Stick-Slip\Smooth Slip as a Function of Ambient Gases and Pressures Disproving Previous Models of Adhesive Wear

1988 ◽  
Vol 140 ◽  
Author(s):  
Chao Gao ◽  
Doris Kuhlmann-Wilsdorf ◽  
David D. Makel
Keyword(s):  
Film Formation ◽  
Surface Film ◽  
Substrate Surface ◽  
Electrical Contact ◽  
Copper Substrate ◽  
Ambient Atmosphere ◽  
Surface Films ◽  
Electrical Contact Resistance ◽  
Stick Slip ◽  
Average Value

AbstractFive different slip modes have been identified for bundles of copper fiberssliding on a smooth copper substrate in atmospheric air, argon and nitrogenat pressures from atmospheric to 0.01 Torr. These are stick-slip, variable sliding, intermittent stick sliding and two kinds of smooth sliding, one apparently a basic property of clean surfaces and the other due to contaminants. These forms of sliding are rather persistent once established, and they follow some trends. Specifically, low-pressure smooth sliding is coordinated with a value of the coefficient of friction (μ) near 0.15 and is seen when the surface film is exceptionally thin, while intermittent stick sliding appears to be due to “pads” on the substrate surface,and variable sliding to small particles caught in between the fibers and the copper substrate. However, the five slip modes are erratic in that under the same conditions one or another or yet a third may be observed, even though the electrical contact resistance (R) depends rather reproducibly on time, load, velocity, ambient atmosphere and pressure. That dependence indicates an equilibrium between film destruction through sliding and film formation, overwhelmingly through the presence of oxygen. In the stick-slip mode the difference between pst tic and ųK itic appears to be roughly proportional to ų 0.15, i.e. tfiee xcess of e average value of the friction coefficient above 0.15, being about 20% for ų 0.3 andvanishing near ų =0.15. During slip episodes, R spikes roughly in proportion to their magnitude. Some tentative interpretations are offered, based on the concept that ų consists of three additive components, namely due to the bulk (ųBulk), due to debris (ųDebris), and dueto scoring of surface films (ųFilm).At any rate, the conclusion that the results contradict all previous models of “adhesive” wearis inescapable.

Film forming behaviour of oil soluble polyalkylene glycols

2015 ◽  
Vol 67 (2) ◽  
pp. 133-138 ◽  
Author(s):  
Martin Greaves ◽  
Ksenija Topolovec Miklozic
Keyword(s):  
Contact Pressure ◽  
Film Formation ◽  
Surface Film ◽  
Electrical Contact ◽  
Electrical Contact Resistance ◽  
Content Type ◽  
Film Forming ◽  
Specific Contact ◽  
Surface Active ◽  
Forming Behaviour

Purpose – The purpose of this paper was to examine the film-forming behaviour of simple compositions of polyalphaolefin (PAO) containing an oil-soluble polyalkylene glycol (OSP) alone, a zinc dialkyl dithiophosphate (ZDDP) alone and then combinations of an OSP and ZDDP. Design/methodology/approach – A Mini-Traction Machine with Spacer Layer Imaging technology was used to evaluate friction and film formation under a specific contact pressure, temperature and slide-to-roll ratio. Electrical contact resistance measurements were used to follow surface film formation. Findings – The inclusion of an OSP to a PAO showed evidence of friction-reducing behaviour with low friction values over the rubbing cycle but no significant tribo-film build up. When a ZDDP (1 per cent) is added to the PAO, a thick tribo-film forms of about 100 nm. Addition of an OSP (10 per cent) shows this film still forms despite the OSP being a polar and surface-active additive. Research limitations/implications – The study was conducted under a narrow range of test conditions (e.g. temperature and contact pressure), and future work will focus on friction and film formation across a broader set of conditions. Practical implications – Despite OSPs being polar and surface-active, they do not interfere with the ZDDP in forming an anti-wear film in a PAO and, therefore, their inherent properties of good deposit control could enhance the performance of modern lubricants. Originality/value – OSPs offer promising benefits as friction reducers in PAOs. The research also suggests that OSPs do not negate the formation of ZDDP anti-wear tribo-films when in combination in a PAO.

