods. To overcome this issue, a finite element model is proposed to obtain the influences of the depth and slope angle of a surface crack on the contact characteristics in a roller bearing. The relationships between the contact characteristics (contact deformation, width and stiffness) and crack sizes (depth and slope angle) are established. To study the influences of the surface crack sizes on the bearing vibrations, a dynamic model of the roller bearing considering the surface crack is also proposed. An experiment is introduced to verify the proposed method. It seems that the crack depth and slope angle can greatly affect the contact and vibration characteristics of the bearing. This study provides a helpful numerical approach for understanding the contact and vibration characteristics of roller bearings with various surface cracks.
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Löwe, Albrecht, Marek Hauptmann, André Hofmann, and Jens-Peter Majschak. "Temperature development of cardboard in contact with high-frequency vibrating metal surfaces." BioResources 14, no. 2 (March 28, 2019): 3975–90. http://dx.doi.org/10.15376/biores.14.2.3975-3990.
Повний текст джерелаАнотація:
The heating of cardboard was studied when it is in contact with ultrasonic sonotrodes, whose vibrations were orientated parallel and perpendicular to the material surface. The parameters that were varied included the contact pressure on the sonotrode, vibration amplitude, and moisture content of the material. It was shown that there was a major decrease in the contact pressure shortly after the beginning of the experiment when the gap between the sonotrode and anvil was kept constant and thus a decrease in the temperature gradient of the material occurred. With parallel vibration, the material heated up from the sonotrode side, whereas heating started from the center of the material in the case of vertical vibration. This suggested that in cases of vertical vibration, heat is mostly generated by internal dissipation, and in cases of parallel vibration, heat is generated by friction losses on the surface. Furthermore, the results revealed the influence of the parameters on the initial temperature gradient, the maximum temperature, and the moisture content of the material.
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Ono, Kyosuke, Hiroshi Yamamura, and Takaaki Mizokoshi. "Computer Analysis of the Dynamic Contact Behavior and Tracking Characteristics of a Single-Degree-of-Freedom Slider Model for a Contact Recording Head." Journal of Tribology 117, no. 1 (January 1, 1995): 124–29. http://dx.doi.org/10.1115/1.2830586.
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This paper presents a new theoretical approach to the dynamic contact behavior and tracking characteristics of a contact slider that is one of the candidates of head design for future high density magnetic recording disk storages. A slider and its suspension are modeled as a single-degree-of-freedom vibration system. The disk surface is assumed to have a harmonic wavy roughness with linear contact stiffness and damping. From the computer simulation of the time history of the slider motion after dropping from the initial height of 10 nm, it is found that the contact vibration of the slider can attenuate and finally track on the wavy disk surface in a low waviness frequency range. As the waviness frequency increases, however, the slider cannot stay on the disk surface and comes to exhibit a variety of contact vibrations, such as sub- and super-harmonic resonance responses and finally comes to exhibit non-periodic vibration. It is also found that, among design parameters, the slider load to mass ratio and contact damping can greatly increase the surface waviness frequency and amplitude for which the stable tracking of a contact slider is possible.
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Keogh, P. S., and M. O. T. Cole. "Rotor vibration with auxiliary bearing contact in magnetic bearing systems Part 1: Synchronous dynamics." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 217, no. 4 (April 1, 2003): 377–92. http://dx.doi.org/10.1243/095440603321509676.
Повний текст джерелаАнотація:
Magnetic bearing systems incorporate auxiliary bearings to prevent physical interaction between rotor and stator laminations. Rotor/auxiliary bearing contacts may occur when a magnetic bearing still retains a full control capability. To actively return the rotor to a non-contacting state it is essential to determine the manner in which contact events affect the rotor vibration signals used for position control. An analytical procedure is used to assess the nature of rotor contact modes under idealized contacts. Non-linearities arising from contact and magnetic bearing forces are then included in simulation studies involving rigid and flexible rotors to predict rotor response and evaluate rotor synchronous vibration components. An experimental flexible rotor/magnetic bearing facility is also used to validate the predictions. It is shown that changes in synchronous vibration amplitude and phase induced by contact events causes existing controllers to be ineffective in attenuating rotor displacements. These findings are used in Part 2 of the paper as a foundation for the design of new controllers that are able to recover rotor position control under a range of contact cases.
