Hybrid Friction Model Research Articles

Influence of manufacturing surface topography on torque and load bearing capacity of hydro-viscous drive clutch under mixed lubrication stage

PurposeHydro-viscous drive (HVD) clutches are widely used in equipment requiring soft start, such as fans and pumps, to transmit torque and adjust speed by changing the gap distance between friction pairs. This paper aims to propose a novel two-parameter evaluation method for HVD during the mixed lubrication stage. The objective is to develop an effective model that establishes the relationship between these parameters and the actual surface topography.Design/methodology/approachIn the presented methods, the fractal features of the real manufacturing surface are calculated based on the power spectrum function by the ultra-depth three-dimensional microscope. After that, the hybrid friction model of the friction plate is established based on mixed elasto-hydrodynamic lubrication theory, boundary friction model and fractal theory. Then the torque and load bearing characteristics of the clutch are obtained, and the influences of the surface fractal features are investigated and discussed. Finally, the Weierstrass–Mandelbrot function is adopted for the surface topography characterization and evaluation.FindingsThe results indicate that the proposed method exhibits good accuracy, while the speed difference between the friction pair exceeds 2,500 rpm. It is concluded that this paper proposed a way to evaluate the torque and loading capacity of HVD considering the real manufacturing surface topography and is helpful for surface optimization.Originality/valueThe originality and value of this study lie in its development of a novel torque and load bearing capacity evaluation method for HVD in mixed lubrication stage, considering manufacturing surface topography and describing the real manufacturing surface.

Dynamic analysis of space robot manipulator considering clearance joint and parameter uncertainty: Modeling, analysis and quantification

Clearance joint as an inevitable nonlinear factor in space robot manipulator modifies dynamic response of the mechanism, justifies deviations between predictions and measurements, and enhances sensitivity of mechanism response to parameter variation. The coupling of clearance joint and parameter uncertainty, therefore, would further significantly influence the kinematic accuracy and dynamic response of a space robot manipulator. In this paper, the dynamic performance of space robot manipulator with consideration of joint clearance and parameter uncertainty is analyzed. Quantification of parameter effect on the dynamic response is also presented. In the analysis, joint elements are modelled as colliding bodies, where the nonlinear contact force model and hybrid friction model are employed to describe the impact-contact phenomena. Motion equations of the mechanism are derived in which nonlinear forces are considered as external forces. Then, the Chebyshev polynomial method is introduced to explicate the relation between the mechanism response and parameters. Based on the Chebyshev polynomial method, dynamic response of the uncertain mechanism could be calculated through the use of interval algorithm, and a sensitivity analysis method is introduced to quantify the parameter effect. The dynamics of a space robot manipulator with joint clearance and parameter uncertainty is further investigated, where the clearance size and friction coefficients are taken as single and multiple uncertain parameters, and effects of the uncertainties on the manipulator response are quantified. This study could help for the design, analysis and test of a space robot manipulator with consideration of both clearance and uncertainty.

An Inverse Approach Towards Determination of Friction in Friction Stir Spot Welding

Friction stir spot welding (FSSW) is a solid-state joining process in which a rotating tool is pressed against two materials to be joined for creating a spot weld. The rotating tool comprises a pin with a shoulder. The pin gets inserted inside the material, whereas the shoulder rubs on the surfaces of the two materials. The process encounters friction at the pin-workpiece and shoulder-workpiece interfaces. In order to carry out a realistic simulation of the process, the knowledge of friction is a must. In most of the published work, scant attention has been devoted to the quantitative determination of friction force. This article proposes an inverse approach to the determination of friction force in FSSW. It is assumed that the frictional behaviour at the pin-workpieces interface is sticking in nature and at times, there is a possibility that frictional shear stress is more than the shear strength of the materials due to welding of asperities. This aspect is analysed by carrying out a number of finite element simulations using DEFORM-3D on a shoulder-less pin and validating it through in-house experiments. Later on, a hybrid friction model (combination of Coulomb’s and constant shear models) is used on the shoulder-workpieces interface. The friction parameters are adjusted through an optimization approach by minimizing the error between experiments and simulation. In a typical case, the friction factor (m) on the pin-workpiece interface was found to be 1.05. Friction at the shoulder-work interface was best represented by a hybrid model, with m = 0.77 for the high-pressure region and µ = 0.29 for the low-pressure region, where µ is the Coulomb’s coefficient of friction. Computations with estimated friction predicted temperatures with a reasonable accuracy. It also predicted fairly accurate torque for a tool of different size.

