Tiêu chuẩn iso 07148 2 2012

© ISO 2012 Plain bearings — Testing of the tribological behaviour of bearing materials — Part 2 Testing of polymer based bearing materials Paliers lisses — Essai du comportement tribologique des matér[.]

General

This part of ISO 7148 provides various test methods to evaluate different contact geometries These test methods are designed to closely align with practical applications, ensuring accurate and relevant testing outcomes.

Test method A — Pin-on-disc

Copyright International Organization for Standardization

Provided by IHS under license with ISO Licensee=University of Alberta/5966844001, User=sharabiani, shahramfs

— basic testing of simple test specimens;

— no increase of sliding surface area due to wear;

— simulation of linear guidance system [see Figure 1b)].

— edge of the pin might wipe off lubricant;

— no injection moulding of the pin with fibre reinforced material;

— no injection moulding of the disc because of problems with shrinkage.

Figure 3 — Test method A — Pin-on-disc

Test method B — Block (or pin)-on-ring

— no injection moulding of the block because of problems with shrinkage and fibre orientation;

— edge of the block might wipe off lubricant;

— no injection moulding of the disc because of problems with shrinkage.

Figure 4 — Test method B — Block (or pin)-on-ring

Test method C — Plain bearing-on-shaft

— best simulation of all possible systems;

— testing of original or scaled bearings;

— long testing time (accelerated testing might cause excessive frictional heating);

— difficult alignment of the test bearing;

— increasing sliding surface area due to wear under boundary lubrication.

Figure 5 — Test method C — Plain bearing-on-shaft

Test method D — Sphere-on-prism

— testing of polymer/polymer or polymer/metal combinations;

— with and without lubrication (test specimen contains reservoir for lubricant);

— testing of lubricant’s interaction with polymers;

— injection-moulded test specimens available;

— self-adjustment of the alignment of the sliding couple;

— increasing sliding surface area due to wear under boundary lubrication.

— plastic deformation might affect results;

— increasing sliding surface area due to wear under dry conditions.

Test method E — Rotation under thrust load

See Figure 7. a) E1 — Sleeve-to-sleeve b) E2 — Sleeve-to-plate Figure 7 — Rotation under thrust load

— basic testing of simple specimens;

— injection-moulded test specimens available;

— shrinkage at sliding surface on injection-moulded specimens affects results.

Data required

For accurate testing, specimens of the same material batch should be conditioned uniformly and have consistent surface finishes Machined and injection-moulded specimens may yield different results due to variations in crystallinity with depth from the surface; therefore, they must be tested separately to ensure reliable comparison.

To ensure the repeatability of test results, it is essential to thoroughly document the structural condition of mating materials, including material specifications and composition such as fillers and fiber reinforcement per ISO 6691, manufacturing methods, and structural properties like density and crystallinity Additionally, mechanical properties such as Shore hardness and compression limits (ISO 4385), as well as compression strength, should be recorded The conditioning state, including moisture content, and surface condition, including roughness parameters like Ra, must also be detailed, specifying surface finish methods such as injection molding, machining, turning, grinding, lapping, polishing, or milling following ISO 2818 standards.

Polymer-based plain bearing materials (pl)

Manufactured components can be produced through various methods such as moulding, injection moulding, or machining They may also be created by cutting bars or tubes to the required length or from semi-finished materials Additionally, parts are often fabricated by cutting from injection-moulded or laminated (composite) plates, ensuring versatile manufacturing options for different applications.

When testing fibre-reinforced polymers, it is essential that the fibres are oriented in the same direction as in the final product, such as parallel or perpendicular to the sliding surface, to ensure accurate and relevant results Proper fibre alignment during testing directly impacts the material's performance and allows for reliable assessment of its structural properties.