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Kartal, Mehmet E., Daniel M. Mulvihill, David Nowell, and Dawid A. Hills. "Measurement of Tangential Contact Stiffness in Frictional Contacts: The Effect of Normal Pressure." Applied Mechanics and Materials 70 (August 2011): 321–26. http://dx.doi.org/10.4028/www.scientific.net/amm.70.321.
Повний текст джерелаАнотація:
The tangential contact stiffness of frictional interfaces affects both the vibration response and structural integrity of structures comprising frictional joints. Vibration and structural response of monolithic structures can be predicted very accurately; however, when assemblies of components involve frictional interfaces, additional damping and compliance are present due to these interfaces. These features make it more challenging to predict the vibration characteristics of assemblies with the same degree of accuracy as can be achieved for single components. If these interface properties can be determined, it should then be possible to significantly enhance current models of the vibration of engineering assemblies. Measurements of both force and displacement in the tangential direction are obtained from a series of in-line fretting tests involving flat pads with rounded corners clamped against the flat surface of a specimen which is oscillated by a hydraulic tensile testing machine. In order to measure the local displacement field very close to the contact interface, the digital image correlation (DIC) method is employed. The effect of normal contact pressure on tangential contact stiffness is investigated. Multiple experiments with the same parameters show good repeatability given the number of variables involved.
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Xu, Junguo, Hiromitsu Tokisue, Hideaki Tanaka, and Masaaki Matsumoto. "Contact Vibration of Micro-Textured Sliders." Journal of Tribology 124, no. 2 (June 26, 2001): 281–87. http://dx.doi.org/10.1115/1.1398290.
Повний текст джерелаАнотація:
We have formed a micro-texture on a pico-slider’s air-bearing surface to reduce the vibration when the slider comes into contact with the disk. The contact between slider and disk was controlled by adjusting the ‘interference height.’ Our measurements show that, at a giving interference height there is a significant less vibration in the textured slider. This lower amplitude of vibration is attributed to the lower friction force, which is in turn due to the smaller area of contact. We have also introduced the concept of interference area and found that it provides a good explanation of measured vibration.
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Wang, Jiqiang. "Active Control of Contact Force for a Pantograph-Catenary System." Shock and Vibration 2016 (2016): 1–7. http://dx.doi.org/10.1155/2016/2735297.
Повний текст джерелаАнотація:
The performance of the high speed trains depends critically on the quality of the contact in the pantograph-catenary interaction. Maintaining a constant contact force needs taking special measures and one of the methods is to utilize active control to optimize the contact force. A number of active control methods have been proposed in the past decade. However, the primary objective of these methods has been to reduce the variation of the contact force in the pantograph-catenary system, ignoring the effects of locomotive vibrations on pantograph-catenary dynamics. Motivated by the problems in active control of vibration in large scale structures, the author has developed a geometric framework specifically targeting the remote vibration suppression problem based only on local control action. It is the intention of the paper to demonstrate its potential in the active control of the pantograph-catenary interaction, aiming to minimize the variation of the contact force while simultaneously suppressing the vibration disturbance from the train. A numerical study is provided through the application to a simplified pantograph-catenary model.
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Yue, M. G. "Belt Vibration Considering Moving Contact and Parametric Excitation." Journal of Mechanical Design 115, no. 4 (December 1, 1993): 1024–30. http://dx.doi.org/10.1115/1.2919251.
Повний текст джерелаАнотація:
The contacting point between belt and pulley is not fixed but moves along the pulley during vibration and that influences on the free span length of the belt. The concept vibrating length is introduced and that will affect the dynamic behavior of the belt. Parametric excitation can occur through periodic variations in belt tension and speed arising from loading of the pulleys by belt-driven accessories and from engines in automotive applications. Violent oscillations develop and resonance will occur when the frequency of excitation is close to twice or three times the natural frequency for varying tension and speed case, respectively.
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Dai, Junjie, Chin-Yin Chen, Renfeng Zhu, Guilin Yang, Chongchong Wang, and Shaoping Bai. "Suppress Vibration on Robotic Polishing with Impedance Matching." Actuators 10, no. 3 (March 14, 2021): 59. http://dx.doi.org/10.3390/act10030059.
