Application Examples

for standardized tests, check 'our tools' page

Compressor fluids under pressure : unexpected effects

WHY ? : Air conditioner compressor fluids have to prevent friction and wear under elevated gas pressure.  Standard Pin&Vee Block tests with gas 'bubbling' through the lubricant do not correlate with field behaviour, especially with CO2 as the cooling medium.  Another simulation with pressurized gas is needed.  We selected the Falex Block on Ring configuration, as it also recreates the line contacts and is able to work at higher speed than the Pin&Vee block machine.

HOW ? : Our Falex Block on Ring machine allows pressurizing the lubricant chamber with a gas, up to 10 bar.  Standard block-on-ring tests are done with and without pressure on the dissolved gas.  Tests with increasing contact loads (EP) and tests with constant load (Anti-wear) are done.

 b2ap3_small_BlockOnRing Applications  b2ap3_small_BlockOnRingConfigs Applications

 

RESULT :

- A sudden loss of lubricity in the CO2 pressurized oil bath can be measured.  Block temperature increases suddenly at 70°C, while lubricant temperature decreases, which indicates that CO2 bubbles are forming in the interface between block and ring. This phenomenon is only seen when the gas is dissolved under pressure in the lubricant.

b2ap3_thumbnail_Divergence Applications

 

- This leads to poor lubrication and increased wear.  Thanks to right additives, this bifurcation can be eliminated and wear prevention can be significantly improved under pressurized conditions.

b2ap3_thumbnail_Results Applications

 

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Synergism between corrosion and wear

WHY ?  : Examples of corrosion are found in many industrial applications ranging from aeronautical, automotive, naval, and the construction industry over home appliances, water systems, pipelines, and ‘bio’ applications. Corrosion phenomena can be significantly accelerated by the simultaneous occurrence of a mechanical load on the surface: the formation of cracks and surface defects, along with surface strain and stress fields lead to faster diffusion of corrosive ions or the destruction of protective layers (depassivation). Thus there is a need to understand the synergy between wear and corrosion.

 

HOW ?  : An electrochemical cell was implemented in the Basalt-N2 tribometer. This setup allows for a fast and accurate measurement of the frictional behaviour of materials under various environments, whereas it is flexible and versatile in loading range (depending on the selecting cantilevers, load can range from 0.2 mN up to 100 N) and different contact geometries (point, line, area contacts) can  be used. In this way both the tribological and electrochemical properties can be monitored and correlated.

 

 b2ap3_thumbnail_PICTURE Applications

 

RESULT  :

- The influence of wear on corrosion mechanisms, and vice versa, can be investigated.

- Mechanical loading and shearing or rupture of the passivating layer accelerate corrosion (seen as sudden drop of the open circuit potential).      

- Corrosion processes can change the surface of the material (formation of oxides, hydroxides) and influence its frictional behavior.

- In the majority of cases, the synergism between corrosion and mechanical loading accelerates wear processes but in some cases the synergy may be positive.

b2ap3_thumbnail_OCP_tribocorrosion Applications b2ap3_thumbnail_COF_tribocorrosion Applications
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Prescreening the ISO20763 & ASTM D7043 Vickers Vane Pump tests

WHY ? : the standard method for evaluating anti-wear of hydraulic fluids in a vane pump, is by the 100 hour ASTM or 250 hour ISO method, using a real Conestoga-built vane pump.  This method takes a long time to run, and requires a lot of fluid.  This makes it difficult to use the method for development or research.

Various lab or bench test methods have been evaluted as a prescreening method, but none of them have shown any satisfactory correlation with real pump wear, so far (as clearly proven by the review of G.E. Totten 1996, Prediction of Hydraulic Fluid Performance: Bench Test Modeling, Dr: George E. Totten, Union Carbide Corp. Roland J. Bishop, Jr., Union Carbide Corp. Gary H. Kling, Caterpillar Inc. Presented at the International Fluid Power Exposition@ and Technical Conference 23-25 April 1996).  Recent attempts to correlate an SRV based test have also failed the correlation test.