Materials of mating component

When selecting mating materials for technical applications, both metallic and polymer-based options can be considered, with the choice aligning with practical usage For optimal performance, mating materials should be compatible, such as using a gear box made of aluminum with injection-molded gears and shafts crafted from polyoxymethylene (POM) It's essential that the mating pair creates a consistent sliding contact, like a rotating POM disc or ball on a fixed pin or aluminum prism, to ensure smooth operation and durability.

In this case, the reverse combination POM pin on aluminium disc leads to errors in evaluation.

Dimensions of test specimens

If dimensions other than those described as follows are used, the results might not be comparable due to the effects of transfer films and heat dissipation.

The disc shall have the following preferred dimensions:

The basic form of the disc is identical to the ring of deep groove ball thrust bearings on the shaft side.

The ring shall preferably have an outside diameter of 40 mm and a width corresponding at least to the width of the block.

The pin shall preferably have a diameter of 3 mm for injection-moulded materials For fibre-reinforced materials, a larger diameter is preferred.

When using a pin with a diameter greater than 7 mm, it is essential to reduce the radius of the sliding track or increase the disc diameter to ensure proper fit and operation Additionally, provisions must be made to prevent the rotation of the pin, maintaining stability and safety in the assembly Proper design considerations are crucial to accommodate larger pins and ensure the overall functionality of the mechanism.

The free length of the pin must not exceed 2 mm, ensuring optimal performance A 3 mm diameter polymer pin can be manufactured from a standard tension bar following ISO 527-3 or ISO 527-2 standards This standardization facilitates reliable correlation of wear and strength tests, enhancing quality control and material testing accuracy.

The preferred basic dimensions of the block are 10 mm × 10 mm × 20 mm, with the option to use a 10 mm length if larger components are unavailable The roughness of the block depends on machining conditions such as milling or turning To ensure proper contact, the radius of the rubbing surface should be at least 1.001 times the radius of the ring; exceeding 1.003 times (line contact) can prolong the running-in period.

The sphere shall preferably have a diameter of 12,7 mm Thermoplastics may be injection-moulded (see Figure 8) Spheres made out of metals are commercially available (balls for ball bearings or valves).

1 six-flat mount with cylindrical hole

Figure 8 — Example of an injection-moulded sphere

The prism should have a specific, preferred shape to ensure optimal performance When injection-moulded, it must feature a uniform wall thickness of 2 mm and include a metallic support to prevent deformation during manufacturing Alternatively, cut plates can be securely fitted into a specially designed mount to maintain shape and stability Proper adherence to these specifications is essential for consistent and reliable optical performance.

Figure 9 — Example of an injection-moulded prism

Figure 10 — Example of machined plates, inserted in a metallic holder

Plain bearing bushes can be manufactured through machining or injection molding, offering versatility in production methods Depending on the testing equipment, these bearings can be produced with various inside diameters, with common sizes including 20 mm, 5 mm, and 1 mm for specialized applications The preferred inside diameters are selected based on specific requirements, with the width-to-diameter ratio typically remaining between 0.75 and 1 for optimal performance.

The test report must specify the bearing's diameter, bearing clearance, wall thickness, and type (bush or half bearing) For smaller plain bearings, a flange is necessary to facilitate secure mounting, as illustrated in Figure 11 Additionally, the sliding surface area should be confined within the cylindrical portion of the plain bearing to ensure proper functionality.

Figure 11 — Example of an injection-moulded plain bearing with step and chamfer in the bore

For accurate testing, the shaft must be manufactured with a maximum circular run-out of 1 μm and a circularity of no more than 5 μm Test specimens, including the test bush and shaft, should be mounted with no more than 0.05° angular deviation before testing and without any normal force applied The shaft diameter must provide sufficient bearing clearance to accommodate thermal expansion of the bush, preventing bore closure and seizure; this clearance typically ranges from 0.003 to 0.01 times the shaft diameter, kept as small as possible to avoid seizure while ensuring reliable operation.

The plate may be made by machining or injection moulding The preferred basic dimensions of the sleeve are shown in Figure 13.

