Stress Relaxation Tester - EB-02



Stress Relaxation Tester - EB-02

ISO 3384, ISO 6914

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Stress Relaxation System Tester - EB-02 Stress Relaxation System Tester - EB-02

Stress Relaxation Tester - EB 02 Relaxation system for continuous measurement in either compression or tension. The Stress Relaxation Tester - EB 02 meets the requirements in ISO 3384, ISO 6914 and ASTM D6147. The relaxation rigs are used in combination with the cell ageing ovens our new range of ovens when testing at elevated temperature.

Stress relaxation tests are very effective for conducting ageing tests, as substantial amounts of information result with little effort, especially when using the continuous measurement system

New Cell Ovens for Stress Relaxation We have now constructed special versions for use in relaxation testing. The height of these ovens is lower and incorporates an integrated draught hood (The Draught Hood is used to eliminate variations in force measurements due to temperature and air effects in the surrounding environment.) to eliminate variation in force measurements due to temperature and air effects.

Relaxation tests are becoming more and more popular for determination of rubber properties. From the beginning stress relaxation tests were used mainly in scientific projects at universities, but a growing use has been shown in recent years. This may be caused by the introduction of stress relaxation tests in product standards, such as sealing rings for pipes. The automotive industry has also started to specify stress relaxation tests for critical sealing products in the cars.

The present standard ISO 3384-1 includes two methods, A and B, which can both be used in air or liquids.

In method A, the compression is applied and all counter force measurements are made at the test temperature.

In method B, the compression is applied and all counter force measurements are made at standard laboratory temperature (23 °C). The test pieces are stored at the test temperature.

ISO 3384-2 is a new second part describing tests with temperature cycling.

ISO 6914 describes the testing of stress relaxation in tension. This can be done by two methods, either on continuously stretched samples or intermittently stretched samples. One type of relaxation instrument is measures continuously and consists of a small rig with a load cell. As temperature stability is a critical parameter, special ovens are available for testing at both elevated and ambient temperatures. The rigs are connected to a data acquisition box connected to a computer for storing the force and temperature data.

Relaxation system for continuous measurement in either compression or tension meets the requirements in ISO 3384, ISO 6914 and ASTM D6147. The relaxation rigs are used in combination with our cell ageing ovens.

Cell Ovens for Stress Relaxation: EB 17, EB 21, EB 22 and EB 23

  • The ovens perform well inside the apparatus requirements in ISO 188, IEC 811 and other equivalent standards.
  • The oven is controlled from a PLC (with a colour touch screen).
  • Integrated draught hood.
  • Special design with controlled air exchange rate and low air speed.
  • The casing consists of steel, painted with powder paint in bluegreen colour.
  • The inner cells are made of aluminum.
  • Temperature controller with 0.1°C setpoint (PLC) or liquid circulator EB 17.
  • Fixed over temperature fuse.
  • Flowmeters with needle valves, for setting the air exchange rate.
  • The air speed is low and is dependent on the air exchange rate only, as specified in ISO 188 method A and IEC 811.
  • Alarm for low air pressure (PLC).
  • Built in air pump.
  • Cooling channels in the casing for low surface temperature.
  • Temperature controlled cooling fan for the electronics cabinet.
  • Indication of power failure (PLC).
  • Run-time meter (PLC).
  • Countdown timer (PLC).
  • Individual cell identifier "Test name".
  • Microfilter for the air which removes 99.99 % of all particles over 0.1 μm.
Stress Relaxation Tester EB 02

EB 02.14-x - The amplifier box communicate via a network connection. This means that the amplifier can be directly connected to the network connector on a PC, or anywhere in a local ethernet network. The box can also have up to 24 channels or connect 12 relaxation rigs. With the amplifiers we can deliver load cells with the ranges of 100 N, 500 N, 1000 N or 2000 N, where the 100 N range is for testing in tension.


Stress Relaxation Tester EB 02



Relaxation rigs arranged for different test methods.

Rig 1 is arranged for testing in compression according to ISO 3384.

Rig 2 is arranged for testing in tension according to ISO 6914 method A.

Rig 3 is arranged for testing in liquid according to ISO 3384.

Stress Relaxation Tester - EB-02
Graph 1
The graph shows F/F0 curves for SBR tested at different temperatures.
Stress Relaxation Tester - EB-02
Graph 2

The blue curves shows the influence of room temperature variations in the force curve. The red curves shows a rig placed in the room temperature box.

