Introduction
This manual applies to the following tester:
Tester Dimensions
Technical Specification
The amplitude can go from 5 µm to 5 mm depending on the setup installed.
One module would not cover the full range of 5 µm to 5 mm, but the instrument would be calibrated either for for small amplitude or large amplitude.
One module would not cover the full range of 5 µm to 5 mm, but the instrument would be calibrated either for for small amplitude or large amplitude.
- Max. Coil Frequency: 200 Hz.
- Displacement range: 10 um - 2.8 mm
Displacement range from the homing position - Resolution: 0.1 um.
- Maximum coil force generated (Fx): 150N
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- Max. Coil Frequency: 500 Hz.
- Displacement range: 10 um - 5 mm
Displacement range from the homing position - Resolution: 0.1um.
- Maximum friction force generated: 1200N
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Fretting Principle
Definition and Lexical Terms
- Fretting
- Small oscillatory movements tangential to the surface
- Wear (and Corrosion) Damage
- The wear debris produced are often retained within the contact due to small amplitude sliding
- Significant localized damage. Damage hidden in contact area
- Fretting Tester (in Instrumentation)
- Linear oscillation tests
- High frequency and low amplitude
Principle Of VoiceCoil
The voice coil is installed on the left of the platform and will generate the lateral
displacement, i.e. lateral oscillation of the fretting test. The Z-motorized stage is applying the normal load, Fz.
displacement, i.e. lateral oscillation of the fretting test. The Z-motorized stage is applying the normal load, Fz.
Tribological tests generate significant vibrations and fluctuations. For correct damping of the measurements, a spring is attached between the Z-motorized stage and the upper holder (ball holder or specific upper sample holder).
The geometry of the upper holder can be re- designed by end-user, according to their testing requirements.
The spring used depends on the range of force applied and the sample holders.
The spring used depends on the range of force applied and the sample holders.
The normal force Fz is applied with the Z-motorized stage
(combined with a spring) and measured with a normal force sensor (in the bottom module, normally a strain gauge).
The system has an active force feedback loop control in order to maintain the constant load (or changing, according to the software program) with the Z-stepper motor.
Low stiffness springs
The lateral oscillation is generating significant vibrations during test. Depending on the force
applied, the Z-motorized stage will follow the force required but the active force feedback
loop control will regulate the normal force applied with different stability.
applied, the Z-motorized stage will follow the force required but the active force feedback
loop control will regulate the normal force applied with different stability.
The spring is installed for dampening and stabilization of the normal force control.
Different springs can be provided in case of changes of range of normal force. The stability
depends on many factors: sample flatness, COF value, force range, amplitude, …
depends on many factors: sample flatness, COF value, force range, amplitude, …
The lateral force FxF is measured with a piezo sensor in the bottom module.
The piezo sensor can measure high frequencies (2 Hz to 300 Hz), covering the VoiceCoil's frequency range of max 200Hz.
Measurements at extremely low frequencies (below 1 Hz) may not be accurate, even though they can be performed.
This is because piezo sensors are designed to measure high-frequency force variations, unlike typical strain gauge sensors.
This is because piezo sensors are designed to measure high-frequency force variations, unlike typical strain gauge sensors.
LVDT Displacement Feeback
The LVDT sensor's amplitude range covers the full stroke displacement range of the VoiceCoil.
- Lvdt-Stroke: The lateral displacement is measured with an LVDT sensor, capturing high-frequency stroke variations that differ from the Lvdt-Position feedback; the raw signal can be displayed as an LVDT sensor reading for stroke or amplitude measurements.
- Lvdt-Position: The position from the position of the VoiceCoil in a static maintened position.
Required Tools and Components
- Sample Holder:
- 6 mm diameter sample holder
- 10 mm diameter sample holder
- 1in (25.4 mm) diameter sample holder
- Low Load Ball Holder:
- Rtec Part Number: SPN030301
- 6mm holder
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- High Load Ball Holder:
- Rtec Part Number: SPN030299
- 0.25 inch holder (6.35mm)
- 0.375 inch holder (9.5mm)
- 0.394 inch holder (10mm)
- 0.5inch holder (12.7mm)
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Optional:
- RMS board
- Rtec Sales Number: SPN09044
- Board to convert up to 2 signals to their RMS value (Convertible to Peak-to-Peak).
Hardware:
- Screws as mentioned below
- Imperial allen keys
- Philips screwdriver
Z Stage Installation
VoiceCoil Module Installation
Low Load Load Cell Installation {{if ll}}
High Load Load Cell Installation {{! ll}}
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Remove the lower sample holder {{! ev}}
You can pull the Lower sample plate for easier access to the holder:
- Unscrew the thumb screw
- Slide the stage out to get access to the sample (disk holder)
- You can now remove the sample holder with the previous sample
{{if hl}}
Prepare the samples and components
Clean the following components before every test:
- Ball
- Lower sample
- Lower sample holder
- Optionally: upper sample metallic holder
- Remove the 2 screws on the sides of the metallic holder to uninstall it.
