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.

scholarly journals Dynamics of Multibody Systems With Spherical Clearance Joints

2005 ◽  
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.

Evaluation of vehicular contact force on bridge joints by vibration responses and object detection

2021 ◽  
Author(s):  
Di Su ◽  
Yuichiro Tanaka ◽  
Tomonori Nagayama
Keyword(s):  
Object Detection ◽  
Contact Force ◽  
Dynamic Contact ◽  
Contact Forces ◽  
Expansion Joints ◽  
Cyclic Movements ◽  
Bridge Joints ◽  
Vibration Responses ◽  
On The Road ◽  
Board System

<p>Expansion joints on bridges should accommodate cyclic movements to minimize imposition of secondary stresses in the structure. However, these joints are highly susceptible to severe and repeated vehicular impact that results their inherent discontinuity. In this paper, a portable on- board system including accelerometers and a drive recorder to evaluate the vehicular contact force on bridge joints is proposed. First, from the acceleration responses of the vehicle, the contact force exerted on the road surface is estimated from a half-car model by Kalman Filter. Next, extraction of the expansion joints is performed by object detection from videos taken by the drive recorder. Finally, a relative comparison of the contact forces acting on joints is performed, with location identification on the map. The proposed system benefits to utilize the dynamic contact forces results from on-board system to detect the potential risky joints more precisely and efficiently.</p>

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 Small nanoparticles, surface geometry and contact forces

2018 ◽  
Vol 474 (2211) ◽  
pp. 20170723 ◽  
Author(s):  
Yoichi Takato ◽  
Michael E. Benson ◽  
Surajit Sen
Keyword(s):  
Contact Force ◽  
Contact Forces ◽  
Spherical Nanoparticles ◽  
Hertz Contact ◽  
Surface Geometry ◽  
Impact Forces ◽  
Nonlinear Contact ◽  
Amorphous Surface ◽  
The Impact ◽  
Small Nanoparticles

In this molecular dynamics study, we examine the local surface geometric effects of the normal impact force between two approximately spherical nanoparticles that collide in a vacuum. Three types of surface geometries—(i) crystal facets, (ii) sharp edges, and (iii) amorphous surfaces of small nanoparticles with radii R <10 nm—are considered. The impact forces are compared with their macroscopic counterparts described by nonlinear contact forces based on Hertz contact mechanics. In our simulations, edge and amorphous surface contacts with weak surface energy reveal that the average impact forces are in excellent agreement with the Hertz contact force. On the other hand, facet collisions show a linearly increasing force with increasing compression. Our results suggest that the nearly spherical nanoparticles are likely to enable some nonlinear dynamic phenomena, such as breathers and solitary waves observed in granular materials, both originating from the nonlinear contact force.

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

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.

Using an Anti-Relaxation Step to Improve the Accuracy of the Frictional Contact Solution in a DVI Framework for Rigid Body Dynamics

2016 ◽  
Author(s):  
Daniel Melanz ◽  
Hammad Mazhar ◽  
Dan Negrut
Keyword(s):  
Frictional Contact ◽  
Rigid Bodies ◽  
Rigid Body Dynamics ◽  
Contact Forces ◽  
Science And Engineering ◽  
Complementarity Condition ◽  
Body Dynamics ◽  
Engineering Problems ◽  
The Impact

Systems composed of rigid bodies interacting through frictional contact are manifest in several science and engineering problems. The number of contacts can be small, such as in robotics and geared machinery, or large, such as in terrame-chanics applications, additive manufacturing, farming, food industry, and pharmaceutical industry. Currently, there are two popular approaches for handling the frictional contact problem in dynamic systems. The penalty method calculates the frictional contact force based on the kinematics of the interaction, some representative parameters, and an empirical force law. Alternatively, the complementarity method, based on a differential variational inequality (DVI), enforces non-penetration of rigid bodies via a complementarity condition. This contribution concentrates on the latter approach and investigates the impact of an anti-relaxation step that improves the accuracy of the frictional contact solution. We show that the proposed anti-relaxation step incurs a relatively modest cost to improve the quality of a numerical solution strategy which poses the calculation of the frictional contact forces as a cone-complementarity problem.

