Influence of Particle Orientation on the Performance of Geogrid Reinforced Ballast

To explore the initial orientation effect of ballast assembly on the reinforcement performance of the geogrid reinforced ballast, particles with random orientation and five prescribed rotational orientations were developed through particle flow code (PFC3D). The evolution laws of the pullout force and the principal directions of the normal contact force were systematically compared and analyzed. Furthermore, the mechanical responses such as pullout force, distribution of axial force, displacement vectors, force chain, and mesoscopic fabric were discussed. According to the displacement vectors of the ballast particles, the average thickness of the stable shear band is determined. The inherent relationships among the force chain, the rotational angle of the normal contact force, and the mesoscopic fabric parameters are revealed. The results show that the pullout force of specimens with the initial orientation of 45° increases monotonously during the pullout process, and the peak value of pullout force appears at the end of the test. The mesostructural analysis also confirms that the evolution of the principal direction of contact normal force is relatively steady during the pullout process, indicating that the specimen with 45° orientation possesses higher systematic stability and ductility. Moreover, the optimum interval from 56.68° to 57.30° is observed to remain in a self-adapting state for ballast assembly.

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Experimental Validation of a Volumetric Planetary Rover Wheel/Soil Interaction Model

Volume 1: 15th International Conference on Advanced Vehicle Technologies; 10th International Conference on Design Education; 7th International Conference on Micro- and Nanosystems ◽

10.1115/detc2013-13486 ◽

2013 ◽

Author(s):

Willem Petersen ◽

John McPhee

Keyword(s):

Contact Force ◽

Interaction Model ◽

Contact Model ◽

Soil Parameters ◽

Model Parameters ◽

Force Model ◽

Normal Contact ◽

Planetary Rover ◽

Normal Contact Force ◽

Contact Force Model

For the multibody simulation of planetary rover operations, a wheel-soil contact model is necessary to represent the forces and moments between the tire and the soft soil. A novel nonlinear contact modelling approach based on the properties of the hypervolume of interpenetration is validated in this paper. This normal contact force model is based on the Winkler foundation model with nonlinear spring properties. To fully define the proposed normal contact force model for this application, seven parameters are required. Besides the geometry parameters that can be easily measured, three soil parameters representing the hyperelastic and plastic properties of the soil have to be identified. Since it is very difficult to directly measure the latter set of soil parameters, they are identified by comparing computer simulations with experimental results of drawbar pull tests performed under different slip conditions on the Juno rover of the Canadian Space Agency (CSA). A multibody dynamics model of the Juno rover including the new wheel/soil interaction model was developed and simulated in MapleSim. To identify the wheel/soil contact model parameters, the cost function of the model residuals of the kinematic data is minimized. The volumetric contact model is then tested by using the identified contact model parameters in a forward dynamics simulation of the rover on an irregular 3-dimensional terrain and compared against experiments.

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Contact Force Distribution and Induced Anisotropy in Granular Materials under Biaxial Test

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.446-449.1927 ◽

2012 ◽

Vol 446-449 ◽

pp. 1927-1934

Author(s):

Min Yun Hu ◽

Qiao Hao Chen ◽

Ying Shen ◽

Xiao Wu Tang

Keyword(s):

Contact Force ◽

Normal Force ◽

Microscopic Analysis ◽

Contact Forces ◽

Force Chain ◽

Particle Flow Code ◽

Biaxial Compression ◽

Biaxial Test ◽

Induced Anisotropy ◽

Structural Anisotropy

A 2-dimensional granular assembly, subjected to isotropic consolidation and biaxial compression, is simulated by applying discrete element method and the particle flow code of PFC2D. The contact force network and distribution are examined and compared to an analogous photoelastic experiment carried out by other studies. The current study shows that the assembly undergoes dilatation and strain-softening after peak strength, and the coordination number (average contact number of particles) increases a little in the initial stage of strain hardening followed by a sharp dropping before the onset of softening. This is correlated with the contact force chain establishment and the evolution of structural anisotropy. The distribution of the normal force and the ratio of tangential to normal force for both the isotropically compressed and sheared stages indicates that the strong normal contacts are crucial for the force chain transmitting stress through assembly. The angular distribution of the contact forces supported this point and could help visualizing the induced anisotropy. These issues are vital for gaining a deeper understanding of the macroscopic behavior of granular material from microscopic analysis.

