Friction Moment Research Articles

Modeling the work of the automotive differential with internal friction in the system for calculating the multi body dynamics

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.

Prediction and validation of dynamic characteristics of a valve train system with flexible components and gyroscopic effect

Flexibility and inner stress of transmission components are main considerations in the development of high-precision and lightweight engines. Gyroscopic effect of rotary shaft and rotor should also be considered in high-speed engines. Therefore, an elastic dynamic model of a valve train system is proposed. The model includes multiaxial flexibilities of camshaft and linkages, gyroscopic effect of the camshaft and cam rotor, centrifugal force of cams and friction force and moment of the cam–tappet pair. Then, the natural frequency, mode shape, pushrod stress and housing vibration are predicted using the proposed model. Results show that the gyroscopic effect of the rotors and camshaft apparently affects the natural frequency of the system by changing the camshaft stiffness. The proposed model can effectively predict the dynamic stress, as proven by a stress experiment. In addition, idling and maximum working speeds are recommended using the predicted model and verified by a vibration experiment. Thus, the proposed model can be an important reference in engine adjustment, improvement of component durability and determination of idling and maximum speeds.

Improvement of Reliability and Ecological Safety of NPP Reactor Coolant Pump Seals

The paper presents the analysis of existing designs of NPP reactor coolant pumps (RCP) rotor sealing systems. The most common design solutions of sealing units that provide the necessary tightness, reliability and service life under high pressure, temperature and sliding speeds typical for RCP, as well as trends for their improvement to increase tightness and environmental safety of activities were identified.
 Designs of impulse seals with a self-adjusting clearance are presented as the most promising assemblies for sealing pump shafts with high parameters. A computer model of impulse mechanical seal as an automatic control system is proposed. A framework for calculating impulse mechanical seals has been developed, allowing the choice of their main geometric parameters to ensure the optimal value of the mechanical clearance and the friction moment on the sealing contact surfaces. Expressions are obtained for constructing the static and flow characteristics of a impulse mechanical seal, the condition for its dynamic stability is determined. The paper presents the shaft sealing system of RCP, main nodes of which are several stages of impulse mechanical seals with a self-regulating clearance.

NUMERICAL ANALYSIS OF THE INFLUENCE OF TEMPERATURE ON THE FRICTION RESISTANCE OF A METAL-POLYMER SLIDING PAIR

The paper presents numerical calculations of polymer sliding bearings during their operation at low temperatures. Calculations of the frictional moment and the contact area were performed for bearing pans made of PA and PEEK. In the numerical model, the influence of temperature on the mechanical properties (modulus of longitudinal elasticity) and tribological properties (coefficient of friction) were taken into account. The diversified influence of the temperature and thickness of the polymer bearing pans was demonstrated with regards to elements made of different polymer materials. At low temperatures (up to T = -50°C), a different (depending on the used polymer) influence of mechanical and tribological properties on the resistance to motion was found. The ABAQUS calculation package and the finite element method (FEM) were used in the calculations.

Intelligent bearing structure and temperature field analysis based on finite element simulation for sustainable and green manufacturing

Intelligent manufacturing is a new mode and trend of sustainable manufacturing development. It optimizes the design and manufacturing process of products and greatly reduces the consumption of resources and energy by virtue of the huge potential of computer modeling and simulation and information communication technology. Under the background of intelligent manufacturing, intelligent bearing is proposed on the basis of traditional bearing products. Intelligent bearing is one of the research and development directions of high-end bearings at home and abroad. Embedded test technology is one of the research fields of intelligent bearings at present. Firstly, based on the finite element model, the structural design problems related to the integration of rolling bearing and sensor are studied. According to the load distribution of bearing, the optimal slot position of bearing is determined. Considering the influence of reducing the bearing capacity, the influence of axial and radial slot ways of bearing outer ring on the maximum deformation and stress of bearing outer ring is studied, and the bearing outer ring is analyzed The relationship between the maximum deformation, maximum stress and the groove size of the outer ring of the bearing is determined to provide the basis for the selection and design of the sensor module. Secondly, according to the friction moment formula, the total heat of the bearing is calculated. Based on the workbench, the temperature field cloud distribution model of the rolling bearing is established to analyze the changes of the speed, the radial load and the temperature of the inner and outer ring of the bearing Finally, according to the slot position and slot size, select the appropriate sensor and rolling bearing integration to achieve the real-time monitoring of the operation state of the bearing.