Preparation of the test specimens

The preparation applies to bearing materials and mating materials.

Before conducting the test, a thorough cleaning procedure must be performed to eliminate any residues of cutting solutions or other substances This ensures the accuracy of test results by preventing potential influences on the sliding behavior of the test specimens Proper cleaning is essential for maintaining the integrity and consistency of the testing process.

After completing the cleaning process, it is essential to avoid touching the sliding surfaces that will come into contact with each other, neither by hand nor with any tools This ensures the integrity and cleanliness of the test specimens for accurate results.

The following cleaning procedures shall be carried out.

Begin by brushing loose particles from the test specimens, then immerse them in three separate baths containing a high-quality solvent with a maximum impurity level of 5 × 10⁻⁴% Suitable solvents include 2-propanol, ethanol, acetone, fluorocarbons, specific water solutions, or cyclohexane, ensuring compatibility with the tested material It is essential to verify that the solvent does not damage the plastic material before use The cleaning procedure details and the selected solvent type must be documented in the test report to ensure transparency and reproducibility.

— The test specimens shall be dried in an oven at a maximum temperature of 60°C.

— Test specimens of polymers which are affected by humidity, e.g polyamides, shall be pre-conditioned prior to the test at standard atmosphere (23°C and 50 % air humidity) for a period of 24 h.

This cleaning method is not suitable for all materials, such as thermoplastic amorphous materials that are incompatible with certain solvents, polymers containing lubricants, or porous fibers These materials should be machined dry, without cutting fluids, or injection-molded without mold release agents Additionally, the sliding surfaces must be handled carefully to avoid contact by hand, ensuring proper maintenance and optimal performance.

7 Test methods and test equipment

General

In order to give manufacturers or users of polymer-based materials for plain bearings the opportunity to simulate different practical applications, different test methods are standardized.

This part of ISO 7148 lays down test methods according to the following categories:

— approximated practical testing of simple test specimens;

— testing of an original component or a scaled-down unit.

ISO 7148 recommends using basic or simulation tests for component selection, ensuring efficiency and reliability Additionally, testing original components, such as full-sized thermoplastic plain bearings, is permitted under variant c), allowing for real-world performance assessment of authentic specimens.

Test method A — Pin-on-disc

This test shall be carried out with pins in accordance with 6.4.4 and discs in accordance with 6.4.2.

The spindle holding the disc must be mounted in precision rolling bearings with zero clearance to ensure stability and accuracy An electric drive should enable continuously adjustable speed settings or, alternatively, facilitate arc-shaped translatory motion through oscillating operation The specimen holder, designed with adequate flexural strength, must feature a guide with minimal friction and no clearance for precise movement Additionally, the loading system should allow for maintaining constant force, incremental increases, or step-by-step loading to accommodate various testing requirements.

The study measures key variables including the coefficient of friction, wear rate, and reference temperature of the specimens, with a thermocouple ideally fitted in the pin to ensure accurate temperature readings It is essential to specify the measurement position of the temperature sensor in the test report The coefficient of friction is determined by measuring the frictional force, while wear is quantified by assessing the linear volume of material removed from the pin, through continuous or intermittent measurements At the conclusion of the test, wear is validated by dimensional measurements of both the disc and pin to identify any transfer film formation or disc wear.

A temperature-measurement probe should be installed on the reverse side of the disc, aligned with the radius of the sliding track of the pin, to accurately monitor the disc's bulk temperature This setup ensures precise temperature measurement critical for performance and safety assessments Compliance with ISO 2012 standards is essential for standardized testing procedures Proper placement of the probe is vital for reliable data collection during operation.

`,`,,,,,```,````,`,,`,`````-`-`,,`,,`,`,,` - stable temperature measured at this point is approximately proportional to the frictional heating and may be used as a way of monitoring the temperature behaviour.

For tests requiring constant temperature of the sliding surface, the temperature of the disc should be controlled.

