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.

Contact of Rough Surfaces: Combined Elastic and Rate-Dependent Effects

2008 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Half Plane ◽  
Contact Force ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Approximation Error ◽  
Tangential Velocity ◽  
Contact Forces ◽  
Tangential Contact ◽  
Force Components ◽  
Approximate Equations

Approximate closed form equations are found for normal and tangential contact forces of rough surfaces in dry friction. Using a viscoelastic asperity behavior, mathematical formulae are derived for normal and tangential components of the contact force that depend not only on the separation of the two surfaces but also the rate of approach and relative sliding. The tangential force over a half-plane, corresponding to the moving direction, is found accounting for the directionality of the tangential component of asperity forces. A statistical approach is forwarded in which dependence of the asperity normal and tangential contact force on relative tangential velocity of two asperities can presented as corrective factors in the mathematical description of normal and tangential force components. These are force directionality corrective coefficient and force-velocity directionality corrective coefficient. Two sets of approximate equations are found for each of the normal and half-plane tangential force components. The simplest forms of the approximate equations achieve accuracy to within five (5) percent error, while other forms yield approximation error within 0.2 percent.

Viscoelastic Contact of Nominally Flat Rough Surfaces

2005 ◽  
Author(s):  
K. Farhang ◽  
A. Lim
Keyword(s):  
Contact Force ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Tangential Velocity ◽  
Surface Profile ◽  
Contact Forces ◽  
Profile Measurement ◽  
Tangential Contact ◽  
Corrective Factor ◽  
Percent Accuracy

Approximate closed-form equations are derived for normal and tangential contact forces of rough surfaces in dry friction. Using an extension of the Greenwood and Tripp model, in which the derivations permit asperity shoulder-to-shoulder contact and viscoelastic asperity behavior. Mathematical formulae are derived for normal and tangential components of the contact force that depend not only on the proximity of the two surfaces but also the rate of approach and relative sliding. A statistical approach is forwarded in which dependence of the asperity tangential contact force on relative tangential velocity of two asperities can be cast as a corrective factor in the mathematical description of tangential force. In this regard two corrective coefficients are derived: force directionality corrective coefficient and force-velocity directionality corrective coefficient. The results show that for a moderate to high load ranges the contact force can be analytically described to within 20 percent accuracy, well below the uncertainties due to surface profile measurement.

A Kinetic Friction Model for Viscoelastic Contact of Nominally Flat Rough Surfaces

2007 ◽  
Vol 129 (3) ◽  
pp. 684-688 ◽  
Author(s):  
K. Farhang ◽  
A. Lim
Keyword(s):  
Contact Force ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Tangential Velocity ◽  
Surface Profile ◽  
Friction Model ◽  
Contact Forces ◽  
Profile Measurement ◽  
Tangential Contact ◽  
Force Velocity

Approximate closed-form equations are derived for normal and tangential contact forces of rough surfaces in dry friction. Using an extension of the Greenwood and Tripp (1970, Proc, Inst. Mech. Eng., 185, pp. 625–633) model, in which the derivations permit asperity shoulder-to-shoulder contact and viscoelastic asperity behavior, mathematical formulae are derived for normal and tangential components of the contact force that depend not only on the proximity of the two surfaces but also the rate of approach and relative sliding. A statistical approach is forwarded in which dependence of the asperity tangential contact force on relative tangential velocity of two asperities can be cast as corrective factors in the mathematical description of tangential force. In this regard two corrective coefficients are derived: force directionality corrective coefficient and force–velocity directionality corrective coefficient. The results show that for a moderate to high load ranges the contact force can be analytically described to within 20% accuracy of that from a numerical integration of the contact equations, well below the uncertainties due to surface profile measurement.

Railway Truck Response to Random Rail Irregularities

1975 ◽  
Vol 97 (3) ◽  
pp. 957-964 ◽  
Author(s):  
Neil K. Cooperrider
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Tangential Force ◽  
Contact Forces ◽  
Guidance Force ◽  
Power Spectral ◽  
Power Spectral Densities ◽  
Rail Irregularities ◽  
Frequency Domain Techniques

This paper discusses the random response of a seven degree of freedom, passenger truck model to lateral rail irregularities. Power spectral densities and root mean square levels of component displacements and contact forces are reported. The truck model used in the study allows lateral and yaw degrees of freedom for each wheelset, and lateral, yaw and roll freedoms for the truck frame. Linear creep relations are utilized for the rail-wheel contact forces. The lateral rail irregularities enter the analysis through the creep expressions. The results described in the paper were obtained using frequency domain techniques to solve the equations of motion. The reported results demonstrate that the guidance force needed when traveling over irregular rail at high speed utilizes a significant portion of the total available tangential force between wheel and rail.