Functional Properties and Microbiological Stability of Fatty Acid Methyl Esters (FAME) under Different Storage Conditions

Biofuels used as biocomponents for transport fuels should meet quality requirements. Their properties have a significant impact on the proper functioning of the engine supply system and the wear of its components. Changes in the performance of biofuel functionality may already occur during storage. Therefore, the present study aimed to evaluate changes in selected rheological and tribological parameters of higher fatty acid esters depending on the time and method of their storage by considering different types of substrates used for their production. The presence of possible microbiological contamination, which may affect the examined parameters of biofuels, was also analyzed. The dynamic viscosity of the biofuels tested changed depending on the substrate used. The biofuel produced from waste oil had the highest viscosity. Tribological studies show that both the linear wear of samples and the friction moment were higher after the storage period. The acid number of the esters did not exceed the permissible value recommended by the standard. The type of raw material used for the production of biodiesel and the conditions of its storage affected biodeterioration, proved by the growth of microorganisms. The highest number of microorganisms was recorded in biofuels prepared from waste oil.

Thermohydrodynamic Characteristics and Stability Analysis for a Journal Hybrid Floating Ring Bearing Within Laminar and Turbulent Mixed Flow Regime

Abstract There exist laminar and turbulent flow in the inner and outer fluid film of the hybrid floating ring bearing at high speed. The finite element method (FEM) and finite difference method (FDM) are used to solve the thermohydrodynamic (THD) lubrication model within the laminar and turbulent mixed flow regime which governs the pressure, temperature, viscosity, and Reynolds number of the two-layer fluid films together for a type of the journal hybrid floating ring bearing with deep/shallow pockets. The static and dynamic characteristics are analyzed including the load capacity, the friction moment, the volume flowrate, the stiffness, and damping coefficients with consideration of the mixed flow and thermal effect based on the floating ring balance. The unitized kinematic model of the shaft and floating ring is proposed to deduce the instability criteria and calculate the threshold rotational speed of a rigid Jeffcott rotor system supported on two hybrid floating ring bearings by the Routh–Hurwitz method. The results present that there are non-uniform pressure and temperature profile within the fluid film field, and the laminar flow and turbulent flow appear at certain positions of film through theory and experiment, separately. The mixed flow effect promotes the bearing load capacity and the friction moment at high speed and eccentricity, and the system threshold speed drops within the mixed flow regime. Therefore, the thermal effect and mixed flow existing in the fluid film should be considered into the lubrication analysis for the floating ring bearing.

Three-Link Mechanism as a Model of a Person on a Swing

We model movements of a person swinging on a swing. We consider a flat three-link hinged mechanism as the main mechanical model of the person sitting on the swing. The first, second, and third links model the human body, two hips that are rigidly connected to the swing, and two shins, respectively. The hinge between the first and second links models two hip joints, while the hinge between the second and third links models two knee joints. In each of the interlink hinges, a control moment, limited in magnitude, is applied. At the point of the support of the swing, the moment of viscous friction acts. A mathematical model of a controlled three-link mechanism is built. In solving the problem of synthesizing the control of a three-link model, the law of the control of a simpler (auxiliary) two-link swing model is preconstructed. Then this law is used to control the three-link model. Motion equations with the control built in the form of feedback, have periodic orbitally asymptotically stable solutions. Depending on the parameters of the model, such solutions describe the oscillations of a swing with a constant amplitude or rotation. The control that damps the swing is also built.

Design and Finite Element Analysis of composite PTFE Compression Packing with C-shape Structure

Gland packing is a sealing device in mechanical equipment like pumps. With the development of science and technology, new materials and new structures have appeared, giving new vitality and advancement to the packing seal. In the process of pump operation, the major problems of gland packing seals are the wear of the filler material and leakage of media through the interface. Hence, In order to improve the sealing performance of a gland packing, Different factors including design structure, the number of packing rings, type of filler material, operating condition like temperature, pressure and speed of shaft can be considered. In this study the finite element analysis of the packing seal is carried out, and the axial stress distribution, bottom pressure and friction moment of the packing seal are obtained according to its design structure and stress condition. Furthermore, the results of finite element analysis are verified by experiments.

Adaptation of the Jellett Integral to the Case of Rolling Friction

In his book A Treatise on the Theory of Friction, Jellett considered the problem of tippe top overturn on a rough base. A key to the solution was the first integral of motion, which is invariant to law of friction; the dot product of the kinetic moment and the radius-vector of the point of contact are constant. The possibilities of generalization of this approach to the case in which the friction force is complemented by a moment of rolling friction are considered.

