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Auteur : Grafiati
Publié le 8 juin 2024

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1

Kailasham, R., Rajarshi Chakrabarti et J. Ravi Prakash. « Rouse model with fluctuating internal friction ». Journal of Rheology 65, no 5 (septembre 2021) : 903–23. http://dx.doi.org/10.1122/8.0000255.

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2

Kul’kov, V. G. « Diffusion model of internal friction in nanocrystalline materials ». Technical Physics 52, no 3 (mars 2007) : 333–38. http://dx.doi.org/10.1134/s1063784207030085.

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3

Sakaguchi, Shuji. « Analysis of Internal Friction on Silicon Nitride with Visco-Elastic Model ». Key Engineering Materials 317-318 (août 2006) : 429–32. http://dx.doi.org/10.4028/www.scientific.net/kem.317-318.429.

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Temperature dependence of internal friction on silicon nitride ceramics with yttria and alumina sintering aids was discussed using 4-elements visco-elastic model. It is known that the internal friction of this ceramic material shows a characteristic peak at around 1040 oC and an exponential increase over 1200 oC. This temperature dependence of internal friction was well approximated with using parallel Maxwell model. The parameters for this model and the relaxation time on this model were obtained. The relaxation time was very short, compared to the transient creep deformation of this ceramics. The analyzed results on internal friction could not be related with the creep deformation.
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4

Ozaki, Shingo, Takeru Matsuura et Satoru Maegawa. « Rate-, state-, and pressure-dependent friction model based on the elastoplastic theory ». Friction 8, no 4 (4 janvier 2020) : 768–83. http://dx.doi.org/10.1007/s40544-019-0321-3.

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AbstractAdhesion is one of essences with respect to rubber friction because the magnitude of the friction force is closely related to the magnitude of adhesion on a real contact area. However, the real contact area during sliding depends on the state and history of the contact surface. Therefore, the friction force occasionally exhibits rate-, state-, and pressure dependency. In this study, to rationally describe friction and simulate boundary value problems, a rate-, state-, and pressure-dependent friction model based on the elastoplastic theory was formulated. First, the evolution law for the friction coefficient was prescribed. Next, a nonlinear sliding surface (frictional criterion) was adopted, and several other evolution laws for internal state variables were prescribed. Subsequently, the typical response characteristics of the proposed friction model were demonstrated, and its validity was verified by comparing the obtained results with those of experiments conducted considering the contact surface between a rough rubber hemisphere and smooth acrylic plate.
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5

Monieta, Jan. « Problems of Friction Force Measurement between Cylindrical Outdoor and Internal Slide Parts ». Multidisciplinary Aspects of Production Engineering 1, no 1 (1 septembre 2018) : 19–25. http://dx.doi.org/10.2478/mape-2018-0003.

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Abstract The article presents the determination of an exemplary measure in the assessment of the technical state of sets of mechanical objects at the stage of manufacture, use and maintenance. The technical state of the assemblies is influenced by the quality of the friction-cooperating elements, the quality of basic functions, the surroundings and the diameter clearance of kinematic node components. Energy wasted to overcome the frictional resistance is a significant part of the energy supplied, which is why current friction losses are minimized. The article includes analysis of the phenomena occurring in the cylindrical pairs in the presence of static and kinetic friction. The many factors affecting the course and values of friction force between cylindrical elements performing relative reciprocating motion have been indicated. The subject of the article is the method of measuring the friction force between a fixed and movable cylindrical element of the mechanical object. The gradual increase of the friction force component takes place by means of easily accessible force. The results of experimental tests of the friction force in different laboratory conditions under are also included. The effect on the measured friction force was investigated: of friction elements geometry and the surface condition after manufacture and/or operation. Scatter results of static friction force depending on the geometry and surface state can be significant. Examples of surface state images are shown. A friction force model was also developed depending on factors affecting its value.
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6

Inaguma, Y. « Friction torque characteristics of an internal gear pump ». Proceedings of the Institution of Mechanical Engineers, Part C : Journal of Mechanical Engineering Science 225, no 6 (11 avril 2011) : 1523–34. http://dx.doi.org/10.1177/0954406211399659.

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This paper describes the influence of pump operating conditions, such as operating pressures, pump speeds, and oil temperatures, on the friction torque characteristics of internal gear pumps for automobiles. Additionally, it presents a new mathematical model reflecting the influence of the oil temperature on the friction torque. In an internal gear pump, the friction torque was affected by oil temperature as well as operating pressure and pump speed. When the operating pressure was high, the influence of oil temperature on friction torque at a pump speed of less than 1000 r/min was contrary to that at a pump speed of greater than 1000 r/min. It was considered that the friction torque is fundamentally composed of three components: the component dependent on the operating pressure, dependent on the pump speed, and independent of both the operating pressure and the pump speed. However, the component dependent on the operating pressure was affected significantly by not only the pump speed but also the oil temperature. In addition, another factor besides the viscosity of the oil existed in the component dependent on the pump speed. A mathematical model for the friction torque characteristic of the internal gear pump was newly established by adding factors including the oil temperature to the Wilson’s model. The new model was able to represent with accuracy the experimental friction torque characteristic in the internal gear pump under various pump operating conditions.
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7

Aleksandrova, N. I. « MODEL OF BLOCK MEDIA TAKING INTO ACCOUNT INTERNAL FRICTION ». Mechanics of Solids 57, no 3 (juin 2022) : 496–507. http://dx.doi.org/10.3103/s0025654422030025.

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8

Babakov, V. A. « Model of plastic body with internal friction and dilatancy ». Soviet Mining Science 23, no 3 (mai 1987) : 191–98. http://dx.doi.org/10.1007/bf02500809.

