Reducing Lateral Contact Forces of Low-Floor LRV Using Friction Control (Development of Creep Force Model and Effectiveness for Independently Rotating Wheels)

In this investigation, a creep force model for contact with friction modifiers is developed and validated by comparing with the experimental results. To this end, a creep force model is developed by introducing a concept of equivalent shear modulus of rigidity, and a two-roller test rig is developed and used for validating the proposed model. Furthermore, relationships between the model parameters and the amount of friction modifiers applied to the contact patch are discussed. It is demonstrated that good agreements are obtained for the creep force characteristics obtained using the proposed model and the two-roller test rig developed in this investigation. Furthermore, it is shown that the proposed model can be used as a semi-empirical model, in which one can define the model parameter as a curve-fitting parameter and, at the same time, physical interpretations regarding the lubrication state between the wheel and rail interface can be obtained using the identified parameters.

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Dynamics of Multibody Systems With Spherical Clearance Joints

Volume 6: 5th International Conference on Multibody Systems, Nonlinear Dynamics, and Control, Parts A, B, and C ◽

10.1115/detc2005-84392 ◽

2005 ◽

Cited By ~ 1

Author(s):

P. Flores ◽

J. Ambro´sio ◽

J. C. P. Claro ◽

H. M. Lankarani

Keyword(s):

Contact Force ◽

Multibody Systems ◽

Contact Forces ◽

Force Model ◽

Clearance Joints ◽

Continuous Contact ◽

Clearance Joint ◽

Contact Force Model ◽

Dynamics Of Multibody Systems ◽

The Impact

This work deals with a methodology to assess the influence of the spherical clearance joints in spatial multibody systems. The methodology is based on the Cartesian coordinates, being the dynamics of the joint elements modeled as impacting bodies and controlled by contact forces. The impacts and contacts are described by a continuous contact force model that accounts for geometric and mechanical characteristics of the contacting surfaces. The contact force is evaluated as function of the elastic pseudo-penetration between the impacting bodies, coupled with a nonlinear viscous-elastic factor representing the energy dissipation during the impact process. A spatial four bar mechanism is used as an illustrative example and some numerical results are presented, being the efficiency of the developed methodology discussed in the process of their presentation. The results obtained show that the inclusion of clearance joints in the modelization of spatial multibody systems significantly influences the prediction of components’ position and drastically increases the peaks in acceleration and reaction moments at the joints. Moreover, the system’s response clearly tends to be nonperiodic when a clearance joint is included in the simulation.

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Decoupling of wheel-rail lateral contact forces from wayside measurements

Transport Infrastructure and Systems ◽

10.1201/9781315281896-12 ◽

2017 ◽

pp. 79-86 ◽

Cited By ~ 1

Author(s):

D. Cortis ◽

M. Bruner ◽

G. Malavasi

Keyword(s):

Contact Forces ◽

Lateral Contact

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Modeling Expected Wear in Revolute Joints With Clearance in Multibody Mechanical Systems

Volume 5: 6th International Conference on Multibody Systems, Nonlinear Dynamics, and Control, Parts A, B, and C ◽

10.1115/detc2007-34196 ◽

2007 ◽

Author(s):

P. Flores ◽

J. Ambro´sio ◽

J. C. P. Claro ◽

H. M. Lankarani

Keyword(s):

Research Work ◽

Contact Forces ◽

Joint Surface ◽

Force Model ◽

Wear Model ◽

Continuous Contact ◽

Revolute Joints ◽

Sliding Motion ◽

Impact Forces ◽

Contact Impact

The main goal of this work is to develop a methodology for studying and quantifying the wear phenomenon in revolute clearance joints. In the process, a simple model for a revolute joint in the framework of multibody systems formulation is presented. The evaluation of the contact forces developed is based on a continuous contact force model that accounts for the geometrical and materials properties of the colliding bodies. The friction effects due to the contact in the joints are also represented. Then, these contact-impact forces are used to compute the pressure field at the contact zone, which ultimately is employed to quantify the wear developed and caused by the relative sliding motion. In this work, the Archard’s wear model is used. A simple planar multibody mechanical system is used to perform numerical simulations, in order to discuss the assumptions and procedures adopted throughout this work. Different results are presented and discussed throughout this research work. From the main results obtained, it can be drawn that the wear phenomenon is not uniformly distributed around the joint surface, owing to the fact that the contact between the joint elements is wider and more frequent is some specific regions.

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Foundation for Virtual Prototyping of Mechanical Power Management Functions in Actuators

BATH/ASME 2018 Symposium on Fluid Power and Motion Control ◽

10.1115/fpmc2018-8895 ◽

2018 ◽

Cited By ~ 2

Author(s):

Jean-Charles Mare ◽

Silvio Akitani

Keyword(s):

Power Management ◽

Virtual Prototyping ◽

Contact Forces ◽

Mechanical Power ◽

System Level ◽

Special Focus ◽

Force Model ◽

Electromechanical Actuators ◽

Normal Contact ◽

Management Functions

Beside the main functions related to the control and transformation of power, safety-critical electromechanical actuators require many additional functions for power routing, protection and limitation. In practice, these functions are implemented mechanically because their realization at motor drive level is not acceptable for performance and reliability reasons. Contact forces play a major role in these mechanical devices (e.g. endstop, lock, brake, torque limiter, etc.), being either functional to serve the need, or parasitic due to their alteration of performance. The virtual prototyping of such mechanical power management functions therefore requires normal and tangent forces to be modelled with the right level of realism and reduced complexity. This communication provides some proposals to be used as foundation for the system-level modelling and simulation of these types of mechanical power elements that can be found in electromechanical actuators. Special focus is given to the model architecting, decomposition and block-diagram implementation, using the example of normal contact forces. The illustrative example concerns an integrated landing gear extension/retraction electromechanical actuator which embeds free-fall and autolock features. It shows how a well implemented single model (e.g. generic normal contact force model) combined with a right model decomposition can meet various modelling needs (e.g. droppable end-stop, lock and shearable axial stop). The proposed models are made compatible for integration in a 2x1D mechanical model architecture (axial and rotational motion) developed by the authors in previous reported work.