Test method B — Block-on-ring

This block-on-ring test evaluates the friction and wear characteristics of conformal blocks and rings, following specific standards The test involves mounting a thermally isolated ring with a maximum radial runout of 25 μm on a continuously adjustable driving shaft The preformed block is securely positioned in a self-adjustable holder, which allows for continuous or step-wise loading to simulate real-world conditions Equipped with precise measurement instruments, the test system continuously monitors the friction coefficient, linear wear of the block, and ring temperature, providing comprehensive data for assessing material performance and durability.

The ring temperature is determined by averaging two measurements taken from thermocouples placed on opposite sides of the test block in the sliding direction Consistent test temperature is crucial for obtaining repeatable measurement results Simple test setups without thermostatic control can only be used for comparative testing To establish material properties and obtain test certificates, tests should be performed using thermally regulated rings or a test shaft with circulating heating or cooling liquids.

Test method C — Plain bearing-on-shaft

The plain bearing-on-shaft test is based on the combination of a plain bearing bush (or two half bearings) and a shaft.

Solid plain bearing bushes are used in test equipment in conjunction with steel shafts, with force applied using devices like springs Wear measurement is conducted using gauges or measuring microscopes to ensure precision For high loads, speeds, or larger diameters (e.g., 20 mm), thermostatic temperature control of both test specimens is often necessary to maintain consistent testing conditions.

The test equipment utilizes a plain bearing bush integrated into a pendulum device, supported by a cantilevered shaft for stability This setup allows precise application of force to the test bearing through weights, enabling accurate measurement of friction forces via the device’s lateral deflection.

A collet chuck securely clamps a removable shaft piece into a precision spindle with a maximum radial runout tolerance of 2 μm, ensuring high running accuracy This spindle is mounted in precision rolling bearings for optimal performance During testing, the supported bearing is positioned on the cantilevered end of the shaft, enabling precise evaluation of bearing performance and accuracy.

Test method D — Sphere-on-prism

The test equipment must enable continuous or step-by-step speed adjustment of the sphere using a variable speed drive, ensuring precise control during testing A balance device applies the system force through weights or a continuously adjustable load setting system for accurate load management Additionally, a control unit is essential to maintain both test specimens at a constant temperature and to regulate environmental parameters such as air humidity and gases within the test area, ensuring reliable and consistent test conditions.

The study analyzes the friction force as a function of sliding speed, applied force, and temperature, highlighting their impact on wear behavior It also assesses the total wear depth of both the sphere and prism specimens, providing comprehensive insights into material degradation Wear measurements are conducted using a dial gauge and continuous monitoring techniques to ensure accurate and reliable results.

`,`,,,,,```,````,`,,`,`````-`-`,,`,,`,`,,` - determining the wear by means of an electronic displacement transducer The volumetric wear rate and the coefficient of wear may be calculated from these data.

Test method E — Rotation under thrust load

The rotation test under thrust load is based on the combination of a sleeve and plate, sleeve-to sleeve or sleeve-to-plate.

This test shall be carried out with the sleeve made of bearing material and the sleeve made from the material of the mating surface component in accordance with 6.4.10.

The spindle holding the specimen must possess sufficient rigidity to withstand applied loads and ensure smooth, vibration-free rotation Additionally, the spindle's run-out should not exceed 0.005 mm to maintain precision and accuracy during operation.

The rotational axis of the specimen holder for bearing material must be aligned with the fixed specimen holder's center to ensure accurate testing The specimen holder should possess sufficient strength and be equipped with a clearance-free guide and a key mechanism to prevent slipping during testing Additionally, the loading system should be capable of maintaining a constant force, gradually increasing it, or applying step-by-step loading, to accommodate various testing requirements.

