Performance Of Sliding Contacts Research Articles

Performance of elastomeric spur gear under dry and oil-lubricated conditions

The fatigue and tribological performance of thermoplastic-based gears have been investigated extensively so far, but no such work has been done on elastomeric gears. In the current work, the feasibility of utilizing elastomeric material for gear applications was investigated. Initially, the sliding contact performance of an elastomeric material under dry and oil-lubricated conditions was examined. Subsequently, the elastomeric gears were subjected to bending and contact loads under dry and oil-lubricated conditions. The elastomeric gear exhibited only tooth root cracks owing to bending fatigue under both dry and oil-lubricated conditions. Unlike thermoplastic-based gears, elastomeric gears do not exhibit thermal deformation or wear failures. The presence of voids in the elastomeric material caused multiple microcracks under dry conditions. Oil-lubricated elastomeric gear controlled crack growth at the tooth root and changed the cracking mode from tensile to shear under the high load condition.

Sliding contact performance of injection moulded and selective laser sintered polyamide under dry and lubricated conditions

PurposeThis paper aims to understand the effect of the manufacturing process on the frictional and wear performance of polyamide.Design/methodology/approachPin specimens were manufactured through injection moulding (IM) and selective laser sintering (SLS) manufacturing processes. The friction and wear performance was evaluated using a pin-on-disc configuration under dry and oil-lubricated conditions. The friction coefficient, wear resistance and surface temperature of specimens were measured, and failure morphology analysis was carried out to understand the mechanism.FindingsSLS material exhibited significantly less friction, wear and surface temperature than IM material under dry conditions. Reduced ductility due to the sintering contributes to reduced friction, wear and heat generation. Under the dry condition, IM material exhibited plastic flow and roll-shaped deformation, whereas SLS material exhibited only local degradation due to its lesser ductility. Lubrication reduced friction and temperature for both SLS and IM materials. The porous nature of the sintered surface absorbed the lubricant and released it while sliding, which is confirmed by the brown-coloured wear track.Originality/valueThe study provides valuable input to the designers on the sliding contact performance of commonly adopted two different manufacturing processes of polymers; IM and SLS manufacturing.

An investigation of material and tribological properties of Sb2O3/Au-doped MoS2 solid lubricant films under sliding and rolling contact in different environments

Abstract Solid lubricant coatings are commonly employed in mechanical systems operating in environments where oil or grease lubrication is not feasible. In particular, solid lubricant coatings are currently being used in rolling element bearings operating in vacuum environments and/or at high temperatures. Although numerous studies have reported the tribological performance of these materials in sliding contact, few if any studies have reported their performance in rolling contact. Since the functional lifetimes of solid lubricant coatings in rolling element bearings are derived from sliding contact experiments, it is beneficial and important to understand if the actual performance of the coatings in rolling contact bears a relationship to their sliding contact performance. In this work, Sb 2 O 3 /Au-doped MoS 2 coatings are deposited onto AISI 52100 and M50 specimens by magnetron sputtering. Mechanical properties are studied by scratch tests and nano-indentation techniques; microstructural analysis is undertaken with Raman spectroscopy and transmission electron microscopy. Friction and wear measurements are performed on specimens in both unidirectional and reciprocating sliding, using ball-on-flat tribometers in both vacuum and humid environments. Friction coefficient values as low as ~ 0.04 and as high as ~ 0.14 are measured at different contact stresses, and depend greatly upon the test environment. Functional lifetimes of the coatings are obtained from rolling contact tests performed in a thrust ball bearing tribometer in standard laboratory conditions.

Single-Shot Performance of RAFIRA

The rapid fire railgun (RAFIRA) developed at the French-German Research Institute of Saint-Louis (ISL) is a medium-caliber (25 mm x 25 mm) system designed to obtain very high fire rates (>50 Hz). It has an acceleration length of 3 m and is therefore comparable with existing close-in weapon systems such as Goalkeeper or Phalanx. In this paper, the single-shot performance of RAFIRA is presented. While RAFIRA has, in the past, mainly been used for multishot studies, its 3.4-MJ power supply allowed testing speed limits of the brush armature technology used at the ISL. The combination of light-weight sabots made from glass fiber-reinforced plastic and multiple metal fiber bundles acting as armatures allowed muzzle velocities in excess of 2 km/s while exhibiting excellent sliding contact performance throughout the launch. Corresponding experimental findings for varying projectile configurations and primary energies are presented and discussed.

The Effect of Lubricant on Electrical Connector’s Sliding Performance

Keywords: electrical contact lubricant contact resistance sliding wear Abstract. The contacts must be reliable in the required life time under practical application. Reliability means that the contact resistance can maintain low and stable. Au-plated contact pairs have been used widely for weak current connectors due to its well electrical and anti-corrosion performance. The high price of gold forces manufacturers to reduce the thickness of Au-plated while maintaining well performance. Increasing thin of Au plating causes the microporosity to increase rapidly, which has harmful effect on the performance of connectors. Appropriate lubricant coated on contact pair is a solution to improve the contact property. This paper focuses on sliding contact performance of gold plated contact pairs coupon with 0.25 m thickness and lubricated with water based lubricant named lub-E under damp heat and corrosion environment respectively. The contact pairs are also exposed in damp heat, corrosion environment respectively to evaluate the anti contamination property. The sliding experiment is conducted at frequency of 1Hz, amplitude of 1cm, and load of 0.5N, 1.0N and 1.5N. Contact resistance data is gotten in every sliding cycle at the condition of DC current 100mA and limited voltage 1.0V. Scanning electron microscopy (SEM) is used to observe the sliding track morphology and X-ray energy dispersive spectroscopy (EDS) is used to analyze the element.

