Friction Force Distribution Research Articles

Можливості підвищення безпеки руху рейкових екіпажів з колесами, що незалежно обертаються

One of the promising ways to achieve high speed and smooth running of rail vehicles during stable movement in straight sections of the track and to improve the characteristics of fitting the vehicles in a curve is the use of independently rotating wheels in their running parts. Such undercarriages are already becoming quite widespread, for example, in urban rail transport vehicles. But independently rotating wheels can rotate in a wheel pair around a common axis with different angular velocities. It follows that during their movement, longitudinal creep forces do not arise, which form the controlling moment and center the wheel pair in the rail track. This can lead to increased angles of attack of the wheels on the rails, increased lateral forces and accelerated wear of the wheels and rails. In turn, this increases the tendency of vehicles with independently rotating wheels to derail by rolling the flange onto the head of the rail. 
 The accumulated global experience of operating similar vehicles confirms this. To overcome the mentioned disadvantages of independently rotating wheels, a number of various technical solutions have been proposed. Some of them relate to ensuring the given elastic-dissipative characteristic of the torsional articulation of the wheels in a wheel pair. A promising direction is the improvement of the characteristics of the connections of wheel pairs with the bogye and bogyes with the vehicle body, the use of mechatronic systems for controlling the position of the wheel pairs in the horizontal plane for their radial installation in curved sections of the track. In this work, attention is paid to the issue of the use in the design of independently rotating wheels of a perspective design scheme that allows independent rotation of the wheel's support surface and its guide surface (flange). The question of the effect of changing the design scheme of the wheel on the safety of movement due to the roll-in of the ridge on the rail head was considered. 
 The influence of a promising design scheme of a wheel in comparison with a traditional design scheme of a wheel on the safety of driving down a rails was investigated. The peculiarities of the distribution of frictional forces in the ridge contact during movement along the rails of the wheels of both design schemes are analyzed. For a wheel of a traditional design scheme, the module and the direction of the friction force vector in the ridge contact are uniquely determined by the geometric characteristics of the contact between the wheel and the rail and the angular speed of the wheel rotation. At the same time, when the wheel of the prospective design scheme moves, the direction and module of the friction force vector of the ridge on the rail also depend on the ratio of the angular velocities of rotation of the supporting surface of the wheel and its guiding surface (flange) around the common axis. The obtained results allow us to draw a conclusion about the expediency of using a promising design scheme in independently rotating wheels to increase the safety of movement of rail vehicles.

Numerical investigations on interactions between 2D/3D conical shock wave and axisymmetric boundary layer at Ma=2.2

Numerical simulation and analysis are carried out on interactions between a 2D/3D conical shock wave and an axisymmetric boundary layer with reference to the experiment by Kussoy et al. [AIAA J, 1980, 18(12): 1477–1487], in which the shock was generated by a 15° half-angle cone in a tube at 15° angle of attack (AOA). Based on the Reynolds-averaged Navier–Stokes equations and Menter's SST turbulence model, the present study uses the newly developed WENO3−PRM1,12 scheme and the PHengLEI CFD platform for the computations. First, computations are performed for the 3D interaction corresponding to the conditions of the experiment by Kussoy et al., and these are then extended to cases with AOA = 10° and 5° For comparison, 2D axisymmetric counterparts of the 3D interactions are investigated for cones coaxial with the tube and having half-cone angles of 27.35°, 24.81°, and 20.96° The shock wave structure, vortex structure, variable distributions, and wall separation topology of the interaction are computed. The results show that in 2D/3D interactions, a new Mach reflection-like event occurs and a Mach stem-like structure is generated above the front of the separation bubble, which differs from the model of Delery for 2D planar shock wave/boundary layer interaction. A new interaction model is established to describe this behavior. The relationship between the length of the circumferentially unseparated region in the tube and the AOA of the cone indicates the existence of a critical AOA at which the length is zero, and a prediction of this angle is obtained using an empirical fit, which is verified by computation. The occurrence of side overflow in the windward meridional plane is analyzed, and a quantitative knowledge is obtained. To further elucidate the characteristics of the 3D interaction, the scale and structure of the vortex and the pressure and friction force distributions are presented and compared with those of the 2D interaction.