In the test report, it is essential to specify the measuring instrument's position for temperature to ensure accuracy The key measured variables include the coefficient of friction, rate of wear, and the reference temperature of the fixed specimen The coefficient of friction is determined through rotational torque measurements, providing insights into the material's frictional behavior Wear assessment involves measuring the volume of material removed from the specimens, with dimensional measurements also applicable for evaluating wear performance These parameters collectively contribute to understanding the material's tribological properties.

This test should be conducted using a sleeve crafted from the same material as the mating surface component, following the guidelines outlined in section 6.4.10 Additionally, the test plate must be made from the bearing material, in accordance with the specifications specified in section 6.4.11.

The spindle holding the specimen must possess sufficient rigidity to withstand applied loads and ensure smooth rotation without unevenness or vibration Additionally, the spindle's run-out should not exceed 0.005 mm to maintain precise and consistent operation.

Ensure that the rotational axis of the specimen (sleeve) holder is aligned with the center of the fixed plate holder for accurate testing The specimen holder must have adequate strength and be equipped with a clearance-free guide and a key to prevent slipping during testing Additionally, the loading system should be capable of maintaining a constant force, increasing continuously, or applying step-by-step loading to accommodate various testing requirements.

The study measures key variables such as the coefficient of friction, wear rate, and the reference temperature of the fixed specimen The coefficient of friction is determined through rotational torque measurements, providing essential data on surface interactions Wear is quantified by calculating the volume of material lost from the specimens, with dimensional changes like thickness reduction also serving as indicators of wear It is important to specify the position of the temperature measuring instrument in the test report to ensure accurate thermal data collection.

General

Plain bearings made of polymers may run dry, i.e without any lubricant, but they may also be lubricated with oil, grease and some other fluids (assuming chemical compatibility).

Lubricated plain bearings are capable of withstanding higher tribological loads, with their endurance largely influenced by the quality of lubrication, whether boundary or hydrodynamic Proper lubrication conditions are essential to ensure optimal performance and longevity of these bearings.

`,`,,,,,```,````,`,,`,`````-`-`,,`,,`,`,,` - solid lubricants to the sliding surfaces on assembly, for example, polytetrafluorethylene (PTFE), graphite and molybdenum disulphide.

Polymers used in lubricants must be compatible with the lubricant, taking into account aging and solubility characteristics to ensure stability over time High surface pressures can cause stress cracks in the contact areas and lead to the formation of oil pools or blisters, particularly in amorphous thermoplastics Additionally, powder-like wear debris can accumulate and thicken the oil or grease, affecting lubrication performance and system efficiency.

Dry (dr)

No lubrication of the test specimens.

Grease (gr)

Lubrication with initial grease only Grease is smeared by means of a small spatula at a controlled volume on the mating surface prior to the start of the test.

Oil (oi)

During assembly, a controlled volume of oil is applied to the fixed test specimen in proportion to its practical application volume The oil selection should ensure it remains within the sliding area, considering surface tension and wettability properties of oils in polymer combinations Caution is necessary, as certain oils may creep from the sliding area due to these factors.

Solid lubricant (so)

Solid lubricant is applied to one or both surfaces before the test by burnishing, lacquer spraying or suitable means.

The tribological behavior of polymer-based materials was evaluated using the pin-on-disc testing method The tests were conducted under dry conditions, with a specific test force of 3 N/mm² and a sliding velocity of 0.1 m/s These parameters ensure precise assessment of material wear and friction characteristics, providing valuable insights into the performance of polymer composites in real-world applications.

The tribological behavior of a polymer-based material was tested using the sphere-on-prism (D) method under lubricated conditions with oil The test was conducted at a specific force per unit area of 10 N/mm² and a sliding velocity of 0.01 m/s These parameters ensure precise evaluation of the material's friction and wear characteristics in lubricated environments.

NOTE For abbreviatied terms, see also Tables 3 and 4.

Environmental conditions

Ambient conditions for the tests should normally be T amb = (23 ± 5) °C and 40 % to 60 % relative humidity Deviations from these conditions shall be noted in the test report.