Повний текст джерелаАнотація:
Installing force-controlled end-effectors on the end of industrial robots has become the mainstream method for robot force control. Additionally, during the polishing process, contact force stability has an important impact on polishing quality. However, due to the difference between the robot structure and the force-controlled end-effector, in the polishing operation, direct force control will have impact during the transition from noncontact to contact between the tool and the workpiece. Although impedance control can solve this problem, industrial robots still produce vibrations with high inertia and low stiffness. Therefore, this research proposes an impedance matching control strategy based on traditional direct force control and impedance control methods to improve this problem. This method’s primary purpose is to avoid force vibration in the contact phase and maintain force–tracking performance during the dynamic tracking phase. Simulation and experimental results show that this method can smoothly track the contact force and reduce vibration compared with traditional force control and impedance control.
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Goldman, P., and A. Muszynska. "Chaotic Behavior of Rotor/Stator Systems With Rubs." Journal of Engineering for Gas Turbines and Power 116, no. 3 (July 1, 1994): 692–701. http://dx.doi.org/10.1115/1.2906875.
Повний текст джерелаАнотація:
This paper outlines the dynamic behavior of externally excited rotor/stator systems with occasional, partial rubbing conditions. The observed phenomena have one major source of a strong nonlinearity: transition from no contact to contact state between mechanical elements, one of which is rotating, resulting in variable stiffness and damping, impacting, and intermittent involvement of friction. A new model for such a transition (impact) is developed. In case of the contact between rotating and stationary elements, it correlates the local radial and tangential (“super ball”) effects with global behavior of the system. The results of numerical simulations of a simple rotor/stator system based on that model are presented in the form of bifurcation diagrams, rotor lateral vibration time-base waves, and orbits. The vibrational behavior of the system considered is characterized by orderly harmonic and subharmonic responses, as well as by chaotic vibrations. A new result is obtained in case of heavy rub of an anisotropically supported rotor. The system exhibits an additional subharmonic regime of vibration due to the stiffness asymmetry. The correspondence between numerical simulation of that effect and previously obtained experimental data supports the adequacy of the new model of impact.
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Zhao, Wei, Liang-Liang Li, and Di Zhang. "Study on vibration characteristics of damping blade with snubber and shroud based on fractal theory." Thermal Science 20, suppl. 3 (2016): 887–94. http://dx.doi.org/10.2298/tsci160201205z.
Повний текст джерелаАнотація:
Snubber and shroud have been widely adopted in steam turbine last stage blades to decrease the vibration stress. The contact surfaces between snubber and shroud own obviously fractal geometry characteristics. Based on fractal geometry theory and finite element nonlinear vibration theory, the fractal friction model that describes friction damping contact could be accurately established. In this paper, the contact fractal elements are set up and the nonlinear vibration response characteristics of a long steam turbine last stage blade with snubber and shroud are calculated. The results show that, with the increase of shroud normal force, the resonant amplitude of the blade experiences a decreasing period followed by an increasing period while the modal damping ratio increases first and then decreases when there is only shroud contact. The regulations are similar when there are both shroud and snubber contacts. The resonant frequency increases until the normal contact forces increase to some degree.
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Li, Hua, Zhen Yin, and Zheng Li. "Study on the Properties of New Ultrasonic Vibration Internal Grinding System." Key Engineering Materials 416 (September 2009): 142–48. http://dx.doi.org/10.4028/www.scientific.net/kem.416.142.
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Based on the FEM, the properties of the vibrator and the shaft in new ultrasonic vibration internal grinding system were studied in this paper. The design method of new ultrasonic vibration internal grinding (UVG) system by using rotary non-contact transmission device was proposed according to the influence of the sleeve length and thickness to ultrasonic vibration shaft. Experiments about the vibrator，the shaft and the ultrasonic vibration internal grinding system were studied by using PSV-400 Laser scanning vibrometer, and the consistency between the new ultrasonic vibration internal grinding prototype and theoretical design was confirmed.
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Lin, Jau-Wen, and M. D. Bryant. "Reductions in Wear Rate of Carbon Samples Sliding Against Wavy Copper Surfaces." Journal of Tribology 118, no. 1 (January 1, 1996): 116–24. http://dx.doi.org/10.1115/1.2837065.
