Model-Based Investigation of Friction During Start-Up of Hydrodynamic Journal Bearings

1995 ◽  
Vol 117 (4) ◽  
pp. 667-673 ◽  
Author(s):  
A. Harnoy
Keyword(s):  
Friction Model ◽  
Journal Bearings ◽  
Time Variable ◽  
Stribeck Curve ◽  
Dynamic Friction ◽  
Stick Slip ◽  
Friction Characteristics ◽  
Start Up ◽  
Variable Friction ◽  
Steady Velocity

An analysis is developed for the time-variable friction during the start-up of a rotor system. The analysis is based on a dynamic friction model that has been developed from the theory of unsteady lubrication and can describe the observed friction characteristics. The model reduces to the Stribeck curve of friction versus steady velocity, and shows hysteresis curves in oscillating velocity. The “Dahl effect” of a presliding displacement before the breakaway is also included. The results indicate that the friction characteristics and energy friction losses, during the start-up, depend on a set of dimensionless parameters that represent the bearing as well as the dynamic system. The study shows that appropriate design and operation can prevent stick-slip friction and minimize wear during start-up.

A Stick-Slip Interactions Model of Soft-Solid Frictional Contacts

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Hongbiao Xiang ◽  
Mitja Trkov ◽  
Kaiyan Yu ◽  
Jingang Yi
Keyword(s):  
Network Structure ◽  
Systems Design ◽  
Friction Model ◽  
Dynamic Friction ◽  
Interaction Patterns ◽  
Contact Interactions ◽  
Solid Contact ◽  
Mechatronic Systems ◽  
Stick Slip ◽  
Frictional Contacts

Modeling of the soft-solid frictional interactions plays an important role in many robotic and mechatronic systems design. We present a new model that characterizes the two-dimensional (2D) soft-solid contact interactions. The new computational approach integrates the LuGre dynamic friction model with the beam network structure of the soft-solid contact. The LuGre dynamic friction model uses the bristle deformation to capture the friction characteristics and dynamics, while the beam network structure represents the elastic contact interactions. We also present a model simplification to facilitate analysis of model properties. The model prediction and validation results are demonstrated with the experiments. The experimental results confirm the effectiveness of the modeling development. We further use the model to compute the influence of the normal load and sliding velocity on the stick-slip interaction patterns and properties. These results explain and provide analytical foundation for the reported experiments in the literature.

An AFM-Based Nanomanipulation Model Describing the Atomic Two Dimensional Stick-Slip Behavior

2007 ◽  
Author(s):  
Fakhreddine Landolsi ◽  
Fathi H. Ghorbel ◽  
James B. Dabney
Keyword(s):  
Friction Model ◽  
Modular Approach ◽  
Dynamic Friction ◽  
Asperity Contact ◽  
Two Dimensional ◽  
Stick Slip ◽  
Complex Interactions ◽  
Proposed Model ◽  
Lattice Periodicity ◽  
Afm Cantilever

A new AFM-based nanomanipulation model describing the relevant physics and dynamics at the nanoscale is presented. The nanomanipulation scheme consists of integrated subsystems that are identified in a modular approach. The model subsystems define the AFM cantilever-sample dynamics, the AFM tip-sample interactions, the contact mechanics and the friction between the sample and the substrate. The coupling between these different subsystems is emphasized. The main contribution of the proposed nanomanipulation model is the use of a new 2D dynamic friction model based on a generalized bristle interpretation of one asperity contact. The efficacy of the proposed model to reproduce experimental data is demonstrated via numerical simulations. In fact, the model is shown to describe the 2D stick-slip behavior with the substrate lattice periodicity. The proposed nanomanipulation model facilitates the improvement and extension of each subsystem to further take into account the complex interactions at the nanoscale.

Friction Modeling and PD Compensation at Very Low Velocities

1995 ◽  
Vol 117 (1) ◽  
pp. 8-14 ◽  
Author(s):  
Pierre E. Dupont ◽  
Eric P. Dunlap
Keyword(s):  
Steady Motion ◽  
Friction Model ◽  
Good Representation ◽  
Friction Modeling ◽  
Stick Slip ◽  
Line Contacts ◽  
Machine Stiffness ◽  
Variable Friction ◽  
Hardened Tool Steel ◽  
Parameter Values

It is a well-known empirical result that stick-slip can often be eliminated from a system by stiffening it. More recently, it has been shown that for a negatively-sloped friction-velocity curve, a frictional lag must be present for machine/controller stiffness to produce this stabilizing effect. In this paper, experiments involving dry and lubricated line contacts of hardened tool steel are described which demonstrate the existence of frictional lag in boundary lubrication. It is also shown that a single-state-variable friction model provides a good representation of the actual friction dynamics. The model and associated parameter values provide a means for computing lower bounds on the machine stiffness and PD gains necessary for steady motion at velocities on the order of microns per second.