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9

Ren, W. « Inverse relaxation-model and relation to recovery internal friction ». Colloid & ; Polymer Science 270, no 10 (octobre 1992) : 990–98. http://dx.doi.org/10.1007/bf00655968.

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10

Giorgio, Ivan, et Daria Scerrato. « Multi-scale concrete model with rate-dependent internal friction ». European Journal of Environmental and Civil Engineering 21, no 7-8 (29 février 2016) : 821–39. http://dx.doi.org/10.1080/19648189.2016.1144539.

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11

Kê, T. S., et B. L. Cheng. « Mechanical model of the bamboo boundary internal friction peak ». Physica Status Solidi (a) 115, no 1 (16 septembre 1989) : 119–24. http://dx.doi.org/10.1002/pssa.2211150110.

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12

Ahmed Ali, Mohamed Kamal, Hou Xianjun, Richard Fiifi Turkson et Muhammad Ezzat. « An analytical study of tribological parameters between piston ring and cylinder liner in internal combustion engines ». Proceedings of the Institution of Mechanical Engineers, Part K : Journal of Multi-body Dynamics 230, no 4 (3 août 2016) : 329–49. http://dx.doi.org/10.1177/1464419315605922.

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This paper presents a model to study the effect of piston ring dynamics on basic tribological parameters that affect the performance of internal combustion engines by using dynamics analysis software (AVL Excite Designer). The paramount tribological parameters include friction force, frictional power losses, and oil film thickness of piston ring assembly. The piston and rings assembly is one of the highest mechanically loaded components in engines. Relevant literature reports that the piston ring assembly accounts for 40% to 50% of the frictional losses, making it imperative for the piston ring dynamics to be understood thoroughly. This analytical study of the piston ring dynamics describes the significant correlation between the tribological parameters of piston and rings assembly and the performance of engines. The model was able to predict the effects of engine speed and oil viscosity on asperity and hydrodynamic friction forces, power losses, oil film thickness and lube oil consumption. This model of mixed film lubrication of piston rings is based on the hydrodynamic action described by Reynolds equation and dry contact action as described by the Greenwood–Tripp rough surface asperity contact model. The results in the current analysis demonstrated that engine speed and oil viscosity had a remarkable effect on oil film thickness and hydrodynamic friction between the rings and cylinder liner. Hence, the mixed lubrication model, which unifies the lubricant flow under different ring–liner gaps, is needed via the balance between the hydrodynamic and boundary lubrication modes to obtain minimum friction between rings and liner and to ultimately help in improving the performance of engines.
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13

Rill, Georg, et Matthias Schuderer. « A Second-Order Dynamic Friction Model Compared to Commercial Stick–Slip Models ». Modelling 4, no 3 (11 août 2023) : 366–81. http://dx.doi.org/10.3390/modelling4030021.

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Friction has long been an important issue in multibody dynamics. Static friction models apply appropriate regularization techniques to convert the stick inequality and the non-smooth stick–slip transition of Coulomb’s approach into a continuous and smooth function of the sliding velocity. However, a regularized friction force is not able to maintain long-term stick. That is why dynamic friction models were developed in recent decades. The friction force depends herein not only on the sliding velocity but also on internal states. The probably best-known representative, the LuGre friction model, is based on a fictitious bristle but realizes a too-simple approximation. The recently published second-order dynamic friction model describes the dynamics of a fictitious bristle more accurately. It is based on a regularized friction force characteristic, which is continuous and smooth but can maintain long-term stick due to an appropriate shift in the regularization. Its performance is compared here to stick–slip friction models, developed and launched not long ago by commercial multibody software packages. The results obtained by a virtual friction test-bench and by a more practical festoon cable system are very promising. Thus, the second-order dynamic friction model may serve not only as an alternative to the LuGre model but also to commercial stick–slip models.
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14

Hsu, Tze-Chi, et Chi-Chia Liu. « “Internal Variables” Effects in Punch Friction Characterization ». Journal of Tribology 120, no 3 (1 juillet 1998) : 510–16. http://dx.doi.org/10.1115/1.2834580.

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Despite the complexity and importance of friction, most current simulations of metal-forming processes use relatively simple friction models such as the Amontons-Coulomb constant friction coefficient. It has been pointed out that simple models are not capable of capturing the influence of process variables such as geometry, speed, and surface topography on friction. A realistic friction model should include the internal variables such as lubricant film thickness, tooling roughness, and workpiece roughness. In the present research, the punch friction tests which use a tensile strip experiment to simulate the stretching of sheet over a punch corner radius in a typical draw die are used to measure the effects of internal variables on friction in various stretching conditions. The measured friction coefficients increase with lower stretching speed and decrease if lubricant is applied at the interface between workpiece and cylindrical pin. Theoretical friction modeling, which includes the different lubrication regimes range from thick film, thin film, mixed regime and boundary regime, are presented. Numerical methods have been used to solve the governing differential equations with the known initial boundary conditions obtained from the experiments. The theoretical prediction shows the same trend as the experimental measurements.
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15

Ledbetter, Hassel, Christopher Fortunko et Paul Heyliger. « Elastic constants and internal friction of polycrystalline copper ». Journal of Materials Research 10, no 6 (juin 1995) : 1352–53. http://dx.doi.org/10.1557/jmr.1995.1352.

