The fretting corrosion of mild steel

1956 ◽  
Vol 236 (1206) ◽  
pp. 411-425 ◽  
Keyword(s):  
Mild Steel ◽  
Electrical Contact ◽  
Fretting Corrosion ◽  
Electrical Contact Resistance ◽  
Wear Rates ◽  
Wide Range ◽  
Simple Rules ◽  
Frictional Forces ◽  
Number Of Cycles ◽  
Unidirectional Motion

A quantitative investigation of the fretting corrosion of mild-steel specimens is described. Measurements have been made of the frictional forces, the degree of damage and the variations in the electrical contact resistance for a wide range of applied loads, vibration amplitudes and number of cycles of motion. In addition, the nature of the fretting corrosion scars and debris has been examined using optical and electron microscopy and electron diffraction. The same sequence of phenomena is observed under all conditions, namely, (i) the formation of intermetallic welds, (ii) the production of black α-Fe 2 O 3 particles and ultimately (iii) the production of fine red-brown α-Fe 2 O 3 particles. However, the magnitude of the frictional forces, the wear rates and the contact resistances are greatly dependent upon the amplitude of vibration. At large amplitudes large intermetallic junctions form soon after the onset of motion and the friction rapidly rises above its initial value. Subsequently the friction drops to a very low value, μ ~ 0·05; this is due to the presence of loose oxidized debris which accumulates and tends to roll between the rubbing contacts. At small amplitudes the scale of the welding is so reduced that no perceptible rise in friction occurs before the friction falls to its final low value. Measurements of the depths of damage in the scars show that the holes which form arise from the original welding mechanism and that they subsequently disappear. At large amplitudes the wear rates obey the same simple rules of wear as are obeyed in unidirectional motion, namely, the wear is proportional to the distance of sliding; the wear rate is proportional to the load and independent of the apparent area of contact. Further-more, there is close agreement in the magnitude of the wear rates in unidirectional motion and during fretting at large amplitudes. At small amplitudes, however, much smaller rates of damage are obtained.

An Innovative System for Fretting Wear Testing Under Oscillating Normal Force

2000 ◽  
Vol 15 (7) ◽  
pp. 1591-1599 ◽  
Author(s):  
M. Z. Huq ◽  
C. Butaye ◽  
J-P. Celis
Keyword(s):  
Contact Resistance ◽  
Normal Force ◽  
Electrical Contact ◽  
Wear Test ◽  
Fretting Wear ◽  
Wear Testing ◽  
Mode Ii ◽  
Test Machine ◽  
Electrical Contact Resistance ◽  
Wide Range

Material damage caused by fretting wear is of significant concern in many engineering applications. This paper describes the design and performance of a new machine for the laboratory investigation of fretting wear under oscillating normal force (fretting mode II). The test machine uses an electromagnetic actuator to impose an oscillating normal force between the contacting bodies at a constant force amplitude over a wide range of frequencies. The principle of the actuation mechanism and the fretting wear induced with this particular wear test configuration are outlined in detail. Normal force and electrical contact resistance were measured on-line during fretting mode II wear tests. The performance of the wear test machine is illustrated by data obtained for different materials combinations, namely, hard materials, such as high-speed steel and (Ti,Al)N coatings oscillating against alumina ball counterbodies, and soft materials, such as a tin coating oscillating against the same. In general, wearing of the counterbodies was observed in the slip region. It has been observed that hard coatings and bulk ceramics are prone to fretting fatigue cracking. The evolution of electrical contact resistance in the case of the self-mated soft tin coatings tested under fretting mode II conditions is also reported.

Use of Intrinsic Electrical Resistance Changes in Shape Memory Alloys as Robust Actuator State and Fault Detection Sensors

2011 ◽  
Author(s):  
Guillermo A. Herrera ◽  
Geoffrey P. McKnight ◽  
Xiujie Gao ◽  
Nancy Johnson ◽  
Alan L. Browne
Keyword(s):  
Robust Control ◽  
Shape Memory ◽  
Electrical Resistance ◽  
Control Method ◽  
Electrical Contact ◽  
Time Derivative ◽  
Electrical Contact Resistance ◽  
Compact Size ◽  
Wide Range ◽  
Property Changes

