The strength of a yarn gives us an idea how much load we can apply on it and it is very important for different process of yarn. On the other hand Q.R of yarn indicates how good or bad the yarn is.

Objects:

To know the strength of the sample.
To know the count of the sample.
To know the tenacity of the sample.
To know the Quality ratio of the sample.
To determine the standard deviation of the sample.
To determine the Co-efficient of variation of the sample.

Theory:

If jute yarn strength and jute yarn count (in lbs/spindle) is found then we can calculate its Q.R by the following formula:

Here,

L = length of the sample
l = unit length of the system
W = wt. Of the sample
w = unit wt. of the system.

A strength tester measures the strength of a yarn.

Strength is a measure of the steady force necessary to break a material and is measured in pound. The m/c works in Constant rate of extension. Assuming the specimen to be extensible and an absence of any dynamic effects, we get from the figure:

Fr = Mgr = MgRsinθ

As the value of MgR and r are constant, therefore

F ∝ sin θ.

According to the applied force the m/c dial gives us the

strength in lb on the basis of this θ.

M/c specification:

Machine Name: Pendulum lever with constant rate of extension.

Brand Name: GOOD BRAND & CO LTD, ENGLAND.

Model No: G B 79522, Capacity: – 100 lb.

Apparatus:

Jute yarn
Wrap reel
Jute strength tester
Electrical balance
Scissor.

Sample:

Size – 25 yds
No. Of Sample = 10.

Atmospheric condition:

Wet condition: – 26 ° c. & Dry condition: – 30° c.
Difference between wet and dry bulb = 30° c-26 ° c. = 4° c
So, relative humidity (RH) = 70 %

Working procedure:

At first we take one lea (120 yds) of yarn from the warp reel.
Then sample is fixed with the upper jaw J₁and the lower jaw J₂.
The m/c is started and observed the dial until the sample is tore out.
When the sample is torn out the m/c is stopped and the reading is taken.
By this way the others’ reading are taken.
Then all the samples are weighted and counts are calculated.
Q.R of the all samples are calculated.
At last average and CV% are calculated.

Data:

SL. No.	Yarn length (yd)	Yarn Strength (lbs)	Avg. Yarn Strength.	SD	CV %
	25	14.5
	25	15
	25	15.2
	25	15
	25	15.5	14.98	0.332	2.21
	25	14.8
	25	13.9
	25	15.6
	25	15.3
10.	25	15

SL. No.	Yarn length (yd)	Sample Weight (lb)	Yarn Count (lbs/spindle)	Avg. Count Ne	SD	CV %
1	25	0.0198	11.4
2	25	0.01865	11.6
3	25	0.0196	10.9
4	25	0.01886	11.7
5	25	0.01986	11.9	11.59	0.219	1.89
6	25	0.01887	11.8
7	25	0.019763	11.6
8	25	0.01965	11.5
9	25	0.01899	11.7
10	25	0.018965	11.8

SL.No.	Yarn length (yd)	Yarn strength (lbs)	Yarn Count (lbs/ spindle)	Q.R. of the given sample	Avg. Q.R.	SD	CV %
1	25	14.5	11.4	123.12
2	25	15	11.6	129.3
3	25	15.2	10.9	139.4
4	25	15	11.7	128.2
5	25	15.5	11.9	130.25	128.9	5.56	4.32
6	25	14.8	11.8	125.4
7	25	13.9	11.6	119.8
8	25	15.6	11.5	135.6
9	25	15.3	11.7	130.76
10	25	15	11.8	127.8

Result :

The strength of Jute yarn is 98 lbs & C.V. % is 2.21 %.
The Q.R. of Jute yarn is 9 & C.V. % is 4.32 %.
The Count of Jute yarn is 59 & C.V. % is 1.89 %.

Remark:

It is considered that fibres having Q.R less than 80 are bad or weak, between 80-100 are average and greater than 100 are strong. From our experiment we see that our samples’ average Q.R is 128.9 and CV% is 4.32 %. This is proved that there are many variations in this range. So finally we can say that these yarns have poor strength. It varied because our testing atmosphere was not standard and the supplied yarn was not uniform and good.

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