Повний текст джерелаАнотація:
Wear rates (μgm/s) versus rotor speed for carbon samples sliding against smooth and wavy copper rotors (250 μm thick copper sheets were attached to smooth and wavy steel and polycarbonate backings) were identical at some speeds, but at other speeds wear rates for the wavy rotors were almost half those of the smooth rotors. Slider vibrations (periodic, with period set by rotation) perpendicular to the sliding surface were measured and Fourier analyzed. Comparison of vibration spectral amplitudes to spectral amplitudes derived from surface profiles identified vibration modes dynamically enhanced by surface waviness on the wavy rotor. At speeds where wear rates on the wavy rotor were most reduced, amplitudes of certain modes in the vibration spectrum were most enhanced. For all these cases, the product of mode number times speed was nearly constant, suggesting resonance. Contact forces and contact voltage drop (due to a mA current flowing from slider to rotor) were measured and plotted versus time during all experiments. Friction coefficients rapidly varied between 0.1 and 0.4, but averaged 0.2. Traces of friction coefficient versus time for both wavy and smooth rotors were similar, even when wear rates plunged on the wavy rotor. There were no large jumps in the contact voltage drop data, suggesting that the slider never disconnected from any of the rotors. Photoelastic visualizations (Bryant and Lin, 1993) of slider-rotor interfaces revealed concentrated contact on the smooth rotors, but none on the wavy rotors. The absence (induced by vibration) of concentrated contact may have caused differences in wear rates. Appreciable reductions (up to 50 percent) in wear rate are possible by adding small surface waves to a rotor that induce micro-vibrations of the slider-spring-rotor contact system. The effect appears most pronounced at resonance.
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Yakimova, Natalya L., Vladimir A. Pankov, Aleksandr V. Lizarev, Viktor S. Rukavishnikov, Marina V. Kuleshova, Elena V. Katamanova, Evgeny A. Titov, and Dina V. Rusanova. "Neurophysiological and morphological effects in the post-exposure vibration period during experimental modeling." Russian Journal of Occupational Health and Industrial Ecology, no. 5 (May 31, 2019): 284–90. http://dx.doi.org/10.31089/1026-9428-2019-59-5-284-290.
Повний текст джерелаАнотація:
Introduction. Vibration disease continues to occupy one of the leading places in the structure of professional pathology. In workers after the termination of contact with vibration generalization and progression of violations in an organism is noted. The pathogenetic mechanisms of the progredient course of disturbances in the nervous system in the post-contact period of vibration exposure remain insufficiently studied.The aim of the study was to test an experimental model of vibration exposure to assess the neurophysiological and morphological effects of vibration in rats in the dynamics of the post-contact period.Materials and methods. The work was performed on 168 white male outbred rats aged 3 months weighing 180–260 g. The vibration effect was carried out on a 40 Hz vibrating table for 60 days 5 times a week for 4 hours a day. Examination of animals was performed after the end of the physical factor, on the 30th, 60th and 120th day of the post-contact period. To assess the long-term neurophysiological and morphofunctional effects of vibration in rats, we used indicators of behavioral reactions, bioelectric activity of the somatosensory zone of the cerebral cortex, somatosensory and visual evoked potentials, parameters of muscle response, morphological parameters of nervous tissue.Results. In the dynamics of the post-contact period observed the preservation of violations of tentatively research, motor and emotional components of behavior. In the Central nervous system instability of activity of rhythms of an electroencephalogram, decrease in amplitude of visual evoked potentials, lengthening of latency of somatosensory evoked potentials, decrease in total number of normal neurons and astroglia is established. In the peripheral nervous system remained changes in indicators: increasing duration and latency, reducing the amplitude of the neuromuscular response.Conclusions: The experimental model allows us to study the long-term neurophysiological and morphological effects of vibration on the body. The formation and preservation of changes in behavioral activity, neurophysiological and morphological effects of vibration from the 30th to the 120th day of the post-contact period were confirmed.
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Wagner, Samuel, Ahmad Alkasimi, and Anh-Vu Pham. "Detecting the Presence of Intrusive Drilling in Secure Transport Containers Using Non-Contact Millimeter-Wave Radar." Sensors 22, no. 7 (April 1, 2022): 2718. http://dx.doi.org/10.3390/s22072718.
Повний текст джерелаАнотація:
We employ a 77–81 GHz frequency-modulated continuous-wave (FMCW) millimeter-wave radar to sense anomalous vibrations during vehicle transport at highway speeds for the first time. Secure metallic containers can be breached during transport by means of drilling into their sidewalls but detecting a drilling signature is difficult because the large vibrations of transport drown out the small vibrations of drilling. For the first time, we demonstrate that it is possible to use a non-contact millimeter-wave radar sensor to detect this micron-scale intrusive drilling while highway-speed vehicle movement shakes the container. With the millimeter-wave radar monitoring the microdoppler signature of the container’s vibrating walls, we create a novel signal-processing pipeline consisting of range–angle tracking, time–frequency analysis, horizontal stripe image convolution, and principal component analysis to create a robust and powerful detection statistic to alarm if drilling is present. To support this pipeline, we develop a statistical model combining the vibrating container and the random vibrations induced by vehicle movement to explore the robustness of the sensor’s detection capabilities. The presented results strongly support the inclusion of a millimeter-wave radar vibration sensor into a transport security system.