Shape memory alloy (SMA) used as electrically controlled on-demand actuators provide engineers new opportunities to create lighter automated components and devices in vehicles due to their compact size, silent operation, and inherently low mass. Outstanding and critical issues are cost-effective and robust control and protection of the SMA actuator element within the device to achieve long lasting service. SMA responds autonomously to external conditions such as temperature and stress and exhibit many property changes during excitation, but many current devices only use SMA as compact actuators; not making use of their intrinsic sensing capabilities. Inherent SMA property changes during use can provide significant utility for improved optimal control strategies. The motivation for this work is to create a robust control method for electrically controlled SMA actuation to simplify device implementation and improve reliability by using intrinsic material property changes. The current work demonstrates the use of electrical resistance feedback in an integrated controller to allow reduction of parasitic mass, cost, and complexity in 2-position devices. Using signal processing and algorithm logic states, we create virtual sensors that successfully identify start of the actuation, end of actuation, reset, and stress overload events. Using electrical resistance to sense the start of actuation allows successful/repeatable performance over a wide range of environmental conditions. Sensing the end of actuation and reset readiness prevents overheating and allows for shorter actuation cycle times, respectively without additional position and state sensors. While many previous efforts have examined the use of resistance in control schemes, one critical need not addressed in previous controllers is the ability to detect stress overload of the SMA during excitation. To protect against unintentional blocked deployment, many current devices include bulky mechanical overload protection systems that prevent stress spikes and SMA damage accumulation. Using resistance feedback, we demonstrate the detection of stress overloads thus extending device lifetime without the need for external mechanisms. The time derivative of the electrical resistance, logic state of the controller, and detection and use of peak/valley widths and thresholds define control events. These events become software based sensors that can augment or replace dedicated external sensors. Software based sensors were successfully employed to control an SMA wire actuator under various environmental temperatures and stress conditions. The control algorithm is not affected to changes in electrical contact resistance, material degradation and other noise sources yielding a powerful method for simple control of two position SMA devices without the need of external sensors.

Pantograph/Catenary Wear Using Multibody System Dynamic Algorithms

2020 ◽  
Author(s):  
Siripong Daocharoenporn ◽  
Mongkol Mongkolwongrojn ◽  
Shubhankar Kulkarni ◽  
Ahmed A. Shabana
Keyword(s):  
Electrical Contact ◽  
Electrical Contact Resistance ◽  
Wear Model ◽  
Contact Wire ◽  
Wear Rates ◽  
Simulation Techniques ◽  
Contact Formulation ◽  
Acceleration And Deceleration ◽  
Electrical Wear ◽  
Railroad Vehicle

Abstract In this investigation, computational multibody systems (MBS) algorithms are used to develop detailed railroad vehicle models for the prediction of the wear resulting from the pantograph/catenary dynamic interaction. The catenary wear is predicted for different motion scenarios that include constant-speed curve negotiation, and acceleration and deceleration on a tangent (straight) track. The effect of the vehicle vibration in these different motion scenarios on the contact force is further used to study the wear rates of the contact wire. The wear model used in this investigation accounts for the electrical and the mechanical effects. The nonlinear finite element (FE) absolute nodal coordinate formulation (ANCF), which is suitable for implementation in MBS algorithms, is used to model the flexible catenary system, thereby eliminating the need for using incremental rotation procedures and co-simulation techniques. The pantograph/catenary elastic contact formulation employed in this study allows for separation between the pantograph pan-head and the contact wire, and accounts for the effect of friction due to the sliding between the pantograph pan-head and the catenary cable. The approach proposed in this investigation can be used to evaluate the electrical contact resistance, contribution of the arcing resulting from the pan-head/catenary separation, mechanical and electrical wear contributions, and effect of the pantograph mechanism uplift force on the wear rate.

Prediction of the Pantograph/Catenary Wear Using Nonlinear Multibody System Dynamic Algorithms

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Siripong Daocharoenporn ◽  
Mongkol Mongkolwongrojn ◽  
Shubhankar Kulkarni ◽  
Ahmed A. Shabana
Keyword(s):  
Multibody System ◽  
Electrical Contact ◽  
Efficient Solutions ◽  
Electrical Contact Resistance ◽  
Contact Wire ◽  
Wear Rates ◽  
Simulation Techniques ◽  
Contact Formulation ◽  
Acceleration And Deceleration ◽  
Electrical Wear

In this investigation, computational multibody system (MBS) algorithms are used to develop detailed railroad vehicle models for the prediction of the wear resulting from the pantograph/catenary dynamic interaction. The wear is predicted using MBS algorithms for different motion scenarios that include constant-speed curve negotiation and acceleration and deceleration on a tangent (straight) track. The effect of the vehicle vibration in these different motion scenarios on the contact force is further used to study the wear rates of the contact wire. The wear model used in this investigation accounts for the electrical and the mechanical effects. The nonlinear finite element (FE) absolute nodal coordinate formulation (ANCF), which is suitable for implementation in MBS algorithms, is used to model the flexible catenary system, thereby eliminating the need for using incremental-rotation procedures and co-simulation techniques. In order to obtain efficient solutions, both the overhead contact line and the messenger wire are modeled using the gradient-deficient ANCF cable element. The pantograph/catenary elastic contact formulation employed in this study allows for separation between the pantograph panhead and the contact wire, and accounts for the effect of friction due to the sliding between the pantograph panhead and the catenary cable. The approach proposed in this investigation can be used to evaluate the electrical contact resistance, contribution of the arcing resulting from the panhead/catenary separation, mechanical and electrical wear contributions, and the effect of the pantograph mechanism uplift force on the wear rate. Numerical results are presented and analyzed to examine the wear rates for different motion scenarios.