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Using ultrasonic-resonance spectroscopy (URS), we measured the elastic constant C and companion internal friction Q−1 of isotropic polycrystalline copper. The annealed material was 0.9999 pure with equiaxed heavily twinned grains averaging about 75 μm diameter. The URS method offers the principal advantage of point contact or loose coupling, thus there was no contribution from a transducer-specimen bond and only small contributions from transducers and fixture. A second advantage is one measurement for all elastic constants and all associated internal frictions. The C's agree with established values. The Q−1's are much lower than pulse-echo-method values. Comparison of measured Q−1 with the Koehler-Granato-Lücke model permits estimating an effective dislocation-loop length. Q−1 (shear) exceeds Q−1 (longitudinal) by a factor of about 1.5.
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16

Duffaut, Kenneth, Martin Landrø et Roger Sollie. « Using Mindlin theory to model friction-dependent shear modulus in granular media ». GEOPHYSICS 75, no 3 (mai 2010) : E143—E152. http://dx.doi.org/10.1190/1.3429998.

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An explicit expression for the effective shear modulus of a random packing of identical spheres is derived as a function of Mindlin’s tangential stiffness with interparticle contact friction. The motivation behind the approach is to incorporate the effect of intergrain friction to predict velocities in unconsolidated sands. The Mindlin friction term, allowing partial slip across the contact area between pairs of spheres, can be viewed as a parameter accounting for the growing macroscopic intergrain friction in sands as burial progresses. Hence, both moduli and velocities will gradually increase as the compressional- to shear-wave velocity ratio [Formula: see text] or Poisson’s ratio [Formula: see text] decreases. An estimate of effective elastic constants in particular shear modulus can be obtained for a spherical grain pack with an arbitrary frictional behavior ranging between two special contact boundary conditions representing infinite friction and zero friction. The proposedmodel predicts a nonlinear transition between the two special grain-contact conditions when compared to previously published linear relationships. Comparison of elastic properties, i.e., dynamic shear-modulus predictions assuming zero contact friction with experimental data on loose glass bead and sand samples undergoing hydrostatic compression, appears to match reasonably well at low confining stress (less than [Formula: see text]) but deviates gradually as stress increases. It is advocated that the increasing effective internal frictional resistance of the experimental core samples control both the frictional attenuation mechanism in loose grain packs under low confining stress for strain amplitudes typical of seismic waves (less than [Formula: see text]) and the higher stress-velocity sensitivity. Circumstantial evidence of this is found in publications describing both laboratory attenuation analysis and consolidation experiments on granular materials with different degrees of competence or static shear strength.
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17

Demenkov, N. P., I. A. Mochalov et D. M. Tran. « Fuzzy Phase Trajectories in Hemispherical Resonator Gyroscopes ». Herald of the Bauman Moscow State Technical University. Series Instrument Engineering, no 1 (134) (mars 2021) : 78–101. http://dx.doi.org/10.18698/0236-3933-2021-1-78-101.

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The paper considers elementary fuzzy oscillator models represented by hard and fuzzy second-order differential equations with hard and fuzzy initial conditions. Linear models describe wave processes in ring resonators of hemispherical resonator gyroscopes.We show that in the case 1 (a hard model with fuzzy initial conditions), when there is no internal friction (model 1), phase trajectories appear as a fuzzy centre shaped as an elliptical ring. When internal friction is present (model 2), phase trajectories appear as a fuzzy focus shaped as a circular logarithmic spiral. In the case 2, for a fuzzy hemispherical resonator gyroscope model with hard initial conditions, when there is no internal friction (model 1), a representative point of a fuzzy phase trajectory does not stop or increase its oscillations with time, meaning that the system is asymptotically unstable, while for the model 2 the origin singularity is a fuzzy stable focus. In the case 3, for a fuzzy hemispherical resonator gyroscope model with fuzzy initial conditions, when there is no internal friction (model 1), there is a fuzzy asymptotic instability in the model 1 of a hemispherical resonator gyroscope, while in the presence of internal friction (model 2), the phase trajectory is also a function of time and controls the asymptotic stability of the fuzzy model 2 of a hemispherical resonator gyroscope. Asymptotic stability is determined for all cases and models
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18

Koo, R. C. H., J. S. H. Kwan, C. Lam, G. R. Goodwin, C. E. Choi, C. W. W. Ng, J. Yiu, K. K. S. Ho et W. K. Pun. « Back-analysis of geophysical flows using three-dimensional runout model ». Canadian Geotechnical Journal 55, no 8 (août 2018) : 1081–94. http://dx.doi.org/10.1139/cgj-2016-0578.

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Predicting the mobility and delineating the extent of geophysical flows remains a challenge for engineers. The accuracy of predictions hinges on the reliability of input parameters of runout models. Currently, limited field data for landslide case histories are available for benchmarking the performance of runout models. Key rheological parameters, such as the equivalent internal friction angle, cannot be measured directly using laboratory experiments and must instead be determined through back-analyses. A series of dynamic back-analyses was carried out for notable landslide case histories in Hong Kong, accounting for the effects of pore-water pressure on the equivalent internal friction angle, using a three-dimensional finite-element mobility model. The recorded and simulated run-out distances, as well as lateral spreading, were compared. Results reveal that the back-analysed equivalent internal friction angles resulting from open-hillslope failures and from channelized geophysical flows range from 25° to 30° and 15° to 20°, respectively. This is attributed to incised geophysical flow channels having an elevated water head and higher degree of saturation compared to open-hillside slope surfaces, wherein the induced elevated pore-water pressure profoundly lowers the equivalent internal friction angle. The back-calculated values may be useful for finite-element-based design of mitigation measures.
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19

Tee, J. W., S. H. Hamdan et W. W. F. Chong. « Predictive tool for frictional performance of piston ring-pack/liner conjunction ». Journal of Mechanical Engineering and Sciences 13, no 3 (27 septembre 2019) : 5513–27. http://dx.doi.org/10.15282/jmes.13.3.2019.19.0445.

