Interpretation of bursting test standards: GB/T7742.1, ISO13938-1, ASTMD3786/D3786M

This article mainly explains the bursting test standard. It covers the test’s principle.And it covers its tools and how to prepare specimens. It also covers the test’s procedure and how to calculate results.

Definition of terms

Test area:

The area of the specimen in the ring gripper.

Bursting Pressure:

The pressure is highest on a specimen. A lower cushion diaphragm clamps it. The pressure continues until the specimen ruptures.

Bursting Force:

The pressure obtained by subtracting the diaphragm pressure from the average bursting pressure.

Diaphragm Pressure:

Applying pressure to a diaphragm requires a specimen. This is to achieve the specimen’s average expansion.

Expansion expansion:

The expansion pressure expands the specimen. It does so by a certain amount, called the expansion height or volume.

Expansion height:

The expansion pressure pushes the specimen up. We measure how far it rises.

Expansion volume:

The liquid volume needed to reach the expansion pressure. Also, the time needed for the specimen to rupture.

Test Standard

Part 1: Hydraulic Method for the Determination of Expansion Strength and Expansion Density of Textile Fabrics (GB/T7742.1-2005)
Textile Fabrics Expansion Characteristics Part 1: Hydraulic Method for the Determination of Expansion Strength (ISO13938-1:1999)
Test Method for Determination of Textile Bursting Strength by Film Bursting Strength Tester Method (ASTMD3786/D3786M:2013)

Test Principle

The test clamps the sample on a stretchy membrane. Liquid pressure under the membrane expands both. The liquid volume increases at a steady rate until the sample breaks. This measures rupture strength and dilatancy.

Instrumentation

The tool must meet GB/T7742.1-2005 and ISO13938-1:1999 standards：

The bursting strength testing machine shall have a constant rate of volume increase in the range of 100 to 500 cm³/min with an accuracy of ±10%. If the burst tester lacks a liquid volume regulator, use an expansion time of (20±5)s. If so, note this in the report.

The accuracy is 2% of the full scale when the bursting force is more than 20% of the full scale. When the bursting height is less than 70mm, the accuracy is -1mm. At the start of the test, the zero point of the measuring spacer should be adjustable. It should adapt to the thickness of the specimen.

The accuracy of the displayed value shall not exceed ±2% if we can display the volume of expansion.

We shall use a test area of 50cm² (79.8mm diameter). Note that you can use other bursting strength test areas such as 100 cm² (112.8 mm diameter), 10 cm² (35.7 mm diameter), and 7.3 cm² (30.5 mm diameter). This is if the best test area is not on existing equipment. Or, it is due to fabrics with more or less stretch, or to other requirements of multi-party agreements.

The clamping device must clamp well. It must not damage, squash, or slip the specimen during the burst strength test. The clamping ring must not obstruct the rounded arch of fabrics. These fabrics have a height greater than half the diameter of the specimen. The inner diameter of the specimen clamping ring shall be accurate to ±0.2 mm. To avoid damage to the specimen, round the inner edge of the ring. It should be the part that touches the specimen.

During the bursting strength test, the cover should enclose the clamping device. It should also clearly show the specimen’s extension.

The diaphragm is less than 2mm thick and stretches a lot. It will be elastic after it expands during use.

ASTMD3786D3786M:2013, The instrumentation shall meet the following requirements:

Use a press-top break film tester. Also, use a motor-powered drive tester to prevent disputes. Only avoid these bursting strength testers if the buyer and seller agree.

The fixture securely holds the test specimen. It keeps it between two annular, horizontal, parallel stainless steel plates. It prevents slippage during testing. Note: Both the top and bottom fixture surfaces have a coaxial aperture. It is (31±0.75) mm wide with a minimum diameter of 75 mm. The fixtures have closed lines covering the surfaces where they place the sample. The lines are not less than 0.8 mm apart and start 0.015 mm from the hole’s edge. The fixtures’ surfaces are metal. We make edges that could cut into rings. The rings have a radius of 0.4 mm or less. A small chamber combines with the lower fixture. In the chamber, a screw forces the hydraulic medium to flow at a rate of (95±5) mL/min to the rubber film.

The pressure gauge is a Bolden-type manometer. It measures in pounds and is accurate to 1% of the maximum value. The manometer holds 25% to 75% of the total capacity.