Stress Relaxation Tester - EB-02 Graph 3
Stress Relaxation Tester - EB-02
Graph 4
Graph 3 and 4 shows the repeatability of the relaxation rigs. Graph 3 is a graph from two tests of the same compound run at different times. Graph 4 is a graph from two samples of the same compond run at the same time in different rigs.

Stress Relaxation Tester - EB-02
Graph 5
Stress Relaxation Tester - EB-02
Graph 6
Graph 5 and 6 shows how to correlate for the spring effect in the load cell and rig, when doing very accurate tests. The spring effect is caused by the expansion of the load cell and rig when the force decreases with time. Graph 5 shows a manual correction done twice during the test, by manual adjustment of the compression. Graph 6 shows a correction done by the software by a mathematical calculation. The correction is not necessary when doing comparative tests.
Relaxation - Sealing Rings
Graph 7


Arrhenius Plot
Graph 8

Graph 7 and 8 shows how to use relaxation data to estimate the life time of a rubber compound for sealing rings, according to the procedure in ISO 11346.

Data from relaxation tests done at three temperatures are plotted in a graph and the "end of life" is determined for each temperature. This data is then plotted in an Arrhenius graph with ln time against 1/T, where T is the temperature in Kelvin. A linear extrapolation can be done for lower temperatures to establish the estimated life time of the tested compound.

Technical Specifications of Stress Relaxation Tester - EB-02
Temperature Control
Range, in compression 500N, 1000N or 2000N
Tension 100N
Accuracy ±0.1% of full range
Resolution, Compression 0.05 or 0.1 or 0.2N
Resolution Tension 0.01N
Dimensions, dia x h 120mm x 450mm
Weight approx 4.5kg
Material Stainless steel
Temperature Sensor PT 100, 1/3 DIN
Temperature Range 200°C (HT=+300)

The Equipment works with continuous stress relaxation measurements in both compression and tension. The basic version can do tests according to ISO 3384 in air. The rig works together with the cell ovens EB 01, EB 07 and the programmable temperature cabinet, EB 02.09.

Options for Stress Relaxation Tester - EB-02
EB 02 HT Relaxation rig for high temperatures up to + 300 °C.
EB 02 TE Relaxation rig for testing in tension (100 N).
EB 02.01 Container and pressure plate (with a hole in the centre) for measurement in liquids, according to ISO 3384.
EB 02.01P Sealed container for testing of stress relaxation in volatile liquids and coolants up to 3 Bar pressure. See below for more info.
EB 02.02 Grips for testing relaxation in tension, according to ISO 6914 (rebuild EB 02 to EB 02 TE)
EB 02.03 Load Cell 100 N for tests in tension, including adapters (rebuild EB 02 to EB 02 TE)
EB 02.05-8 Room Temperature Box, 23 °C, for testing at standard laboratory temperature. Keeps the temperature constant within ±0.2 °C. The box can take 8 rigs.
EB 02.12 Container for testing in liquids in tension.
EB 02.14-1 Amplifier box with inputs for 1 load cell and 1 Pt 100 sensor (1 rig).
EB 02.14-2 Amplifier box with inputs for 2 load cells and 2 Pt100 sensors (2 rigs).
EB 02.14-4 Amplifier box with inputs for 4 load cells and 4 Pt 100 sensors (4 rigs).
EB 02.14-6 Amplifier box with inputs for 6 load cells and 6 Pt 100 sensors (6 rigs).
EB 02.14-8 Amplifier box with inputs for 8 load cells and 8 Pt 100 sensors (8 rigs).
EB 02.14-12 Amplifier box with inputs for 12 load cells and 12 Pt 100 sensors (12 rigs).
EB 17 Programmable Cell Oven, -40 °C to +200 °C, for six rigs.
EB 17HT Programmable Cell Oven, -40 °C to +250 °C, for six rigs.
EB XX * Cell Ovens with 3 to 6 cells, temperature between +40 °C up to +200 °C.
EB XX*HT Cell Ovens with 4 to 6 cells, High Temperature up to +300 °C.
EC 05 This software evaluates results from relaxation tests according to ISO 3384 and ISO 6914.
EC 04 Computer.
EC 06 UPS 1000 VA double converting.
*XX applies to EB 21, EB 22 & EB 23
NOTE: Our stress relaxation rigs are also available in acid proof steel.
 

See Also

 

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