Experimental Study of Normal Contact Force Between a Rolling Pneumatic Tyre and a Single Asperity

2017 ◽  
Vol 09 (06) ◽  
pp. 1750081 ◽  
Author(s):  
Yuan-Fang Zhang ◽  
Julien Cesbron ◽  
Hai-Ping Yin ◽  
Michel Bérengier
Keyword(s):  
Contact Force ◽  
Numerical Models ◽  
Force Transducer ◽  
Contact Forces ◽  
Exterior Surface ◽  
Normal Contact ◽  
Single Asperity ◽  
Direct Measurements ◽  
Time Signals ◽  
Force Signal

This paper proposes a novel experimental test apparatus that permits direct measurements of tyre/asperity normal contact forces under rolling conditions without interfacial layer. A reduced-sized pneumatic tyre is set rolling on the exterior surface of a cylindrical test rig simulating a smooth road surface except a single asperity of simple geometric shape connected to an embedded force transducer. Distinct asperity geometries lead to similar shapes of force signal but different magnitudes whose relationships with the indentation have exponents close to those in classical analytical solutions. By analyzing the time signals of the contact force and their frequency contents for different rolling speeds, the quasi-static nature of the contact, commonly assumed in numerical models, is verified.

Shape Optimal Design of Contact Springs of Electronic Connectors

2002 ◽  
Vol 124 (3) ◽  
pp. 178-183 ◽  
Author(s):  
Yeh-Liang Hsu ◽  
Yuan-Chan Hsu ◽  
Ming-Sho Hsu
Keyword(s):  
Contact Force ◽  
Printed Circuit Boards ◽  
Normal Force ◽  
Optimization Techniques ◽  
Contact Forces ◽  
Design Parameters ◽  
Original Design ◽  
Insertion Force ◽  
Element Analysis ◽  
Normal Contact

An electronic connector provides a separable interface between two subsystems of an electronic system. The contact spring is probably the most critical component in an electronic connector. Mechanically, the contact spring provides the contact normal force, which establishes the contact interface as the connector is mated. However, connector manufacturers have a basic struggle between the need for high normal contact forces and low insertion forces. Designing connectors with large numbers of pins that are used with today’s integrated circuits and printed circuit boards often results in an associated rise in connector insertion force. It is possible to lower the insertion force of a connector by redesigning the geometry of the contact spring, but this also means a decrease in contact normal force. In this paper, structural shape optimization techniques are used to find the optimal shape of the contact springs of an electronic connector. The process of the insertion of a PCB into the contact springs of a connector is modeled by finite element analysis. The maximum insertion force and the contact normal force are calculated. The effects of several design parameters are discussed. The geometry of the contact springs is then parameterized and optimized. The required insertion force is minimized while the normal contact force and the resulting stress are maintained within specified values. In our example, the insertion force of the final contact spring design is reduced to 68.3% of that of the original design, while the contact force and the maximum stress are maintained within specified values.

Wheel–Rail Impact at Crossings: Relating Dynamic Frictional Contact to Degradation

2017 ◽  
Vol 12 (4) ◽  
Author(s):  
Zilong Wei ◽  
Chen Shen ◽  
Zili Li ◽  
Rolf Dollevoet
Keyword(s):  
Plastic Deformation ◽  
Contact Force ◽  
Frictional Contact ◽  
Point Contact ◽  
Strain Analysis ◽  
Dynamic Contact ◽  
Contact Forces ◽  
Fe Method ◽  
Normal Contact ◽  
The Impact

Irregularities in the geometry and flexibility of railway crossings cause large impact forces, leading to rapid degradation of crossings. Precise stress and strain analysis is essential for understanding the behavior of dynamic frictional contact and the related failures at crossings. In this research, the wear and plastic deformation because of wheel–rail impact at railway crossings was investigated using the finite-element (FE) method. The simulated dynamic response was verified through comparisons with in situ axle box acceleration (ABA) measurements. Our focus was on the contact solution, taking account not only of the dynamic contact force but also the adhesion–slip regions, shear traction, and microslip. The contact solution was then used to calculate the plastic deformation and frictional work. The results suggest that the normal and tangential contact forces on the wing rail and crossing nose are out-of-sync during the impact, and that the maximum values of both the plastic deformation and frictional work at the crossing nose occur during two-point contact stage rather than, as widely believed, at the moment of maximum normal contact force. These findings could contribute to the analysis of nonproportional loading in the materials and lead to a deeper understanding of the damage mechanisms. The model provides a tool for both damage analysis and structure optimization of crossings.

