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.

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

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.

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.

scholarly journals Closed-Form Equations for Contact Force and Moment in Elastic Contact of Rough Surfaces

2011 ◽  
Vol 2011 ◽  
pp. 1-14 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Closed Form ◽  
Half Plane ◽  
Contact Force ◽  
Normal Force ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Compressive Load ◽  
Angular Misalignment ◽  
Tangential Contact ◽  
Applied Forces

It is reasonable to expect that, when two nominally flat rough surfaces are brought into contact by an applied resultant force, they must support, in addition to the compressive load, an induced moment. The existence of a net applied moment would imply noneven distribution of contact force so that there are more asperities in contact over one region of the nominal area. In this paper, we consider the contact between two rectangular rough surfaces that provide normal and tangential contact force as well as contact moment to counteract the net moment imposed by the applied forces. The surfaces are permitted to develop slight angular misalignment, and thereby contact moment is derived. Through this scheme, it is possible to also define elastic contribution to friction since the half-plane tangential contact force on one side of an asperity is no longer balanced by the half-plane tangential force component on the opposite side. The elastic friction force, however, is shown to be of a much smaller order than the contact normal force. Approximate closed-form equations are found for contact force and moment for the contact of rough surfaces.

Thermoelastic Modeling of Rotor Response With Shaft Rub

2010 ◽  
Vol 77 (6) ◽  
Author(s):  
S. Ziaei-Rad ◽  
E. Kouchaki ◽  
M. Imregun
Keyword(s):  
Friction Coefficient ◽  
Critical Speed ◽  
Normal Force ◽  
Contact Point ◽  
Tangential Force ◽  
Bending Moment ◽  
Contact Forces ◽  
Mass Unbalance ◽  
Deceleration Rate ◽  
The Time Domain

This paper studies the effects of shaft rub on a rotating system’s vibration response with emphasis on heat generation at the contact point. A 3D heat transfer code, coupled to a 3D vibration code, was developed to predict the dynamic response of a rotor in the time domain. The shaft bow is represented by an equivalent bending moment and the contact forces by rotating external forces. The seal ring is modeled as a linear spring, which exerts a normal force to the rotor. The tangential force is then calculated as the product of the normal force with the friction coefficient. Stable or unstable spiraling and oscillating modes were seen to occur in well defined shaft speed zones. In the main, for the configurations studied, the shaft vibration was found to be unstable for speeds below the first critical speed and stable for speeds above the first critical speed. Limit cycle behavior was observed when the phase angle between the unbalance force and the response was around 90 deg. The vibration behavior with rub during startup and shutdown was studied by considering the effects of acceleration/deceleration rate, friction coefficient, and mass unbalance. It was found that friction coefficient and increasing mass unbalance amplified the rub effects while acceleration/deceleration rate reduced it.

Contact Moment and Friction Force in Elastic Contact of Two Rough Surfaces

2007 ◽  
Author(s):  
A. Sepehri ◽  
K. Farhang
Keyword(s):  
Friction Force ◽  
Half Plane ◽  
Contact Force ◽  
Normal Force ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Compressive Load ◽  
Angular Misalignment ◽  
Tangential Contact ◽  
Applied Forces

It is reasonable to expect that when two nominally flat rough surfaces are brought into contact by an applied resultant force, they must support, in addition to the compressive load, an induced moment. The existence of a net applied moment would imply non-even distribution of contact force so that there are more asperities in contact over one region of the nominal area. In this paper we consider the contact between two rectangular rough surfaces that provide normal and tangential contact force as well as contact moment to counteract the net moment imposed by the applied forces. The surfaces are permitted to develop slight angular misalignment and through this contact moment is derived. Through this scheme it is possible to also define elastic contribution to friction since the half-plane tangential contact force on one side of an asperity is no longer balanced by the half-plane tangential force component on the opposite side. The elastic friction force however is shown to be of a much smaller order than the contact normal force.

Reconstruction of the Dynamic Rail-Wheel Contact Forces

2003 ◽  
Author(s):  
Svenja Kirchenkamp ◽  
Dirk So¨ffker
Keyword(s):  
Contact Force ◽  
Normal Force ◽  
Elastic Beam ◽  
Contact Forces ◽  
Force Estimation ◽  
Measurement Device ◽  
Tangential Contact ◽  
Proportional Integral ◽  
First Time ◽  
Displacement Measurements

This contribution introduces a virtual measurement device for the reconstruction of the in practice unmeasureable railwheel contact forces. For this aim the Proportional-Integral (PI)-Observer is used. Then, the concept of a measurement sleeve at the axle bearing is shown. With the displacement measurements resulting from the sleeve using the PI-Observer, an estimation of the tangential contact force and the dynamic normal force is possible. Using the simulation of the rail-wheel contact, the feasibility of the estimation of the contact force behavior is shown. As an outlook for further applications of the PI-Observer in the context of rail-wheel contact force estimation, the reconstruction of contact forces by using acceleration measurements is demonstrated by an example of an elastic beam for the first time.

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.

Elastic Contact of Rough Surfaces Subject to Combined Force and Moment

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Half Plane ◽  
Normal Force ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Contact Forces ◽  
Elastic Contact ◽  
Force Component ◽  
Angular Misalignment ◽  
Tangential Contact ◽  
Applied Forces

In this paper we consider the contact between two rectangular rough surfaces that provide normal and tangential contact forces, as well as contact moment, to counteract the net moment imposed by the applied forces. The surfaces are permitted to develop a slight angular misalignment, and thereby contact moment is derived. Through this scheme it is possible to also define elastic contribution to friction, since the half-plane tangential contact force on one side of an asperity is no longer balanced by the half-plane tangential force component on the opposite side. The elastic friction force, however, is shown to be of a much smaller order than the contact normal force.

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.

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.

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