The hydraulic system controls the pressure on the film. It continues to do this until glycerol distends the sample. The glycerol flows at a rate of (95±5) mL/min. A piston controls glycerol displacement. It is in the device’s pneumatic regulator chamber. The chamber fluid should be pure (96%) propanetriol, which is UPS chemically pure. The hydraulic system containing the manometer is set up to prevent vibration. First, the sample breaks. Then, we keep the pneumatic chamber’s volume constant. We do this until we record the full top break pressure and the pressure needed to expand the film.

The bursting strength tester uses a calibrated aluminum foil. The foil has an expansion breaking strength of 70 to 790 kPa (10 to 115 psi). Testers use it to test all operating characteristics.

Specimen preparation

GB/T7742.1-2005 and ISO13938-1:1999

Take 5 laboratory samples with a test area of 50cm².

ASTMD3786/D3786M:2013

Take 10 lab samples. Each is at least a square with a 25mm side or a circle with a 125mm diameter.

Test procedure

GB/T7742.1-2005 and ISO13938-1:1999, the test procedure is as follows:

Before the test, humidify the samples in a standard atmosphere. This ensures that the test is done in the right atmosphere.

Set a constant volume growth rate of 100 to 500 cm³/min. Or, do a pre-test. Then, adjust the test for swelling time of (20±5)s.

The researcher placed the specimen flat and tension-free on the diaphragm. During the burst strength test, they used a clamping ring to clamp it and prevent slipping. Set the dilatancy recording device to the zero position. Then, tighten the safety cap as the bursting strength machine says. Apply pressure to the specimen until it expands.

After bursting, reset the bursting strength testing machine . Record the bursting force, height, or volume. If the specimen bursts close to the edge of the clamping ring, report this fact. Repeat the test on different parts of the fabric to achieve a minimum number of 5 tests. If both parties agree, they may also increase the number of tests.

Measurement of diaphragm pressure. Expand the diaphragm without a sample in the same test area. Use the same volume increase rate or bursting time as before. Stop when it reaches the average bursting height or volume you got with a sample. At that time, we consider the bursting strength to be the “diaphragm pressure”.

ASTMD3786/D3786M:2013, the test procedure is as follows:

Put the sample under the tripod. Press it firmly against the plate. Press the handle as far right as possible.

Trigger the operating handle to the left so that the film is extended.

While the film is stretching, hold the grip of the operating handle below or to the right. At the moment of sample breakage, turn the grip. This moves the operating lever to the neutral position. Record the total breakage force at this point.

After the break, release the clamping handle on the sample. Then, turn the wheel counterclockwise to the start. This will release the tension on the film. Record the pressure needed to expand the film.

Calculation of results

We calculate the test results for GB/T7742.1-2005 and ISO13938-1:1999 as described below:

Calculate the average value of the swelling breaking strength in kilopascals (kPa). Subtract the diaphragm pressure from this value. The result is the bursting force, rounded to three significant figures.

Find the mean bursting height in millimetres (mm). Then, trim the result to two significant figures.

If needed, find the average bursting volume in cm³. Round it to three significant figures.

If needed, find the coefficient of variation (CV). Also, find the 95% confidence intervals for bursting force and bursting height. Round CV to the nearest 0.1% and round the confidence intervals to match the mean value.

In accordance with ASTMD3786M:2013, we calculated the test results as described below:

We calculated each sample’s swelling strength by subtracting stent pressure from stretching pressure.

Record the breaking force and its average value for each sample.

Manual calculation of the test results may be wrong. But, most HydroBurst testers on the market automatically generate the results. They also support one-click export for data sharing.

HydroBurst Burst Strength Tester

The HydroBurst Bursting Strength Tester uses the hydraulic drum explosion method. It measures the expansion force and degree of expansion of fabrics and paper. When you pull it in all directions, it works. This is the resistance of materials to bursting. 7742.1-2005, ISO 13938-1-2019, ASTM D3786/D3786M-18(2023), EN 12332-2-2002 and other standards.

For more information on textile testing methods/standards
or textile testing machines, contact us:
What’s App: +86 180 2511 4082
Tel: +86 769 2329 4842
Fax: +86 769 2329 4860
Email: [email protected]