HOW ? : We have studied the wear mechanism that takes place in a vane pump, and with the help of some special test specimens - designed for the Falex Multispecimen machine - recreated the vane contact vs. ring conditions, and the pressure pulses created by the inlet and outlet ports.  By using these custom specimens and a recirculating oil system, we can run a wear test with similar test conditions, in 22 to 44 hours.  By careful experimental design, we can run the test without creating excessive heat or catastrophic failure, so we focus on simulating the normal working conditions of a vane pump.

 

 b2ap3_thumbnail_Falex-Vane-specimens Applications b2ap3_thumbnail_WorkingLimits Applications b2ap3_thumbnail_ComparisonWear Applications

RESULT : 

  • we can simulate the same wear mechanism as in the Vane pump test (and as in real vane pumps)
  • we can rank the wear rate of different hydraulic fluids, correlating with the wear rate ranking in the Vane pump test
  • we can monitor in situ the coefficient of friction and online wear, giving us more information about the mechanism and evolution during the test
  • we can avoid the excessive heating of the test specimens

 

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Friction and wear of thin layers for MEMS

WHY ?  : Evaluating frictional and wear characteristics of very thin nanostructured layers with macro scale tribometers, in the Newton load range, can create unrealistic conditions.  Wear phenomena are highly dependent on the contact conditions: such high loads are not relevant in the case of MEMS. The adhesive and capillary components that contribute to friction, in a micro-contact, can not be simulated with high load devices.  Therefore, there is an increasing need to use new tribological testers and procedures to obtain a better understanding of surface interactions on an appropriate scale.

HOW ? : The Basalt-N2 tribometer can bridge the gap between the macro-load (conventional pin-on-disk) and nano-load (atomic force microscopes AFM) tribometers. Its versatile loading system, and by selecting cantilevers or strain gauges a load range of 0.2 mN up to 100 N is possible. In the case, loads between 500 mN and 2 N were investigated. Different contact geometries (point, line, area contacts) and sliding velocities can also be used. Due to the high sensitivity of this tester the transition between different phases can be successfully recorded (e.g. sliding between coated and uncoated components).  

b2ap3_thumbnail_PICTURE wear - Application examples | FACTLABS.ORG

 

RESULT :

- Conventional macro-load scale wear testers are not suitable for studying the wear behavior of thin layers, because the high initial contact pressure results in severe deformation and/or fracturing of the coating.

- Meso-load testing was useful as it allowed to record accurately the frictional behavior of the coating without damaging it, and with a minimum substrate effect.

- Thanks to the high sensitivity of this meso-load tester, surface phenomena such as oxidation and/or debris formation can be easily detected by monitoring the evolution of the coefficient of friction of the tribosystem. 

b2ap3_thumbnail_Load-scales wear - Application examples | FACTLABS.ORG

b2ap3_thumbnail_load-scale_COF_cracks wear - Application examples | FACTLABS.ORG

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Cost efficient data collection for statistical analysis of wear - TRL 6

WHY ?  : One of the most difficult industrial issues related to tribology is the prediction of long term wear or material durability.  In many components and products, materials with or without lubrication are used to reduce wear and maintain functionality of the component.  Required ‘wear life’ may be thousands of hours.  Contrary to the determination of a ‘coefficient of friction’ – which can be done in a few hours, the determination of wear and wear rate under realistic conditions is a long term test. The challenge is twofold : perform low wear rate experiments with many repeats at an economically acceptable cost.  The only way to do this is by a multistation approach (performing many wear experiments simultaneously). 

HOW ?  : Parallel tests were performed in our TRL6 prototype 10-station cross-cylinder block-on-cylinder tester. With this method, we test parallel and simultaneously different bulk or coated materials (metals, alloys, polymers, ceramics and composites), at moderate contact pressures and for a prolonged period of time. Adhesive or mild abrasive wear mechanisms are representative for the “actual” applications.