Friction patterns guide actin network contraction

The shape of cells is the outcome of the balance of inner forces produced by the actomyosin network and the resistive forces produced by cell adhesion to their environment. The specific contributions of contractile, anchoring and friction forces to network deformation rate and orientation are difficult to disentangle in living cells where they influence each other. Here, we reconstituted contractile actomyosin networks in vitro to study specifically the role of the friction forces between the network and its anchoring substrate. To modulate the magnitude and spatial distribution of friction forces, we used glass or lipids surface micropatterning to control the initial shape of the network. We adapted the concentration of Nucleating Promoting Factor on each surface to induce the assembly of actin networks of similar densities and compare the deformation of the network toward the centroid of the pattern shape upon myosin-induced contraction. We found that actin network deformation was faster and more coordinated on lipid bilayers than on glass, showing the resistance of friction to network contraction. To further study the role of the spatial distribution of these friction forces, we designed heterogeneous micropatterns made of glass and lipids. The deformation upon contraction was no longer symmetric but biased toward the region of higher friction. Furthermore, we showed that the pattern of friction could robustly drive network contraction and dominate the contribution of asymmetric distributions of myosins. Therefore, we demonstrate that during contraction, both the active and resistive forces are essential to direct the actin network deformation.

Modelling of rolling-contact fatigue pitting phenomena by phase field method

The paper proposes a novel numerical framework for modelling of the pitting damage mechanism, based on the application of the three-layered residual control staggered phase-field algorithm. Proposed numerical framework can be applied to all contacting mechanical elements subjected to rolling contact fatigue, but in this paper, it is applied on gears. More precisely, gear teeth flanks subjected to the rolling-contact fatigue conditions are investigated, which consequently results in governing pitting mechanisms. Loading of the teeth flanks is imposed via moving load, with assumption of the full-film lubrication and pressure distribution according to the elastohydrodynamic lubrication theory, as well as Hertzian theory. The Coulomb's law is used to compute the friction force distribution. The numerical framework is embedded into finite element software ABAQUS via user subroutines. The validity of the proposed numerical scheme is tested by comparison to the examples from the literature. The main mechanisms of the pitting formation have been verified, i.e., surface- and subsurface-initiated pitting formation. Furthermore, an influence of the microstructure has been considered in the modelling of pitting phenomena. It has been demonstrated that the proposed numerical framework provides satisfactory results, and it is able to capture governing pitting mechanisms.

An approach to grid-to-rod fretting wear modeling using dynamic mortar contact

This article presents the development of a grid-to-rod fretting (GTRF) modeling methodology that utilizes dynamic mortar contact. We leverage a recently developed computational framework for modeling thermomechanical contact in dynamic simulations from the nuclear fuel performance code Bison. Usage of mortar contact ensures a smooth distribution of normal and frictional contact forces, displacements, and velocities on the contact interface, thus facilitating an accurate computation of wear. The integration within an advanced nuclear fuel performance code enables analysis of complex interactions between the fuel, cladding, and spacer grid. Such interactions include swelling, creep, fuel fragmentation, burnup, plenum pressure, and fission gas release. Our methodology is demonstrated via the modeling of two spacer grid geometries and the influence of fuel-cladding mechanical contact on the generation of fretting wear.

A combined experimental and analytical method to determine the EHL friction force distribution between rollers and outer raceway in a cylindrical roller bearing

Friction force is a crucial factor causing power loss and fatigue spalling of rolling element bearings. A combined experimental and analytical method is proposed to quantitatively determine the elastohydrodynamic lubrication (EHL) friction force distribution between rollers and outer raceway in a cylindrical roller bearing (CRB). An experimental system with the instrumented bearing and housing was developed for measuring radial load distribution and friction torque of bearings. A simplified model of friction force expressed by dimensionless speed, load, and material parameters was given. An inequality constrained optimization problem was established and solved by using an experimental data-driven learning algorithm for determining the uncertain parameters in the model. The effect of speed, load, and lubricant property on friction force and friction coefficient was discussed.

Pressure distribution in the drafting zone measured by film pressure sensors

Frictional force distribution in the drafting zone is a key factor to control the fiber movement during drafting, and hence to determine the quality of the drafted strands. The frictional force is usually expressed by pressure acting on the strand or fibers in the drafting zone. In order to investigate the pressure distribution in the drafting zone, a device was designed with a film pressure sensor, by which the pressure distribution in different drafting forms and drafting parameters was measured. The effects of drafting parameters, such as the linear density of the strand, roller settings, etc., on the pressure distribution were discussed.