Evaluation of Friction Damping in Dovetail Root Joints Based on Dissipation Energy on Contact Surfaces

2009 ◽  
Author(s):  
Kunio Asai ◽  
Shigeo Sakurai ◽  
Takeshi Kudo ◽  
Norihiko Ozawa ◽  
Taizo Ikeda
Keyword(s):  
Contact Force ◽  
Contact Stiffness ◽  
Relative Displacement ◽  
Contact Angles ◽  
Forced Response ◽  
Contact Forces ◽  
Friction Damping ◽  
Normal Contact ◽  
Tangential Contact ◽  
Contact Surfaces

It is necessary to increase and estimate friction damping at contact interfaces to reduce vibratory stresses in turbines. The hysteresis behavior between tangential contact force and relative displacement should be precisely estimated to improve the accuracy of fiction-damping estimates. There is a difficulty in establishing a general model of hysteresis because tangential contact stiffness depends on many parameters, such as normal contact force, contact geometry, surface roughness, and wear status. We discuss a procedure to empirically calculate friction damping in dovetail root joints using the tangential contact stiffness estimated from measured natural frequencies and the micro-slip model whose coefficients were experimentally obtained from special fretting tests. Instead of the multi-harmonic balance methods, we calculated the friction damping on the basis of the energy dissipation at contact surfaces to discuss the effects of the tangential contact stiffness on several physical values, i.e., tangential and normal contact forces, natural frequency, and micro-slip. In our model, the linear forced response analysis was conducted by taking into consideration the non-linearity between the tangential contact force and the relative displacement by defining the actual and imaginary tangential contact stiffness. We confirmed that the numerically calculated damping ratios are quantitatively in very good agreement with the measured ones under different contact angles, input gravity levels, and contact forces. This indicates that if the tangential contact stiffness is accurately estimated, friction damping with our method can be precisely estimated under different test conditions. We also showed that the estimated tangential contact stiffness for dovetail root joints are smaller than those obtained by the fretting tests at high input gravity. This is probably because the contact interface partially separates during a cyclic loading in the former case; this results in the decrease of the contact area and contact stiffness.

Computational and Experimental Analysis of Mechanical Systems With Revolute Clearance Joints

2013 ◽  
Author(s):  
Sony Cheriyan ◽  
Paulo Flores ◽  
Hamid M. Lankarani
Keyword(s):  
Contact Force ◽  
Computational Models ◽  
Mechanical Systems ◽  
Contact Forces ◽  
Force Model ◽  
Connecting Rod ◽  
Normal Contact ◽  
Clearance Joints ◽  
Coulomb’S Friction ◽  
Experimental Apparatus

The main objective of this work is to present a computational and experimental study on the contact forces developed in revolute clearance joints. For this purpose, a well-known slider-crank mechanism with a revolute clearance joint between the connecting rod and slider is utilized. The intra-joint contact forces that generated at this clearance joints are computed by considered several different elastic and dissipative approaches, namely those based on the Hertz contact theory and the ESDU tribology-based for cylindrical contacts, along with a hysteresis-type dissipative damping. The normal contact force is augmented with the dry Coulomb’s friction force. An experimental apparatus is use to obtained some experimental data in order to verify and validate the computational models. From the outcomes reported in this paper, it is concluded that the selection of the appropriate contact force model with proper dissipative damping plays a significant role in the dynamic response of mechanical systems involving contact events at low or moderate impact velocities.

scholarly journals Dynamic Response of Multibody Systems with Multiple Clearance Joints

2012 ◽  
Vol 7 (3) ◽  
Author(s):  
Paulo Flores ◽  
Hamid M. Lankarani
Keyword(s):  
Contact Force ◽  
Multibody Systems ◽  
Equations Of Motion ◽  
Physical And Mechanical Properties ◽  
Contact Forces ◽  
Force Model ◽  
Normal Contact ◽  
Clearance Joints ◽  
Continuous Contact ◽  
Dissipative Term

