Monday, May 14, 2012
1. To find out the strength and quality ratio of yarn.
2. To assume about the quality of yarn.
Theory:
Quality ratio is the ratio in percent of single yarn strength (lb) and yarn count (lb/spyndle). Single yarn strength in lb Jute yarn count in lb/spyndle i.e. Quality Ratio = X 100 .Again, count lb/spyndle is the weight of yarn in lbs per 14400 yards.
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| Figure: The pendulum lever principle |
Here, L = length of the sample & l = unit length of the system
W = wt. Of the sample & w = unit wt. of the system.
A lea strength tester measures the strength of one lea yarn. One lea means 120 yards. 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 .
Apparatus:
1.Wrap reel
2. Lea strength tester
3. Electrical balance
M/c specification:
The Lea Strength Tester
Goodbrand & Co. Ltd.
Capacity: 25 lb
Testing atmosphere:
Temperature – 29oC and relative humidity – 76%
Standard atmosphere: temperature – 20oC and relative humidity - 65%.
Sample:
Size for count – 25 yards and for strength – 24 inches Jute yarn.
No. of sample for count – 5 and for strength – 20.
Working Procedure:
1. At first 25 yards jute yarn is measured by wrap reel and in this way 5 samples are taken for count testing.
2. Then all the samples are weighted and counts are calculated.
3. Now a single 24 inches yarn from 1st sample is fixed between the jaw J1 and J2.
4. The m/c is started and observed the dial until the yarn is torn out.
5. When the yarn is torn out the m/c is stopped and the reading is taken.
6. By this way the reading of other yarns from other samples are taken.
7. Quality ratio of the all samples are calculated.
8. At last average and CV% are calculated.
Data:
Yarn count:
SL no. | Length in yds | Weight in gms | Count (lb/spyndle) | Average |
1 | 25 | 23.8 | 30.22 | 29 |
2 | 24.7 | 31.37 | ||
3 | 21.78 | 27.66 | ||
4 | 21.95 | 27.87 | ||
5 | 22.05 | 28 |
Yarn strength and quality ratio:
SL no. | Length in inches | Weight in lbs | Average | Quality ratio | Average |
1 | 24 | 20.3 | 20.13 | 70 | 73.25 |
2 | 24.4 | 84 | |||
3 | 25 | 86 | |||
4 | 19.6 | 67 |
Calculation:
The strength of jute yarn is 20.13 lbs and quality ratio is 73.25.
Remark:
It is considered that fibres having quality ratio less than 80 are bad or weak, between 80-100 are average and greater than 100 are strong. From our experiment we see that the quality ratio of the sample is less than 80 and CV% is 5.89. This proves that there are many variations in this test. So finally we can say that these yarns are averagely low strength fibres. But it may be vary because our testing atmosphere is not standard.
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