scholarly journals Study of the Rolling Friction Coefficient between Dissimilar Materials through the Motion of a Conical Pendulum

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5032 ◽  
Author(s):  
Stelian Alaci ◽  
Ilie Muscă ◽  
Ștefan-Gheorghe Pentiuc
Keyword(s):  
Contact Point ◽  
Dissimilar Materials ◽  
Characteristic Parameter ◽  
Rolling Friction ◽  
Rolling Contact ◽  
Inclined Plate ◽  
Wide Range ◽  
Reaction Forces ◽  
Laboratory Device ◽  
Angular Amplitude

The rolling friction phenomenon is encountered in a wide range of applications and when two different materials are involved, quantitative characterization is necessary. The parameter to be determined is the coefficient of rolling friction, for whose estimation a methodology is proposed, based on the damped oscillation of a conical pendulum. The pure rolling contact between a sphere and a plane is obtained when a steel ball is the bob of the pendulum, which rolls on an inclined plate made from a second material from the contacting pair. The mathematical model of the motion of a conical pendulum constructed from a revolution body supported on an inclined plane in the presence of the rolling friction is developed. The dynamic equations of the rigid body with fixed point are applied and the differential equation of motion of the pendulum is obtained together with the expressions of the reaction forces in the contact point. For different pairs of materials, tests are performed on a laboratory device. The damped oscillatory motion of the conical pendulum is video-captured for the estimation of the angular amplitude variation. A program for image processing is developed for measuring the values of angular elongations from the analysis of each frame of the video and, finally, the coefficient of rolling friction is obtained. For all the materials tested, a linear decrease in angular amplitude is detected and the slope of angular amplitude can be considered as a characteristic parameter related to the coefficient of rolling friction between the two materials.

scholarly journals A Mixed Numerical-Experimental Method to Characterize Metal-Polymer Interfaces for Crash Applications

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 818
Author(s):  
Jonas Richter ◽  
Moritz Kuhtz ◽  
Andreas Hornig ◽  
Mohamed Harhash ◽  
Heinz Palkowski ◽  
...  
Keyword(s):  
Experimental Parameter ◽  
Dissimilar Materials ◽  
Calibration Method ◽  
Parameter Determination ◽  
Failure Behavior ◽  
Cohesive Elements ◽  
Interface Failure ◽  
Wide Range ◽  
Polymer Metal ◽  
Metal Polymer

Metallic (M) and polymer (P) materials as layered hybrid metal-polymer-metal (MPM) sandwiches offer a wide range of applications by combining the advantages of both material classes. The interfaces between the materials have a considerable impact on the resulting mechanical properties of the composite and its structural performance. Besides the fact that the experimental methods to determine the properties of the single constituents are well established, the characterization of interface failure behavior between dissimilar materials is very challenging. In this study, a mixed numerical–experimental approach for the determination of the mode I energy release rate is investigated. Using the example of an interface between a steel (St) and a thermoplastic polyolefin (PP/PE), the process of specimen development, experimental parameter determination, and numerical calibration is presented. A modified design of the Double Cantilever Beam (DCB) is utilized to characterize the interlaminar properties and a tailored experimental setup is presented. For this, an inverse calibration method is used by employing numerical studies using cohesive elements and the explicit solver of LS-DYNA based on the force-displacement and crack propagation results.

Threshold Stress Criterion in New Wheel/Rail Interaction for Limiting Rail Damage Under Heavy Axle Loads

1992 ◽  
Vol 114 (3) ◽  
pp. 284-288 ◽  
Author(s):  
S. Kumar ◽  
S. P. Singh
Keyword(s):  
Threshold Stress ◽  
Rolling Friction ◽  
Contact Stresses ◽  
Rolling Contact ◽  
Internal Damage ◽  
Stress Criterion ◽  
Plasticity Region ◽  
Proper Design ◽  
Axle Loads ◽  
Qualitative Discussion

