Radial Friction Research Articles

Optimum Winding Tension and Nip-load into Wound Webs for Protecting Wrinkles and Slippage

This paper describes the novel optimization method of wind-up tension to prevent wound roll defects, mainly star defect (wrinkling) and telescoping (slippage), based on the optimum design technique. Modified Hakiel model with air entrainment effects is applied to analyze in-roll stress distributions in the radial and tangential directions. In the present optimization method, the wind-up tension is gradually changed in the radial direction to minimize the tangential stresses under the constraint of nonnegative tangential stresses. At the same time, we consider the friction conditions to prevent the slippage between web layers due to a decrease of radial stresses and friction force. Successive quadratic programming, which is a typical mathematical programming method, is used as the optimization technique. The optimized wind-up tensions are obtained for various winding conditions, and we confirmed theoretically and experimentally that the in-roll stress distributions are very much improved for preventing both wrinkling and slippage simultaneously by the optimization method being proposed.

Modelling for tensile strength of friction welded aluminium pipes by ANFIS

In this study, fuzzy model has been proposed to predict the tensile strength of radial friction welded aluminium pipes. The model is of multi-input single-output (MISO) type having two inputs signals; rotational speed (RPM) and forge load and tensile strength as output. The adaptive neuro-fuzzy inference system (ANFIS) technique of fuzzy based systems for modelling and simulation of the complex systems has been employed. The performance of the model is authenticated by evaluating the predicted results with the practical results obtained by conducting the confirmation experiments. The proposed model can be used for intelligent online adaptive control mode.

Unsteady mhd flow with variable viscosity: Applications of spectral scheme

The magnetohydrodynamic time-dependent von Karman swirling electrically conducting viscous fluid flow having a temperature-dependent viscosity due to a rotating disk impulsively set into motion is considered in this study. Alternative to the finite-difference methods frequently used to solve this flow, we propose here a better technique based on the spectral Chebyshev collocation in the direction normal to the disk and forward marching in time. When applied to the unsteady mhd flow in consideration, the devised numerical scheme is capable of generating the settlement of the flow into the well-known steady state for large times. The energy equation that incorporates the effects of viscous dissipation and Joule heating, and also coupled with the Navier–Stokes and continuity equations, is also treated by the method and the physical parameters of paramount interest as such the radial and tangential skin friction coefficients, the torque and the rate of heat transfer from the disk surface are numerically calculated that are shown to approach their steady state counterparts for the entire family of magnetic interaction and viscosity variation parameters.

Friction behavior modeling and analysis in micro/meso scale metal forming process

Currently, a lot of know-how in conventional metal forming process cannot be directly applied to micro/meso forming processes due to so-called size effects. As a very important phenomenon in metal forming process, friction size effects are observed with an increasing degree of miniaturization. For microforming application, the input data of friction behaviors becomes critical to obtain accurate results for process simulation and traditional friction models are not reliable. In this paper, the evolution of friction behaviors from micro size to macro size is studied and a new uniform friction model is proposed based on the assumption of open-close lubricant pockets. A function of real contact area (RAC) α RC and normal press p / σ 0 is established by introducing size/scale factor λ to describe the influence of size effects. Therefore, the development of the friction behavior from micro/meso scale to macro scale could be depicted by this new uniform friction model. It indicates that the friction curves of micro/meso size are between those of the dry friction (upper boundary) and conventional lubricant friction (lower boundary). Moreover, finite element (FE) simulations are performed, based on the new friction model, to analyze the friction size effects in ring compression process. It is found that the radial friction forces with the change of inner and outer diameters are totally different and their tendencies are in good accordance with the experimental results. The new uniform friction model enables more flexible modeling of friction behaviors.

Fuzzy modelling for burst pressure strength in radial friction welding of GI pipes

The service of the welded tubular joints of circular pipes that are used to transfer fluid at high pressures is generally evaluated on the basis of their ability to endure the high pressures of the flowing fluid. In this paper, a practical and consistent fuzzy logic based model is presented to predict the burst pressure strength of tubular joints of GI pipes that are welded with the technique of friction welding. The model is based on two input signals: rotational speed and forge load. The adaptive neuro-fuzzy inference system (ANFIS) technique of fuzzy-based systems for modelling and simulation of the complex systems has been employed, which combined modelling function of fuzzy inference with the learning ability of artificial neural network. The set of rules has been generated directly from the experimental data using ANFIS. The performance of the model is validated by comparing the predicted results with the actual practical results obtained by conducting the confirmation experiments. The proposed model can be used for intelligent online adaptive control mode.

