INTERNATIONAL BACALAUREATE

MARA COLLEGE BANTING

EXTENDED ESSAY

SUBJECT: PHYSICS HL

a) RESEARCH QUESTION: What are the magnitude of forces needed to separate two pieces of fabric which are sewn together along the width with hand stitches (Running stitch, backstitch, and ‘Lilit Ubi’?) when distance between two consecutive stitches,d/mm, is varied (2.0, 3.0, 4.0 ,5.0, 6.0, 7.0, 8.0, 9.0, 10.0) mm ± 0.5 mm while the thickness of sewing thread, material of sewing thread, type of fabric used, and length of fabric are fixed ?

NAME: AMIR, NURUL HIDAYAH

ADVISOR: MS. WAN SALEHATON

CANDIDATE NUMBER: 000592-065

SESSION: MAY 2012

WORD COUNT: 3994

0

1)INTRODUCTION

Force is not something that can be seen directly. However, its effect or effects can be

seen in our daily lives. Force can cause objects to change their direction, shape, and speed. In

short there are four basic types of forces which are gravitational forces , electroweak force,

and nuclear force.1

When I did an experiment on ‘strength of material’ during my physics lab session, I

was exposed to many types of general force that can be applied to an object. Tension,

compression, torsion, shears force, and others. The different forces are actually due to

electromagnetic reaction between the particles in an object as a result of the electrical charge

that they have.2

One day, my bag was torn apart due to the heavy load of the books it had to carry. I

sew it and unfortunately, short after that, it ripped apart again. This incident has sparked an

idea for me to do my EE. Did I not sew close enough? Did I not use the correct hand stitch?

How would the decreasing stitches distance affect the strength of it?

By obtaining empirical evidences of effect of variables on strength of stitches, it is

hoped that the hand stitches can be further specified or customised according to need.

Thus, the specified research questions have been developed to study the tensile

strength of hand stitches. Tensile strength is defined as the ultimate strength of a material

subjected to tensile loading. It is the maximum stress developed in a material in a tensile test.

3

1 K.A. Tsokos (2010). Physics for the IB Diploma (5th Edition) ,Edinburgh: Cambridge University Press.2 Kerr, Ruth (2008). Physics (3rd edition). Victoria : IBID Press.3 INSTRON. (n.d) .Material Testing e-book. Retrieved 15th July 2011 from : http://www.instron.com/subscribe/Instron Material Test Guide.pdf

1

a) What are the magnitude of force needed to separate two pieces of fabric which are

sewn together along the width with hand stitches (Running stitch, backstitch, and

‘Lilit Ubi’?) when distance between two consecutive stitches,d/mm, is varied (2.0,

3.0, 4.0 ,5.0, 6.0, 7.0, 8.0, 9.0, 10.0) mm ± 0.5 mm while the thickness of sewing

thread, material of sewing thread, type of fabric used, and length of fabric are

fixed ?

For that purpose, an extensive research has been done mainly in Universiti Putra

Malaysia’s mechanical engineering lab to obtain the data. The methods would be explained

further in the body of the essay.

For the intended investigation, the focus is mainly on the maximum tension that can

be withstood by two pieces of fabric connected by hand stitches with the distance between

two consecutive stitches (determined by the closest distance between one needle piercing

hole and another). The investigation would also compare three types of handstitches which

are running stitch, backstitch, and ‘Lilit Ubi’.

The relationship between the force (tension) required to fail the stitches and the

distance between two consecutive stitches will be generalised if any presents.

2

2)PLANNING

2.1)Research Question

What are the magnitude of force needed to separate two pieces of fabric which are

sewn together along the width with running stitches (backstitch, and ‘Lilit Ubi’?)

when distance between two consecutive stitches,d/mm, is varied (2.0, 3.0, 4.0 ,5.0,

6.0, 7.0, 8.0, 9.0, 10.0) mm ± 0.5 mm while the thickness of sewing thread, material

of sewing thread, type of fabric used, and length of fabric are fixed ?

2.2)Hypothesis

All forces applied to the sample during testing were in the form of tension.

There are three possible hypothesis for the experiment:

1) The further the distance between two consecutive stitches, the lower the tension

needed to fail the seam. This is because as distance is increased, number of stitches

per cm would decrease. Thus, higher tension would be subjected to individual

stitches.

2) As the stitches are made closer, the fabric would be more ruptured or damaged due to

needle punctures. Thus, the less tension will be needed to separate the two clothes

sewn together.

3) When the three types of stitches are compared, the running stitch would need less

tension to fail the seam. ‘Lilit Ubi’ would require higher tension, while clothes sewn

with backstitch will require highest tension to separate the clothes together.

The hypothesis is made based on the assumption that the stitch which uses

more thread could bear more tension, and among the three type of stitches, backstitch

3

uses longest thread compared to the other two types when the seam is made over the

same length.

2.3)Variables

Type Variables Method of control

Independent The distance between two

consecutive stitches ,d /mm

Points having distances of

(2.0, 3.0, 4.0 ,5.0, 6.0, 7.0,

8.0, 9.0, 10.0) mm ± 0.5 mm

apart are measured along the

margin as shown in figure

using 300.0 mm plastic ruler

as guide for piercing needle.

Type of hand stitches Three different hand stitches

is compared (backstitch,

running stitch, ‘Lilit Ubi)

Dependant tension needed to separate

two pieces of fabric which

are sewn together along the

width

The fabrics sewn together are

pulled apart using Instron

3365 Dual Column Tabletop

Universal Testing Systems

and the tension is read by

using Bluehill software in

unit N.