  • Up to 9 kilometers of sliding distance can be realised in a single day, on 10 wear contacts simultaneously.
  • To measure the wear damage, we use weight loss measurements, optical and/or confocal microscopy.  10 data points collected efficiently

 

b2ap3_thumbnail_10-station Applications   

 

RESULT :

  • The wear of various materials can be measured in a time efficient and economical way, realistic wear rates simulate actual applications.
  • Statistical analysis of the wear data provides a higher confidence level and allows outlier analysis.
  • Reliability testing of materials becomes economically possible.

b2ap3_thumbnail_10-station_ranking-polymers Applications

 

 

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How can we test the performance of cutting fluids for aluminum alloys ?

WHY ?  : Nowadays there is a great demand to use lightweight materials, such as aluminium alloys. One of their application possibilities is in the forming industry. In such demanding applications the use of a cutting fluid is essential to lubricate cutting edge and cool down the workpiece. Until now, to evaluate the efficiency of cutting fluids, ASTM D3233 tests on a Falex Pin-and-Vee Block tester were performed. However, this procedure was developed on hard tool steels and thus it is not appropriate for soft materials, such as aluminum alloys. In this application study and a modification of this procedure is proposed for testing of cutting fluids for soft materials and alloys.          

HOW ?  : By recording the frictional torque, measured during a modified ASTM D3233 Procedure A (continuous load increase) test, performed in Falex Pin-and-Vee Block tester. Aluminum alloy Pins and/or hard tool steel Vee blocks with standardized finish were used to simulate the aluminum cutting emulsion performance. The Pin-and-Vee Block tester was updated, so that a cooling emulsion is directly sprayed into the contact. In this way similar conditions to the “actual” application are obtained. From these tests the torque curves were obtained, so as to evaluate the performance of cutting fluids in the transition between boundary and extreme pressure regimes.

b2ap3_thumbnail_Falex-PinVee Applications  

 

RESULT :

- A modification for ASTM D3233 Procedure A was proposed for testing of cutting fluids on aluminum alloys.

- Based on the torque curve, the efficiency of a cutting fluid can be evaluated.

- The effect of additive on the performance of cutting fluids can be measured.

- A ranking of cutting fluid is possible.

b2ap3_thumbnail_Henkel-graph-1 Applications

b2ap3_thumbnail_Effect-of-concentration--of-additives_updated Applications b2ap3_thumbnail_Comparison-different-additives_updated Applications

 

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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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Friction measurements on complex shapes

WHY ?  : One challenge in tribology is to measure friction and wear on complex shapes, such as gears, with precision. Most of the existing setup try to simulate this complicated contact with a simplified ball-on-flat configuration. However, the more you simplify, the more you deviate from the actual application. In this application study we present an approach to evaluate the sliding contacts on complex gears.

HOW ?  : A Basalt-S2 was modified to perform reciprocating sliding tests on bare and coated gears. Holders for the gears were designed and 3D printed, a standardized steel cylinder was used as the countermaterial to create a line contact. The load and contact pressures were calculated by Hertzwin software to be in accordance with the in-field conditions. To ensure the same contacting surface between gears and countermaterial, a self-aligning holder was manufactured to hold the cylinder in contact with one of the spirals of the gear. The evolution of the coefficient of friction was continuously monitored, whereas the wear damage on both the spirals of the gear was measured by confocal microscopy.

b2ap3_thumbnail_S2-machine wear - Application examples | FACTLABS.ORG

               

RESULT :

- The Basalt-S2 was modified to measure the tribological behavior of gears.

- Differences in the friction between bare and coated gears can be recorded.

- Coatings can improve the wear resistance of gears.

b2ap3_thumbnail_COF_coated-vs-uncoated wear - Application examples | FACTLABS.ORG

b2ap3_thumbnail_wear-on-gear wear - Application examples | FACTLABS.ORG

 

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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 wear - 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 wear - Application examples | FACTLABS.ORG

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

 

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Abrasion by powders during powder processing

WHY ?  : One issue in the pharmaceutical industry, is the abrasion of processing components for pressing the powders. The intensity of the abrasion phenomena strongly depends on the composition and size of the processed powders. Up to date there is no fixed procedure on how to evaluate such abrasion phenomena, in conditions that simulate the realistic process.