- Remove the 4 screws from the ball holder to remove it from its support.
How to remove the upper sample metallic holder?
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Proper sample preparation is essential for accurate, repeatable, and comparable tribological fretting results.
Please follow the standard cleaning guidelines outlined below.
Surface contamination can significantly affect Coefficient of Friction (COF) measurements.
“Before each test clean the ball and the disk with toluene, rinse with acetone, dry with filtered compressed air or high-purity nitrogen.”*
This procedure applies to all HFRR configurations
regardless of load (200-1000 g) or frequency (50-100 Hz), as specimen contamination mechanisms remain identical.
regardless of load (200-1000 g) or frequency (50-100 Hz), as specimen contamination mechanisms remain identical.
ISO 12156-1 § 7.3
Hard-copy references
*From ISO 12156-1:2018 § 7.3 and ASTM D6079-20 § 7.2 (identical wording)
Procedure validated by the CEC T-06-06 and ASTM RR-D02-1582 round-robins.
Procedure validated by the CEC T-06-06 and ASTM RR-D02-1582 round-robins.
- ISO 12156-1:2018-05, clause 7.3.
- ASTM D6079-20, clause 7.2.
- CEC T-06-06 Final Report 2006, § 5.2 & A3.
- ASTM RR-D02-1582 (HFRR precision statement).
- Solvents
- Toluene ≥ 99 % (CAS 108-88-3) – first wash, removes hydrocarbons.
- Acetone ≥ 99 % (CAS 67-64-1) – final rinse, removes toluene + traces.
- Do NOT use isopropanol – leaves a film (CEC T-06-06 A3).
- Do NOT use white spirit – 15 % aromatics (CEC data 2004).
- Ultrasonic bath
- 5 min, 40 kHz, 50 °C, toluene in fume hood or with appropriate PPE (A-P3 mask).
- 3 min, at controlled room temperature (20 ± 5 °C)
- Discard each solvent after 10 parts max (CEC T-06-06 § 5.2).
- Drying
- 0.2 µm in-line filter on compressed air or N₂ 5.0.
- 30 s at 45° angle to avoid dust settling.
Paper tissue – Kimwipe/Whatman 105”(low-lint cellulose) is explicitly allowed by both standards and the CEC round-robin reports.
Microfiber left fluorinated residues (FTIR 1215 cm⁻¹ band) that shifted wear scar by +7 µm (RR-D02-1582 p. 18).
- Storage
- PTFE box, N₂ atmosphere, use within 4 h (ASTM D6079-20 § 7.2 Note 3).
- Inspection
- 50× microscope – no spot > 5 µm (ISO 12156-1:2018 § 7.3 Note 2).
- If spot seen, repeat step 2.
- Non-reusable parts
- Ball: Discard if wear > 5 µm or fatigue ring visible (ISO § 6.1).
- Disk: Discard if Ra > 0.02 µm or HV 30 outside 190–210 (ISO § 6.2).
Disk circularity must be < 0.5 µm (ISO § 6.2)
- Weekly machine clean-up
- Bath, holder, shaft – toluene + acetone + Kimwipe wipe.
- Linear rail – Fomblin Y25 oil (no silicone).
- Seal – replace every 500 tests (CEC T-06-06 B4).
Install the lower sample holder {{! ev}}
- Fix the sample in the sample holder and tighten the screws to fix the sample disk.
depending on the accessory delivered
- Place the sample holder on the base plate and ensure the pins are properly inserted as shown below. Then, tighten the four screws with the 7/64 tool.
⚠️ Tighten the disk holder securely to maintain the liquid container and ensure proper stroke displacement during tests.
You can now push back the plate and tighten the thumb screw.
{{if hl}}
Lower sample ECR holder Installation {{if ev}}
- Connect 2 Black cables from Keithley “Input” or “Force” and “Sense” black connectors to the sample holder.
- Install the Sample holder on the Load Cell using 4 screws.
- Secure the sample on the sample holder using a Philips head screwdriver.
Install the Low Load Upper Sample Holder {{if ll}}
Holder variation
The upper sample holder can have different geometries.
Geometries of sample holders can be adapted to the different applications. Lower holder can be for a disk or a square sample Upper holder can be for a ball, a pin or a specific sample.
- Place the holder onto the suspension bar.
- Tighten the 2 side screws to secure the holder onto the suspension.
Install the High Load Upper Sample Holder {{! ll}}
- Remove the previous ball from the holder by untightening the screw.
- Take a ball which was previously cleaned following the previously explained method.
- Install the ball in the holder while upside down and tighten the side screw to secure it in place.
- Secure the ball holder to the tester using the provided screws
It is recommended to center the ball holder but you can slightly adjust towards the front or the back of the tester to avoid testing an already contaminated surface.
Next Page → Software Test Configuration
You are ready to perform the test under the specific conditions.
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