Fixed Fabric used The fabric used is of the

same type to ensure that the

tensile strength, thickness,

4

and material are same.

Sewing thread used The sewing thread used are

from the same bundle to

ensure that the tensile

strength, the thickness, and

thee materials are the same.

Dimension of the cloth used

in experiments

The clothes are cut according

to 50x80 mm including 10

mm margin for sewing.

Uncontrolled variables Temperature and pressure of

atmosphere

The experiment is done in a

condition where the

temperature and pressure of

the atmosphere cannot be

controlled.Environmental

conditions might not be the

same.

2.4)Apparatus and Materials:

Sewing thread, sewing needle, cloth, scissors, 30 cm plastic ruler, Instron 3365 tensile tester

unit, needlepoint pen.

5

2.5)Methods:

2.5.1)Preparation of samples

1) Before the lab sessions are carried out, all the materials needed are prepared.

Materials needed are inclusive of sewing threads of different brands, and of fabrics

which are sewn together along the side according to the required specifications. The

fabrics would be sewn as follow dimension:

50x80 mm with 10 mm margin at the end of the cloth included. The 50x50 mm area is for

clamping , the 10 mm margin is for sewing.

6

Sewing line

Clamping area

Sewing line

Margins of 10 mm are marked at widths of both clothes, with points for stitches (indicating

distances between two consecutive stitches) are marked along the margin as shown in figure.

The distances between two consecutive stitches for each type of stitches in different

experiments are as required. Two pieces of fabrics are superimposed on the margin for

sewing line. They are then sewn along the line for sewing as shown in figure below:

2.5.1.1)RUNNING STITCH4

4 Hidup, U.M .(n.d.). Jahit Penyambung retrieved 23rd July 2011, from Dunia Jahitan Anda: http://ejahitanonline.tripod.com/jahitsambung.htm

7

d

2.5.1.2)BACKSTITCH5

2.5.1.3)‘LILIT UBI’6

5 Hidup, U.M .(n.d.). Jahit Penyambung retrieved 23rd July 2011, from Dunia Jahitan Anda: http://ejahitanonline.tripod.com/jahitsambung2.htm 6 Hidup, U.M .(n.d.). Jahit Penyambung retrieved 23rd July 2011, from Dunia Jahitan Anda: http://ejahitanonline.tripod.com/jahitsambung2.htm

8

d

d

2.5.2)Lab Session:

a) Preset of the instruments

The tensile tester is connected to a computer dedicated to it where the software Bluehill is

installed. Before the experiments is started, the specifications are set as follow:

Rate of extension applied: 2mm per minute

Pre-force applied to sample before reading is taken: 5N

Type of test: tensile

3 sets of data were stored in every graph. The data is then saved in the designated

folder. The method of testing the tensile strength of fabric is called Grab test7

b) Determination of strength of fabric

A cloth of specific fabric is chosen and cut into a strip of length 50 mm x 30 mm. A margin

of 50.0x30.0 mm are added at both ends (that makes the total length to be 150.0 mm with

width of 30.0 mm). One end is clipped at a stationary point and the other end is clipped at a

dynamic point of the tensile tester, which will provide the tension to the cloth and measure

the tension. The cloth is pulled at a constant rate slowly until the cloth tears apart totally. The

tension required to do so is observed by using Bluehill software and recorded. The

experiment is repeated 3 times to reduce random error that might occur due to lack of

repetitions.

7 How To Determine Seam Strength (n.d). Retrieved 30th of July 2011. From My textile Notes: http://mytextilenotes.blogspot.com/2009/06/how-to-determine-seam-strength.html?dhiti=1.

9

c) Determination of strength of thread

A string of thread about 200.0 mm is cut. Two marks are made to indicate a 50.0 mm gap.

The string is clamped to the tensile tester machine with the marks at the edge of the clamp.

The tension is applied at a constant rate by the tensile tester until the string snaps. The

reading taken by using Bluehill software is then recorded.

d) Determination of relationship between distances between two consecutive stitches

with tension needed to separate two clothes which are sewn together.

1) Lilit Ubi

The sample diagram on the structure of Lilit Ubi is as shown in the diagram above. The

cloth sewn with ‘Lilit Ubi’ using sewing thread with margins of 10 mm and distance

between two consecutive stitches of 2 mm are clamped to the tensile tester. One to static

point and the other to the pulling point. The clamps positions were adjusted a bit to

straightened the sample by using the ‘up’ and ‘down’ button on the machine before the

experiment is started. The clothes are pulled apart by supplying tension at a constant rate that

has been set earlier using Instron universal tensile tester until the stitches snap and the clothes

are separated. The steps were repeated to obtain 3 sets of data for d=2.0 mm. The force

required to do so is read by using Bluehill software and recorded. The steps are repeated by

increasing the distances between two consecutive stitches to 3 mm, 4 mm, 5 mm, 6 mm, 7

mm, 8 mm , 9 mm, and 10 mm. Results were tabulated.

2) Backstitch

A sample which has been sewn with d = 2.0 mm with backstitch (as shown in figure) is

clamped to the tensile tester. The experiment procedures for samples sewn with backstitch

were exactly the same as that of Lilit Ubi. Results were tabulated.

10

3) Running stitch.

A sample which has been sewn with d = 2.0 mm with running stitch (as shown in figure) is

clamped to the tensile tester. The experiment procedures for samples sewn with backstitch

were exactly the same as that of Lilit Ubi. Results were tabulated.