Dynamic analysis of vehicle start-up judder based on elasto-plastic friction model and dry clutch maneuvering characteristic

2018 ◽  
Vol 233 (2) ◽  
pp. 455-469 ◽  
Author(s):  
Renfei Yuan ◽  
Guangqiang Wu
Keyword(s):  
Friction Model ◽  
Step Response ◽  
Negative Slope ◽  
Stick Slip ◽  
Clamp Force ◽  
Powertrain System ◽  
Start Up ◽  
Clutch Engagement ◽  
Engagement Process ◽  
Dry Clutch

This paper presents a detailed investigation of the dry clutch engagement process, and vehicle start-up judder phenomenon that could result in the deterioration of vehicle ride comfort. Elasto-plastic friction model is elaborated through the slider-pulley system, which shows some friction characteristics such as presliding, stick-slip motion, Stribeck effects, etc., and applied to dry clutch. The axial compression characteristics of three elastic parts, which include diaphragm spring, cushion spring, and link strip have been taken into consideration, and nonlinear relationship between the release bearing travel and the clutch clamp force is also established. The powertrain system model of front-engine and front-wheel-drive vehicle equipped with manual transmission is set up to recreate the start-up judder phenomenon in the numerical simulation and analyze its mechanism. The sudden transfer of the engine torque during the clutch engagement process results in the initial judder, which can be supposed as the step response of system and is initially weakened due to the damping of the powertrain system. Then the judder gradually strengthens and gets in the most severe vibrance when the clutch is about to get in to the fully engaged state, which is related to the frictional characteristics that forms a closed-loop positive feedback system, as well as the frequent state transitions between sliding state and engaged state. The positive slope of Stribeck effect as well as the reduction of absolute value of negative slope can both effectively suppress the start-up judder, and the apparent judder occurs only if the negative slope is outside of a certain range, instead of in all of the range. In addition, the fluctuation of clutch clamp force can aggravate the start-up judder, in which a more chaotic oscillation is emerged.

Stick-Slip Interactions of the Soft-Solid Contact: An Integrated LuGre/Beam Network Model Approach

2015 ◽  
Author(s):  
Mitja Trkov ◽  
Haijun Han ◽  
Jingang Yi ◽  
Yanjie Liu
Keyword(s):  
Network Model ◽  
Systems Design ◽  
Friction Model ◽  
Dynamic Friction ◽  
Solid Contact ◽  
Mechatronic Systems ◽  
Stick Slip ◽  
New Model ◽  
Comparison Results ◽  
Model Approach

Contact model of the soft-solid interactions plays an important role for robotic and mechatronic systems design. We present a new model of the soft-solid contact that integrates the LuGre dynamic friction model with the beam network model. The LuGre dynamic friction model uses the bristle deformation to capture the friction characteristics and dynamics while the beam network model represents the elastic contact interactions. The new model is applied to a fingertip-like stick-slip interaction application. We present the model prediction and validation results with the experiments. The comparison results demonstrate the effectiveness of the modeling development.

scholarly journals Study on Friction in Automotive Shock Absorbers Part 1: Friction Simulation Using a Dynamic Friction Model in the Contact Zone of an FEM Model

Vehicles ◽  
2021 ◽  
Vol 3 (2) ◽  
pp. 212-232
Author(s):  
Ludwig Herzog ◽  
Klaus Augsburg
Keyword(s):  
Ride Comfort ◽  
Viscous Friction ◽  
Simulation Method ◽  
Friction Model ◽  
Model Parameters ◽  
Dynamic Friction ◽  
Friction Modeling ◽  
Shock Absorbers ◽  
Operation Conditions ◽  
Wide Range

The important change in the transition from partial to high automation is that a vehicle can drive autonomously, without active human involvement. This fact increases the current requirements regarding ride comfort and dictates new challenges for automotive shock absorbers. There exist two common types of automotive shock absorber with two friction types: The intended viscous friction dissipates the chassis vibrations, while the unwanted solid body friction is generated by the rubbing of the damper’s seals and guides during actuation. The latter so-called static friction impairs ride comfort and demands appropriate friction modeling for the control of adaptive or active suspension systems. In this article, a simulation approach is introduced to model damper friction based on the most friction-relevant parameters. Since damper friction is highly dependent on geometry, which can vary widely, three-dimensional (3D) structural FEM is used to determine the deformations of the damper parts resulting from mounting and varying operation conditions. In the respective contact zones, a dynamic friction model is applied and parameterized based on the single friction point measurements. Subsequent to the parameterization of the overall friction model with geometry data, operation conditions, material properties and friction model parameters, single friction point simulations are performed, analyzed and validated against single friction point measurements. It is shown that this simulation method allows for friction prediction with high accuracy. Consequently, its application enables a wide range of parameters relevant to damper friction to be investigated with significantly increased development efficiency.

Modeling of Piezo-Actuated Stick-Slip Micro-Drives: An Overview

2012 ◽  
Vol 81 ◽  
pp. 39-48 ◽  
Author(s):  
Ha Xuan Nguyen ◽  
Christoph Edeler ◽  
Sergej Fatikow
Keyword(s):  
Mechanical Model ◽  
Integrated Model ◽  
Friction Model ◽  
Fundamental Importance ◽  
Future Research ◽  
Stick Slip ◽  
Research Activities ◽  
Model Combining ◽  
Friction Models

This paper gives an overview about problems of modeling of piezo-actuated stick-slip micro-drives. It has been found that existing prototypes of such devices have been investigated empirically. There is only few research dealing with the theory behind this kind of drives. By analyzing the current research activities in this field, it is believed that the model of the drive depends strongly on the friction models, but in most cases neglecting any influences of the guilding system.These analyses are of fundamental importance for an integrated model combining friction model and mechanical model offering promising possibilities for future research.

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