This paper presents a qualitative discussion of the effects of increasing new (initial) wheel-rail contact stresses on the degree of damage to the rail due to heavy axle loads. The importance and need of heavy axle loads and its relationship to rail damage as a result of the increasing wheel-rail contact stresses is discussed. Various mechanisms of energy absorption/losses due to free rolling and modes of rail damage are presented. These modes include surface and internal damage due to wear, contact shear, plasticity, fatigue, shelling, crack formation, etc. The concept of threshold stress observed in free rolling friction much earlier by Drutowski is discussed and analyzed. It is believed by the authors that the threshold stress is s material property. This concept of threshold stress, based on sharply increased rates of wear in free rolling contact, is then presented and analyzed. Considerations of increased plasticity-region development, due to increasing contact stresses and their relationship to increased rates of wear seen in experiments, is utilized to determine an upper bound of contact stresses for new wheel and rail under heavy axle load conditions. It is indicated that new wheel-rail profiles, which will achieve contact stresses below the threshold stress, will enable the U.S. railroads to carry heavy axle loads without serious future damage to the rails. It is concluded that a satisfactory solution for maintaining rail integrity under heavy axle loads is possible with proper design accompanied with laboratory experimentation for the new steels as they may be used in the rails.

Viscosity Effect on Thermocapillary Rupture of Falling Liquid Films

2010 ◽  
Author(s):  
Dmitry Zaitsev ◽  
Andrey Semenov ◽  
Oleg Kabov
Keyword(s):  
Heat Flux ◽  
Film Thickness ◽  
Inclination Angle ◽  
Theoretical Models ◽  
Liquid Films ◽  
Liquid Viscosity ◽  
Inclined Plate ◽  
Film Rupture ◽  
Generalize Data ◽  
Wide Range

Rupture of a subcooled liquid film flowing over an inclined plate with a 150×150 mm heater is studied for a wide range of liquid viscosity (dynamic viscosity μ = (0.91–17.2)x10−3 Pa·s) and plate inclination angle with respect to the horizon (Θ = 3–90 deg). The main governing parameters of the experiment and their respective values are: Reynolds number Re = 0.15–54, heat flux q = 0–224 W/cm2. The effect of the heat flux on the film flow leads to the formation of periodically flowing rivulets and thin film between them. As the heat flux grows the film thickness between rivulets gradually decreases, and, upon reaching a certain threshold heat flux, qidp, the film ruptures in the area between the rivulets. The threshold heat flux increases with the flow rate of liquid and with the liquid viscosity, while the plate inclination angle has little effect on qidp. Criterion Kp, which is traditionally used in the literature to predict thermocapillary film rupture, was found to poorly generalize data for high viscous liquids (ethylene glycol, and aqueous solutions of glycerol) and also data for Θ≤45 deg. The criterion Kp was modified by taking into account characteristic critical film thickness for film rupture under isothermal conditions (no heating), deduced from existing theoretical models. The modified criterion has allowed to successfully generalize data for whole ranges of μ, Re, Θ and q, studied.

scholarly journals Electrical Discharges in Oil-Lubricated Rolling Contacts and Their Detection Using Electrostatic Sensing Technique

Sensors ◽  
2022 ◽  
Vol 22 (1) ◽  
pp. 392
Author(s):  
Kamran Esmaeili ◽  
Ling Wang ◽  
Terry J. Harvey ◽  
Neil M. White ◽  
Walter Holweger
Keyword(s):  
High Current Density ◽  
Rolling Contact ◽  
Voltage Measurement ◽  
Electrical Discharges ◽  
Steel Rolling ◽  
Bearing Life ◽  
Wide Range ◽  
Robust Techniques ◽  
Rolling Elements ◽  
Current Densities

