Application Examples

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Friction modifiers put to the test. Can we influence friction?

WHY ?  : In the effort to reduce CO2 exhaust, an important approach is to reduce friction in the engine.  One part of the mix of options are ‘friction modifying additives’, such as the well-known GMO, which are known to reduce friction by 5, 10 or 20%. However, the difficult task is to prove the effect of friction modifiers in the engine, since existing engine tests measure the interaction of all sliding and moving components, as well as lubricant viscosity and other effects. In order to isolate and evaluate the efficiency of friction modifiers, a precision frictional approach is required. 

HOW ?  : The high precision tribometer Basalt-S2 was used. Applied loads and friction are measured with mN precision, using a ball-on-flat contact geometry. This creates realistic contact pressures.  Due to the high sensitivity of this tester, differences between the base oils and friction modifiers were successfully recorded.  

b2ap3_thumbnail_S2-machine automotive - Application examples | FACTLABS.ORG 

 

RESULT :

- The effect of different modifiers can be separated by the precision microtribometer.

- Measurements are repeatable enough to draw significant conclusions.

- A ranking of base oils and oils containing friction modifiers is reached.

- A friction reduction of 10 to 18% in the moving contact is possible with the use of the right friction modifier.

b2ap3_thumbnail_Modifiers_COF-evolution automotive - Application examples | FACTLABS.ORG

b2ap3_thumbnail_Modifiers_COF-comparison automotive - Application examples | FACTLABS.ORG

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Pre-screening the tribological properties of shock absorbers

WHY

Shock absorber component testing is expensive and time-consuming and this is a limiting factor in developing new materials for this application. There is a need to develop a pre-screening method to get a quick but accurate evaluation of the tribological behavior of materials, without losing too much correlation with the actual conditions (geometry, wear mechanism, load, speed, number of cycles etc.).

b2ap3_large_Aim-for-videos_shock-absorbers Applications b2ap3_large_Wear-mechanisms Applications

HOW

A Cameron Plint TE-77 high frequency friction machine is modified to fit actual components of a shock absorber (rod and bearing). This set-up alloys for a reciprocating motion under variable frequencies, loads and/or displacements. The tests can be performed under dry or lubricated conditions, according to the specifications of the application. During the test, friction is continuously monitored and recorded. This is an important advantage over component test benches: changes in friction can be linked to surface changes (e.g. formation of wear particles) and/or a failure of the lubricating film. Different rod diameters can be tested. The wear on both rod and bearing can be evaluated by optical and confocal microscopy. 

 

 

RESULT 

  • A new adapter and test method was developed on a TE-77 high frequency friction machine to evaluate the frictional properties of shock absorbers on component level.
  • In situ monitoring of the coefficient of friction of the tribosystem allows to pinpoint changes in surface condition and/or lubricating film.
  • The wear mechanisms observed after testing are similar to in-field damage.
  • A ranking of different materials and coatings for shock absorber applications is possible.

b2ap3_thumbnail_Shock-absorber-graphs Applications

 

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Simulation of wear in roll-slip contacts

WHY ?  : The steering system of cars is based on a rack and pinion system. Over time, the metal on these gears wears out, resulting in a loose fitting. Some other applications also make use of a rack and pinion system to translate a rotary drive motion into a linear displacement.  The wear and tear of such systems occurs through a roll-slip mechanism. Therefore a tribological method needs to be developed to simulate such roll-slip contacts and their failure mechanisms.

HOW ?  : A modification on the Falex Multispecimen machine allows for a 2-rollers on disk geometry. During each turn these rollers rotate and slide simultaneously, simulating a roll-slip contact. The speed and load can be adjusted to achieve similar contact conditions as in the actual application. The contact can be either dry or lubricating, whereas the rollers and/or disks can be bare or coated materials. In this application series we investigated the use of coatings to decrease the friction and wear of the tribo-system, whereas the contamination of lubricant with hard particles (e.g. sand) was also taken into consideration.   

b2ap3_thumbnail_Falex-Multispecimen automotive - Application examples | FACTLABS.ORG 

 

RESULT :

- A roll-slip contact can be simulated by a Falex Multispecimen tester.

- Coatings can improve the wear resistance and frictional performance of roll-slip contacts.

- The presence of hard particles is a major risk for degrading the performance of a lubricant in roll-slip contacts.

b2ap3_thumbnail_Effect-of-coating-on-COF automotive - Application examples | FACTLABS.ORG

b2ap3_thumbnail_effect-of-sand-on-wear-evolution_roll-slip automotive - Application examples | FACTLABS.ORG b2ap3_thumbnail_effect-of-sand-on-roll-slip-wear automotive - Application examples | FACTLABS.ORG

 

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Testing of oils for the automotive industry

WHY ?  : A variety of oils for the automotive industry is available in the market. These oils have different composition, additives and can operate under different conditions (motion, load, speed and temperature). A method need to be used to prescreen the performance and endurance of these oils under different conditions, which are relevant to the automotive industry.    

HOW ?  : A TE-77 high frequency friction machine developed by Phoenix tribology, was used. This set-up alloys for a reciprocating motion under variable frequencies, loads, temperatures and/or displacements. During the test the friction, temperature of the bath and contact potential potential are continuously monitored and recorded. In this way variations in those parameters can be linked to changes in the oil (e.g. activation or depletion of additives), to surface changes (growth or removal of an oxide layer), to changes in the lubrication regime (in accordance with Stribeck curves) etc. After testing, the wear on both the plate and countermaterial are evaluated by optical and confocal microscopy.

 

b2ap3_thumbnail_TE-77 Applications  

 

RESULT :

- TE-77 is a versatile machine that can test the reciprocating sliding wear of oils.

- The evolution of the coefficient of friction can be linked to temperature changes.

- Different oils can be ranked under various loading, speed and temperature conditions.

- The presence of contaminants (particles) in the oil can have a significant effect in its performance.

b2ap3_thumbnail_TE77_effect-of-T-on-COF Applications b2ap3_thumbnail_TE77_effect-of-particles Applications

b2ap3_thumbnail_TE77_endurance-of-oils Applications

 

 

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