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Fundamental understanding of piston ring-pack lubrication is essential in reducing engine friction. This is because a substantial portion of engine frictional losses come from piston-ring assembly. Hence, this study investigates the tribological impact of different piston ring profiles towards engine in-cylinder friction. Mathematical models are derived from Reynolds equation by using Reynolds’ boundary conditions to generate the contact pressure distribution along the complete piston ring-pack/liner conjunction. The predicted minimum film thickness is then used to predict the friction generated between the piston ring-pack and the engine cylinder liner. The engine in-cylinder friction is predicted using Greenwood and Williamson’s rough surface contact model. The model considers both the boundary friction and the viscous friction components. These mathematical models are integrated to simulate the total engine in-cylinder friction originating from the studied piston ring-pack for a complete engine cycle. The predicted minimum film thickness and frictional properties from the current models are shown to correlate reasonably with the published data. Hence, the proposed mathematical approach prepares a simplistic platform in predicting frictional losses of piston ring-pack/liner conjunction, allowing for an improved fundamental understanding of the parasitic losses in an internal combustion engine.
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20

Petrova, L. P., N. M. Ignatenko et A. A. Bulgakova. « Features of Internal Friction in Ferromagnets ». Izvestiya of Altai State University, no 4(126) (9 septembre 2022) : 44–47. http://dx.doi.org/10.14258/izvasu(2022)4-06.

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Based on the application of two model descriptions proposed by A.A. Rodionov, it is shown that description of internal friction of magnetic materials in various magnetoelastic states subjected to alternating elastic fields should consider not only the magnetic component but also the non-magnetic component along with its changes in the presence of the magnetic field. The magnetic component of internal friction is associated with the movement of domain boundaries (DG) (hysteresis attenuation (amplitude-dependent — irreversible displacements of DG)) and amplitude-independent (reversible displacements of DG without separation from the fixing points) with reversible and irreversible rotations of spontaneous magnetization vectors. The non-magnetic component is determined by several components, all of which can dominate over a particular region of frequencies, temperatures, external influences, and initial structural states of the system under study. It depends on the type of defects, their concentrations, and spatial and orientation distribution in crystals. The paper proposes an approach to separate the internal friction in magnetic materials into magnetic and non-magnetic components which can be extended to materials with domains and domain boundaries including antiferromagnets, ferroelectrics, ferromagnets, etc. This approach leads to an expansion of the previously used ideas about the method of separating the magnetic component from the recorded spectrum of internal friction.
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21

Teng, Yun Nan, Xiao Peng Li, Hui Ma et Bang Chun Wen. « Study on Vibration Friction Mechanism and Vibration Response Analysis Based on Vibration Compaction System ». Applied Mechanics and Materials 16-19 (octobre 2009) : 84–87. http://dx.doi.org/10.4028/www.scientific.net/amm.16-19.84.

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Friction of two objects or inner friction of loose materials in vibration case can present different characteristics that are different from conventional conditions. The practice shows that vibration can reduce friction coefficient and friction force between two objects, lighten abrasion of objects, reduce energy consumption and increase greatly working efficiency. The mechanism of friction in vibration case was revealed in this paper. The Curve of vibration intensity to internal friction of soil was given. The investigation indicated that friction converts from static to sliding in vibration case. The internal friction is reduced with frequency increasing and there exists the optimal vibration intensity to make internal friction least. At last, nonlinear dynamic model of vibration friction system about compaction equipment was established and its resonance response was obtained.
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22

Takahashi, Eisuke, et Osamu Kaneko. « Data-Driven Internal Model Controller for Mechanical Systems with Friction ». IFAC-PapersOnLine 54, no 14 (2021) : 233–38. http://dx.doi.org/10.1016/j.ifacol.2021.10.358.

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23

Costantini, G., et F. Marchesoni. « Internal Friction Peaks at Low Temperatures : a Kink Model Analysis ». Le Journal de Physique IV 06, no C8 (décembre 1996) : C8–187—C8–190. http://dx.doi.org/10.1051/jp4:1996838.

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24

Fugmann, S., et I. M. Sokolov. « Internal friction and mode relaxation in a simple chain model ». Journal of Chemical Physics 131, no 23 (21 décembre 2009) : 235104. http://dx.doi.org/10.1063/1.3274678.

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25

Gołoś, Krzysztof. « A model of the hysteresis loop caused by internal friction ». International Journal of Pressure Vessels and Piping 54, no 3 (janvier 1993) : 429–34. http://dx.doi.org/10.1016/0308-0161(93)90015-l.

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26

Benchaita, M. T., et F. E. Lockwood. « Reliable model of lubricant-related friction in internal combustion engines ». Lubrication Science 5, no 4 (juillet 1993) : 259–81. http://dx.doi.org/10.1002/ls.3010050402.

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27

Ettouney, O. M., et K. A. Stelson. « An Approximate Model to Calculate Foldover and Strains During Cold Upsetting of Cylinders Part II : Use of the Foldover Model to Estimate Friction ». Journal of Engineering for Industry 112, no 3 (1 août 1990) : 267–71. http://dx.doi.org/10.1115/1.2899585.

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This paper addresses an approach to calculate the friction coefficient during nonuniform compression of cylinders. The approach combines new friction-calibration curves (prepared using the finite-element analysis) that relate friction to workpiece shape and the foldover model from Part I. Foldover in upsetting is used in the same way that the change in internal diameter is used in the ring test to determine friction. However, the new approach has the advantage that measurements are taken directly from the workpiece. Comparisons of friction values calculated from the ring test and the new approach showed good agreement.
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28

Кульков, В. Г., et А. А. Сыщиков. « Внутреннее трение на границах зерен, содержащих протяженные поры ». Письма в журнал технической физики 45, no 3 (2019) : 23. http://dx.doi.org/10.21883/pjtf.2019.03.47267.17580.