Study on the Distribution of Frictional Forces on Z-yarn Continuous Implanted Preforms and Their Applications

To improve the quality and efficiency of Z-directional 3D preform forming, the Z-yarn frictional force distribution model of the preform and its wear mechanism were investigated. In this study, a tensile force measuring device was designed to measure the force required to replace the guide sleeve, which is equivalent to the Z-yarn frictional forces. The frictional force is proportional to the number of preform layers and is applied to the preform decreased from the corner, edge, sub-edge, and middle in order. A back propagation neural network model was established to predict the friction at different positions of the preform with different layers, and the error was within 1.9%. The wear of Z-yarn was studied at different frictional positions and after different times of successive implantation into the preform. The results showed that with an increase in the number of Z-yarn implantations and frictional forces, the amount of carbon fiber bundle hairiness gradually increased, and the tensile fracture strength damage of the fiber was increasingly affected by the frictional forces. In the corner position of the preform, when the number of implantations was 25, the fiber fracture strength decreased non-linearly and substantially; in order to avoid fiber fracturing in the implantation process, the Z-yarn needs to be replaced in time after 20–25 cycles of continuous implantation. This study solves the problem of difficulty in measuring the force required for individual replacements owing to the excessive number of guide sleeves, puts forward the relationship between fiber wear, preform position, and implantation times, solves the phenomenon of fracture in the preform during Z-direction fiber implantation, and realizes the continuous implantation of fibers.

Friction Force Distributions on Micro-Patterned Surfaces under Lubricated Condition

In this study, we characterized the lubrication properties of two different nanostripe patterns comprising micro- and nanogrooves. The friction coefficient distribution was measured using a convex lens as a slider. For the zigzag pattern, friction force depended on the scanning lines when the slider slid along the direction of the apex of the zigzag grooves. For the straight groove pattern, though the friction coefficients were found to periodically undulate along the scan lines with a period equal to the unit pattern, the phase of the undulation was affected by the scanning line. Numerical calculations were conducted to calculate the oil film thickness, and we discussed the relation between the distribution of the friction force and the oil film thickness.

An Integrated Tread Beam/LuGre Tire-Road Friction Model

Tire-road interactions modeling is critical for the development of enhanced safety of modern vehicles. This paper presents an integrated tread beam/LuGre tire-road contact friction model and an iterative force computation method to predict frictional forces at any given wheel slips. Steady-state friction force distribution is computed by solving the LuGre dynamic friction model with a power series method. A tread beam model is then used to capture the variation of the normal load on the tire-road contact patch and compute the load-shift impact under vehicle maneuvers. The use of the tread beam model bridges the local friction force estimates by the LuGre model with the global contact behavior under tire dynamics conditions. Numerical results are compared with those obtained by the finite element method and the comparison confirms the integrated modeling approach. This work provides an enabling practical tool for computing tire-road friction forces under dynamic conditions.

Small‐Sized Deformable Shear Sensor Array for Direct Monitoring of Quantitative Shear Distribution

AbstractAn array of shear sensors is essential in tactile sensation as well as the pressure sensors. Surprisingly, however, the shear sensor array is rarely investigated mainly due to the structural complexity to measure the horizontal forces from various directions and also due to the mechanical softness required for preventing the slip of an object. Here, an array of small shear sensors that can recognize both shear force and shear rotational angle is fabricated. All the device components are made of deformable materials to acquire the softness of the sensor. This work presents a novel design for the small‐sized shear sensor array and the required material conditions for the design. By using an ion gel as the capacitive sensing material, the shear sensor array shows high sensitivity and excellent reliability under repeated shear forces. This work demonstrates playing computer game with the shear sensor and sensing the frictional force distribution, which is possible through the recognition of multiple shear stimuli and spatial shear distribution (force, rotational angle) when static/dynamic shear forces are simultaneously applied from various directions.

Study on the accelerated-point distribution of floating fibers in the drafting zone

The motion of floating fibers in the drafting zone has a significant effect on the sliver quality after drafting. In this study, the distribution of the accelerated point of floating fibers in the drafting area was simulated based on the distribution of fibers and frictional forces during the drafting process. The simulated results denoted that the acceleration distribution of the floating fibers was more concentrated and closer to the front roller as the drafting ratio increases. The distributions of accelerated points of the floating fibers became more and more decentralized and further away from the front roller as the gauge length grew when the other parameters remained constant. In the simulation, the frictional forces of the other floating fibers moving at high velocity and low velocity and the actual contact relationships of fibers in the drafting zone were taken into consideration. Moreover, whether the fiber lengths are identical or not, the simulated accelerated-point distributions of the floating fibers were demonstrated to conform more to the actual values compared to other models. Hence, the developed model can offer effective reference from the point of view of the distribution of accelerated points in order to realize the simulation of roller drafting.