Mesoscopic model for colloidal particles, powders, and granular solids

A simulation model is presented, comprising elastic spheres with a short-range attraction. Besides conservative forces, radial and shear friction, and radial noise are added. The model can be used to simulate colloids, granular solids, and powders, and the parameters may be related to experimental systems via the range of attraction and the adhesion energy. The model shares the simplicity and speed of dissipative particle dynamics, yet the predictions are rather nontrivial. We demonstrate that the model predicts the correct scaling relations for fracture of granular solids, and we present a schematic phase diagram. This shows liquid-vapor coexistence for a sufficiently large interaction range, with a surface tension that follows Ising criticality. For smaller interaction range only solid-vapor coexistence is found, but for a very small attractive interaction range stable liquid-vapor coexistence reappears due to pathological stability of the solid phase. At very low temperature the model forms a glassy state.

Researches on the ring stiffness condition in radial–axial ring rolling

The radial–axial ring rolling technology is used mainly to manufacture large rings in many industrial fields. During rolling process the ring may be collapsed or deformed unexpectedly under the pressure of guide roll, and in this case the ring is wasted. To prevent ring collapsing is necessary for smooth rolling. On the basis of rolling theory, the forces exerted to ring in radial–axial ring rolling process were analyzed, and the stiffness model of ring was proposed. The stiffness condition was derived and the influencing factors of ring stiffness condition were explained. The ring stiffness condition in radial–axial ring rolling is related to the factors of ring size, rolling ratio, position angel of guide roll, rolls sizes, position of cones, radial and axial feed speed and friction condition. The effect laws of some factors on ring stiffness condition were revealed by FEM simulation. The stiffness condition can be used as a rule of design and manufacturing for radial–axial ring rolling.

A novel model of ultrasonic motors with effect of radial friction in contact mechanism

This paper is concerned with a development of the contact model of traveling wave type rotary piezoelectric ultrasonic motor, which takes into account a new three-dimensional operation mechanism between the stator and rotor. First the vibration characteristics and harmonic response of the stator are analyzed based on the mathematical model. With the derivation of the kinematical equations representing the motion of the stator surface points, the three-dimensional driving mechanism is investigated at the contact interface between the stator and rotor. We found that the distributed contact forces have not only the axial and circumferential components but also the radial component at the interface. The traditional contact model should be improved by the consideration of radial friction at the interface. So we defined driving angle α, which describes how the radial friction distributes at the interface. Furthermore it is shown that the radial friction can lead to considerable energy losses. A set simulation of motor performances based on the proposed contact mechanism is found in good agreement with experimental results. We also tried to explain how the applied normal preload force on rotor affect the natural frequency of stator by the contact interface, as is shown in our experiments.

Analysis and optimization of dynamically loaded porous metal sliding bearings under conditions of elastohydrodynamic lubrication

PurposeThis paper aims to develop a simulating model of a journal porous metal bearing under elastohydrodynamic conditions and combined (radial, friction and thermal) load distribution and to carry out structural optimization.Design/methodology/approachThe structure analysis is carried out for each kind of load separately and for the combined load distribution of the bearing, where a dynamically loaded porous metal bearing is simulated. This simulating model is developed by finite elements method using the structure analysis module of the CATIA V5 software. Further, a parameter optimization of a porous metal bearing is presented considering the elastic deformations of the bearing shell.FindingsIt is revealed that the bearing, even at points with maximum displacements, could not reach the mounting clearance value during its operational life. Relatively small bearing dimensions produce very high values of eigenfrequency response (over 150 kHz) and common dynamic loads met in all sorts of sliding bearing are not dangerous for bearing damage compared with static loads. In the stage of structural optimization based on the correlation between stress and geometric bearing parameters like wall thickness and outer diameter, the influence of finite element dimension on calculated results can be also analyzed and a proper choice of the latter is achieved.Research limitations/implicationsThe present porous bearing optimization model with the aid of CATIA V5 module for optimum design uses only single objective optimization. For a complete optimum design a multi‐objective optimization has to be carried out.Practical implicationsThe analysis under dynamic load conditions proved that relatively small dimensions of bearing commonly used in micro technique and precision mechanics result in extended safe and reliable operation.Originality/valueThis paper provides a methodology for bearing stress and deformation analysis in the elastic range and on the basis of this analysis it is possible to develop an optimization model for porous bearings offering help to designers for the selection of optimal bearing dimensions considering the bearing load caused by dynamic radial force, friction and temperature variation.