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AbstractA model of internal friction at a grain boundary containing equidistant parallel cylindrical pores is presented. Variable shear stress induces a mutual displacement of the interfacial regions matched at the segments between pores depending on their position. The values of scattered energy at each segment and total internal friction are determined. The temperature dependence of the internal friction has a form of a wide peak.
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29

Dorofeyev, O. « Determinative ratios of a rheological model of a discrete medium with a variable angle of internal friction ». Problems of Tribology 25, no 1 (26 mars 2020) : 69–77. http://dx.doi.org/10.31891/2079-1372-2020-95-1-69-77.

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30

Alvarez, Luis, Jingang Yi, Roberto Horowitz et Luis Olmos. « Dynamic Friction Model-Based Tire-Road Friction Estimation and Emergency Braking Control ». Journal of Dynamic Systems, Measurement, and Control 127, no 1 (21 juin 2004) : 22–32. http://dx.doi.org/10.1115/1.1870036.

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An adaptive control scheme for emergency braking of vehicles is designed based on a LuGre dynamic model for the tire-road friction. The wheel angular speed and longitudinal vehicle acceleration information are used to design a fast convergence observer to estimate the vehicle velocity and the internal state of the friction model. The unknown parameters of the dynamic friction model are estimated through a parameter adaptation law. A Lyapunov-based state estimator and a stabilizing braking controller are designed to achieve near to maximum braking capability of the vehicle. Underestimation of the maximum friction coefficient, a very desirable feature from the perspective of safety, is guaranteed by a proper choice of adaptation gains and initial values of the estimated friction parameters.
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31

Kailasham, R., Rajarshi Chakrabarti et J. Ravi Prakash. « How important are fluctuations in the treatment of internal friction in polymers ? » Soft Matter 17, no 30 (2021) : 7133–57. http://dx.doi.org/10.1039/d1sm00613d.

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The Rouse model with internal friction (RIF) is shown with polymer kinetic theory (PKT) to pre-average internal friction and to neglect fluctuations, significantly affecting the model's prediction of properties at equilibrium and in shear flow.
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32

Vodička, Roman. « Comparing various influences on adhesive contact with friction ». Selected Scientific Papers - Journal of Civil Engineering 14, no 2 (1 décembre 2019) : 7–18. http://dx.doi.org/10.1515/sspjce-2019-0013.

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AbstractA general computational model covering many types of frictional contact interfaces between visco-elastic bodies is considered for some cases physically relevant in numerical analysis of contact in civil engineering structures. The relations between mechanical quantities and internal parameters of the model are illustrated in a couple of simplified examples including cohesive contact combined with Coulomb friction and/or interface plasticity. The computations are implemented a semi-implicit time discretisation, quadratic programming algorithms, and the boundary-element method.
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33

Kakar, Rajneesh. « Rheological model of Love wave propagation in viscoelastic layered media under gravity ». Multidiscipline Modeling in Materials and Structures 11, no 3 (12 octobre 2015) : 424–36. http://dx.doi.org/10.1108/mmms-01-2015-0003.

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Purpose – The purpose of this paper is to deal with the propagation of Love waves in inhomogeneous viscoelastic layer overlying a gravitational half-space. It has been observed velocity of Love waves depends on viscosity, gravity, inhomogeneity and initial stress of the layer. Design/methodology/approach – The dispersion relation for the Love wave in closed form is obtained with Whitaker’s function. Findings – The effect of various non-dimensional inhomogeneity factors, gravity factor and internal friction on the non-dimensional Love wave velocity has been shown graphically. The authors observed that the dispersion curve of Love wave increases as the inhomogeneity factor increases. It is seen that increment in gravity, inhomogeneity and internal friction decreases the damping phase velocity of Love waves but it is more prominent in case of internal friction. Originality/value – Surface plot of Love wave reveals that the velocity ratio increases with the increase of non-dimensional phase velocity and non-dimensional wave number. The above results may attract seismologists and geologists.
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34

Ding, Jiefa, Shijun Wang, Haoran Huang, Fengqian Pan, Yunxing Wu, Yanchang Gu et Yan Zhang. « Prediction Model of Residual Soil Shear Strength under Dry–Wet Cycles and Its Uncertainty ». Water 15, no 22 (10 novembre 2023) : 3931. http://dx.doi.org/10.3390/w15223931.

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Granite residual soil is widely distributed in Southeast Fujian. Large-scale engineering construction leads to the exposure of residual soil slopes to the natural environment. Affected by seasonal climate factors, the soil of slopes experiences a dry–wet cycle for a long time. The repeated changes in water content seriously affect the shear strength of soil, and then affect the stability of the slope. In order to explore the influence of the dry–wet cycle on the shear strength of granite residual soil in Fujian, an indoor dry–wet cycle simulation test was carried out for shallow granite residual soil on a slope in Fuzhou, and the relationship between water content, dry–wet cycle times, and the shear strength index, including the cohesion and internal friction angle of the granite residual soil, was discussed. The results show that when the number of dry–wet cycles is constant, the cohesion and internal friction angle of the granite residual soil decrease with an increase in water content. The relationship between the cohesion, internal friction angle, and water content can be described using a power function. Meanwhile, the fitting parameters of the power function are also a function of the number of wet and dry cycles. The prediction formulas of the cohesion and internal friction angle considering the number of dry–wet cycles and water content are established, and then the prediction formula of shear strength is obtained. The ratio of the predicted value of shear strength to the test value shall be within ±15%. An error transfer analysis based on the point estimation method shows that the overall uncertainty of the predicted value of shear strength caused by the combined uncertainty of the predicted value of cohesion and the internal friction angle and the single-variable uncertainty of the predicted value of shear strength caused only by the uncertainty of the predicted value of either the cohesion or internal friction angle increases first and then decreases with an increase in the number of dry–wet cycles. All increase with an increasing water content. The maximum standard deviation of the proposed shear strength prediction model of granite residual soil is less than 9%.
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Liu, Cheng, Yanjun Lu, Yongfang Zhang, Lujia Tang, Cheng Guo et Norbert Müller. « Investigation on the Frictional Performance of Surface Textured Ring-Deformed Liner Conjunction in Internal Combustion Engines ». Energies 12, no 14 (18 juillet 2019) : 2761. http://dx.doi.org/10.3390/en12142761.