A Study of Improving Running Safety of a Railway Wagon with an Independently Rotating Wheel’s Flange

The main objective of this work is to study the possibilities of improving the running safety of a railway wagon with independently rotating wheels by changing their design symmetrically mounted on an axle. The article provides a discussion of the advantages and disadvantages of using the independently rotating wheels in a bogie of railway wagons. Their increasing tendency of derailment is described. The influence of a perspective constructive scheme (PKS) of railway wagon wheels in comparison with a traditional constructive scheme (TKS) on running safety due to the climbing of a wheel flange onto a rail is studied. This work introduces a conceptual proposition of a technical solution to railway wheel design as well as containing the results of both analytical calculations as well as the results of multibody simulations. A PKS wheel design for a railway wheel is designed that allows independent rotation of its tread surface and of a guiding surface (i.e., of a flange) to each other, which both are arranged symmetrically on a wheelset axle. It brings features of the distribution of friction forces generating in a flange contact when the wheel with a TKS and with PKS move on a rail. It is possible to conclude with the help of the obtained results that the use of wheels with the PKS is advisable for the reduction of the running resistance as well as for increasing the running safety of railway wagons.

Tire Wear Reduction Based on an Extended Multibody Rear Axle Model

To analyze the influence of suspension kinematics on tire wear, detailed simulation models are required. In this study, a non-linear, flexible multibody model of a rear axle system is built up in the simulation software MSC Adams/View. The physical model comprises the suspension kinematics, compliance, and dynamics as well as the non-linear behavior of the tire using the FTire model. FTire is chosen because it has a separate tire tread model to compute the contact pressure and friction force distribution in the tire contact patch. To build up the simulation model, a large amount of data is needed. Bushings, spring, and damper characteristics are modeled based on measurements. For the structural components (e.g., control arms), reverse engineering techniques are used. The components are 3D-scanned, reworked, and included as a modal reduced finite element (FE)-model using component mode synthesis by Craig–Bampton. Finally, the suspension model is validated by comparing the simulated kinematic and compliance characteristics to experimental results. To investigate the interaction of suspension kinematics and tire wear, straight line driving events, such as acceleration, driving with constant velocity, and deceleration, are simulated with different setups of wheel suspension kinematics. The influence of the setups on the resulting friction work between tire and road is examined, and an exemplarily calculation of tire wear based on a validated FTire tire model is carried out. The results demonstrate, on the one hand, that the chosen concept of elasto-kinematic axle leads to a relatively good match with experimental results and, on the other hand, that there are significant possibilities to reduce tire wear by adjusting the suspension kinematics.

Improvement of methods for pile foundations design on settlement

Introduction. The paper describes a new approach for pile foundations design. The system of mechanical impacts is described in a new way for the pile foundation design based on the foundation settlement taking into account the distribution of elastic deformation of the pile material in a soil base.
 
 Materials and methods. In contrast to the existing approaches to determining the pile settlement due to elastic deformations of the pile material, all impacts in the form of load from the pile cap, friction forces on the pile lateral surface and the actual reaction at the pile tip are taken into account differentially according to the principle of forces independence. The new design equation is proposed to describe the distribution of friction forces on the lateral surface of the pile. The friction forces in a homogeneous soil of the base are represented as a parabolic distribution function, and not as a linearly increasing one, as established in the standards.
 
 Results. As a result, the equation is obtained for a pile settlement design due to the elastic strain of pile material. An example of calculating the pile settlement according to the proposed method and comparing the results with existing methods is given. Negative friction forces from the reaction of the soil under the lower end of the pile increase the value of the elastic deformation of the pile shaft.
 
 Conclusions. The refined equation for calculating the elastic component of the pile settlement makes it possible to obtain a lower value of the settlement in comparison with the standard approach by taking into account the influence of friction forces of the soil along the pile lateral surface. The proposed method for pile foundations design based on the settlement can serve as a justification for the reserve of the load-bearing capacity of the pile foundation according to the settlement criterion which will allows obtaining a certain economic effect.

Analysis of WWER-1000 Fuel Deformation Using the Refueling Machine Control System

The analysis of the geometric dimensions of fuel assemblies, whose change may lead to mashing of the cassettes in the core, is performed at this stage only after removing the fuel assemblies from the reactor. This paper considers the possibility of analyzing the mashing of WWER-1000 cassettes using the control system of the reloading machine. Based on data from an industrial experiment at the Rostov NPP, a typical distribution of friction forces over the height of the WWER-1000 reactor core is assessed.