11

3)DATA COLLECTION AND ANALYSIS

The raw data for the experiment is attached together in the appendices part. The

following is the summary of the data and summary of processed data.

For ease of reading, the maximum tension held by sample is labelled as follows:

Type of stitches Average maximum tension

held by sample

Maximum tension held per

mm of sample

RUNNING STITCH P P

BACKSTITCH Q Q

‘LILIT UBI’ R R

The maximum tension is identified as the peak of the graph obtained during the tensile

testing. Example is as follow:

Picture: graph obtained for tensile testing of Running stitch for d= 3.0 mm

The maximum tension held is Load at Maximum Tensile Stress (N)

12

3.1)Table of Average Maximum Tension

3.1.1)Held by Samples Sewn with Different Type of Handstitch

Distance between

two consecutive

stitches,d/mm

(±0.5 mm)

Average maximum

tension held by

running stitch

seam, P/N (±0.5%)

Average maximum

tension held by

backstitch seam,

Q/N (±0.5%)

Average maximum

tension held by

‘Lilit Ubi’seam,

R/N (±0.5%)

2.0 107.2209 136.9358 133.2854

3.0 127.1643 114.8000 124.9881

4.0 66.3454 75.9544 96.8875

5.0 37.3545 53.1455 57.4727

6.0 23.2410 43.1273 45.8382

7.0 43.9769 29.4266 51.5121

8.0 16.8654 29.2310 48.7828

9.0 36.1698 21.4757 35.4139

10.0 15.8292 22.6388 30.5100

Table 1 : Distance between two consecutive stitches,d/mm (±0.5 mm), average maximum

tension held by running stitch seam, P/N (±0.5%), average maximum tension held by

backstitch seam, Q/N (±0.5%), and average maximum tension held by ‘Lilit Ubi’seam, R/N

(±0.5%)

13

3.1.2)Strength of fabric used as sample

Trial Tension required to snap

fabric, F/N (±0.5%)

1 287.2723

2 241.3992

3 268.9295

mean 265.8670

Table 2: tension required to snap fabric, F/N (±0.5%) sample in 3 trials and mean tension

needed

3.1.1) Strength of string used

Trial Tension required to snap thred,

F/N (±0.5%)

1 8.5163

2 7.4941

3 5.8228

Mean 7.2777

Table 3: Tension required,F/N (±0.5%) to snap thread in tree trials and mean.

The data from table 1 is graphed as follow:

14

1) RUNNING STITCH

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.00.0000

20.0000

40.0000

60.0000

80.0000

100.0000

120.0000

140.0000Average tension held by sample ,P/N vs

Separation between two consecutive stitches,d/mm

Separation between two cosecutive stitches, d/mm

Average tension held by sample ,P/N)

*Uncertainty: X-axis:± 0.5 mm

Y-axis: too small to be seen (0.5%)

15

2) BACKSTITCH

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.00.0000

20.0000

40.0000

60.0000

80.0000

100.0000

120.0000

140.0000

160.0000

The Maximum tension held by sample, Q/ N vs distance between two consecutive stitches, d/mm

Distance between two consecutive stitches, d/mm

The Maximum tension held by sample, Q/ N

*Uncertainty: X-axis:± 0.5 mm

Y-axis: too small to be seen (0.5%)

16

3) ‘LILIT UBI’

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.00.0000

20.0000

40.0000

60.0000

80.0000

100.0000

120.0000

140.0000

The Maximum tension held by sample, R/ N vs distance between two consecutive stitches, d/mm

Distance between two consecutive stitches, d/mm

The Maximum tension held by sample, R/ N

*Uncertainty: X-axis:± 0.5 mm

Y-axis: too small to be seen (0.5%)

17

3.2)Conversion to S.I unit

The data is then converted to S.I unit (in m) from mm. All the absolute uncertainties are also

calculated .

3.2.1)RUNNING STITCH

Distance between

two consecutive

stitches, d/m

(±0.0005 m)

Maximum tension

held by sample , P /N

(±0.5%)

Tension held by sample

per m of cloth, p / (N

m-1 )

absolute uncertainty

of N, ∆p/ (N m-1 )

0.002 107.2209 2144.4176 32.1663

0.003 127.1643 2543.2855 38.1493

0.004 66.3454 1326.9081 19.9036

0.005 37.3545 747.0895 11.2063

0.006 23.2410 464.8202 6.9723

0.007 43.9769 879.5384 13.1931

0.008 16.8654 337.3079 5.0596

0.009 36.1698 723.3960 10.8509

0.010 15.8292 316.5843 4.7488

Table 4: Distance between two consecutive stitches, d/m (±0.0005 m), Maximum tension

held by sample , P /N (±0.5%), Tension held by sample per m of cloth, p / (N m -1 ) and

absolute uncertainty of N, p.