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In internal combustion engines (ICEs), the frictional performance of ring-liner conjunction (RLC) has drawn special attention because it greatly affects the fuel efficiency of the engines. In recent years, surface texture (i.e., micro dimples or grooves) has emerged as a promising approach to improve the frictional performance of RLC. However, most current studies on surface textured RLC were conducted by assuming that the liner was ideally circular and the lubrication condition was either fully flooded or starved. In this study, to evaluate the frictional characteristics of an RLC with surface texture on the ring, a numerical model of lubrication is presented by considering the liner deformation, as well as the coexistence of the fully flooded and staved lubrication conditions in an engine cycle. On this basis, the frictional properties of a surface textured RLC are analyzed, and the impacts of the liner deformation and temperature on the friction-reducing effect of the surface texture are also evaluated. The results show that the surface texture on the ring can effectively reduce the power dissipation and friction dissipation of an RLC, and the reductions vary with the liner temperature and deformation. Large reductions in the power dissipation and friction dissipation of an RLC are obtained when the liner temperature is low or the liner deformation is small.
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36

Chichekin, I. V., et A. A. Shuranova. « Modeling the work of the automotive differential with internal friction in the system for calculating the multi body dynamics ». Izvestiya MGTU MAMI 15, no 4 (15 décembre 2021) : 73–82. http://dx.doi.org/10.31992/2074-0530-2021-50-4-73-82.

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The work is devoted to the operation of an automobile differential of suspended friction modeling in the system for calculating the dynamics of coupled bodies. The model was developed in the RecurDyn application for calculating the dynamics of rigid and deformable bodies from the FunctionBay company. The aim of the work is to develop a mathematical model of the differential with friction washers and to confirm the adequacy of its operation. The developed mathematical model of the differential is tested for the possibility of its subsequent use in modeling the transmission of a vehicle in the calculating the dynamics of coupled bodies system. In this work, a model of the differential has been created and described in detail. The model was used for the analysis of kinematics and dynamics. Methods of modeling a simple symmetric differential and a self-locking one are shown based on one mathematical model. The well-known analytical dependences describing the kinematic and force laws of the ratio of angular velocities and torques between the output links and the differential housing are given. A method for calculating and modeling the friction torque in the differential was selected and described. An equation describing the frictional moment in the differential is presented. A virtual test bench was developed and described. Afterwards it was used for differential operation simulation. Load modes that are equivalent to various driving conditions of a real automobile are selected, their quantitative parameters are given. In this work, the criteria for evaluating the performance of the differential model are selected. The results of modeling for all load modes are given. According to those results the adequacy of the developed mathematical model of the differential with friction washers is proved. The proposals on the use of the developed model are given.
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37

Zhang, Yanyan, Ziyuan Ma, Yan Feng, Ziyu Diao et Zhentao Liu. « The Effects of Ultra-Low Viscosity Engine Oil on Mechanical Efficiency and Fuel Economy ». Energies 14, no 8 (20 avril 2021) : 2320. http://dx.doi.org/10.3390/en14082320.

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The development of a sustainable powertrain requires improved thermal efficiency. Reducing frictional power losses through the use of ultra-low viscosity oil is one of the most effective and economical ways. To assess the potential for efficiency enhancement in a new generation of future engines using low-viscosity oils, a technical analysis was conducted based on numerical simulation and theoretical analysis. This study proposes a numerical method coupling the whole multi-dynamics model and lubrication model under mixed lubrication regimes. Then, load distribution was calculated numerically and verified experimentally. Finally, this paper compares the bearing load and frictional energy loss of the main bearings when using The Society of Automotive Engineers (SAE) 15W40 and SAE 0W20 oil. The results indicate that the application of ultralow-viscosity lubricant can reduce the hydraulic friction loss up to 24%, but the asperity friction loss would increase due to the reduction in load capacity. As a result, the design of a new generation of high efficiency internal combustion engines requires careful calculation and design to balance the trade-off relations between hydraulic friction and asperity friction.
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38

Drori, Israel, et Benson Honig. « A Process Model of Internal and External Legitimacy ». Organization Studies 34, no 3 (mars 2013) : 345–76. http://dx.doi.org/10.1177/0170840612467153.

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We report the results of a longitudinal case study depicting the relationship between internal and external legitimacy at Orion, an emergent creative professional firm. We address the following questions: How do different types of legitimacy emerge, and how do they interact to shape organizational evolution? Introducing a staged process model, we demonstrate that organizational legitimacy is a product of action, which is continually reproduced and reconstructed by members of an organization in concert with external legitimation activities. Internal and external legitimacy evolve through a process of emergence, validation, diffusion and consensus, sometimes recursively repeating the cycle when imbalances result in conflict and friction.
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39

KONG QING-PING et LI YONG. « A MODEL FOR LOW FREQUENCY INTERNAL FRICTION DUE TO EXTENDED DISLOCATIONS ». Acta Physica Sinica 37, no 7 (1988) : 1157. http://dx.doi.org/10.7498/aps.37.1157.