Validation of Friction Model Parameters Identified Using the IHB Method Using Finite Element Method

A hybrid friction model was recently developed by Azizian and Mureithi (2013) to simulate the friction behavior of tube‐support interaction. However, identification and validation of the model parameters remains unresolved. In previous work, the friction model parameters were identified using the reverse harmonic method, where the following quantities were indirectly obtained by measuring the vibration response of a beam: friction force, sliding speed of the force of impact, and local displacement at the contact point. In the present work, the numerical simulation by the finite element method (FEM) of a beam clamped at one end and simply supported with the consideration of friction effect at the other is conducted. This beam is used to validate the inverse harmonic balance method and the parameters of the friction models identified previously. Two static friction models (the Coulomb model and Stribeck model) are tested. The two models produce friction forces of the correct order of magnitude compared to the friction force calculated using the inverse harmonic balance method. However, the models cannot accurately reproduce the beam response; the Stribeck friction model is shown to give the response closest to experiments. The results demonstrate some of the challenges associated with accurate friction model parameter identification using the inverse harmonic balance method. The present work is an intermediate step toward identification of the hybrid friction model parameters and, longer‐term, improved analysis of tube‐support dynamic behavior under the influence of friction.

Dynamic analysis of planar mechanical systems considering stick-slip and Stribeck effect in revolute clearance joints

The phenomena of friction in clearance joints have time- dependent nonlinear characteristics, which could lead to undesirable and unstable dynamic behavior of mechanical systems. Various mathematical models have been proposed to describe friction force in clearance joints. However, most of the previous models have different limitations, such as discontinuity at zero velocity or disability of detecting stick-slip motion. In this paper, a hybrid friction model is presented to analyze the dynamics of planar mechanical systems, considering sliding, sticking and Stribeck effect in revolute clearance joints. According to the kinematic analysis, the relative tangential motion between the journal and the bearing is categorized as sticking state, sliding state and transitional state. In the sticking state, an assumed acceleration constraint for the contact points is proposed to estimate the static friction force. This method not only eliminates the calculation of the implicit external force, but also accurately reflects the sticking process in accordance with the friction physics. Furthermore, the Stribeck effect is introduced in the description of the friction force in the sliding state, revealing the influence of the sliding velocity on the friction force. The stick-slip motion could also be accurately described by the Stribeck effect, which guarantees the continuity of the friction force during the transition process. Finally, a space robot manipulator is taken as an example to demonstrate the hybrid friction model. Dynamics of the space robot manipulator with Coulomb friction model, LuGre friction model, Wojewoda friction model and the hybrid friction model are compared, respectively. And the effects of clearance size, static friction coefficient and sliding friction coefficient on the dynamics of the manipulator are also analyzed.