NOTE For some polymers, e.g polyamides, tighter control of the environmental conditions can be required, i.e T amb = (23 ± 2) °C and relative air humidity (50 ± 5) %.

To ensure the repeatability of measurement results, all test programs should be conducted in air under standard atmospheric conditions and at a specified specimen temperature, which must be controlled and selected based on the relevant requirements.

Mounting of the test specimens

To ensure accurate measurements, mount the cleaned mating surface material in the test equipment and measure radial and axial run-out, as well as any misalignment if applicable, using precise instruments like a precision indicator For polymer-based test specimens, securely position the cleaned sample in the specimen holder without bonding or jointing methods, unless small sample size requires alternative fastening, which must be fully documented in the test report Proper preparation and measurement techniques are essential for reliable testing results in polymer material performance assessments.

Test variables

The following parameters may generally be chosen as test variables:

— test force or specific force per unit area;

— temperature of the test specimens.

The sliding motion can involve continuous rotation, rotary oscillation, or axial reciprocation, with specific test variables agreed upon by the contracting parties, such as the manufacturer and user, for particular applications For general testing, recommended regimes are provided to ensure consistent results Test conditions should be tailored to the polymer-bearing material's properties, including the 0.2% compression limit (R d0.2) and maximum permissible temperature (T lim), to prevent mechanical or thermal damage Additionally, three distinct test stages should be defined based on force per unit area (p) and sliding velocity (U), ensuring that the testing parameters maintain the integrity of the materials.

Test stage Specific force per unit area, p

The thermal constant of the test equipment, denoted as Q T, is calculated using the formula Q T = (lim − T amb) / (f p U), where it is determined from preliminary measurements This constant is essential for understanding the relationship between the actual bearing temperature, T, the ambient temperature, T amb, and the test parameters, p and U Accurate measurement of Q T enables precise assessment of bearing performance under specific testing conditions.

There are nine possible combinations of test variables p and U, enabling the characterization of wear behavior after testing These variable combinations can be tailored according to the application, configured either by line, column, or as individual parameters For heated specimens, specifying the specimen temperature allows these variable combinations to be correlated with specific temperature values, enhancing the accuracy of wear analysis.

Table 3 — Test conditions — Specific forces per unit area

Variant Specific force per unit area, p

Table 4 — Test conditions — Sliding velocities

Different testing variants involving specific test force per unit area and sliding velocity can be combined freely; however, it is important to note that combining high specific test force per unit area with high sliding velocity is not suitable for dry running conditions.

Tests involving various combinations of test force per unit area, sliding velocity, and temperature can be agreed upon between the supplier and customer For accurate results, lubricated tests must be conducted under conditions that simulate the specific force and sliding velocity of real-world applications.

Hydrodynamic lubrication, where the lubricant effectively separates sliding surfaces, can be established even at low velocities depending on the lubricant's viscosity and the applied test force per unit area This condition helps prevent wear after the bearing has undergone the running-in period, ensuring prolonged component lifespan Proper understanding of these factors is crucial for optimizing bearing performance and reducing maintenance costs.

For wear tests, it is essential to select sliding velocity and specific load parameters that induce a boundary lubrication regime, particularly when evaluating lubricants and their viscosity effects Consistency in testing conditions is crucial, ensuring all tests are conducted under the same parameters to enable accurate comparison and effective evaluation of different materials' wear performance.

Preferred test parameters for test method sphere-on-prism are given in Table 5 These are standard test conditions.

Table 5 — Test parameters for test method sphere-on-prism

Normal force F n 30 N 1 N to 50 N Sliding velocity U 0,028 m/s 0,01 m/s to 0,1 m/s Test duration t Ch 100 h 10 h to 500 h Lubricants (oi/gr) 0,2 g 0,1 g to 0,5 g

Normal force F n 1 N, 3 N, 6 N 0,5 n to 50 N Sliding velocity U 0 to 0,2 m/s 0 to 0,5 m/s Ambient temperature T amb 25°C -35°C to +150°C

Running-in

The test system shall be run in prior to the commencement of the test proper.