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40

Abramov, O. V., et V. A. Kuyumchyan. « Phenomenological model of microplastic deformation and amplitude dependence of internal friction ». Strength of Materials 21, no 6 (juin 1989) : 798–802. http://dx.doi.org/10.1007/bf01531400.

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41

Scerrato, Daria, Ivan Giorgio, Angela Madeo, Ali Limam et Felix Darve. « A simple non-linear model for internal friction in modified concrete ». International Journal of Engineering Science 80 (juillet 2014) : 136–52. http://dx.doi.org/10.1016/j.ijengsci.2014.02.021.

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42

TATIBOUËT, J., J. PEREZ et R. VASSOILLE. « HIGH TEMPERATURE INTERNAL FRICTION IN ICE Ih : A NEW DISLOCATION MODEL ». Le Journal de Physique Colloques 46, no C10 (décembre 1985) : C10–339—C10–342. http://dx.doi.org/10.1051/jphyscol:19851075.

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43

Monieta, Jan. « Method and a Device for Testing the Friction Force in Precision Pairs of Injection Apparatus of the Self-Ignition Engines ». Energies 15, no 19 (21 septembre 2022) : 6898. http://dx.doi.org/10.3390/en15196898.

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This article reviews the state of the knowledge and technology in the field of friction-loss measurements in internal combustion piston engines. The dependencies that describe the loss of energy in combustion engines and injection apparatus are presented. Currently, very little can be found in the literature on the study of frictional forces in injection apparatus, but mainly in the piston–cylinder group, so this work significantly fills that gap. The aim of this article is to construct a device and to develop a method for assessing the technical state of injector nozzles to minimize friction losses in internal combustion engines at the stages of evaluation, design, production and operation. This article presents a stand for determining the maximum friction forces due to gravity loading by water-jet control. This article also presents test results on the maximum friction force between a needle and a body of injector nozzles in piston combustion engines on a designed and purpose-built stand outside of the combustion engine. Various designs and injector nozzles are made from various types of alloy steel for marine and automotive piston internal combustion engines fueled with distillation or residual fuels, and are tested. The research concerned conventional elements for the injection apparatus as well as electronically controlled subsystems. Precision pairs of injection equipment are selected for the tests: new ones are employed after the storage period and operated in natural conditions. The elements dismantled from the internal combustion engines are tested in the presence of fuel or calibration oil of similar properties. The maximum static frictional forces under the hydrostatic loading are measured, alongside the parameters for the dynamic movement of the nozzle needles from bodies of the injector nozzle as time, speed, acceleration and dynamic force. The influence of the angular position of the needle in relation to the bodies of the precision pairs conventional internal combustion engines, the diametral clearance between the nozzle body and needle, and the surface conditions on the values of the maximum friction force are also presented. Errors in shape and position result in the uniqueness of the friction force at the mutual angular position of the needle in relation to the nozzle body, and the decrease in diametral clearance and deterioration of the surface state increase the friction losses. A model was elaborated of the influence of various factors on the value of the maximum friction force.
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44

Ciancio, Armando, Vincenzo Ciancio et Bruno Felice Filippo Flora. « A Fractional Rheological Model of Viscoanelastic Media ». Axioms 12, no 3 (27 février 2023) : 243. http://dx.doi.org/10.3390/axioms12030243.

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The mechanical behaviour of materials can be described by a phenomenological relationship that binds strain to stress, by the complex modulus function: M(ω), which represents the frequency response of the medium in which a transverse mechanical wave is propagated. From the experimental measurements of the internal friction obtained when varying the frequency of a transverse mechanical wave, the parameters that characterize the complex module are determined. The internal friction or loss tangent is bound to the dissipation of the specific mechanical energy. The non-equilibrium thermodynamics theory leads to a general description of irreversible phenomena such as relaxation and viscosity that can coexist in a material. Through the state variables introduced by Ciancio and Kluitenberg, and applying the fractional calculation due to a particular memory mechanism, a model of a viscoanelastic medium is obtained in good agreement with the experimental results.
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45

Kohta, Masushi, Shunji Yunoki et Junko Sugama. « Effect of prophylactic dressings to reduce pressure injuries : a polymer-based skin model ». Journal of Wound Care 33, Sup2 (1 février 2024) : S4—S9. http://dx.doi.org/10.12968/jowc.2024.33.sup2.s4.

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Objective: This study evaluated the effect of pressure injury (PI) prophylactic dressings used for patients at high risk of PI development to reduce friction, shear force and pressure, and their combined force, in an original polymer-based skin model. Method: A low-friction outer-layer hydrocolloid (LFH) dressing and a multilayered silicone foam (MSF) dressing were used. Before application, compression and friction properties were measured. Our original experimental model—the ‘simulated skin-shearing test’—consisted of: a weight; a polyurethane-based skin model containing a three-axis tactile sensor; dressings; a table covered with bedsheets; and a mechanical tester, by which the interface friction force, internal shear force and pressure were measured continuously during skin model movements. An estimated combined force generated by internal shear and pressure was represented as a vector. A model with no dressing was used as a control. Results: The LFH dressing had significantly higher compression strength versus the MSF dressing. In contrast, the dynamic coefficient of friction was lower for the LFH dressing versus the MSF dressing (p<0.05). In simulated skin-shearing test results, shear forces were 0.45N and 0.42N for LFH and MSF dressings, respectively, with no significant difference. The estimated combined force was lower for the MSF dressing compared with that of the LFH dressing and control. Conclusion: The shear force-reducing effect in the skin model was equivalent between the LFH and MSF dressings. However, the MSF dressing significantly reduced the force generated by a combination of internal shear force and pressure compared with the LFH dressing.
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46

Wang, Yaxiang, Jiawei Tian, Yan Liu, Bo Yang, Shan Liu, Lirong Yin et Wenfeng Zheng. « Adaptive Neural Network Control of Time Delay Teleoperation System Based on Model Approximation ». Sensors 21, no 22 (9 novembre 2021) : 7443. http://dx.doi.org/10.3390/s21227443.