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A Theoretical Model for the Normal Contact Force of Two Elastoplastic Ellipsoidal Bodies

Journal of Applied Mechanics ◽

10.1115/1.4048320 ◽

2020 ◽

Vol 88 (3) ◽

Author(s):

Verena Becker ◽

Marc Kamlah

Keyword(s):

Theoretical Model ◽

Contact Force ◽

General Description ◽

Element Analysis ◽

Normal Contact ◽

Normal Contact Force ◽

Static Contact ◽

Elliptical Contact ◽

Individual Grains ◽

Force Displacement

Abstract To model the mechanical behavior of granular materials, a reliable description of the material properties is indispensable. Individual grains are usually not perfectly spherical. In batteries, for instance, lithium nickel manganese cobalt oxide (NMC) is a frequently used material, consisting out of particles with possibly ellipsoidal like shapes. As particles may plastically deform under increasing stresses, the paper presents a theoretical model for the normal contact force of elastoplastic ellipsoidal bodies for the use in the context of mechanical discrete element method (DEM). The model can be considered as extension of the elastic, elastic-plastic, fully plastic Thornton model by using a more general description to incorporate elliptical contact areas. The focus is on a normal contact force description as continuous function of time for all regimes, elastic, elastoplastic, and fully plastic loading, as well as unloading from elastoplastic loading, while the evolution of the plastic contact area is not considered here. All underlying formulae to describe the force-displacement relationship for the static contact problem are derived, partly based on finite element analysis (FEA). To verify the new model, FEAs are performed and their results compared with the model predictions.

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Real-time normal contact force control for robotic surface processing of workpieces without a priori geometric model

The International Journal of Advanced Manufacturing Technology ◽

10.1007/s00170-021-07497-2 ◽

2022 ◽

Author(s):

Jian Li ◽

Yisheng Guan ◽

Haowen Chen ◽

Bing Wang ◽

Tao Zhang ◽

...

Keyword(s):

Real Time ◽

Contact Force ◽

Force Control ◽

Geometric Model ◽

A Priori ◽

Surface Processing ◽

Normal Contact ◽

Normal Contact Force ◽

Contact Force Control

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Normal and Angular Motions at Rough Planar Contacts During Sliding With Friction

Journal of Tribology ◽

10.1115/1.2920919 ◽

1992 ◽

Vol 114 (3) ◽

pp. 567-578 ◽

Cited By ~ 29

Author(s):

D. P. Hess ◽

A. Soom

Keyword(s):

Nonlinear Equations ◽

Contact Force ◽

Contact Area ◽

Normal Contact ◽

Frictional Contacts ◽

Normal Contact Force ◽

The Real ◽

Real Area Of Contact ◽

Real Area ◽

Contact Vibrations

The planar dynamics of a rough block in nominally stationary or sliding contact with a counter-surface is studied in this work. Starting with the Greenwood-Williamson model of a rough surface, the analysis of elastic contact deflections is extended to accommodate angular as well as normal motions. The real area of contact and the normal contact force are obtained in terms of the relative approach and orientation of the surfaces. It is shown that angular and normal motions at frictional contacts are generally coupled. The contact area and normal contact force are shown to be nonlinearly related to the normal and angular motions. However, the contact area remains proportional to the normal load, even in the presence of angular motions. When the friction force is assumed to be proportional to the real area of contact, the coefficient of sliding friction will be unchanged by small relative rotations between the sliding bodies. Based on this contact and friction model, the nonlinear equations of motion that describe the planar contact vibrations of a sliding block can be written directly. Although a detailed analysis of the stability and response characteristics of these nonlinear equations is beyond the scope of the present work, a limited comparison of calculations and measurements taken on both stationary and sliding blocks indicate that the small amplitude contact vibrations are reasonably well captured by the model developed in this work.

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Elastic-Plastic Finite-Element Analysis of Repeated, Two-Dimensional Wheel-Rail Rolling Contact under Time-Dependent Load

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/09544062jmes201 ◽

2006 ◽

Vol 220 (5) ◽

pp. 603-613 ◽

Cited By ~ 3

Author(s):

Z. F. Wen ◽

X. S. Jin

Keyword(s):

Finite Element ◽

Residual Stresses ◽

Contact Force ◽

Rolling Contact ◽

Time Dependent ◽

Two Dimensional ◽

Normal Contact ◽

Normal Contact Force ◽

Residual Strains ◽

Harmonic Variation

A study was performed using a finite-element model to obtain stresses, strains, and deformations for repeated, two-dimensional rolling contact of a locomotive driving wheel and a rail under time-dependent load. An advanced cyclic plasticity model was used with a commercial finite element code via a material subroutine. The time-dependent load was considered a harmonic variation of the wheel-rail normal contact force. The normal contact pressure was assumed to follow the Hertzian distribution and the tangential force followed the Carter distribution. A wavy profile is formed on the running surface of the rail subjected to the harmonic variation of the normal (vertical) contact force. The developed wavelength of the profile corresponds to the frequency of the normal contact force for the actual train speed. The creepage or rolling-sliding condition plays an important role in the residual strains and deformations, but its influence on the residual stresses is insignificant. The residual stresses at the surface decrease with increasing rolling passes and gradually tend to stabilize. The residual strains and surface displacements increase with increasing rolling cycle, but the increases in residual strain and surface displacement per rolling pass (ratchetting rate) decay. The residual stresses, strains, and deformations near the wave trough of the residual wavy deformation are larger than those near the wave crest. For any given creepage including zero value, when the number of rolling passes increases, the surface depth of the wavy-deformed surface increases but the ratchetting rate decays. The results are useful in investigating the influence of plastic deformation on rail corrugation.