Electrical Contact Resistance Between Gas Diffusion Layers and Bipolar Plates for Applications to PEM Fuel Cells

2004 ◽  
Author(s):  
V. Mishra ◽  
F. Yang ◽  
R. Pitchumani
Keyword(s):  
Fuel Cells ◽  
Contact Resistance ◽  
Electrical Contact ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Surface Geometry ◽  
Electrical Contact Resistance ◽  
Gas Diffusion Layers ◽  
Diffusion Layers ◽  
Wide Range

The electrical contact resistance between gas diffusion layers and bi-polar flow channel plates is one of the important factors contributing to the operational voltage loss in fuel cells. Effective analysis and design of fuel cells therefore need to account for the contact resistance in deriving the polarization curve for the cell. Despite its significance, relatively scant work is reported in the open literature on the measurement and modeling of the contact resistance in fuel cell systems, and the present work aims to fill this void. Experimental data are reported for the first time to show the effects of different gas diffusion layer materials and contact pressure on the electrical contact resistance. A fractal asperity based model is adopted to predict the contact resistance as a function of pressure, material properties, and surface geometry. Good agreement is observed between the data and the model predictions for a wide range of contacting pressures and materials.

Measurement and Prediction of Electrical Contact Resistance Between Gas Diffusion Layers and Bipolar Plate for Applications to PEM Fuel Cells

2004 ◽  
Vol 1 (1) ◽  
pp. 2-9 ◽  
Author(s):  
V. Mishra ◽  
F. Yang ◽  
R. Pitchumani
Keyword(s):  
Fuel Cells ◽  
Contact Resistance ◽  
Electrical Contact ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Surface Geometry ◽  
Electrical Contact Resistance ◽  
Gas Diffusion Layers ◽  
Diffusion Layers ◽  
Wide Range

The electrical contact resistance between gas diffusion layers and bipolar flow channel plates is one of the important factors contributing to the operational voltage loss in polymer electrolyte membrane (PEM) fuel cells. Effective analysis and design of fuel cells therefore need to account for the contact resistance in deriving the polarization curve for the cell. Despite its significance, relatively scant work is reported in the open literature on the measurement and modeling of the contact resistance in fuel cell systems, and the present work aims to fill this void. Experimental data are reported for the first time to show the effects of different gas diffusion layer materials and contact pressure on the electrical contact resistance. A fractal asperity based model is adopted to predict the contact resistance as a function of pressure, material properties, and surface geometry. Good agreement is observed between the data and the model predictions for a wide range of contacting pressures and materials.

Epitaxial ferroelectric thin films

1994 ◽  
Vol 52 ◽  
pp. 572-573
Author(s):  
S. G. Ghonge ◽  
E. Goo ◽  
R. Ramesh ◽  
R. Haakenaasen ◽  
D. K. Fork
Keyword(s):  
Single Crystal ◽  
Work Function ◽  
Nonvolatile Memory ◽  
Ferroelectric Properties ◽  
Electrical Contact ◽  
Memory Devices ◽  
Ferroelectric Films ◽  
Si Substrates ◽  
Electro Optic ◽  
Wide Range

Microstructure of epitaxial ferroelectric/conductive oxide heterostructures on LaAIO3(LAO) and Si substrates have been studied by conventional and high resolution transmission electron microscopy. The epitaxial films have a wide range of potential applications in areas such as non-volatile memory devices, electro-optic devices and pyroelectric detectors. For applications such as electro-optic devices the films must be single crystal and for applications such as nonvolatile memory devices and pyroelectric devices single crystal films will enhance the performance of the devices. The ferroelectric films studied are Pb(Zr0.2Ti0.8)O3(PLZT), PbTiO3(PT), BiTiO3(BT) and Pb0.9La0.1(Zr0.2Ti0.8)0.975O3(PLZT).Electrical contact to ferroelectric films is commonly made with metals such as Pt. Metals generally have a large difference in work function compared to the work function of the ferroelectric oxides. This results in a Schottky barrier at the interface and the interfacial space charge is believed to responsible for domain pinning and degradation in the ferroelectric properties resulting in phenomenon such as fatigue.

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