Application Examples

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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.

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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.

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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.).

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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.

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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.

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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.   

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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.

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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 Applications - Results from #20 - Results from #20 - Results from #20 - Results from #20 - Results from #20 - Results from #20 - Results from #20 - Results from #20 

 

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 Applications - Results from #20 - Results from #20 - Results from #20 - Results from #20 - Results from #20 - Results from #20 - Results from #20 - Results from #20

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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.

 

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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.

 

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 b2ap3_thumbnail_Wear-evaluation-of-wires Applications

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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.

 

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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.

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High speed sliding behavior of polymer coatings

WHY ?  : Nowadays polymer based coatings are applied in all walks of life, due to their excellent corrosion resistance, low friction and cost, good surface finish, molding ability and low density. However, one of the main issue of these coatings is their relatively poor performance in terms of wear. Especially, when sliding under high speeds, frictional heating can lead to a softening of the coating and accelerate the wearing-off process. Evaluating the high speed sliding performance of polymer coatings is a key issue in many applications.     

HOW ?  : A Basalt-S2 was used to measure the friction of various polymer coatings, under high speed sliding conditions. The coefficient of friction is continuously monitored and recorded. The wear damage was quantified by 3D confocal microscopy, the wear mechanisms identified by optical microscopy.

 

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RESULT :

- The high speed performance of different polymer coatings can be measured by the Basalt-S2.

- A ranking of different coatings is possible.

- The wearing-off of the coating leads to a fluctuation of the coefficient of friction.

- A 3D representation of the coefficient of friction (triboscopy) reveals differences in homogenity and stability of the coatings.

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b2ap3_thumbnail_Wear-evaluation Applications

 

 

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How can we measure the friction on wiper blades ?

WHY ?  : Wiper blades are of great importance to the safety of the driver. In reality they can operate under different speeds (various scales in the car) or under different lubrication conditions (from dry to wet with thin or thick film of water). To simulate these conditions in lab scale you need to have a versatile apparatus and you will need to use the actual components to be as close to reality as possible.  

HOW ?  : A Basalt-S2 was used to simulate the motion of the wiper blades (reciprocating nonlinear sliding motion). A sprinkler can be added to the apparatus to spray different volumes of water at different intervals. The aim is to simulate the “actual” conditions. Glass was used as a countermaterial. In this application we first present the effect of water in the friction of commercial wipers and secondly we compare different wipers for the same conditions (speed, load, water volume) to have a ranking. With the same setup the effect of particles (e.g. sand, dust etc.) can also be studied by either changing the composition of the water that is sprayed onto the glass, or by applying a layer soil/dust directly on the glass.

 

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RESULT :

- The Basalt-S2 can be used to measure the friction of wiper blades in contact with glass.

- The frictional behavior of a wiper strongly depends on the speed, water volume and particle concentration.

- A ranking between different commercial wiper blades at various conditions is possible.

 

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Hairstyling from a tribology point of view…

WHY ?  : In everyday life people use hairstyling products such as waxes or gels, to improve the holding of hair and improve/change its appearance. However, in the market there are many products available, claiming to have different characteristics (e.g. strong hold, silky/smooth touch…). To define the performance of such products, tribology comes into play. In particular two parameters are important. The friction determines how easy a wax or gel can be applied, whereas the stickiness and tackiness determine their holding ability.    

HOW ?  : For this application case the updated Basalt-N2 was used, operated at the mN range. In particular, two different test procedures are developed to evaluate the friction and stickiness/tackiness of commercial waxes and gels. To investigate the frictional behavior, a scratch test was performed on a thin film of wax or gel on a metallic substrate. The counter material was a silicone disk that simulates the area contact between the finger skin and the hairstyling media. Different sliding speeds, applied loads and sliding distances can be used to evaluate and compare different contact conditions. The stickiness/tackiness of waxes or gels was measured based on approach-retraction curves. In this procedure a silicone counter body gradually approaches the thin film of wax or gel, until a pre-set contact load is reached. Then, the silicone moves away from the greased substrate under well controlled conditions, until complete physical separation is achieved.  During this approach-retraction cycle, the force on the load sensor is measured as a function of time and distance moved. 

 

 b2ap3_large_PICTURE Applications

 

RESULT  :

- Both the friction and stickiness of gels and waxes can be measured by the Basalt-N2. This dual approach can be used to provide a ranking on the stickiness behaviour of commercial hairstyling products.

- Wax appears to stick more than gel : higher pull-off force. But its stickiness decreases sharply after the first cycle.

- Gels have a lower friction than waxes. The coefficient increase during sliding as the gel piles around the silicone counter material.

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