Unsteady flow and heat transfer of viscous incompressible fluid with temperature-dependent viscosity due to a rotating disc in a porous medium

This paper studies the effect of a porous medium and temperature-dependent viscosity on the unsteady flow and heat transfer for a viscous laminar incompressible fluid due to an impulsively started rotating infinite disc. The unsteady axi-symmetric boundary layer equations are solved using three methods, namely, (i) perturbation solution for small time, (ii) asymptotic analysis for large time and (iii) the finite difference method together with the Keller box elimination technique for intermediate times. The solutions are obtained in terms of local radial skin friction, local tangential skin friction and local rate of heat transfer at the surface of the disc, for different values of the pertinent parameters: the Prandtl number Pr, the viscosity variation parameter e and porosity parameter m. The computed dimensionless velocity and temperature profiles for Pr = 0.72 are shown graphically for different values of e and m.

Effect of plastic deformation on the toughness behaviour of radial friction welds in Ti–6Al–4V–0.1Ru titanium alloy

A simulation trial of radial friction welding (RFW) in Ti–6Al–4V–0.1Ru titanium alloy was carried out in order to study the effect of plastic deformation (forging) on the fracture toughness of the simulated consumable ring zone (SCRZ). The simulation specimens were subjected to a comparable RFW thermal cycle and then submitted to different forging forces, producing three levels of plastic deformation. Metallographic examinations were carried out to observe the microstructural transformations generated by the thermomechanical cycle. The mechanical properties characterisation included microhardness and fracture toughness tests. The results indicated that the simulated thermomechanical cycle was successful in producing microstructures similar to those developed by a practical RFW operation, being the β-grain size of the SCRZ dependent on the degree of plastic deformation. The results also indicated that fracture toughness of the SCRZ was practically independent of the deformation level imposed.

Mechanics and Sliding Friction in Belt Drives With Pulley Grooves

The steady mechanics of a two-pulley belt drive system are examined where the pulley grooves, belt extension and wedging in the grooves, and the associated friction are considered. The belt is modeled as an axially moving string with the tangential and normal accelerations incorporated. The pulley grooves generate two-dimensional radial and tangential friction forces whose undetermined direction depends on the relative speed between belt and pulley along the contact arc. Different from single-pulley analyses, the entry and exit points between the belt spans and pulleys must be determined in the analysis due to the belt radial penetration into the pulley grooves and the coupling of the driver and driven pulley solutions. A new computational technique is developed to find the steady mechanics of a V-belt drive. This allows system analysis, such as speed/torque loss and maximum tension ratio. The governing boundary value problem (BVP) with undetermined boundaries is converted to a fixed boundary form solvable by a general-purpose BVP solver. Compared to flat belt drives or models that neglect radial friction, significant differences in the steady belt-pulley mechanics arise in terms of belt radial penetration, free span contact points, tension, friction, and speed variations.

The Research of Radial Friction Welding

The paper provides the explanation on generality and differences between radial Pressure friction welding and radial friction welding, describes the technological characteristics of radial friction welding. It also includes current situation of research on radial friction welding, existing problems and what to de done next.

Revisiting the first-principles approach to the granular gas steady state

We extend a Fokker-Planck formalism, previously used to describe the behavior of a cooling granular gas, with a Hertzian contact potential and viscoelastic radial friction, giving a velocity dependent coefficient of restitution. In the present work, we study the more general case of a steady-state with finite kinetic energy, far from equilibrium, due to the coupling to an external energy-feeding mechanism. Also from first-principles, we extend the validity of the former results.

Recent developments in high productivity pipeline welding

Installation of new pipelines is predicted to grow at a rapid rate over the next twenty years, due in part to the increase use worldwide of combined cycle power generation plant using natural gas a fuel. The need to construct large diameter pipelines over long distances has led to an increased demand to improve the productivity of pipeline girth welding. Many novel techniques have been tried in the past to achieve productivity gains, including laser welding, flash butt welding, homopolar welding, and radial friction welding. In spite of the failure to gain wide acceptance, there is still current development aimed at achieving their eventual implementation. Single wire mechanised gas metal arc welding (GMAW) remains the dominant pipe girth welding technique, and has been optimised in the past to produce the maximum productivity possible with this process. Continued development of GMAW with dual torch, tandem GMAW welding and novel techniques for GMAW roots is leading to further significant gains in arc welding productivity. This paper describes a new development, the CAPS project, (Cranfield Automated Pipe-welding System), where tandem GMAW in a narrow groove has been applied to pipeline girth welding with two tandem torches in a single welding head. The CAPS system offers welding productivity three to four times higher than that possible with the conventional single wire GMAW technique, while still producing a weld which is very similar to that generated by single wire welding. The development of the system is described, as well as recent successful trials under field conditions. The development of high power lasers has spurred a current high level of interest in the possibility of application to pipeline welding, and current research is described in which the feasibility of pipeline laser welding has been established.