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Abd Alsamieh, Mohamed. "Numerical investigation of elastohydrodynamic contacts subjected to harmonic load variation." Industrial Lubrication and Tribology 71, no. 6 (August 12, 2019): 832–41. http://dx.doi.org/10.1108/ilt-12-2018-0461.
Повний текст джерелаАнотація:
Purpose The purpose of this paper is to study the behavior of elastohydrodynamic contacts subjected to forced harmonic vibrations including the effect of changing various working parameters such as frequency, load amplitude and entrainment speed. Design/methodology/approach The time-dependent Reynolds equation is solved using the Newton–Raphson technique. The film thickness and pressure distribution are obtained at every time step by simultaneous solution of the Reynolds equation and film thickness equation including elastic deformation. Findings The frequency of vibration, load amplitude and entrainment speed are directly related to the film thickness perturbation, which is formed during load increasing phase of the cycle. The film thickness formed during load increasing phase is larger than that formed during load decreasing phase with larger deviation at a higher frequency or load amplitude and vice versa for lower frequency or load amplitude. The entrainment speed of the contact has an opposite effect to that of the frequency of vibration or load amplitude. Originality/value Physical explanations for the behavior of elastohydrodynamic contact subjected to forced harmonic vibration are presented in this paper for various working parameters of frequency, load amplitude and entrainment speed.
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Ono, Kyosuke, and Kan Takahashi. "Analysis of Bouncing Vibrations of a 2-DOF Tripad Contact Slider Model With Air Bearing Pads Over a Harmonic Wavy Disk Surface." Journal of Tribology 121, no. 4 (October 1, 1999): 939–47. http://dx.doi.org/10.1115/1.2834159.
Повний текст джерелаАнотація:
In this study, the authors numerically analyzed the bouncing vibrations of a two-degree-of-freedom (2-DOF) model of a tripad contact slider with air bearing pads over a harmonic wavy disk surface. The general features of bouncing vibrations were elucidated in regard to the modal characteristics of a 2-DOF vibration system and design parameters such as contact stiffness, contact damping, air hearing stiffness, the rear to front air bearing stiffness ratio, static contact force and the coefficient of friction. The design of a contact slider was discussed in terms of tracking ability and wear durability. In addition, two sample designs of a perfect contact slider with sufficient wear durability were also presented.
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Sun, Ke Xue, Xian Jun Li, Man Li, Qing Yun Yan, Xie Feng Cheng, and Hao Zheng. "Study on Non-Contact Optical Vibration Senor." Applied Mechanics and Materials 433-435 (October 2013): 233–36. http://dx.doi.org/10.4028/www.scientific.net/amm.433-435.233.
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The vibration measurement is one of the new application in the optical sensor. This paper studies a new non-contact optical vibration sensor, and implements the Optical fiber vibration sensor based on FPGA. The totally available measurement range arrived over 300um, and the accuracy of 0.1 um can be obtained . This fiber optic vibration sensor has a low cost, good reliability, and high accuracy measurements.
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Bryja, Danuta, and Wojciech Chojnacki. "Two-way Hertzian spring in numerical analysis of coupled train-track system vibrations." Transportation Overview - Przeglad Komunikacyjny 2019, no. 11 (November 1, 2019): 1–11. http://dx.doi.org/10.35117/a_eng_19_11_01.
Повний текст джерелаАнотація:
The paper presents and compares two methods for simulation the train-track system vibrations, differing in the wheel-rail contact model used. In the first method, two-way Hertzian spring is used, in the second – a non-deformable constraint. In both methods, a flat computational model is assumed, consisting of an Euler-Bernoulli beam resting on a Winkler-type elastic foundation with damping and a set of rail vehicles modeled by dynamic systems with ten degrees of freedom. The results of numerical analysis are presented, in order to determine an influence of the contact constraints’ deformability on the vibration simulations. It is found that the replacement of non-deformable contact constraints by two-way Hertzian springs has no significant effect on track vibration simulations and has a little effect on vibration simulations of vehicle body and bogie. The developed simulation method can be used for numerical studies of the phenomenon of instantaneous detachments of wheels from rails, after minor modifications directed to introduce one-way Hertzian springs (i.e. not carrying tensile forces) being a more accurate contact model.