18

The data above can be graphically represented as follow:

0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.0110.0000

500.0000

1000.0000

1500.0000

2000.0000

2500.0000

3000.0000

Tension held by sample per m of cloth, p / (N m-1 ) vs Distance between two consecutive stitches, d/m

distance between two consecutive stitches, d/m

Tension held by sample per m of

cloth, p / (N m-1 )

Uncertainties: X-axis : ±0.0005 mm

Y-axis: some are too small to be seen (±1.5%)

19

3.2.2)BACKSTITCH

Distance between

two consecutive

stitches,m /0.0005

m

Average maximum

tension held by

sample, Q/ N

Tension held by

sample per m of

cloth , q/(Nm-1)

absolute uncertainty

of q, ∆q, / (N m-1 )

0.002 136.9358 2738.7155 41.0807

0.003 114.8000 2296.0005 34.4400

0.004 75.9544 1519.0875 22.7863

0.005 53.1455 1062.9103 15.9437

0.006 43.1273 862.5463 12.9382

0.007 29.4266 588.5321 8.8280

0.008 29.2310 584.6198 8.7693

0.009 21.4757 429.5133 6.4427

0.010 22.6388 452.7765 6.7916

Table 5: Distance between two consecutive stitches, d/m (±0.0005 m), Maximum tension

held by sample , Q/N (±0.5%), Tension held by sample per m of cloth, q / (N m -1 ) and

absolute uncertainty of N, q /(N m-1 )

20

0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.0110.0000

500.0000

1000.0000

1500.0000

2000.0000

2500.0000

3000.0000

The Maximum tension held by sample per mm, q/ N m vs distance between two consecutive stitches, d/m

Distance between two consecutive stitches, d/m

The Maximum tension held by sample per m,

q/ N

Uncertainties: X-axis : ±0.0005 m

Y-axis: too small to be seen (± 1.5%)

21

3.2.3)‘LILIT UBI’

Distance between

two consecutive

stitches, d/m

(±0.0005 m)

Maximum tension

held by sample , R /N

(±0.5%)

Tension held by

sample per mm of

cloth, r / (N m-1 )

absolute uncertainty

of r , ∆r/ (N m-1 )

0.002 133.2854 2665.7077 39.9856

0.003 124.9881 2499.7625 37.4964

0.004 96.8875 1937.7505 29.0663

0.005 57.4727 1149.4545 17.2418

0.006 45.8382 916.7647 13.7515

0.007 51.5121 1030.2412 15.4536

0.008 48.7828 975.6568 14.6349

0.009 35.4139 708.2783 10.6242

0.010 30.5100 610.1999 9.1530

Table 6: Distance between two consecutive stitches, d/m (±0.5 m), Maximum tension held

by sample , R /N (±0.5%), Tension held by sample per mm of cloth, r / (N m-1 ) and absolute

uncertainty of r, r /(N m-1 )

22

0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.0110.0000

500.0000

1000.0000

1500.0000

2000.0000

2500.0000

3000.0000

The Maximum tension held by sample per m, / N m vs distance between two consecutive stitches, d/m

Distance between two consecutive stitches, d/m

The Maximum tension held by

sample per m, r/ N

Uncertainties: X-axis : ±0.5 mm

Y-axis: some are too small to be seen (±1.5%)

23

3.3)Finding Mathematical Relationship

The values of y and x axes are then multiplied in order to determine a constant

value, which is derived from the average product of distance between two consecutive

stitches,d and Tension held by sample per m of cloth , p or q or r.

This constant is then used to derive a formula to model the strength of cloth

sewn with the running stitch, backstitch , and Lilit Ubi. The full listing of values of d ∙p, d∙q,

and d∙r can be found in the appendices . The following is a summary which consists of

average value of d∙p, d∙q, and d∙r, as well as their percentage uncertainties. The average

values of d.p, d.q, and d.r are now known as kp,kq, and kr repectively.

Type of handstitches Values of k /N Absolute

uncertainties of k, ∆

k /N

Percentage

uncertainties of k

Running Stitch 4.6980 0.5379 11.4491

Backstitch 5.1246 0.3358 6.5531

Lilit Ubi 6.5914 0.2749 4.1701

Table 7: Type of handstitches, Values of k/N , Absolute uncertainties of k, ∆k /N, and

Percentage uncertainties of k

The theoretical maximum magnitude of tension bearable by cloth,Fp sewn using

running stitch is then modelled using the equation :

Fp = kp ∙ 1/d ∙ l

Unit: Newton, N.

24

Where kp = constant for running stitch = 4.6980 N ± 11.4491%

d = distance between two consecutive stitches in m

l = length of cloth sewn

As for the following tables, the l is set to be 1 m so that the values can be compared with the

value derived from experimental data , p .

The theoretical maximum magnitude of tension bearable per metre for each hand

stitch are then compared to respective value of maximum tension held by sample per m of

cloth obtained from the experimental data. The differences between the two values are found

and percentage difference is obtained. The average percentage difference is an overview of

how accurate is the estimation model.

25

3.3.1)RUNNING STITCH

Distance

between two

consecutive

stitches, d/

m (±0.0005

m)

Maximum

tension held by

sample per m

of cloth, p / (N

m-1 )

Theoretical

maximum

magnitude of

tension bearable

per m, Fp / N

Uncertainties of

theoretical values

(∆Fp)

Percentage

difference

between

experimental

and theoretical

data

(|Fp-p| / p) ·

100) / %

0.002 2144.4176 2349.0185 856.1955 8.7101

0.003 2543.2855 1566.0123 440.2959 62.4052

0.004 1326.9081 1174.5092 281.2841 12.9755

0.005 747.0895 939.6074 201.5371 20.4892

0.006 464.8202 783.0062 154.8975 40.6365

0.007 879.5384 671.1481 124.7794 31.0498

0.008 337.3079 587.2546 103.9386 42.5619

0.009 723.3960 522.0041 88.7649 38.5805

0.010 316.5843 469.8037 77.2784 32.6135

mean 32.2247

Uncertainty of percentage difference 5.9661

Table 8: Distance between two consecutive stitches, d/ m (±0.0005 m) , Theoretical

maximum magnitude of tension bearable per m, Fp / N, Uncertainties of theoretical values (∆