scholarly journals The Wear Process During the “Running-In” of Steel in Lubricated Sliding

1987 ◽  
Vol 109 (4) ◽  
pp. 587-591 ◽  
Author(s):  
M. Suzuki ◽  
K. C. Ludema
Keyword(s):  
Contact Resistance ◽  
Surface Film ◽  
Electrical Contact ◽  
Mineral Oil ◽  
Entrance Region ◽  
Engine Oil ◽  
Small Range ◽  
Electrical Contact Resistance ◽  
Metallic Contact ◽  
Wear Process

Steel cylinders were slid against flat steel disks, using a liquid lubricant, in order to study the progression of events associated with “running-in.” It was found that, when using mineral oil, the electrical contact resistance varied over a small range of high values indicating no metallic contact, whereas with engine oil a high resistance with an intermittent negligible contact resistance was found. A surface film forms from the additives in the engine oil which produces lower wear, slightly higher friction, a retarded running-in, and a rougher surface finish in the direction of sliding than does the mineral oil. A film which is composed only of Fe3O4 is formed when mineral oil is used. In addition, the mineral oil lubricated surfaces develop a conforming waviness across the sliding tracks. The oxide must have enhanced this surface conformity since it was not seen in the surfaces lubricated with engine oil. The role of the oxide may be further seen in experiments in which wear debris that accumulated in the entrance region of specimen contact was removed at frequent intervals. Little conforming waviness was seen in the latter case, suggesting that oxide which gathered in the entrance region abraded grooves in the steel surfaces. After the oxides were dislodged the friction increased and the contact resistance decreased for a time, indicating that the oxide acted like a solid lubricant.

The Degradation of Electrical Contact Resistance of Metal Films at Low Contact Force

2004 ◽  
Author(s):  
Daniel J. Dickrell ◽  
Michael T. Dugger
Keyword(s):  
Contact Resistance ◽  
Contact Force ◽  
Environmental Control ◽  
Surface Film ◽  
Electrical Contact ◽  
Electrical Contact Resistance ◽  
Small Surface ◽  
Underlying Mechanisms ◽  
Cyclic Degradation ◽  
Current Reduction

The quality of electrical contact resistance is important to the performance and reliability of metal-contact microelectromechanical system (MEMS) relays and switches. The cyclic degradation of contact resistance was examined for a metal multilayer sphere-on-flat contact at low contact force. The relationships between the degradation and underlying mechanisms, particularly surface contamination effects, were investigated through experimentation and analysis. Results indicated that the degradation severity could be significantly decreased with environmental control and contact current reduction. Micro-arcs at very small surface gaps, which can decompose adsorbed contaminants and leave an insulating surface film, were proposed as a cause of the resistance degradation.

Corrosion Resistant Coatings for Aluminum by Hydrothermal Film Formation in Alkaline Li-Salt Solutions

1996 ◽  
Vol 432 ◽  
Author(s):  
R.G. Buchheit ◽  
M.A. Martinez ◽  
C.B. Cooper
Keyword(s):  
Transition Metal Oxides ◽  
Film Formation ◽  
Surface Film ◽  
Al Alloys ◽  
Surface Films ◽  
Salt Solutions ◽  
Corrosion Resistant ◽  
Inorganic Coatings ◽  
Coated Surfaces ◽  
Corrosion Resistant Coatings

AbstractNew methods of forming corrosion resistant inorganic coatings on Al and Al alloys are required due to environment and work safety hazards associated with the currently used Cr-based coatings technologies. In this paper we report on certain specific aspects of Al surface film formation that can be exploited to form highly corrosion resistant coatings. The aspects discussed include: formation of hydrotalcite surface films, Li2[Al2 (OH)6]2 CO3nH2O, by exposure to Li-salt solutions, elimination of unwanted Cu compounds that accumulate surface films formed on Cubearing Al alloys, and generation of high corrosion resistance by precipitating transition metal oxides on to alkaline hydrotalcite coated surfaces.