The reliability of rolling element bearings has been substantially undermined by the presence of parasitic and stray currents. Electrical discharges can occur between the raceway and the rolling elements and it has been previously shown that these discharges at relatively high current density levels can result in fluting and corrugation damages. Recent publications have shown that for a bearing operating at specific mechanical conditions (load, temperature, speed, and slip), electrical discharges at low current densities (<1 mA/mm2) may substantially reduce bearing life due to the formation of white etching cracks (WECs) in bearing components, often in junction with lubricants. To date, limited studies have been conducted to understand the electrical discharges at relatively low current densities (<1 mA/mm2), partially due to the lack of robust techniques for in-situ quantification of discharges. This study, using voltage measurement and electrostatic sensors, investigates discharges in an oil-lubricated steel-steel rolling contact on a TE74 twin-roller machine under a wide range of electrical and mechanical conditions. The results show that the discharges events between the rollers are influenced by temperature, load, and speed due to changes in the lubricant film thickness and contact area, and the sensors are effective in detecting, characterizing and quantifying the discharges. Hence, these sensors can be effectively used to study the influence of discharges on WEC formation.

A numerical study of the influence of lateral geometry irregularities on mechanical deterioration of freight tracks

2012 ◽  
Vol 226 (6) ◽  
pp. 575-586 ◽  
Author(s):  
Kalle Karttunen ◽  
Elena Kabo ◽  
Anders Ekberg
Keyword(s):  
Numerical Study ◽  
Contact Point ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Field Measurements ◽  
Rolling Contact ◽  
Railway Track ◽  
Operational Conditions ◽  
Track Geometry ◽  
Track Maintenance

Optimisation of railway track maintenance requires knowledge of how a deteriorated track geometry will affect subsequent loading and damage of the track. This is the scope of the current study where, in particular, the influence on track shift forces and rolling contact fatigue is investigated through numerical simulations. To this end, track geometries are obtained from field measurements. Lateral irregularities are extracted and scaled to represent different levels of geometry deterioration. Multibody simulations of dynamic train–track interaction featuring two freight wagon types are performed under different operational conditions. Track shift forces and rolling contact fatigue damage are further evaluated from simulation results. It is found that track shift forces tend to follow a normal distribution for moderate levels of lateral track geometry irregularities, and that an approximate linear relationship between standard deviations of lateral irregularities and track shift forces can be established. The relation between lateral track irregularity magnitude and rolling contact fatigue is more complex. Increasing levels of lateral irregularities will decrease the fraction of curve length affected by rolling contact fatigue for sharp curves, whereas for shallow curves it increases. As detailed in the article, this is caused by the lateral movement of the contact point as imposed by the track irregularities. Furthermore, the influence of wheel/rail friction and wear is investigated.

scholarly journals INTERFACE MAGNETISM IN FERROMAGNETIC METAL–COMPOUND SEMICONDUCTOR HYBRID STRUCTURES

SPIN ◽  
2011 ◽  
Vol 01 (01) ◽  
pp. 45-69 ◽  
Author(s):  
AIDAN T. HINDMARCH
Keyword(s):  
Significant Proportion ◽  
Dissimilar Materials ◽  
Free Energy Density ◽  
Compound Semiconductor ◽  
Ferromagnetic Metal ◽  
Hybrid Structures ◽  
Intimate Contact ◽  
Interface Magnetism ◽  
Wide Range ◽  
Nanoscale Thin Film

Interfaces between dissimilar materials present a wide range of fascinating physical phenomena. When a nanoscale thin-film of a ferromagnetic metal is deposited in intimate contact with a compound semiconductor, the properties of the interface exhibit a wealth of novel behavior, having immense potential for technological application, and being of great interest from the perspective of fundamental physics. This article presents a review of recent advances in the field of interface magnetism in (001)-oriented ferromagnetic metal/III–V compound semiconductor hybrid structures. Until relatively recently, the majority of research in this area continued to concentrate almost exclusively on the prototypical epitaxial Fe / GaAs (001) system: now, a significant proportion of work has branched out from this theme, including ferromagnetic metal alloys, and other III–V compound semiconductors. After a general overview of the topic, and a review of the more recent literature, we discuss recent results where advances have been made in our understanding of the physics underpinning magnetic anisotropy in these systems: tailoring the terms contributing to the angular-dependent free-energy density by employing novel fabrication methods and ferromagnetic metal electrodes.

