This document discusses yarn strength testing. Yarn strength is an important indicator of quality and ability to withstand loads during weaving and knitting without breaking. There are different machines that can test single yarn strength at varying speeds, from 300 tests per hour to over 30,000 tests per hour. Key properties measured include breaking force, elongation, and variation within samples. Understanding yarn strength helps predict performance and end breaks during processing.

1. YARN STRENGTH
by
R.PASUPATHY

2. Why do we test textiles?
To find “HOW STRONG THEY ARE”!
This indicates that the strength of fibres
and fibrous structures is commonly
regarded as the CRITERION of
QUALITY

3. YARN TYPES BASED Warp
ON
ENDUSE Weft
Hosiery
Industrial yarns
and Sewing threads

4. PROPERTIES IMPORTANT FROM THE
POINT OF YARN QUALITY
 Linear density or count
 Twist
 Tensile properties
 Regularity or Evenness
 Hairiness

5. Yarn strength
Is an indication of the yarn quality with
reference to its end use. (warp, weft,
hosiery, industrial yarns, sewing thread,
etc
Breaking strength aids in predicting the
performance in actual use
Extensibility, elasticity etc are also
important tensile characteristics.

6. YARN STRENGTH
single yarn strength lea strength
Yarn strength

7. TENSILE PROPERTIES OF YARN
2 4 6
100
200
Peak Load
Elongation%
Breaking
Strength
(g)
THE BREAKING FORCE IS THE HIGHEST FORCE VALUE WHICH IS REGISTERED
WHEN CARRYING OUT A TENSILE TEST. Tenacity is the specific strength at break.

8. The strength of a yarn depends on
various factors
1. Characteristics of the fibre used
2. Processing conditions
3. Twist inserted during spinning
4. Atmospheric conditions
5. Type of testing (speed of testing)
6. The previous history of the specimen
7. Capacity of the machine used

9. YARN STRENGTH
In winding warping, sizing, weaving ,
knitting etc, the yarn is generally used
in the form of Individual Strands
Short term variations are reflected in
single strand strength test

10. Yarn strength
Machines available for strength evaluation
Lea strength tester
Single yarn strength tester

11. Yarn strength
The tensile testing of yarns has always
been an important quality control
procedure.
Tensile force & elongation values
provide indications….as to whether the
raw material is suitable
Makes possible for forecasting with
respect to subsequent processing and
the end product

12. SINGLE YARN STRENGTH
 Uster Tensorapid
 Uster Tensojet
• Breaking tenacity
g/tex, cN/tex
• Breaking elongation
%
• Breaking energy
• Time to break
• Mean value
• Standard deviation
• 95% confidence levels
• Coefficient of variation
(CV%)
• Individual values
• Stroke diagram
• Freq-distributions
Additional Information

13. Uster Tensorapid single yarn strength tester

14. Uster TensoJet single yarn strength tester

15. Tensile test results
1. Mean breaking strength
2. CV % of strength
3. Mean breaking elongation %
4. CV% of elongation at break
5. Tenacity or RKm Value

16. Influence of Moisture on Tensile
characteristics
Textile Fibres
Hydrophobic
Hygroscopic
Moisture affects the force to break and elongation values
in the case of Hygroscopic fibres

17. To obtain reproducible results Tensile
tests are to carried out at standard
testing conditions  21 +/- 1 C, 65%
RH +/- 2%
All yarns which absorb moisture exhibit a
higher elongation with increasing RH%

18. Ultra high speed Tensile testing
USTER Tensorapid – 300 tests/hour
USTER Tenso Jet – 30000 tests/hour
UTJ-4(ultra high speed tensile testing)-42 times faster
than the fastest test with UTR
- Fully automatic measurements at extremely high speeds
of 400m/min
- Testing of all common staple fibre yarns
- Makes possible a means of forecasting the suitability of
the yarn for subsequent processing, particularly with
respect to end breaks.
- Detection of seldom-occurring weak places
- With continuously increasing speeds of textile
machinery, the reduction of end breaks is a primary
technological problem

19. Aids in prediction of the number of strength or elongation
related end-breaks to be expected at the weaving machine.

22. Even an apparently high yarn quality can occasionally fall
short of the Process requirements as a result of weak places.
Fault free yarns show an ELLIPTIC SCATTER

23. The mean breaking force of a yarn is not the decisive criterion, but seldom occurring or isolated
weak places, which in the most unfavourable case coincide with the highest loads on the weaving
machine leading to a breakage.

25. With the new generation tensile testing
equipments..
-detailed information and objective data is provided with respect
to the measured values
- Graphical format of the results like stroke diagrams, scatter
plots, histograms of both force and elongation are available
- With tensile testing not only the mean
value of the breaking force but the
variation is equally important
- Higher variation can mean more
extreme values

26. UTJ4_Yarn strength results
The number of end-breaks on a
weaving machine is proportional to the
number of isolated weak places in the
yarn. Hence, to detect isolated weak
places the number of tests has to
drastically increased, which is possible
with UTJ4

27. Yarn strength
Each yarn is subjected to peak loads
during weaving and knitting, which the
yarn must resist without breaking in
order that the number of end-breaks
and the number of machine stops will
be contained at a minimum