Fp) , Percentage difference between theoretical and experimental data (Fp-p| / p) · 100) / %)

26

0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.0110.0000

500.0000

1000.0000

1500.0000

2000.0000

2500.0000

3000.0000

Graph of Theoretical maximum magnitude of tension bearable per m, F/N and Maximum tension held by sample

per m of cloth, p / (N m-1 ) vs Distance between two consecutive stitches, d / m (±0.0005 m)

F/(N m)

Distance between two consecutive stitches, d/ m (±0.0005 m)

Theoretical maximum magnitude of tension bearable

per m, F/N and Maximum tension held by sample per

m of cloth, p / (N m-1 )

Fp/ (N)

p/ (N m -1)

Uncertainties: x-axis: ±0.0005 m

y-axis: Fp :refer table 8

p : ±1.5%

27

3.3.2)BACKSTITCH

Distance

between two

consecutive

stitches, d/ m

(±0.0005 m)

Maximum

tension held by

sample per m of

cloth, q / (N m-1

)

Theoretical

maximum

magnitude of

tension bearable

per m, Fq / N

Absolute

uncertainties of

theoretical

values, ∆ Fq / N

Percentage

difference between

theoretical and

experimental data

((|Fq-q| /q) · 100) /

%

0.002 2738.7155 2562.3155 808.4890 6.8844

0.003 2296.0005 1708.2104 396.6418 34.4097

0.004 1519.0875 1281.1578 244.0998 18.5715

0.005 1062.9103 1024.9262 169.6567 3.7060

0.006 862.5463 854.1052 127.1455 0.9883

0.007 588.5321 732.0902 100.2665 19.6093

0.008 584.6198 640.5789 82.0137 8.7357

0.009 429.5133 569.4035 68.9469 24.5679

0.010 452.7765 512.4631 59.2052 11.6470

mean 14.3466

Uncertainty of percentage difference 3.7135

Table 9: Distance between two consecutive stitches, d/ m (±0.0005 m) , Maximum tension

held by sample per m of cloth, q / (N m -1 ), Theoretical maximum magnitude of tension

bearable per m, Fq / N, Uncertainties of theoretical values (∆Fq) , Percentage difference

between theoretical and experimental data. ((|Fq-q| /q) · 100) / %

28

0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.0110

500

1000

1500

2000

2500

3000

Graph of Theoretical maximum magnitude of tension bearable per m, F/N and Maximum tension held by sample

per m of cloth, q / (N m-1) vs Distance between two consecutive stitches, d/ m (±0.0005 m)

F/(Nm)Power (F/(Nm))

Distance between two consecutive stitches, d/ m (±0.0005 m)

Theoretical maximum

magnitude of tension bearable per

m, F/N and Maximum tension held by sample per m of cloth, q / (N -

m-1)

Fq/ (N)

q/ (N m-1)

Uncertainties : x-axis : (±0.0005 m)

y-axis : Fq : refer to table 9

q: ± 1.5%

29

3.3.3)‘LILIT UBI’

Distance

between two

consecutive

stitches, d/ m

(±0.0005 m)

Maximum tension

held by sample

per m of cloth, r /

(N m-1 )

Theoretical

maximum

magnitude of

tension bearable

per m, Fr/N

Absolute

uncertainties of

theoretical

values (∆Fr) /N

Percentage

difference between

theoretical and

experimental data

((|Fq-r| /r) · 100) /

%

0.002 2665.7077 3295.723 961.3662 19.1161

0.003 2499.7625 2197.149 457.8151 13.7730

0.004 1937.7505 1647.861 274.7004 17.5918

0.005 1149.4545 1318.289 186.8031 12.8071

0.006 916.7647 1098.574 137.3597 16.5496

0.007 1030.2412 941.6351 106.5269 9.4098

0.008 975.6568 823.9307 85.8545 18.4149

0.009 708.2783 732.3829 71.2292 3.2912

0.010 610.1999 659.1446 60.4443 7.4255

Mean 13.1532

Uncertainty of percentage difference 1.7583

Table 10: Distance between two consecutive stitches, d/ m (±0.0005 m), maximum tension

held by sample per m of cloth, r / (N m-1 ), theoretical maximum magnitude of tension

bearable per m, Fr/N, absolute uncertainties of theoretical values (∆Fr) /N, and percentage

difference between theoretical and experimental data (|Fr-r|/r · 100) / %

30

0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.0110

500

1000

1500

2000

2500

3000

3500

Graph of Theoretical maximum magnitude of tension bearable per m, F r/N and Maximum tension held by sample per m of

cloth, r / (N m-1 ) vs Distance between two consecutive stitches, d/ m (±0.0005 m)

F/ (Nm)

Distance between two consecutive stitches, d/ m (±0.0005 m)

Theoretical maximum magnitude of tension bearable per m, F r/N

and Maximum tension held by sample per m of

cloth, r / (N m-1)

Fr/ (N)

r/ (N m-1)

Uncertainties: x-axis : (±0.0005 m)

y-axis : Fr : refer table 10

r : ±1.5%

31

3.4)Summation of Analysis of Theoretical Model .

Type of hand stitch Average percentage difference

between theoretical and

experimental value , N%

Uncertainties of the percentage

difference N%

Running Stitch (P) 32.2247 5.9661

Backstitch (Q) 14.3466 3.7135

Lilit Ubi (R) 13.1532 1.7583

Table 11: Type of hand stitch, Average percentage difference between theoretical and

experimental value and uncertainties of the percentage difference.