A Theoretical Model of Uniform Flow Distribution for the Admission of High-Energy Fluids to a Surface Steam Condenser

2001 ◽  
Vol 123 (2) ◽  
pp. 472-475 ◽  
Author(s):  
J. Wang ◽  
G. H. Priestman ◽  
D. Wu
Keyword(s):  
Static Pressure ◽  
Flow Distribution ◽  
General Characteristic ◽  
Characteristic Parameter ◽  
High Energy ◽  
Momentum Effect ◽  
Wide Range ◽  
Branching Flow ◽  
Pipe Geometry ◽  
Perforated Pipe

An analytical study is made of the perforated pipe distributor for the admission of high-energy fluids to a surface steam condenser. The results show that for all perforated pipes there is a general characteristic parameter MkD/Lf, which depends on the pipe geometry and flow properties. Four cases are considered based on the value of the characteristic parameter M. (1) When M⩾1/4, momentum controls and the main channel static pressure will increase in the direction of the streamline. (2) When 1/6⩽M<1/4, the momentum effect balances friction losses and the pressure will decrease to a minimum, and then increase in the direction of flow to a positive value. (3) When 0<M<1/6, friction controls and the pressure will decrease to a minimum, then increase slowly, but the total pipe static pressure difference will always be negative. (4) When M=0, a limiting case when the ratio of the length to the diameter is infinite. This analysis is useful not only for the design of perforated pipe distributors for turbine condensers over a wide range of dimensions, fluid properties, and side hole pressure but also for many other technical systems requiring branching flow distribution.

Interfacial Microstructure and Strength of Friction Welding of Steel Tube to Aluminium Tube Plate Using an External Tool

2011 ◽  
Vol 383-390 ◽  
pp. 877-881 ◽  
Author(s):  
S. Muthukumaran ◽  
C. Vijaya Kumar ◽  
S. Senthil Kumaran ◽  
A. Pradeep
Keyword(s):  
Friction Welding ◽  
Thermal Power ◽  
Welding Process ◽  
Dissimilar Materials ◽  
Industrial Applications ◽  
Interfacial Microstructure ◽  
Steel Tube ◽  
Tube Plate ◽  
Wide Range ◽  
Interface Hardness

Joining of dissimilar materials is of increasing interest for a wide range of industrial applications like nuclear, thermal power. The automotive industry, in particular, views dissimilar materials joining as a gateway for the implementation of lightweight materials. Friction welding of tube to tube plate using an external tool is an innovative friction welding process and is capable of producing high quality leak proof weld joints. In the present study, friction welding of steel tube to commercial aluminum tube plate using an external tool with and without tube projection have been performed. The joints were evaluated by mechanical testing and metallurgical analysis. The results of bonding interface hardness and joint strength reveal that steel tube with projection are better than the steel tube without projection.

Incipient Slip Conditions in the Rolling Contact of Tyred Wheels

2010 ◽  
Vol 224 (10) ◽  
pp. 2049-2054 ◽  
Author(s):  
S Reina ◽  
D A Hills ◽  
D Dini
Keyword(s):  
Contact Problem ◽  
Closed Form ◽  
Rolling Contact ◽  
Simplified Model ◽  
Practical Case ◽  
Closed Form Solutions ◽  
Steel Wheel ◽  
State Of Stress ◽  
Wide Range ◽  
Tractive Rolling

The contact problem of a driving tyred wheel, pressed and rolling over an elastically similar half-plane, is considered. Although applicable to a wide range of shrink-fitted assemblies, the simplified model is solved to study the practical case of an elastically similar steel tyre mounted on a locomotive steel wheel subjected to tractive rolling. The behaviour of the system at the tyre—substrate interface is studied using closed-form solutions to calculate the state of stress within the tyre. Conditions leading to incipient slip and/or plasticity are identified and mapped for different loads and geometries.

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