Identification of Friction Model Parameters Using the Inverse Harmonic Method

A hybrid friction model has been developed by Azizian and Mureithi (2013, “A Hybrid Friction Model for Dynamic Modeling of Stick–Slip Behavior,” ASME Paper No. PVP2013-97249) to simulate the general friction behavior between surfaces in contact. However, identification of the model parameters remains an unresolved problem. To identify the parameters of the friction model, the following quantities are required: contact forces (normal and tangential or friction forces), the slip velocity, and the displacement in the contact region. Simultaneous direct measurement of these quantities is difficult. In the present work, a beam clamped at one end and simply supported with the consideration of friction at the other is used as a mechanical amplifier of the friction effects at the microscopic level. Using this simplified approach, the contact forces, the sliding velocity, and the displacement can be indirectly obtained by measuring the beam vibration response. The inverse harmonic balance method is a new method based on nonlinear modal analysis which is developed in this work to calculate the contact forces. The method is based on the modal superposition principle and Fourier series expansion. Two formulations are possible: a harmonic form formulation and a subharmonic form formulation. The approach based on subharmonic forms coupled with spline fitting gave the best results for signal reconstruction. Signal reconstruction made it possible to accurately identify the parameters of the hybrid friction model with a multiple step approach.

Analytical and numerical analyses of local loading forming process of T-shape component by using Coulomb, shear and hybrid friction models

The Coulomb friction model, shear friction model and hybrid friction model were employed to analyze the local loading forming process by using slab method (SM) and finite element method (FEM). The results indicated that predicted results by shear friction model and hybrid friction model are almost the same, but there exists a notable difference between Coulomb friction and the other two friction models. The rib cavity will be filled better under Coulomb friction model, and difference of rib height after forming process between Coulomb friction model and shear friction model increases at first and then decreases with the increase in width of local loading.

Experimental and Simulation of Friction Effects in an Open-Die Microforging/Extrusion Process

Friction effects during a progressive microforming process for production of micropins of various diameters were experimentally investigated and were analytically modeled, using a hybrid friction model. The response surface method and ANOVA analysis were used to generalize the findings for various pin diameters. Besides, it was shown that to get an accurate result in simulation, the friction model must be considered locally instead of a global friction model for the whole process. The effect of friction factor on the final micropart dimensions (the effect on the instantaneous location of the neutral plane) and the forming pressure were investigated. The results showed a reduction in the friction factor as die diameter increased. Following that, the optimum frictional condition to obtain the highest micropart aspect ratio was defined as the maximum friction on the interface between the die upper surface and the punch surface, together with a minimum friction inside the die orifice.

A Hybrid Physical-Dynamic Tire/Road Friction Model

We present a hybrid physical-dynamic tire/road friction model for applications of vehicle motion simulation and control. We extend the LuGre dynamic friction model by considering the physical model-based adhesion/sliding partition of the tire/road contact patch. Comparison and model parameters relationship are presented between the physical and the LuGre dynamic friction models. We show that the LuGre dynamic friction model predicts the nonlinear and normal load-dependent rubber deformation and stress distributions on the contact patch. We also present the physical interpretation of the LuGre model parameters and their relationship with the physical model parameters. The analysis of the new hybrid model's properties resolves unrealistic nonzero bristle deformation and stress at the trailing edge of the contact patch that is predicted by the existing LuGre tire/road friction models. We further demonstrate the use of the hybrid model to simulate and study an aggressive pendulum-turn vehicle maneuver. The CARSIM simulation results by using the new hybrid friction model show high agreements with experiments that are performed by a professional racing car driver.

Progressive microforming process: towards the mass production of micro-parts using sheet metal

Although there is considerable published literature on micro-metal forming processes, there is still a lack of research towards implementing these processes commercially. Some of the challenges are handling of micro-parts and process intermittency. This work demonstrates the feasibility of producing symmetric micro-parts using a progressive forming set-up. Such a progressive forming process alleviates the challenges in handling and removal of micro-parts. Micro-pins with diameters of 0.3, 0.5, and 0.8 mm were successfully manufactured without defects. Experimental observations together with process simulation results showed that this process has three main stages: (1) indentation at the very beginning, (2) upsetting, and (3) extrusion predominantly occurring at the very end stage of the stroke. The bulk of the pin forming occurs at the end stroke of the process (extrusion stage). The effects of punch/pin diameter ratio on the pin aspect ratio and the maximum forming load were also investigated. In addition, the finite element results also revealed that a hybrid friction model was required to be implemented for better fit with experimental results as compared to the shear and Coulomb friction models.