Saturday, March 28, 2020

FABRIC TEARING STRENGTH TESTING BY FALLING PENDULUM TYPE TESTER



FABRIC TEARING STRENGTH TESTING:

The term tearing of the fabric is the required force which initiates the tearing in the fabric. The tearing force required to initiate the tearing  of the fabric from the split in the centre of the fabric specimen or continuous tearing of the fabric is called tearing strength of the fabric. It is also termed as tearing resistance of the fabric. The tearing strength of the fabric is measured in kilograms, pounds, grams, and Newtons etc. The tearing strength of the fabric is measured in both directions ( warp and weft) separately.


FABRIC TEARING STRENGTH TESTING:

The tearing of the tearing strength of the fabric is performed in following steps:

APPARATUS USED:

1 - Falling pendulum ( Elmendorf) type  fabric tearing strength tester.

2 - Scissor

3 - fabric.

4 - Marking pen

5 - Magnifying glass

6 - Needle

7 - Measuring scale

SPECIMEN PREPARATION:

First of all, the warp and weft directions are identified with the help of magnifying glass. The specimen is cut with the help of scissor. 5 specimens from each direction ( warp and weft) are prepared. The specimen is prepared with the help of template supplied with tearing strength tester by instrument manufacturer. 

The all four sides of the specimen  are aligned accurately by fraying of the broken ends or picks from the sides with the help of a needle. If we cut oversized specimen and align one warp side and one weft side before making final specimen, and place the template just over the bore aligned sides precisely. Now makes the two remaining sides with the help of template. We can prepare specimen by following this practice. A centre mark is also made in the each specimen. Please see below figure:





TESTING PROCEDURE:

1 - First of all, the pendulum is set at it's starting position. The pointer ( force recording mechanism) is set to zero position.

2 - The specimens of the warp set are tested.

3 - The long sides of the specimen places in the centre of gripping clamps.

4 -  The centre position of the specimen in the clamps is fixed with the help of centre mark made in the specimen.



5 - This centre mark is kept in bottom direction  of the clamps.

6 - The bottom side is placed in the clamps in such a way that it touch the specimen stopper precisely.

7 -  The top edge of the specimen is kept parallel to the edges of the clamps.

8 - Now, a cut ( slit ) of 20 mm is made in the test specimen with the help of by pressing the handle of the slitting knife inbuilt in the instrument.

9 - We are ready to press the release lever. This release lever is pressed manually.

10 - The pendulum falls rapidly and tears the cloth when release lever is pressed.

11 - The reading is recorded in the note pad .

PRECAUTIONS:

• The specimen should be prepared precisely.

• The clamps should be tightened properly.

• There should be no slippage in clamps during tearing of specimens.

• The pointer should be at zero position.

FABRIC TEARING STRENGTH CALCULATION:

The calculation of tearing strength is given in below picture:

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