A general methodology for the dynamic modeling and analysis of planar multibody systems with multiple clearance joints is presented. The inter-connecting bodies that constitute a real physical mechanical joint are modeled as colliding components, whose dynamic behavior is influenced by the geometric, physical and mechanical properties of the contacting surfaces. A continuous contact force model, based on the elastic Hertz theory, together with a dissipative term associated with the internal damping, is utilized to evaluate the intra-joint normal contact forces. The incorporation of the friction phenomenon, based on the classical Coulomb’s friction law, is also included in this study. The suitable contact force models are embedded into the dynamic equations of motion for the multibody systems. In the sequel of this process, the fundamental methods to deal with contact-impact events in mechanical systems are presented. Finally, two planar mechanisms with multiple revolute clearance joints are used to demonstrate the accuracy and efficiency of the presented approach and to discuss the main assumptions and procedures adopted. The effects of single versus multiple clearance revolute joints are discussed.

Out-of-round railway wheels—wheel-rail contact forces and track response derived from field tests and numerical simulations

2003 ◽  
Vol 217 (2) ◽  
pp. 135-146 ◽  
Author(s):  
A Johansson ◽  
J C O Nielsen
Keyword(s):  
Numerical Simulations ◽  
Contact Force ◽  
Impact Load ◽  
Numerical Models ◽  
Field Tests ◽  
Fatigue Cracking ◽  
Contact Forces ◽  
Rolling Contact ◽  
Local Defect ◽  
Different Types

The influence of different types of railway wheel out-of-roundness (OOR) on the vertical dynamic wheel-rail contact force and track response is investigated through extensive field tests and numerical simulations. The response from a freight train, provided with a number of different types of severe wheel tread damage, is studied. Two different axle loads are used in combination with different train speeds in the range 30-100km/h. The wheel defects are wheelflats, local spalls due to rolling contact fatigue cracking, long local defects and polygonal wheels (periodic OOR). The vertical wheel-rail contact force was measured using a strain gauge based wheel impact load detector. Strain gauges and accelerometers were positioned on rails and sleepers to measure the track response. Most of the magnitudes of measured impact forces were found to be lower than the current impact load limit that is used in Sweden to determine when a defective wheel should be removed for repair. Only the long local defect caused larger force magnitudes than the wheel removal criterion. Measured responses are used to calibrate and validate numerical models for simulation of train-track interaction. Results from one linear and one state-dependent track model are compared.

An Experimental Study of Contact Forces During Oblique Elastic Impact

2009 ◽  
Vol 76 (3) ◽  
Author(s):  
Philip P. Garland ◽  
Robert J. Rogers
Keyword(s):  
Contact Force ◽  
High Speed ◽  
Steel Wire ◽  
Tangential Force ◽  
Tangential Velocity ◽  
Force Transducer ◽  
Contact Forces ◽  
Elastic Impact ◽  
Experimental Apparatus ◽  
Force Time

Low and high speed impacts frequently occur in many mechanical processes. Although widely studied, rarely are normal and tangential force time-waveforms measured, as generally these are very difficult measurements to do accurately. This paper presents, for the first time, a comprehensive set of experimentally obtained contact force waveforms during oblique elastic impact for a range of initial velocities and incidence angles. The experimental apparatus employed in this study was a simple pendulum consisting of a spherical steel striker suspended from a steel wire. The contact force time-waveforms were collected using a tri-axial piezoelectric force transducer sandwiched between a spherical target cap and a large block. The measured contact forces showed that loading was essentially limited to the normal and tangential directions in the horizontal plane. Analysis of the maximum normal and tangential forces for the near glancing angles of incidence indicated a friction coefficient that varies linearly with initial tangential velocity. The essential features of tangential force reversal during impact predicted by previous continuum models are confirmed by the experimental force results.