THE USE OF ADDITIVE MANUFACTURING TECHNOLOGY TO MANUFACTURE SLIDE BEARING SLEEVES – A PRELIMINARY STUDY

The paper presents the application of an unconventional method of manufacturing bearing sleeves as well as the carrying out of preliminary research in which the manufactured components were used on a real object. Additive manufacturing methods are increasingly being used, which leads to the rapid development of technologies and their applications. The MultiJet Printing technology was used in the research, which allows precise 3D printing of sleeves made of polymeric materials. The first part of the article deals with the selected manufacturing method and the preparation of a model. The study aimed at evaluating the usefulness of bearings manufactured using the 3D printing technology to support slow-speed rotors. The preliminary research described focuses on the study of operating parameters such as the moment of friction and the bearing node temperature as a function of rotational speed during operation. Experimental tests were carried out at low rotational speeds. This paper presents and determines the scope of the application of bearings manufactured using 3D printing technology.

Lubrication characteristics of the slipper–swash-plate interface in a swash-plate-type axial piston pump

An analytical approach based on a hydrodynamic lubrication model is presented to understand the bearing capacity, leakage, and friction moment of the slipper–swash-plate interface in a swash-plate-type axial piston pump. Furthermore, how the shaft speed, load pressure, and slipper attitude influence the lubrication performance of the interface is analyzed. The research shows that the slipper attitude has a significant effect on the pressure distribution. To improve the lubrication performance, a grooved sealing-land design is proposed, and the location and geometric parameters of the groove are analyzed. The results indicate that the optimal lubrication performance is achieved when the groove is 2.0–3.0 mm wide and 5–20 µm deep at its inner boundary.

Quantifying the influence of pile diameter on the load transfer curves of laterally loaded monopile in sand

Although the load transfer curves (i.e., p-y curves) recommended by the current industry standards are regarded as questionable for the recently emerging large diameter monopile, the influence of pile diameter and bending stiffness on the p-y curves in sand has not been systematically quantified. Nor have the underlying mechanisms of the diameter dependent p-y curves been well understood. This study presents a series of well calibrated three-dimensional finite-element (FE) analyses, aiming to quantify p-y curves of laterally loaded piles with different pile diameters and bending stiffness in sand, and to reveal the underlying mechanisms. It is found that the p-y curves in the API [6] code, which are valid for piles with a small diameter (D = 1 m), overestimate the initial stiffness while underestimates the soil resistance of a large-diameter pile (D = 5 m) by more than 90%. The numerical analyses further reveal that the modification of the p-y curves with the increasing pile diameter is mainly associated with the altered soil deformation mechanisms around the increasingly stiff pile. On the other hand, the influences of the skin friction, base shear and base moment of the large-diameter pile (with D up to 5 m) on the p-y curves are almost negligible. New p-y curves considering the effect of failure mechanism of large diameter monopile in dense sand is proposed, which are shown to yield better predictions for large-diameter piles than the existing p-y curves.

Simultaneous optimization of placement and parameters of rotational friction dampers for seismic-excited steel moment-resisting frames

The present paper proposes the simultaneous optimization of the placement and parameters of rotational friction dampers (RFDs) for the seismic protection of a nonlinear steel moment-resisting frame (SMRF). In that respect, the placement and parameters of RFDs in the framework of an optimization problem is simultaneously optimized for a ten-story SMRF subjected to an artificial earthquake. In the optimization problem, the placement of RFDs and their frictional moment and the length of their vertical rigid beam are considered as the design variables, and the ratio of the maximum seismic input energy to the maximum cumulative dissipated energy by the RFDs is selected as the objective function. The mixed discrete-continuous optimization problem is solved by a hybrid of binary and real-coded modified particle swarm optimization (BRPSO). Furthermore, the effect of the number of RFDs is investigated on the seismic performance of the SMRF. The optimization results reveal that a significant portion of the input seismic energy is dissipated by the RFDs and at the same time reducing the amount of the cumulative hysteretic energy of the structure. Therefore, the seismic damage in the structure is significantly reduced. Furthermore, the appreciable reduction of the seismic responses of the structure is not observed by increasing the number of the RFDs. Finally, the results of the seismic assessment indicate that the optimized RFDs obtained for the artificial earthquake can guarantee the structure subjected to real earthquakes.

Dynamic parameters identification of a haptic interface for a helicopter flight simulator

Abstract. The haptic interface force feedback is one of the key factors for a reliable flight simulation. This paper addresses the design and control implementation of a simple joystick-like haptic interface to be used for a helicopter flight simulator. The expression of the haptic interface force is obtained by dynamic analysis of the haptic interface operation. This paper proposes a new strategy aiming at avoiding the use of an expansive and complex force/torque sensor. Accordingly, specific dynamic model is implemented by including Stribeck friction to describe the friction moment. Experimental data are processed as based on a genetic algorithm for identifying the dynamic parameters in the Stribeck friction model. This allows to obtain the friction moment parameters of the haptic interface, as well as the torque distribution due to gravity and the rotational inertia parameters of the haptic interface for the calculation of the haptic interface force. Experimental tests are carried out and results are used to validate the proposed dynamic model and dynamic parameter identification method and demonstrate the effectiveness of the proposed force feedback while using a cheap photoelectric sensor instead of an expansive force/torque sensor.