Finite Element Investigation of Friction Condition in a Backward Extrusion of Aluminum Alloy

Finite element simulations are being widely used to increase the efficiency and effectiveness of design of bulk metal forming processes. In such simulations, proper consideration of friction condition is important in obtaining reliable results. For this purpose, the shear friction factor is widely used for bulk deformation analyses. In the earlier work, it was found that a radial tip was formed on the extruded end of the workpiece and that the radial tip distance had a linear relationship with the forming load in the tip test. In order to characterize the global average shear friction factor, a linear relationship between the nondimensionalized radial tip distance and shear friction factor was numerically determined in this study for AL6061-O for various lubrication conditions. The global average friction condition at the bottom die interface was determined to be about 60 percent of the one at the punch in the backward extrusion under the present conditions.

Unsteady flow of viscous incompressible fluid with temperature-dependent viscosity due to a rotating disc in presence of transverse magnetic field and heat transfer

This paper studies the effect of a magnetic field and temperature-dependent viscosity on the unsteady flow and heat transfer for a viscous laminar incompressible and electrically conducting fluid due to an impulsively started rotating infinite disc. The unsteady axisymmetric boundary layer equations are solved using three methods, namely, (i) perturbation solution for small time, (ii) asymptotic analysis for large time and (iii) finite difference method together with Keller box elimination technique for intermediate times. The solutions are obtained in terms of local radial skin friction, local tangential skin friction, and local rate of heat transfer at the surface of the disc, for different values of the pertinent parameters: the Prandtl number Pr, the viscosity variation parameter ε and magnetic field parameter m. The computed dimensionless velocity and temperature profiles for Pr=0.72 are shown graphically for different values of ε and m.

Modelling and Simulation of Rotary Compressor in Refrigerator

This paper presents the modeling approach that can predict transient behavior of rotary compressor. Mass and energy conservation laws are applied to the control volume, real gas state equation is used to obtain thermodynamic properties of refrigerant. The valve equation is solved to analyze discharge process also. Dynamic analysis of vane and roller is carried out to gain friction work. From the above modeling, the performance of rotary compressor with radial clearance and friction loss is investigated numerically. The performance of each refrigerant is estimated, respectively by applying R12, R134a, and R290/ R600a mixture.

Effect of Entrance and Exit Areas on the Pressure Drop and Velocity Distribution in Regenerator Matrix.

In order to examine the effect of entrance and exit areas on the velocity distribution in stacked wire screens, which are the most familiar regenerator matrices of Stirling cycle machines, the pressure drop across them and the velocity distribution at their exit are measured for different mesh numbers, flow rates, entrance areas, exit areas and stack thicknesses. The results show that the effective flow area ratio, which is an index for the uniformity of the velocity, is independent of the mesh number and the Reynolds number but dependent on the entrance and exit areas and the stack thickness. In addition, a simple theoretical flow model has been formulated based on the isotropy of the friction factor, which is confirmed by the measurement of axial and radial friction factors. The calculation using this model gives an effective flow area ratio and a velocity distribution that agree well with experimental ones.

A study of specimen thickness effects in the impact tests on polymers by numeric simulations

Experimental data of polymer behaviour at high strain rates in the literature, mostly obtained with a split Hopkinson pressure bar (SHPB), shows a dependence on the thickness of the specimen. This paper investigates this so-called thickness effect and tries to clarify the doubts on the equilibrium assumption in SHPB tests on polymers by numerical simulations. Fictitious specimens of different thickness with rate sensitive polymer-like constitutive model (Eyring's model) are used to simulate basic data of SHPB test. The comparison between the given behaviours and those derived from the simulated tests provides an objective appreciation of the quality of tests on polymers (with thin or thick specimen). Results of the simulation prove that the equilibrium assumptions can still be safely used in the case of test on polymers, and indicate that the thickness effect is mainly due to the radial inertia and friction considerations.