Sunday, April 5, 2020


Fabric bursting strength testing by constant rate of traverse (CTR) ball burst test method:

Bursting strength of the fabric:

When the fabric is subjected to pressure, the fabric begins to expand in all the possible directions at the same time. When the applied pressure increases gradually, the fabric begins to burst after crossing the pressure limit. This pressure limit is called bursting strength. Thus we can say that “the pressure required to burst the fabric surface is termed as bursting strength of the fabric”. It is measured in pounds (lbs.) per inchor kilograms per Centimeter2. The bursting strength of the fabric is the very important property for parachute fabric. Type of yarn and material used in the fabric, the count and construction of the fabric greatly affect the bursting strength of the fabric.

Apparatus used:

1 - Constant traverse rate ( CTR) ball burst fabric strength tester.

2 - Fabric

3 - Measuring scale.

4 - Scissor.

Constant traverse rate ( CTR) steel ball fabric bursting strength tester:

This method is used to measure the bursting strength of those fabrics which have very high degree of elongation. The example of such type of fabric is knitted fabric. This instrument works upon constant rate of traverse ( CTR) of a steel ball. The steel wall exerts bursting pressure upon the specimen at constant traverse rate. The bursting strength of the fabric having very  high elongation can be tested by this method:

Specimen preparation:

Spread the fabric over table and cut a disc of 125 square mm. You can also cut a disc of 125 mm. diameter.  Actually, the size of specimen is kept according to size of specimen clamps. The specimen's disk diameter is always kept slightly more than the diameter of specimen clamp.

Testing procedure:

The specimen is placed between two clamping disc. We have taken green fabric. The clamping discs are tightened securely. When specimen is fixed between clamps, there should be no tension over the specimen. You can see in below diagram: 

This machine is equipped with digital load cell which measures the bursting force during fabric bursting. The reading of the load cell is reset before starting bursting process. The initial reading of the load cell should be zere.

Now the technician pushes the start button. The steel ball begins to move downward direction at constant traverse rate. The steel ball traverses with the help of a suitable gear box and electric motor installed inside the machine. The steel ball gets touched to specimen after traveling of few downward distance and starts to press the specimen. The specimen gets rupture after crossing the limit of bursting force. The maximum bursting force gets recorded automatically in the digital load cell. 

The technician pushes stop button now. He observes that bursting load recorded in the digital load cell.

The bursting strength of the fabric is measured in kilograms, Newtons, and pounds ( lbs. )

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