ASTM D623 Rubber Compression Flexing Fatigue and Heat Generation
Written by Rebecca Reiff-Musgrove
ASTM D623 contains test methods to compare the compressive fatigue characteristics and rate of heat generation of vulcanized rubbers. It describes two methods for applying a rapidly oscillating compressive stress under controlled conditions. Results include the measured temperature rise, degree of specimen dimensional changes and time to fatigue failure (in certain test conditions). In order to fully understand the test setups, procedures, and results requirements, it is important to review the full standard.
The test methods in ASTM D623 describe highly bespoke apparatuses, either the Goodrich Flexometer or the Firestone Flexometer, which apply a high-frequency, cyclic compression at a constant applied load. However, the standard Instron ElectroPuls® E3000 with WaveMatrix™ software and its Advanced Amplitude Control Module can achieve the same effect without the need for highly specialized equipment.
Instron can advise on appropriate accessories for testing at ambient and non-ambient temperatures.
|ASTM D623 Test Setup|
ElectroPuls E3000 Test Instrument
5 kN Dynacell™ Dynamic Load Cell
|WaveMatrix Software with Advanced Amplitude Control Module|
A typical test method in WaveMatrix using the ElectroPuls E3000 would be:
- Move the actuator in position control until a small contact force is measured.
- Ramp the actuator in load control to the required constant load (ASTM D623 Test Method A specifies loads of 160 N, 245 N, or 489 N).
- Hold at the static load for 5 seconds to allow the specimen material to relax.
- Apply the cyclic compressive oscillation in displacement control at the required amplitude and frequency (ASTM D623 Test Method A recommends strokes of 4.45 mm, 5.71 mm, or 6.35 mm, at 30 Hz). Use Advanced Amplitude Control to maintain the required constant mean force at a constant displacement amplitude.
A key result from ASTM D623 is the temperature rise. WaveMatrix supports temperature measurement from a thermocouple transducer, allowing the temperature rise during the test to be recorded.
Instron provides chambers appropriate for testing at non-ambient temperatures, ASTM D623 recommended testing at 50°C or 100°C.
More precise displacement data can be gathered using a 2601 series LVDT (linear displacement transducer) attached to the platens.
If the applied loads are small in your application, more accurate data can be obtained using a smaller force cell. Instron supports dynamic force transducers down to 250 N.