The ISL Rapid Fire Railgun Project RAFIRA—Part II: First Results

This paper reports on the rapid fire railgun (RAFIRA) project recently launched at French-German Research Institute of Saint-Louis (ISL) with the aim of investigating the multishot capacity of the armature technology used at the ISL. The latter is characterized by the use of multiple metal fiber brush armatures. The project started with the development of a new medium-caliber launcher (25 mm t 25 mm) named RAFIRA and a suitable loading system, as described in part I of the set of papers. This part II summarizes the major results obtained with RAFIRA in a single-shot mode and briefly explains the method of optimizing its performance. The experimental realization of the loading system described in part I is presented. First results regarding the performance of this loader are presented. Suitable conditions allowing multishot experiments were worked out. This paper concludes by presenting the first multishot experiments performed using the ISL armature technology. Already in the first tests, RAFIRA has accelerated projectiles up to more than 1000 m/s while achieving cadences around 30 Hz. The sliding contact performance of these experiments is briefly discussed.

New Carbon–Copper Composite Material Applied in Rail-Type Launching System

During the operation of a rail-type electromagnetic launching system, the state of the sliding friction between armature and rail, friction drag, contact resistance, etc., directly affect the system operation and performance. Carbon-copper composite material can be used on the parts of the armature which contacts the rails. It should not only provide good conductivity, but lubrication, as well; thus, the performance is improved compared with using metal sliders. The carbon-copper composite material introduced in this paper uses improved material preparation and composite material molding crafts. It is possible to make a composite material in which a 3-D metal net is obtained: something that cannot be obtained by conventional copper-graphite powder metallurgy or by metal impregnation. Graphite particles are distributed uniformly within the net, improving abrasion resistance and voltage drop over common carbon-copper composite material. The static tests showed that this new type of composite material has better electrical performance than former brush material in the same conditions, and the dynamic tests showed that the temperature rise is not big when the brush with this new composite material is switched on with big current and the surface abrasion is smaller during sliding. The good conductivity and sliding contact performance are important for application in electromagnetic launching systems

Sliding contact performance of multiple brush armatures

In a previous paper experiments (muzzle velocity v/sub 0/<1200 m/s, applied energy per shot E/sub prim/<0.7 MJ) concerning the contact transition of multiple brush armatures were presented and a corresponding physical model was proposed. This work deals with the continuation of these experiments performed at the ISL-railgun facility EMA3 (l=3 m, regular caliber=15/spl times/30 mm/sup 2/). This time, E/sub prim/ was increased up to 0.9 MJ. The use of both, quasisegmented rails allowing a higher acceleration due to an increased inductance gradient L' and a new sabot-technique resulted in v/sub 0/ up to 1900 m/s. The contact behavior in the velocity range between 1200 m/s and 1900 m/s is qualitatively clarified and some integral quantities describing the armature performance are given. The quantitative analysis of the armature mass loss shows both, friction and Joule losses playing an important role. The multiple brush armatures used might be designed to show excellent sliding behavior and their contact transition velocities might be greater than 1700 m/s.

Solid lubrication of ball bearings for spacecraft mechanisms

Solid lubricant coatings are commonly employed in mechanical systems operating in environments where oil or grease lubrication is not feasible. In particular, solid lubricant coatings are currently being used in rolling element bearings operating in vacuum environments and/or at high temperatures. Although numerous studies have reported the tribological performance of these materials in sliding contact, few if any studies have reported their performance in rolling contact.Since the functional lifetimes of solid lubricant coatings in rolling element bearings are derived from sliding contact experiments, it is beneficial and important to understand if the actual performance of the coatings in rolling contact bears a relationship to their sliding contact performance. In this work, Sb2O3/Au-doped MoS2 coatings are deposited onto AISI 52100 and M50 specimens by magnetron sputtering. Mechanical properties are studied by scratch tests and nano-indentation techniques; microstructural analysis is undertaken with Raman spectroscopy and transmission electron microscopy. Friction and wear measurements are performed on specimens in both unidirectional and reciprocating sliding, using ball-on-flat tribometers in both vacuum and humid environments. Friction coefficient values as low as ~ 0.04 and as high as ~ 0.14 are measured at different contact stresses, and depend greatly upon the test environment. Functional lifetimes of the coatings are obtained from rolling contact tests performed in a thrust ball bearing tribometer in standard laboratory conditions.

Development of a 300 kW 3000 rev/min d.c. machine using thyristor-assisted commutation

The principle of thyristor-assisted commutation was easily demonstrated on small laboratory-type machines, but the commercial significance of the concept could only be investigated by constructing a machine of a size where commutation would normally be a problem. A 300 kW, 3000 rev/min version was built and the performance of this prototype is described. In particular, it is explained how the problematic sliding-contact performance of this type of machine was satisfactorily achieved using (eventually) only commutators and brushgear of conventional construction. Companion papers describe the commutating-time calculations and the terminal characteristics of the machine.