HOW ?  : A modification on the Falex Multispecimen machine was prepared to simulate powder pushing over a pressing disk. In the updated setup a knife - similar to the actual application - was attached to the machine. Powder is supplied and continuously refreshed from the center of the contact. This refreshment and distribution is essential to avoid attrition or poor repeatability.  After completion of a test, the wear mechanisms on both knife and disk are investigated by optical microscopy. Changes in the cutting tip were evaluated by comparing the tip angle before and after the tests with a confocal microscope. The wear damage was assessed by measuring the width of the scar of the knife before and after testing.

 

b2ap3_thumbnail_Falex-Multispecimen wear - Application examples | FACTLABS.ORG 

 

RESULT :

- A methodology was developed to evaluate the abrasion of components used for powder processing in the pharmaceutical industry.

- The wear mechanisms were assessed and correlated to the one met in the actual application.

- The use of coatings to improve the abrasion resistance and lifetime such components was considered.

 b2ap3_thumbnail_wear-on-knife wear - Application examples | FACTLABS.ORG

b2ap3_thumbnail_58HRC-beforetest-200-a wear - Application examples | FACTLABS.ORG b2ap3_thumbnail_HSS_50_2 wear - Application examples | FACTLABS.ORG

 

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How can we measure the friction and wear of wires in sliding contacts?

WHY ?  : In our everyday life we come across and use applications were wire are operated in a sliding contact. Some indicative examples are elevators, car doors, canopies etc. In the majority of these applications friction there are limitation in terms of friction (e.g. the wire in a canopy should slide smoothly), whereas after a period of time localized wear of the wire can occur in the contact due to combination of the motion and the loading (e.g. wire in an elevator).    

HOW ?  : A Basalt-N2 was used to perform reciprocating sliding tests between wires and metallic countermaterials. Holders having different diameters were designed and manufactured to clamp the different wires. To maintain the same contacting surface during each test and between different tests, a self-aligning holder was manufactured to correctly align and hold the cylinder in contact with the wire. The load and contact pressures were calculated by Hertzwin software to be in accordance with the in-field conditions. The evolution of the coefficient of friction was continuously monitored, whereas the wear damage on both the wire and the countermaterial (tool steel cylinder) was measured by 3D confocal microscopy. Multiple tests were performed per wire to evaluate the repeatability of tribological data and to perform a statistical analysis.

 

b2ap3_thumbnail_PICTURE Applications  

 

RESULT :

- A new method to measure the friction and wear on wires in sliding contacts was developed for the Basalt-N2.

- Very high repeatability in friction data.

- Differences in the friction and wear of various commercial wires could be discerned.

- Statistical analysis of tribological data increases the confidence levels and helps to point-out outliers.

 

b2ap3_thumbnail_COF_duplicate-tests Applications b2ap3_thumbnail_Comparison-wires Applications

 b2ap3_thumbnail_Wear-evaluation-of-wires Applications

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Fast screening polymer coatings on cables

WHY

Various types of polymers can be used on steel cables, to provide a controlled-friction and noise-reducing coating when used on pulleys.  An efficient way to prescreen the behaviour of different types of polymers, in terms of frictional stability and durability, is needed.

Samples

HOW

Typical loading stresses in the application are estimated and recalculated to a cylinder-on-cylinder contact situation.  In this way, cylindrical test samples can be used.  The coated steel wire is used as one of the two parts of the friction test.  The countermaterial is a hard steel pin, representing steel pulleys that the coated wire is running over.

To simulate the most severe conditions in the pulley-cable contact, pure sliding is used in the lab test.  A reciprocating motion is selected, to allow testing on a short piece of coated cable  (for the prescreening stage, no long coils of coated material can be used).

The Basalt-N2 is used to rub a steel pin over the coated cables and compare the friction coefficient and relative durability of the coatings with one another

 

RESULTS 

  • Direct comparison of frictional behaviour of different polymer coatings measured immediately on the coated cable : production influences are included in the test.
  • Ranking of friction for different materials

b2ap3_large_FrictionResult Applications

  • Ranking of durability of different materials

b2ap3_large_WearDepth Applications

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