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Evaluating the Effect of Natural Third Body Layers on Friction Using the Virginia Tech Roller Rig

2019 Joint Rail Conference ◽

10.1115/jrc2019-1292 ◽

2019 ◽

Author(s):

Ahmad Radmehr ◽

Karan Kothari ◽

Mehdi Ahmadian

Keyword(s):

Virginia Tech ◽

Contact Forces ◽

Third Body ◽

Traction Coefficient ◽

The Coefficient Of Friction ◽

Creep Force ◽

Series Of Experiments ◽

Roller Rig ◽

Friction Reducer ◽

Material Wear

In this study, the effect of natural third body layers on the coefficient of friction and contact forces is evaluated using the Virginia Tech-Federal Railroad Administration (VT-FRA) roller rig facility. The test rig allows us to precisely control the contacting surfaces to study its effect on the wheel-rail interface forces and moments. Experiments have shown while running the tests, a slight amount of wear occurs at the running surfaces. The worn material deposits at the surface and behaves like a “natural” third-body layer at the contact, resulting in changes in traction coefficient and creep forces. The material wear and its accumulation on the running surfaces change with wheel longitudinal load and creepage. A series of organized time-based experiments have been conducted with the running surfaces cleaned at the beginning of the test to study the effect of material wear accumulation on selected parameters including traction coefficient and creep forces over time. In order to highlight the effect of the natural third body layer on the wheel-rail contact forces, a series of experiments were conducted, in which the wheel and roller surfaces were cleaned in one case and left uncleaned in another. The results of the experiments are quite revealing. They indicate that when the running surfaces are cleaned after each test, the maximum creep force (or adhesion) is far lower than when the running surfaces are not cleaned, i.e., the natural third-body layer is allowed to accumulate at the surfaces. The results indicate that the wear debris act as a friction enhancer rather than a friction reducer.

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Dynamic Analysis and Wear Prediction of Planar Five-Bar Mechanism Considering Multiflexible Links and Multiclearance Joints

Journal of Tribology ◽

10.1115/1.4035478 ◽

2017 ◽

Vol 139 (5) ◽

Cited By ~ 8

Author(s):

Gengxiang Wang ◽

Hongzhao Liu

Keyword(s):

Contact Force ◽

Dynamic Performance ◽

Contact Forces ◽

Force Model ◽

Displacement Curve ◽

Wear Depth ◽

Wear Model ◽

Clearance Joint ◽

Contact Force Model ◽

Cylindrical Joint

Effects of wear and member flexibility on the dynamic performance of a planar five-bar mechanism with joint-clearance are investigated. The equation of motion of the mechanism is derived based on the absolute nodal coordinate formulation (ANCF). In order to enhance the accuracy of the contact force, the slope of the load–displacement curve of the cylindrical joint with clearance is used. The contact deformation couples the joint wear to the contact state. The contact force model of Flores and coworkers is improved, by the introduction of the stiffness coefficient. The wear depth is predicted by using the Archard's wear model. Simulations show that the multiclearance joints can generate stronger contact forces relative to single clearance joint case. This leads to more severe wear in the joint. However, the mechanism with multiple flexible links can absorb more of the energy arising from the clearance joint, and this improves the wear phenomenon.

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Effect of Parameter Optimization of Contact Force Models on the Impact Dynamic Responses

14th Biennial Conference on Mechanical Vibration and Noise: Dynamics and Vibration of Time-Varying Systems and Structures ◽

10.1115/detc1993-0089 ◽

1993 ◽

Author(s):

H. M. Lankarani ◽

F. Wu

Keyword(s):

Energy Absorption ◽

Contact Force ◽

Multibody System ◽

High Energy ◽

Contact Forces ◽

Dynamic Responses ◽

Particle Model ◽

Force Model ◽

High Energy Absorption ◽

The Impact

Abstract Reducing the severity of an impact to a structure or a multibody system is a significant aspect of engineering design. This requires the knowledge of variations of the resulting contact forces and also how these contact forces can be reduced. This paper presents an optimization methodology for the selection of proper parameters in the contact/impact force models so as to minimize the maximum value of the contact force. A two-particle model of an impact between two solids is considered, and then generalized to the impact analysis between two bodies of a multibody system. The concept of effective mass is presented in order to compensate for the effect of joint forces or impulses. The system is reduced to a single degree-of-freedom mass-spring-damper vibro-impact system. A single differential equation of motion in the direction of relative indentation of local contact surfaces is derived. Different contact force models of hysteresis form including linear and nonlinear models are described. An optimization problem is then formulated and solved by using the method of modified feasible direction for constrained minimization. A numerical integrator is used at every design iteration to obtain the system dynamic response for a given set of design variables. The objective function is to minimize the peak acceleration of the system equivalent mass resulting from the contact force. Comparison of the system with optimal parameters and non-optimal one shows that the peak contact force is greatly reduced for the optimal one. Since these parameters reflect the material properties (stiffness and damping) of the impacting bodies or surfaces, suitable materials may then be selected based upon the information provided by this optimization procedure. It is observed that the materials, which have good crashworthiness properties should posses capability of dissipating impact energy both in the forms of permanent indentation and internal damping friction. Based upon the analysis of the impact responses, mechanism of energy dissipation, and the typical force-indentation diagram for the high energy absorption materials obtained from experiments, a new contact force model is proposed which could precisely describe the impact response of high energy-absorption materials.

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