Influence of the Wheel and Rail Interpolation Scheme on the Contact Evaluation in Railway Dynamics

2005 ◽  
Author(s):  
J. Pombo ◽  
J. Ambro´sio
Keyword(s):  
Three Dimensional ◽  
Contact Forces ◽  
Railway Vehicle ◽  
Interpolation Scheme ◽  
Normal Contact ◽  
Contact Points ◽  
Rail Vehicles ◽  
Direct Measurements ◽  
Spatial Geometry ◽  
Conventional Rail

The dynamic behavior of the railway vehicles is strongly influenced by the complex interaction between the wheels and rails. In conventional rail vehicles the wheelsets are assembled with two wheels that are not free to rotate independently. Hence, their treads are profiled in order to allow them to negotiate curves without slipping. The dynamics of guidance depends on the wheel-rail contact forces resultant from the vehicle interaction with the track. In this work a methodology for the accurate geometric description of track models is proposed in the framework of multibody dynamics. It includes the representation of the track spatial geometry and its irregularities. The wheel and rail surfaces are parameterized with a formulation that allows using any wheel and rail profiles obtained from direct measurements or design requirements. A methodology is proposed to find online the coordinates of the contact points between wheel and rail surfaces, even for the most general three dimensional motion of the wheelset. A formulation for the description of the normal contact forces, which result from the wheel-rail interaction, is also presented. The tangential creep forces in the wheel-rail contact area are evaluated using: Kalker linear theory; Heuristic force method; Polach formulation. All methodologies proposed here are implemented in a general multibody code. The advantages and drawbacks of the computational tool are discussed with emphasis on the influence of the interpolation scheme used to parameterize the wheel and rail profiles. The discussion is supported through the dynamic analysis of the wheelset of the railway vehicle ML95 on a straight track.

Three-Dimensional Wear Prediction of Four-Degrees-of-Freedom Parallel Mechanism With Clearance Spherical Joint and Flexible Moving Platform

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Gengxiang Wang ◽  
Hongzhao Liu
Keyword(s):  
Contact Force ◽  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Contact Forces ◽  
Force Model ◽  
Spherical Joint ◽  
Normal Contact ◽  
Tangential Contact ◽  
Moving Platform

Three-dimensional (3D) wear of the clearance spherical joint in four-degrees-of-freedom (DOF) parallel mechanism is predicted based on Archard's wear model. The flexible moving platform is treated as thin plate element based on absolute nodal coordinate formulation (ANCF). The tangent frame is introduced to formulate the constraint equation of universal joint. One of the spherical joints is treated as clearance joint. The normal and tangential contact forces are calculated based on Flores contact force model and modified Coulomb friction model. In order to predict 3D wear, the normal contact force, tangential contact velocity, and eccentricity vector are decomposed in the global coordinate system. Simulation results show that 3D wear occurred in three directions are not uniform each other.

scholarly journals Non-smooth dynamic modeling and simulation of an unmanned bicycle on a curved pavement

2022 ◽  
Vol 43 (1) ◽  
pp. 93-112
Author(s):  
Kaiming Zhang ◽  
Xudong Zheng ◽  
Zhang Chen ◽  
Bin Liang ◽  
Tianshu Wang ◽  
...  
Keyword(s):  
Dynamic Model ◽  
Friction Force ◽  
Contact Force ◽  
Contact Point ◽  
Rigid Bodies ◽  
Contact Forces ◽  
Force Model ◽  
Lagrange Equations ◽  
Stick Slip ◽  
Normal Contact

AbstractThe non-smooth dynamic model of an unmanned bicycle is established to study the contact-separate and stick-slip non-smooth phenomena between wheels and the ground. According to the Carvallo-Whipple configuration, the unmanned bicycle is reduced to four rigid bodies, namely, rear wheel, rear frame, front fork, and front wheel, which are connected by perfect revolute joints. The interaction between each wheel and the ground is simplified as the normal contact force and the friction force at the contact point, and these forces are described by the Hunt-Crossley contact force model and the LuGre friction force model, respectively. According to the characteristics of flat and curved pavements, calculation methods for contact forces and their generalized forces are presented. The dynamics of the system is modeled by the Lagrange equations of the first kind, a numerical solution algorithm of the dynamic equations is presented, and the Baumgarte stabilization method is used to restrict the drift of the constraints. The correctness of the dynamic model and the numerical algorithm is verified in comparison with the previous studies. The feasibility of the proposed model is demonstrated by simulations under different motion states.

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