3.5)DATA CALCULATIONS

32

3.5.1)Conversion of unit from mm to m

1mm=1 x 103m

2.0 mm = 2.0 x 103m

=0.002 m

3.5.2)Calculation of the average maximum tension held by sample

Average tension : Σ maximumtension∈three trials

3

=(83.5585+92.7545+145.3496)

3

= 107.2209 N

3.5.3)Calculation of tension held per m of sample

Tension held per metre of sample = Average maximumtensionheld bysample

length of sample∈mmx 1000

=107.2209

50x1000

=2144.4176 N m-1

3.5.4)Absolute uncertainty of tension held per m of sample

∆( pl)

(pl)

=∆ (p)

p·∆ ll

where p=tension held per metre

length of sample in N

l= length of sample in mm

33

∆ ( pl )=¿)( 2144.4176)

=32.1663 Nm-1

3.5.5)Values of k for Running stitch, backstitch, and ‘Lilit Ubi’ stitch

Step 1: multiplying the y-values (p/q/r) –> tension held by sample per metre with

the x-values (d) –> distance of separation between two consecutive stitches in m

Eg: (d·p) = (0.002)( 2144.4176)

= 4.2888 N

Step 2: Summing up all products for the stitch and dividing it with n which is 9

Eg: RUNNING STITCH

k=

Σ (d · p)n

=4.2888+7.6299+5.3076+3.7354+2.7889+6.1568+2.6985+6.5106+3.16589

k= 4.6980 N

3.5.6)Uncertainty for k

k=(d.p max-d.pmin) /n

= (7.6299-2.6985)/9

=0.5379 N

34

3.5.7)Estimated theoretical magnitude of maximum tension which can be held by

sample ,F

F = (k) (1/d) (l) Where k=constant obtained for the stitch

used in N

d= distance of separation between

two consecutive stitches in m

l = length of sample sewn in m

eg: F= (0.5379 ) (1/0.002) (1)

F = 2349.0185N

3.5.8)Uncertainties of estimated theoretical magnitude of maximum tension which can

be held by sample,F

FF

=∆ kk

+ ∆ dd

Eg: F=( 0.53794.6980

+ 0.00050.002 )¿2349.0185)

∆ F=¿±856.1955 N

3.5.9)Percentage difference between theoretical estimation and experimental data,

Percentage difference : (|Fp-p| · 100) Where Fp= theoretical magnitude of maximum

tension which can be held by sample in N

p=experimental value of maximum

tension that can be held by sample

(|Fp-p| · 100) = (|2349.0185-2144.4176|) · 100

35

=8.7101%

3.5.10) Mean percentage difference theoretical estimation and experimental data

Eg: mean percentage difference for p

Mean percentage difference = Σpercentage differences

9

=

8.7101+62.4052+12.9755+20.4892+31.0498+42.5619+38.5805+32.61359

= 32.2247 %

3.5.11)Uncertainty of percentage difference theoretical estimation and experimental

data

Eg: for running stitch (refer table 4)

(%)=(%max-%min) / n

=(62.4052-5.9661)/9

= ±5.9661 %.

36

4)CONCLUSION AND EVALUATION

4.1)Conclusion

From the experiment, generally the tension needed to fail the seam in clothes sewn

with running stitch is the lowest, while the highest is ‘Lilit Ubi’. When the constant k is

compared with all the three k, it is found that k value for Lilit Ubi is the highest which is

(6.5914±0.2749)N, followed by backstitch with k value of (5.1246±0.3358)N and lastly

running stitch (4.6980±0.5379) N. This significance of this value is demonstrated in the

mathematical model to find estimated maximum magnitude of tension a sample can stand

when it is sewn with the hand stitch. The mathematical model F = (k)·(1/d)·(length of cloth

sewn in m) gives higher value when k is increased. F also turns out higher if d or distance

between two consecutive sewing decreases.

Initial hypothesis suggested that backstitch will have the higher tension requirement

to separate the two cloth joined together by the seam. This is because backstitch requires

more thread (needs longer thread) compared to the other two. As the length of thread

increases, the amount of tension capable of being withstood by the seam would increase.

However, the experiment has shown that length of thread is not the only factor affecting seam

strength. Regarding the Lilit Ubi, the construction of the seam covers wider area of the cloth.

Thus, the distribution of tension is done over a wider area. Backstitch and running stitch

covers the cloth only in a straight line so the tension supplied by the tensile tester cannot be

37

distributed widely. That is why eventhough ‘Lilit Ubi uses less thread compared to

backstitch, it can withstand greater tension.

For all the three stitches, a similar pattern can be observed. The maximum tension

held by the sample is inversely proportional to the distance between two consecutive stitches.

When the distance between two consecutive stitches is increased, the number of stitches per

unit length decreases. The tension applied would be distributed in the individual stitches

connecting the clothes. If there is less stitches, then the tension per stitch would be higher.

Then it would be easier for the seam to fail. Besides that, the higher the number of stitches

per unit length, more thread is used. This will increase the strength of the hand stitch.

One of the hypotheses made for the experiment was as the stitches are made closer,

the fabric would be more ruptured or damaged due to needle punctures. Thus, the less tension

will be needed to separate the two clothes sewn together .The theory about closeness of

stitches could lead to fabric damage cannot be tested in this experiment. The variable distance

between two consecutive stitches is not small enough to cause damage due to excessive

needle piercing. Besides that, the fabric chosen to do the experiment is thick and strong. The

damage is unlikely to happen.