The running-in period varies based on material type, surface condition, and specimen alignment It should be concluded when the coefficient of friction stabilizes within a narrow range, or when the wear rate becomes consistent within a small variation—if not, a wear versus sliding distance graph should be prepared Additionally, the period ends when the temperature of the test specimens remains steady within a small scatter range.

In critical cases, it is essential to fulfill at least two or all three specific criteria to ensure accurate wear measurement The measured wear must be at least ten times the measurement uncertainty to guarantee reliability A running-in period of 0.5 to 3 hours is typically sufficient for most polymer-based bearing materials, optimizing performance and longevity.

Carrying out the tests

For general application tests, test variables should be selected according to section 10.3, allowing for single variable combinations, a complete force range, or all nine test variable combinations Each test must be performed at least three times to ensure accuracy and reliability When testing with different variable combinations, new bearing material specimens should be used for each test to maintain consistency and validity.

General

The test report must include the designation of the test as specified in Clause 9, a detailed description of the mating parts including material, geometry, finishing methods, and surface roughness Ra, as well as comprehensive information on the cleaning procedures, solvents used, and surface treatments applied Additionally, the report should provide a description of the test equipment used to ensure clarity and reproducibility of results.

`,`,,,,,```,````,`,,`,`````-`-`,,`,,`,`,,` - e) environmental conditions; f) lubrication conditions; g) force, sliding velocity, temperature data and test procedure for the test programme.

Test results

The evaluation of individual test results should include the coefficient of friction, which depends on sliding speed, force, and temperature after running-in; the linear wear rate in millimetres per kilometre (mm/km) and volumetric wear rate in cubic millimetres per kilometre (mm³/km) during steady-state conditions; and the coefficient of wear measured in cubic millimetres per Newton-kilometre (mm³/N·km), provided steady-state conditions are achieved Additionally, it is essential to document the surface condition of the mating parts before and after testing, including wear status, presence of cracks or layers, and characteristics of wear debris Any interactions between lubricants and polymers due to tribochemical reactions should be noted The report must also specify the location, date, and operator responsible for conducting the test.

Unless otherwise agreed, the test report shall include the following information:

Test ISO 7148-2 – … Symbol Unit Test specimen Mating specimen Specimens:

Type/name Chemical composition Method of production Kind of treatment Mechanical properties:

Coefficient of friction under steady-state conditions f -

Linear wear rate w l mm/km

Volumetric wear rate w v mm 3 /km

Coefficient of wear K w mm 3 /(Nãkm)

Test ISO 7148-2 – … Symbol Unit Test specimen Mating specimen

Location: Date: Operator: a This is including radial clearance for plain bearing tests (see 5.4) b In some cases, it may be necessary to report the temperature created during the sliding motion

In such cases, the temperature should be measured nearest to the sliding surface and provided in the test report.

[1] ISO 175, Plastics — Methods of test for the determination of effects of immersion in liquid chemicals

[2] ISO 4378-1, Plain bearings — Terms, definitions, classification and symbols — Part 1: Design, bearing materials and their properties

[3] ISO 4378-2, Plain bearings — Terms, definitions, classification and symbols — Part 2: Friction and wear

[4] ISO 4378-3, Plain bearings — Terms, definitions, classification and symbols — Part 3: Lubrication

[5] ISO 7148-1, Plain bearings — Testing of the tribological behaviour of bearing materials — Part 1:

Tiêu đề	Plain bearings — Testing of the tribological behaviour of bearing materials — Part 2: Testing of polymer-based bearing materials
Trường học	University of Alberta
Chuyên ngành	Tribological behaviour of bearing materials
Thể loại	Tiêu chuẩn
Năm xuất bản	2012
Thành phố	Geneva

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Số trang	30
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