A comprehensive comparative investigation of frictional force models for dynamics of rotor-bearing systems

Vibrations of a rotor-bearing system (RBS) can be affected by the frictional forces between the components of the inherent bearings. Thus, an in-depth investigation of the influences of the frictional moments of the bearings on the vibrations of the RBS can be helpful for understanding the vibration mechanisms in the rotating machinery. In this study, an improved dynamic model of a RBS considering different frictional force models is presented. A comparative investigation on the influences of the empirical and analytical frictional force models on the vibration characteristics of the RBS is proposed. The empirical frictional force models include Palmgren’s and SKF’s models. The analytical frictional force model considers the rolling friction caused by the radial elastic material hysteresis, slipping friction between the ball and races, viscosity friction caused by the lubricating oil, and contact friction between the ball and cage. The influences of the external load and rotational speed on the vibrations of the RBS are analyzed. The comparative results show that the analytical frictional force model can give a more reasonable method for formulating the effects of the friction forces in the bearings on the vibrations of the RBS. The results also demonstrate that the friction forces in the bearings can significantly affect the vibrations of the RBSs.

FUNCTIONAL CALCULATION OF DRUM BRAKE OF AUTOMOBILES AND MOTORCYCLES

Refined formulae are given for the functional calculation of drum brake mechanisms with fixed axes of rotation of the shoes and with self-aligning shoes. Keywords: FUNCTIONAL CALCULATION, DRUM BRAKE MECHANISM, BRAKING TORQUE (FRICTION MOMENT), OPTIMAL, INCLINATION ANGLE, SUPPORT SURFACE, SELF-ALIGNING SHOE

Improvement of tribological characteristics of rubbing surfaces as one of ways to increase energy efficiency of power plants

In this study, the team of authors solves the problem of increasing the energy efficiency of power plants by reducing losses while lowering the coefficient of friction. This problem is solved with the help of a multifunctional additive to lubricating oils, which are a surface-active substance (surfactant) capable of changing the friction conditions of contacting surfaces in a small amount when introduced into tribological units. The tests were carried out on a friction machine II5018 on a block-roller friction pair (the material of the roller is gray cast iron SCh20, the material of the block is steel 65). During the study, the moment and coefficient of friction were determined. A friction coefficient decrease of up to 50 % was obtained, which proves the effectiveness of the proposed compositions.

Effects of second-generation and indoor sports surfaces on knee joint kinetics and kinematics during 45° and 180° cutting manoeuvres, and exploration using statistical parametric mapping and Bayesian analyses

The aim of the current investigation was to examine the influence of second-generation (2G) and indoor surfaces on knee joint kinetics, kinematics, frictional and muscle force parameters during 45° and 180° change of direction movements using statistical parametric mapping (SPM) and Bayesian analyses. Twenty male participants performed 45° and 180° change of direction movements on 2G and indoor surfaces. Lower limb kinematics were collected using an eight-camera motion capture system, and ground reaction forces were quantified using an embedded force platform. ACL, patellar tendon and patellofemoral loading, was examined via a musculoskeletal modelling approaches, and the frictional properties of the surfaces were examined using ground reaction force information. Differences between surfaces were examined using SPM and Bayesian analyses. Both SPM and Bayesian analyses showed that ACL loading parameters were greater in the 2G condition in relation to the indoor surface. Conversely, SPM and Bayesian analyses confirmed that patellofemoral/patellar tendon loading alongside the coefficient of friction and peak rotational moment were larger in the indoor condition compared to the 2G surface. This study indicates that the indoor surface may improve change of direction performance owing to enhanced friction at the shoe--surface interface but augment the risk from patellar tendon/patellofemoral injuries, whereas the 2G condition may enhance the risk from ACL pathologies.

Influence of friction forces in limiter-eyelet contact on twisting angles of the rubber elements of tracked system hinges

The article presents a study of the influence of the radial deformation limiters of rubber-metal compounds of tracked systems on the loading of rubber elements. Description of the mathematical model of the dynamic behaviour of a tracked propulsion unit with rubber-metal hinges is presented. Dynamic calculations using the software package based on the equations were performed. The analysis of the results of the computer calculation revealed the influence of friction forces and moments in the contact zone of the limiter-eyelet.