4.2)Limitations of the Mathematical Model in estimating the Strength of seam

The development of the mathematical model used to predict the estimated

(theoretical) magnitude of maximum tension (F = (k)·(1/d)·(length of cloth sewn in m)) can

be used only if a certain condition is followed:

1) The force required to rupture the fabric must be more than the force required to snap

the stitches.

38

If the fabric used are weak (for example rayon and silk), the force required to

separate the two fabric joined by stitches would be less as the fabric is more likely to rupture

first before the thread.

2) The number of thread used must be single

This is because the model was developed using samples which are used using

single thread. Increasing the number of thread would increase the strength of the seam.

However, the experiment did not include number of threads as a variable so the mathematical

relationship between number of threads and strength of seam could not be estimated.

3) The type of thread used.

Beside number of thread, type of thread used can also influence the strength of

stitches as different types of thread have different tensile strength values.

The model also assumes that all the tension applied goes to the seam only and did not

significantly contributed to the elongation of the fabric ,if there’s any.

4.3)Errors and Limitations Analysis

The instrument and software used in conducting the experiments are reliable and

highly accurate. This is because the sensitivity of them are very high with errors of only

0.5%8 The systematic error in the experiment would also contributed by the use of plastic

ruler to measure distance between two consecutive stitches. This is because the smallest scale

for the plastic ruler is 1.0 mm and it has an error of (±0.5mm). However, the scale smaller

than millimetre is micrometre which could only be measured using micrometer screw gauge.

8 INSTRON. 3360 Series Dual Column Tabletop Universal Testing Systems . 3360 series dual column tabletop universal testing systems. Retrieved 28th of July 2011. http://www.instron.us/wa/product/3300-Dual-Column-Testing-Systems.aspx?

39

For this experiment, micrometer screw gauge is unsuitable as it is used to measure thickness

of something, not the distance or separation between two points on a 2-D plane.

The random error and the inconsistencies in the data collection might be contributed

by the following factors:

i) The sewing is done by hands. Thus, the force applied to the needle and thread

while sewing is unknown. Currently there is no machine capable of sewing

backstitch, running stitch, and ‘Lilit Ubi.

ii) The inconsistencies of the thickness of the thread could lead to uneven tension

distribution when the samples are being tested for tensile strength. The thinner

part of the thread would be weaker and the tendency to break at the point is

higher.

However, for each test carried out, the threads used were from the same batch. This is

to reduce the random error. A better quality thread which has a more uniform thickness

should have been used so that the force distribution within the thread will be more even. This

would reduce the probability of having weak points.

iii) The process of sewing the clothes is done by superimposing two clothes and

sewing along the marked line. The penetration of needle could be inaccurate to

the marks on both clothes because the clothes were not in fixed positions. This

may lead to uneven distribution of tension in the seam.

Previously the clothes was fixed using paperclip before sewing it. In future , the

samples should have been fixed to a fixed clamp which will ensure that the samples are

properly stretch and not moving much when it is being sewn. This technique can improve

40

accuracy of needle penetrations and thus, the distance of separation between two consecutive

stitches.

iv) The rupture happened after the experiments were not observed closely enough.

Thus, it is not known whether the seam failure was really due to seam failure, fabric

tear, or thread slipping through the holes. Anyone it might be, I should have observed the

samples more closely the variables may change as the stated possible conditions happen.

4.4)Suggestion for Future researches

In this experiment, I focused only on the effect of distance between two consecutive

stitches on strength of seam in three types of hand stitches. However, I have not investigated

the factor of the tensile strengths of thread and fabric on the maximum tension that can be

held by two clothes sewn together. Future research may be made to investigate the

mathematical relationship between tensile strength of sewing thread and the strength of seam.

41

5) APPENDICES

5.1) Raw Experimental Data

5.1.1) RUNNING STITCH

Tensile strength tests for running stitch

Maximum tension held by sample /N

(±0.5%)

Average

tension

held by

stitch, P/N

(±0.5%)

Distance between two consecutive

stitches,d/mm (±0.5 mm)

Trial 2 trial 2 Trial 3

2.0 83.5585 92.7545 145.3496 107.2209

3.0 129.3712 131.2037 120.9180 127.1643

4.0 69.9297 59.5308 69.5758 66.3454

5.0 48.0853 39.1488 24.8293 37.3545

6.0 13.5692 25.3716 30.7822 23.2410

7.0 39.1553 38.4775 54.2979 43.9769

8.0 19.4394 16.4124 14.7444 16.8654

42

9.0 34.7080 37.7827 36.0187 36.1698

10.0 10.0811 19.0802 18.3264 15.8292

Table 1.1 : Distance between two consecutive stitches, d/mm (±0.5 mm), Maximum tension

held by stitch /N (±0.5%) and average tension held by stitch, P/N (±0.5%)

5.1.2) BACKSTITCH Maximum tension held by sample, N /

(±0.5%)

Average

maximum

tension held

by seam, Q/N

(±0.5%)

Distance

between two

consecutive

points , d/ mm

(±0.5mm)

Trial 1 Trial 2 Trial 3

2.0 109.3797 138.0477 163.3799 136.9358

3.0 117.4891 132.0591 94.8519 114.8000

4.0 66.9354 80.4522 80.4756 75.9544

5.0 52.1429 48.1365 59.1572 53.1455

6.0 42.7351 35.9608 50.6860 43.1273

7.0 27.1563 31.8127 29.3108 29.4266

8.0 17.8425 30.3625 39.4880 29.2310

9.0 23.9716 19.0483 21.4071 21.4757

43

10.0 15.0934 32.8531 19.9700 22.6388

Table 1.2: Distance between two consecutive points , d/ mm (±0.5mm), Maximum tension

held by sample, N / (±0.5%) and Average maximum tension held by seam, Q/N (±0.5%)

