Application Examples

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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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How to measure the friction and adhesion of skin creams

WHY ?  : Skin creams are commonly used to improve skin health and create a smooth, soft, and moist perception. This is achieved by altering the surface roughness, friction, and adhesion of skin surface. Despite the fact that there are many commercial creams available, there is no consistent approach to determine their frictional and adhesive properties.

HOW ?  : Two different test procedures are developed to evaluate the friction and adhesion of commercial skin creams. To investigate the frictional behavior, a reciprocating sliding was performed by applying a film of cream on an artificial skin. As a counter material, silicone was used to simulate the actual tribosystem. Different sliding speeds, applied loads and sliding distances can be used to evaluate and compare different contact conditions. In addition, the adhesion of the skin creams was measured based on approach-retraction curves. In this procedure a silicone counter body gradually approaches the artificial skin with the cream, 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_thumbnail_PICTURE Tetra Basalt-N2 - Application examples | FACTLABS.ORG

 

RESULT  :

- The frictional behavior of various creams can be investigated in an accurate and efficient way, under realistic conditions.

- The same apparatus and setup can also be used to measure the adhesion and separation energy of creams on artificial skin. 

b2ap3_thumbnail_COF_skin-vs-silicone-and-cream-page-001 Tetra Basalt-N2 - Application examples | FACTLABS.ORG b2ap3_thumbnail_Cream_adhesion-page-001 Tetra Basalt-N2 - Application examples | FACTLABS.ORG

 

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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 Tetra Basalt-N2 - 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 Tetra Basalt-N2 - Application examples | FACTLABS.ORG

b2ap3_thumbnail_load-scale_COF_cracks Tetra Basalt-N2 - Application examples | FACTLABS.ORG

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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 Tetra Basalt-N2 - 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 Tetra Basalt-N2 - Application examples | FACTLABS.ORG

b2ap3_thumbnail_Modifiers_COF-comparison Tetra Basalt-N2 - Application examples | FACTLABS.ORG

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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 Tetra Basalt-N2 - 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 Tetra Basalt-N2 - Application examples | FACTLABS.ORG

b2ap3_thumbnail_wear-on-gear Tetra Basalt-N2 - 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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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.

 

b2ap3_thumbnail_S2-machine Applications  

 

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.

b2ap3_large_3D-COF_evolution_comparison Tetra Basalt-N2 - Application examples | FACTLABS.ORG

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.

 

b2ap3_large_S2-machine Applications  

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.

 

b2ap3_large_Wiper-blade-A_COF_Dry-sliding_with-label Applications b2ap3_large_Wiper-blade-A_COF_Wet-sliding_with-label Applications
b2ap3_large_Wiper-blade-A_COF_Wet-sliding_with-label Applications b2ap3_large_Wiper-blade-B_COF_Wet-sliding_with-label 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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