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Research on Normal Motion of Specimen of Ultrasonic Feeding

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.433-440.3826 ◽

2012 ◽

Vol 433-440 ◽

pp. 3826-3830

Author(s):

Liang Li ◽

Mian Zheng

Keyword(s):

Contact Force ◽

Structural Model ◽

Contact Process ◽

Low Frequency ◽

Normal Velocity ◽

Normal Contact ◽

Nonlinear Dynamical ◽

Normal Contact Force ◽

Theoretical Results ◽

Good Agreement

In this paper, a micro structural model is applied to study the normal contact process of the specimen of the ultrasonic feeding. Firstly, the normal velocity of the specimen with the actuation of the oscillator is calculated by solving the nonlinear dynamical equation of the specimen. The theoretical results of the normal velocity are in good agreement with the experimental results under the same conditions. The theoretical results indicate that for the low frequency of the oscillator, at most time, the normal contact force is zero, whereas for the high frequency the normal contact force is periodical. In addition, the theoretical results also indicate the contact time between specimen and the oscillator in a period decreases with the increasing amplitude of the oscillator.

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Quantitative Study on the Contact Force and Force Chain Characteristics of Ore Particle Systems during Ore Drawing from a Single Drawpoint under the Influence of a Flexible Barrier

Geofluids ◽

10.1155/2020/1270761 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13

Author(s):

Qingfa Chen ◽

Shikang Qin ◽

Shiwei Wu

Keyword(s):

Contact Force ◽

Particle System ◽

Vertical Direction ◽

Particle Systems ◽

Force Chain ◽

Contact Network ◽

Normal Contact ◽

Strong Force ◽

Flexible Barrier ◽

Initial Stage

It is of great significance to carry out quantitative research on the contact force chain characteristics of ore particle systems during ore drawing to reveal the microscopic and mesoscopic characteristics of ore particle systems during implementation of the synchronous filling shrinkage stoping method. Based on the particle discrete element method, combined with the relevant knowledge of contact mechanics and statistical mechanics, microscopic properties of the ore particle system were studied quantitatively. (1) The probability distributions of the normal and tangential contact forces during ore drawing from a single drawpoint under a flexible barrier are similar, and both show exponential decay. (2) In the regions on both sides of the model, the ore particles will not be released because they are far from the drawpoint; there, the coordination number is stable, and the density of contact network is large. In the upper part of the drawpoint, ore particles flow, the coordination number fluctuates violently, and the density of contact network is small. (3) In the initial stage, the stress distribution of the ore particle system is uniform, and the strong force chain does not show obvious directivity. After that, the directions of the strong force chains in the ore particle system are inclined to the vertical direction, and the strong force chains mainly bear the load in the vertical direction. (4) In the initial stage of drawing, the normal contact force is mainly concentrated in the vertical direction. With the progression of drawing, the normal contact force at an angle of 30° to the horizontal direction increases gradually, and the number of the main direction of the average contact force distribution changes from one to three (the vertical direction and the direction with a ±30° angle to the horizontal direction).

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An Electronic Force Sensor for Medical Jet Injection

Journal of Medical Devices ◽

10.1115/1.4043196 ◽

2019 ◽

Vol 13 (2) ◽

Author(s):

Nickolas P. Demas ◽

Ian W. Hunter

Keyword(s):

Contact Force ◽

Mean Absolute Error ◽

Force Sensor ◽

Absolute Error ◽

Jet Injection ◽

Lateral Direction ◽

Normal Contact ◽

Normal Contact Force ◽

Force Magnitude ◽

Lateral Contact

In medical jet injection, a narrow fluid drug stream is propelled at high velocity into skin without a needle. Previous studies have shown that the volume delivered is highly dependent on a number of factors. This paper details the development of an electronic force sensor for medical jet injection and shows that the normal contact force exerted on the tissue by the nozzle is an additional factor affecting volume delivered. Using this sensor, we measure the forces at the nozzle tip in the normal direction with a sensitivity of 18 μN, calibrated over a range from 1 N to 8 N with a mean absolute error of 8 mN, and a maximum overload of 300 N. We further measure forces at the nozzle tip in the lateral direction with a sensitivity of 8 μN, calibrated over a range from 0.1 N to 7 N, with a mean absolute error of 101 mN for lateral contact force magnitude and 1.60 deg for lateral contact force direction. Experimental validation confirms that the force sensor does not adversely affect the accuracy and precision of ejected volume from the jet injector. We use this setup to examine the effect of normal contact force on volume delivered into postmortem porcine tissue. Experimental results demonstrate that volume delivered with normal contact force between 4 N and 8 N is significantly more accurate and precise compared to volume delivered with normal contact force between 0 N and 3.9 N.

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