5.1.3) ‘LILIT UBI’

Maximum tension held by sample, N / (±0.5%) Average maximum tension held by seam, R/N (±0.5%)

Distance

between two

consecutive

points , d/ mm

(±0.5mm)

Trial 1 Trial 2 Trial 3

2.0 130.1267 161.7949 107.9346 133.2854

3.0 132.1029 132.9121 109.9494 124.9881

4.0 103.3597 101.6183 85.6846 96.8875

5.0 45.8798 56.6240 69.9144 57.4727

6.0 55.7781 29.3036 52.4330 45.8382

7.0 54.1820 24.5049 75.8493 51.5121

8.0 42.1249 44.9274 59.2962 48.7828

44

9.0 39.6071 35.8428 30.7918 35.4139

10.0 38.2377 20.3867 32.9056 30.5100

Table 3: Distance between two consecutive points , d/ mm (±0.5mm), Maximum tension

held by sample, N / (±0.5%) and Average maximum tension held by seam, R/N (±0.5%)

5.2) The Products of Distance Between Two Consecutive Stitches and Tension Held by Sample Per Metre of Cloth.

5.2.1) RUNNING STITCH

Distance between

two consecutive

stitches,d/ m

( ±0.0005 m)

Tension held by

sample per m of

cloth, p / (N m-1 )

Values of d∙p / (N) Uncertainties of d∙p

∆(d.p) / N

0.002 2144.4176 4.2888 1.1365

0.003 2543.2855 7.6299 1.3861

0.004 1326.9081 5.3076 0.7431

0.005 747.0895 3.7354 0.4296

0.006 464.8202 2.7889 0.2742

0.007 879.5384 6.1568 0.5321

0.008 337.3079 2.6985 0.2091

0.009 723.3960 6.5106 0.4594

0.010 316.5843 3.1658 0.2058

45

Average of d.p , kp /

N

4.6980 0.5379

% uncertainty of

d.p

11.4491

Table 4: Distance between two consecutive stitches,d/ m ( ±0.0005 m), Tension held by sample per m of cloth, p / (N m-1 ), Values of d∙p / (N) and Uncertainties of d∙p, ∆(d.p) / N.

5.2.2) BACKSTITCH

Distance between

two consecutive

stitches,m /0.0005

m

Tension held by

sample per m of cloth,

q / (N m-1 )

Values of d∙.q / (N) Uncertainties of d∙q ∆

(d . q) /N

0.002 2738.7155 5.4774 1.4515

0.003 2296.0005 6.8880 1.2513

0.004 1519.0875 6.0764 0.8507

0.005 1062.9103 5.3146 0.6112

0.006 862.5463 5.1753 0.5089

0.007 588.5321 4.1197 0.3561

0.008 584.6198 4.6770 0.3625

0.009 429.5133 3.8656 0.2727

0.010 452.7765 4.5278 0.2943

Average of d.q , kq / N 5.1246 0.3358

% uncertainties of d.q 6.5531

46

Table 5: Distance between two consecutive stitches,d/ m ( ±0.0005 m), Tension held by sample per m of cloth, q / (N m-1 ), Values of d∙q / (N) and Uncertainties of d∙q , ∆ (d.q) / N.

5.2.3) ‘LILIT UBI’

Distance

between two

consecutive

stitches,d/ m

(±0.0005 m)

Tension held by

sample per m of cloth,

r / (N m-1 )

Values of d.r / (N) Uncertainties of dr ∆

(d.r) /N

0.002 2665.7077 5.3314 1.4128

0.003 2499.7625 7.4993 1.3624

0.004 1937.7505 7.7510 1.0851

0.005 1149.4545 5.7473 0.6609

0.006 916.7647 5.5006 0.5409

0.007 1030.2412 7.2117 0.6233

0.008 975.6568 7.8053 0.6049

0.009 708.2783 6.3745 0.4498

0.010 610.1999 6.1020 0.3966

47

Average d. r, kr / N 6.5914 0.2749

% uncertainties of d.r 4.1701

Table 6: Distance between two consecutive stitches,d/ m (±0.0005 m), tension held by sample per m of cloth, r / (N m-1 ), values of d.r / (N), uncertainties of d.r ∆(d.r) /N

6) BIBLIOGRAPHY

Hidup, U.M .(n.d.). Jahit Penyambung retrieved 23rd July 2011, from Dunia Jahitan

Anda: http://ejahitanonline.tripod.com/jahitsambung.htm

Hidup, U.M .(n.d.). Jahit Penyambung retrieved 23rd July 2011, from Dunia Jahitan

Anda: http://ejahitanonline.tripod.com/jahitsambung2.htm

How To Determine Seam Strength (n.d). Retrieved 30th of July 2011. From My textile

Notes:http://mytextilenotes.blogspot.com/2009/06/how-to-determine-seam-

strength.html?dhiti=1.

INSTRON. 3360 Series Dual Column Tabletop Universal Testing Systems . 3360

series dual column tabletop universal testing systems. Retrieved 28th of July

2011.http://www.instron.us/wa/product/3300-Dual-Column-Testing-

Systems.aspx?

INSTRON. (n.d) .Material Testing e-book. Retrieved 15th July 2011 from:

http://www.instron.com/subscribe/Instron Material Test Guide.pdf

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Kerr, Ruth (2008). Physics (3rd edition). Victoria : IBID Press.

49