Theoretical modeling and numerical simulation of dynamic contact characteristics of a spherical pump with variable friction coefficient

2021 ◽  
pp. 135065012110162
Author(s):  
Dong Guan ◽  
Li Jing ◽  
Xue Han ◽  
Lihui Wang ◽  
Junjie Gong
Keyword(s):  
Friction Coefficient ◽  
Contact Force ◽  
Structural Parameters ◽  
Dynamic Contact ◽  
Cylinder Block ◽  
Normal Contact ◽  
Variable Friction ◽  
Resistance Performance ◽  
The Relationship ◽  
Maximum Contact

In this paper, the dynamic contact characteristics between a piston system and a cylinder block in a spherical pump are studied theoretically and numerically. The theoretical contact model between a piston and a cylinder is established based on its structural and operational properties, to obtain the maximum contact force quantitatively. The effects of different structural parameters and working pressures on the contact force are analyzed and discussed. The relationship between friction coefficient and rotation speed is presented. The contact pairs are modeled numerically using the finite-element method and augmented Lagrange algorithm to obtain both the tangential and normal contact characteristics. Both static and dynamic contact characteristics of the piston are analyzed and discussed. These proposed studies can provide practical suggestions on improving the wear resistance performance and durability of the spherical pump.

scholarly journals Impact of Tip Design and Thermocouple Location on the Efficacy and Safety of Radiofrequency Application

2021 ◽  
Author(s):  
Junji Yamaguchi ◽  
Masateru Takigawa ◽  
Masahiko Goya ◽  
Claire Martin ◽  
Miki Amemiya ◽  
...  
Keyword(s):  
Multivariate Analysis ◽  
Contact Force ◽  
Contact Forces ◽  
Catheter Placement ◽  
Efficacy And Safety ◽  
Surface Areas ◽  
Rf Applications ◽  
The Impact

Background & Objectives The FlexAbilityTM SE catheter has a laser-cut 8Fr 4-mm flexible tip irrigated through laser-cut kerfs with a thermocouple 0.3mm from the distal end. The TactiCathTM SE catheter has an 8Fr 3.5-mm tip and 6-irrigation port with a thermocouple 2.67mm proximal to the tip. We investigated the impact of these differences on the efficacy and safety of RF-applications. Methods RF applications at a range of powers (20W, 30W, and 40W), contact forces (5g, 15g, and 25g), and durations (10-60s) using perpendicular/parallel catheter orientation, were performed in excised porcine hearts. Lesion characteristics and incidence of steam pops were compared. Results 540 lesions were examined. The FlexAbilityTM SE catheter produced smaller lesion depths (4.0mm vs. 4.4mm, p=0.014 at 20W; 4.6mm vs. 5.6mm, p=0.015 at 30W), surface areas (22.7mm2 vs. 29.2mm2 at 20W, p=0.005; 23.2mm2 vs. 28.7mm2, p=0.009 at 30W) and volumes (126.1mm3 vs. 175.1mm3, p=0.018 at 20W; 183.2mm3 vs. 304.3mm3, p=0.002 at 30W) with perpendicular catheter placement. However, no differences were observed with parallel catheter placement. Steam-pops were significantly less frequently observed with the FlexAbilityTM SE catheter (4% vs. 22%, p<0.001) irrespective of catheter direction to the tissue. Multivariate analysis showed that use of the TactiCathTM SE catheter, power ≥40W, contact force ≥25g, RF duration >30s, parallel angle and impedance drop ≥20Ω were significantly associated with occurrence of steam-pops. Conclusions The FlexAbilityTM SE catheter reduced the risk of steam-pops, but produced smaller lesions with perpendicular catheter placement compared to the TactiCathTM SE catheter.

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.

Analysis on Dynamic Contact Force in High Power Density Gear Transmission Based on Flexible Model

2013 ◽  
Vol 328 ◽  
pp. 547-551
Author(s):  
Hai Sheng Feng ◽  
Li Qin Wang ◽  
De Zhi Zheng ◽  
Le Gu
Keyword(s):  
Power Density ◽  
Contact Force ◽  
High Power ◽  
Dynamic Contact ◽  
Gear Transmission ◽  
High Power Density ◽  
Normal Contact ◽  
Rigid Model ◽  
Simulation Results ◽  
Flexible Model

Recently, most of researchers pay more attention to the flexible model for solving dynamic contact force in high power density gear transmission. But, the detailed formula of the contact force parameters is not given. Therefore, in this paper the detailed calculation of coefficient of restitution (COR) is proposed, which can solve the elastoplastic contact deformation problems compared with other method. To improve the simulation efficiency, a flexible model based on ADAMS and Hertzian theory is presented. According to the simulation results, the normal contact force of the flexible model is much higher than that of the rigid model in plastic contact deformation. Meanwhile, the normal contact force delay exists in flexible model compared with rigid model. At last, the flexible model simulation results are close to the theoretical result in steady state. Consequently, the flexible model can be applied to analyze dynamic characteristic in reasonable time and many revolutions of the high power density gear transmission.

Sign in / Sign up

Export Citation Format

Share Document