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Sabri, M., Ahmad Kamal Ariffin, and Mohd Jailani Mohd Nor. "Free Vibration of Tire Road Contact." Key Engineering Materials 462-463 (January 2011): 843–48. http://dx.doi.org/10.4028/www.scientific.net/kem.462-463.843.
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In this paper, a simulation procedure for tread patch to the road under consideration of contact effects is introduced. In particular, the treadband has been treated as an infinite tensioned beam resting on an elastic foundation. A contact model specially suited for the contact pairing rubber and rough road is developed. The main objective is here to predict the vibration generated from a system mentioned above by locating harmonic point forces representing the exitation of treadband at the contact patch. The simulations are carried out by means of the Finite Element Method in a structure vibration of tire. Exemplary simulation results are presented for 3D models of tire tread block and road. This model can be used as a tire design guide for selecting parameters which produce the minimum noise radiation.
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REN, W. "Contact Vibration Characteristic of Electromagnetic Relay." IEICE Transactions on Electronics E89-C, no. 8 (August 1, 2006): 1177–81. http://dx.doi.org/10.1093/ietele/e89-c.8.1177.
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Le Bot, A., E. Bou-Chakra, and G. Michon. "Dissipation of Vibration in Rough Contact." Tribology Letters 41, no. 1 (August 15, 2010): 47–53. http://dx.doi.org/10.1007/s11249-010-9683-4.
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Suda, Yoshihiro, and Hisanao Komine. "Contact vibration with high damping alloy." Wear 191, no. 1-2 (January 1996): 72–77. http://dx.doi.org/10.1016/0043-1648(95)06717-5.
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Jackson, Robert L., and Santosh Angadi. "Modelling of Lubricated Electrical Contacts." Lubricants 10, no. 3 (February 22, 2022): 32. http://dx.doi.org/10.3390/lubricants10030032.
Повний текст джерелаАнотація:
Electrical contacts, although critically important for a wide range of applications, are susceptible to degradation due to fretting corrosion, especially when sliding and vibrations occur. To overcome fretting corrosion and sliding wear, lubricants are often used. However, the use of lubricants can cause other detrimental issues. Lubricants usually consist of non-conductive fluids such as hydrocarbons and fluorocarbons. Due to fluid dynamics, when sliding, vibration or other excitation occurs, these fluids can cause prolonged gaps between the conducting metal surfaces. Practically, this has been observed in data centers where vibrations due to technician maintenance or even earthquakes can occur. Depending on the viscosity and roughness of the surfaces, the time it takes these connector surfaces to return to solid conductive contact can be many seconds or longer. This work uses a novel theoretical model of the coupled fluid and solid mechanics between the rough metallic surfaces to evaluate these intermittent breaks in contact due to sliding. The influence of variation in lubricant properties, roughness, contact radius and contact force are considered by the model.
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Huntley, J. M., T. Tarvaz, M. D. Mantle, A. J. Sederman, L. F. Gladden, N. A. Sheikh, and R. D. Wildman. "Nuclear magnetic resonance measurements of velocity distributions in an ultrasonically vibrated granular bed." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372, no. 2015 (May 13, 2014): 20130185. http://dx.doi.org/10.1098/rsta.2013.0185.
Повний текст джерелаАнотація:
We report the results of nuclear magnetic resonance imaging experiments on granular beds of mustard grains fluidized by vertical vibration at ultrasonic frequencies. The variation of both granular temperature and packing fraction with height was measured within the three-dimensional cell for a range of vibration frequencies, amplitudes and numbers of grains. Small increases in vibration frequency were found—contrary to the predictions of classical ‘hard-sphere’ expressions for the energy flux through a vibrating boundary—to result in dramatic reductions in granular temperature. Numerical simulations of the grain–wall interactions, using experimentally determined Hertzian contact stiffness coefficients, showed that energy flux drops significantly as the vibration period approaches the grain–wall contact time. The experiments thus demonstrate the need for new models for ‘soft-sphere’ boundary conditions at ultrasonic frequencies.