Viscoelastic Contact of Rough Surfaces in Relative Normal and Sliding Motion

2008 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Contact Force ◽  
Tangential Force ◽  
Three Dimensional ◽  
Tangential Velocity ◽  
Asperity Contact ◽  
Sliding Motion ◽  
Force Velocity ◽  
Force Components ◽  
Viscoelastic Contact ◽  
Approximate Equations

Mathematical formulae are derived for normal and tangential components of the contact force that depend not only on the proximity of the two surfaces but also the rate of approach and relative sliding. The development of the contact model is based on the asperity shoulder-shoulder contact leading to slanted asperity contact force. Thus an asperity force contains both normal and tangential components. Three dimensional consideration of asperity contact force yields directionally dependence of both the normal and tangential force components. A previously reported statistical approach is employed in which the dependence of the asperity normal and tangential contact force components on relative tangential velocity of two asperities are cast as corrective factors in the mathematical description of normal and tangential force components. The two corrective coefficients are the force directionality corrective coefficient and the force-velocity directionality corrective coefficient. Approximate equations are found for each of the normal and half-plane tangential force components that achieve accuracy within five (5) percent error.

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.

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 Contact Forces in a Screw Feeding Process

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Yunfei Shi ◽  
Xiliang Zhang ◽  
Shoujuan Cui ◽  
Kui Ma
Keyword(s):  
Contact Force ◽  
Normal Force ◽  
Bulk Material ◽  
Distinct Element ◽  
Tangential Force ◽  
Particle Diameter ◽  
Contact Forces ◽  
Slip Model ◽  
Screw Feeder ◽  
Feeding Process

The contact force between particles is analysed in this paper. Firstly, theoretical analysis is carried out based on the Hertz–Mindlin (no slip) model. Secondly, the normal force and tangential force are, respectively, simulated in single/double-flight screw feeders with the discharging device at three rotating speeds (60 rpm, 90 rpm, and 120 rpm) using different diameter particles (3 mm,  5 mm, and 7 mm) by the extended distinct element method (EDEM) software. Finally, the simulation results show that the particle diameter has the biggest impact on average contact force in the feeding process. This research provides theoretical basis for the study of the rule of bulk material movement in the screw feeder and the development of the high-precision feeding machine.

Normal and Tangential Forces Combine to Convey Contact Pressure during Dynamic Tactile Stimulation

2021 ◽  
Author(s):  
David Gueorguiev ◽  
Julien Lambert ◽  
Jean-Louis Thonnard ◽  
Katherine J. Kuchenbecker
Keyword(s):  
Contact Pressure ◽  
Contact Force ◽  
Tangential Force ◽  
Surface Friction ◽  
Contact Forces ◽  
Force Vector ◽  
Haptic Interactions ◽  
Tangential Forces ◽  
Haptic Stimulation ◽  
Better Than

Abstract Humans need to accurately process the contact forces that arise as they perform everyday haptic interactions, but the mechanisms by which the forces on the skin are represented and integrated remain little understood. In this study, we used a force-controlled robotic platform and simultaneous ultrasonic modulation of the finger-surface friction to briefly and independently manipulate the normal and tangential forces during passive haptic stimulation by a flat surface. When participants were asked whether the contact pressure on their finger had briefly increased or decreased, they could not distinguish the normal force from the tangential force. Instead, they integrated the normal and tangential components of the force vector into a multidimensional computation of the contact force. We additionally investigated whether participants relied on three common contact-force metrics. Interestingly, the change in the amplitude of the force vector predicted participants’ responses better than the change of the coefficient of dynamic friction and the change of the angle of the contact force vector. Thus, intensive cues related to the amplitude of the applied force may be meaningful for the sensing of contact pressure during haptic stimulation by a moving surface.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

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