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A bilateral neural network adaptive controller is designed for a class of teleoperation systems with constant time delay, external disturbance and internal friction. The stability of the teleoperation force feedback system with constant communication channel delay and nonlinear, complex, and uncertain constant time delay is guaranteed, and its tracking performance is improved. In the controller design process, the neural network method is used to approximate the system model, and the unknown internal friction and external disturbance of the system are estimated by the adaptive method, so as to avoid the influence of nonlinear uncertainties on the system.
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47

Bielak, Jacobo, Haydar Karaoglu et Ricardo Taborda. « Memory-efficient displacement-based internal friction for wave propagation simulation ». GEOPHYSICS 76, no 6 (novembre 2011) : T131—T145. http://dx.doi.org/10.1190/geo2011-0019.1.

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The characterization of anelastic losses due to material internal friction has become increasingly important in geophysical exploration and other seismological applications, as these losses greatly affect the amplitude and dispersion of seismic waves. Anelasticity is usually specified in terms of the material’s quality factor, [Formula: see text]. Different viscoelastic models have been used to represent [Formula: see text] as a function of frequency. Most of these models are defined in terms of stresses and strains as the primary variables. Thus, in three dimensions, a separate model needs to be associated with each of the six strain components. We introduce an internal friction model that uses, instead, displacements as primary variables. For a fiber, the proposed model consists of a set of three distinct elements in parallel with different relaxation mechanisms: namely, two elements that consist of a spring and a dashpot in series (Maxwell) and a third element that consists of a spring and a dashpot in parallel (Voigt). In addition to saving memory, this formulation is particularly suitable for finite-element schemes. The model exhibits an almost constant quality factor within the frequency range of interest, with a tolerance of 5% with respect to the target [Formula: see text] value, and provides a close approximation to the variation of the phase-velocity with frequency—as has been observed in empirical data. The extension of this model to 3D anelastic problems and its use in idealized cases, such as an infinite-space, a half-space, and a layered half-space, and the comparison of results with semi-analytical reference solutions obtained from theory and previous, similar studies, corroborates the validity of the proposed model for incorporating anelastic losses in wave propagation problems.
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48

Orjuela Abril, Sofia, Marlen Del Socorro Fonseca-Vigoya et Carlos Pardo García. « Study of the Cylinder Deactivation on Tribological Parameters and Emissions in an Internal Combustion Engine ». Lubricants 10, no 4 (7 avril 2022) : 60. http://dx.doi.org/10.3390/lubricants10040060.

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In the present investigation, a study is carried out using numerical simulation on the effects of cylinder deactivation on tribological parameters and emissions in an internal combustion engine. For the development of the research, a tribological model was used to predict the characteristics of the lubrication film, friction conditions, blow-by gas, and deformation of the piston rings. Additionally, the construction of a CFD model was carried out to describe the kinematic movement of the engine piston. The analysis of results allowed for the demonstration of the active cylinders presenting an increase of 21.53% and 7.65% in the pressure and temperature in the cylinder wall. Additionally, the active cylinders present a reduction of 11.33% in the minimum thickness of the lubrication film and an increase in the friction force due to asperities, which implies an increase of 33% in power losses due to friction. The implementation of technologies such as cylinder deactivation causes an increase in combustion gas leaks caused by the increase in pressure of the active cylinders. However, the use of this technology allows reducing 9.09%, 8.26%, and 7.41% in CO, HC, and NO emissions. Although the use of technologies such as cylinder deactivation allows significant fuel savings, it is necessary to consider the negative effects caused by this technology, such as the increase in combustion gas leaks and the increase in power loss by the greatest frictional forces.
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49

Yang, Lixin, et Xianmin Zhang. « An approximate internal model-based neural control for serial robots with multiple clearance joints ». Advances in Mechanical Engineering 10, no 12 (décembre 2018) : 168781401881232. http://dx.doi.org/10.1177/1687814018812320.

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A dynamic model of serial robots with multiple clearance joints is developed. The contact phenomenon in the clearance joint is modeled by a continuous dissipative Hertz contact theory, and the friction force is calculated based on the modified Coulomb’s friction law. A neural network method is employed to predict the dynamic response, which avoids the problem in solving the differential algebraic equations. An approximate internal model-based neural control method is proposed to control the undesired effects arising from the joint clearances. The validity of the proposed method is verified by simulation results.
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Novitskyi, Maksym, Yurii Novitskyi et Andrii Slipchuk. « THE POSSIBILITY OF USING STRUCTURAL DAMPING IN THE DESIGN OF A PREFABRICATED TURNING CUTTER TO REDUCE THE AMPLITUDE OF SELF-OSCILLATIONS IN THE PROCESS OF METAL CUTTING ». Ukrainian Journal of Mechanical Engineering and Materials Science 9, no 4 (2023) : 42–48. http://dx.doi.org/10.23939/ujmems2023.04.042.

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A mathematical model of four mass oscillating circuit cutting machine was developed and studied in this paper. The influence of the internal friction in the joints of structural elements on the machine tool vibration amplitude and details. Effective self-oscillation amplitude blanking tool is possible by choosing the optimal parameters of the tool body frictional connection with tool holders
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