Theory of Corrosion of Alkali-Borosilicate Glass

1982 ◽  
Vol 15 ◽  
Author(s):  
David E. Clark ◽  
Larry L. Hench
Keyword(s):  
Nuclear Waste ◽  
Film Formation ◽  
Surface Film ◽  
Soda Lime ◽  
Surface Films ◽  
Glass Corrosion ◽  
Commercially Important ◽  
Corrosion Mechanisms ◽  
Exchange Network ◽  
Dissolution And Precipitation

ABSTRACTThe alkali-borosilicate (ABS) system provides the basis for a wide variety of commercially important products among which are the nuclear waste glasses. Although a large number of investigations have been undertaken in the last five years, the corrosion mechanisms of the ABS glasses have not been characterized nearly as well as for the soda-lime-silicate (NCS) glasses commonly used for containers. It is well known that the corrosion of the latter glasses involves ion exchange, network dissolution, and precipitation mechanisms resulting in the development of one of five types of surface films. In the present paper we compare the corrosion behavior to the ABS and NCS glasses and discuss our current understanding of ABS glass corrosion in terms of mechanisms, kinetics, surface film formation and thermodynamics.

Deformation and Fracture of Oxides Fabricated on 304L Stainless Steel via Pulsed Laser Irradiation

2012 ◽  
Vol 1424 ◽  
Author(s):  
Samantha K. Lawrence ◽  
Douglas D. Stauffer ◽  
Ryan C. Major ◽  
David P. Adams ◽  
William W. Gerberich ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Electrical Contact ◽  
Constant Load ◽  
Laser Exposure ◽  
Ambient Atmosphere ◽  
304L Stainless Steel ◽  
X Ray Diffraction ◽  
Electrical Contact Resistance ◽  
Deformation And Fracture ◽  
Unique Approach

ABSTRACTLocalized heating of metals and alloys using a focused laser beam in ambient atmosphere produces dielectric oxide layers that have characteristic optical appearances including different colors. Nanoindentation probed the deformation and fracture of laser-fabricated oxides on 304L stainless steel. Conductive nanoindentation measured electrical contact resistance (ECR) of the same colored oxides indicating a correlation between laser exposure, conductance during loading, current-voltage (I-V) behavior at constant load, and indentation response. Microscopy and X-ray diffraction examined the microstructure and chemical composition of the oxides. Combining techniques provides a unique approach for correlating mechanical behavior and the resulting performance of the films in conditions that cause wear.

An Investigation of Dry Adhesive Wear

1959 ◽  
Vol 81 (1) ◽  
pp. 56-65 ◽  
Author(s):  
R. P. Steijn
Keyword(s):  
Wear Rate ◽  
Adhesive Wear ◽  
Film Formation ◽  
Electrical Contact ◽  
Surface Oxidation ◽  
Hard Material ◽  
Electrical Contact Resistance ◽  
Sliding Motion ◽  
Wear Tests ◽  
Made In

Sliding-motion experiments under unlubricated conditions have been carried out on various metals, and the results are discussed in terms of the simple wear theory advanced by Archard. Oxide-film formation has been studied by electrical contact-resistance measurements made in conjunction with wear tests. The effects on the wear rate and basic wear formula are discussed. For the ring apparatus, a modified expression for the wear formula is suggested to incorporate surface oxidation. Although it was found that the sliding of a soft material on a hard material follows simple wear rules, discrepancies are reported for the wear of brass against brass. In these experiments, the wear rate is affected by the geometry of the apparent area of contact.

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