Research on hydrodynamic characteristics of cylinder planing

This paper selects SST k-w turbulence model and VOF wave to construct a numerical calculation model of moving body planning on a flat free surface based on STAR-CCM+ numerical simulation software. The construction model is checked through foreign classic literature, and the numerical simulation results are in good agreement with the experimental results. The hydrodynamic numerical errors are less than 5%, which is within the engineering error range. The model can be used for the numerical simulation of the planning cylinder. In this paper, it is used to simulate the planing process of cylinder with different speeds and different submerged depths, and the flow field characteristics and hydrodynamic characteristics in the planing process are obtained. The results show that waves appear at the tail and the tail liquid splashes to form a water splash during the planing process of the cylinder on a flat surface. The higher the speed of the planning cylinder is, and the deeper the submersion depth, the more pronounced waves at the tail. When the cylinder has a Fr number Cv≥8, the hydrodynamic force of the cylinder is almost unchanged, and it is not affected by the speed. But when Cv=3, the hydrodynamic characteristic coefficient is higher. The drag coefficient is 20% higher than that in the high-speed (Cv≥8) planing process. The lift coefficient is 3 times of high-speed planing lift coefficient. It is related to the surface pressure and frictional force distribution of cylinder during the low-speed planing. There is a linear relationship between the drag coefficient and the submerged depth during the cylinder planing at different submerged depths.

Influence of lowering groundwater level on the behavior of pile in soft soil

The article presents the results of numerical analysis of the development of negative skin friction forces of a single pile by lowering the level of the groundwater ta-ble in soft clay soils. The analysis is conducted with a three-dimensional model (3D) us-ing the ABAQUS software package. Results from the present work are found to be in congruent with the available published results. Moreover, the influence of lowering of the groundwater table in distribution of negative skin friction and axial forces on the pile as well as the maximum relative displacement between the soil and pile at various stages has been observed. The compression of the pile material is also taken into con-sideration in the study. Based on the results of the current numerical analysis, an equa-tion has been proposed for estimating the additional load on the pile, which is caused by negative frictional forces.

Моделювання сходження сипкого матеріалу з відцентрового конусного дискового дозатора

Aim. Development of an analytical model and study of particle movement on the surface of a conical disk rotary dispenser-mixer of bulk material. Method. The particle, which is placed on the conical disk, is subjected to gravity directed vertically downwards, the pressure force of the vertical component of the bulk component. The force of the normal reaction of the surface of the conical disk is directed perpendicular to the cone generating line of the dispenser disk at a given point where the material particle is located. Cartesian coordinate system. The x-axis is directed along the generator line from the vertex, the y-axis is perpendicular to the x-axis and z-axis and is directed towards the rotation of the disk, and the z-axis is directed vertically upwards. The centrifugal force vector is directed along the radius. The Coriolis force is directed tangentially perpendicular to the x-axis in the opposite direction to the direction of rotation of the disk. The friction force, as the resulting force vector, is directed in the opposite direction from the direction of movement of the particle on the disk due to the centrifugal force. The force of friction of the particle on the surface of the disk decomposes into normal and radial projections. Considering an elementary particle as a material point, the differential equation of motion in vector form. Projecting the vector equality on the X and Y axis, we obtain a system of differential equations of particle motion. The numerical Runge-Kutta solution using the rkfixed function in the MathCad environment was used to solve the differential equations. Results. The speed and trajectory of the particles of bulk material depends on the angle of the conical disk and the frequency of its rotation. As the angle of the cone generating line increases, the duration of movement of the particle on the surface of the cone and the distance of movement decreases. The smoothness of movement is determined by the angle between the velocity vectors vx and vy. Smooth change of the direction of the vector of the resulting speed makes it possible to increase the accuracy of dosing the material and increases the discreteness. Scientific novelty. For the first time, a system of differential equations of motion of a material particle on a conical dispenser of centrifugal type was obtained, which takes into account the distribution of particle friction forces on the disk surface on normal and radial projections and their solution by the Runge-Kutta numerical method. Practical value. The application of the obtained system of differential equations and the algorithm of their solution makes it possible to model the design and technological parameters of the disk conical centrifugal dispenser of bulk materials.

Distribution and change of stresses, slippage, tension, and friction forces in wound rolls (Simulation of center winding without nip)

Distribution and change of stresses, slippage, tension, and friction forces in wound rolls (Simulation of center winding without nip)