LAB 1 FORMAL MEASUREMNET.docx

UNIVERSITI TENAGA NASIONAL

COLLEGE OF ENGINEERING

DEPARTMENT OF MECHANICAL ENGINEERING

MESB333 – MEASUREMENT LAB

EXP. TITLE : EXPERIMENT 1: STRAIN MEASUREMENT

AUTHOR : REDZA RABANI BIN MD ROSLI (ME093300)

……………..Individual Report……………..

SECTION : 05B

GROUP NUMBER : 03

GROUP MEMBER :

INSTRUCTOR : FEVILIA NURNADIA BINTI ADRIA SYAIFOEL

PERFORMED DATE DUE DATE* SUBMITTED DATE26/08/2015 26/08/2015

*Late submission penalty: Late 1 day: 20%, Late 2 days: 40%, Late 3 days: 60%, More than 3 days: not accepted

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TABLE CONTENTNo.

TOPIC PAGE

1.0 Summary 3

2.0 Objective 4

3.0 Theory 5-13

4.0 Equipment 14-19

5.0 Procedure 19-22

6.0 Data, Observation And Result 23-34

7.0 Analysis And Discussion 35-36

8.0 Conclusion 37

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SUMMARY:

Strain Gauge experiment was divided into four different parts, which are

bending system, torsion system, tension system and optional tension system

specimen. The experiments were carried out using Strain Gauge Trainer SM1009 with

the aid of Digital Strain Display and Versatile Data Acquisition System (VDAS)

Hardware and Software.

The first bending experiment was objectively to show how to measure strains

in bended object and compare the results with theory. The graph of Calculated Stress,

σ vs Displayed Strain, μɛ is plotted to gain the value of theoretical Young’s Modulus

of the mild steel beam. Next, the torsion experiment has two different procedures in

order to show how to connect and use shear and torque (torsional) strain gauges to

measure strains in twisted object as well to show how to compare displayed strains

with theory for a torsion beam.

Furthermore, the main purpose of conducting the tension experiment which

had been done with three different procedures was to demonstrate how to connect and

use strain gauges to measure strains in two dimensions. And, this experiment mainly

objective to demonstrate how to compare the displayed tensile strains in two

dimensions with theory and prove Poisson’s ratio. Finally, the optional tension system

specimen experiment was performed in order to test and find the tensile properties of

different test specimens apart from mild steel.

In this experiment conducted with different procedures has the same error

which is human error. There are improper use of equipment and error while setting up

the equipment. The errors can be avoided to increasing the accuracy of data obtained

from the experiment.

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OBJECTIVES:

To show how to measure strains in bended object and compare the results with

theory.

To show how to connect and use shear and torque (torsional) strain gauges to

measure strains in twisted object.

To show how to compare displayed strains with theory for a torsion beam.

To show how to connect and use strain gauges to measure strains in two

dimensions.

To show how to compare the displayed tensile strains in two dimensions with

theory and prove Poisson’s ratio.

To use the strain gauge trainer to test and find the tensile properties of

different test specimens.

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THEORY:

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EQUIPMENTS:

- Strain Gauge Trainer SM1009, Digital Strain Display, Versatile Data Acquisition System (VDAS) Hardware and Software.

Figure 1: The Strain Gauge Trainer

Figure 2: The Digital Strain Display

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Figure 3 The VDAS Hardware and Software

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TECHNICAL DETAILS

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PROCEDURES:

Experiment 1: The Bending System

1. The ‘Bending System Experiment’ is selected using VDAS software. A blank

result table is created.

2. The specimen dimension is read and recorded from the software.

3. The bending system strain gauges are connected to the strain display as a full

bridge.

4. The knife-edge hanger is carefully slide onto the beam to the 420 mm position.

5. The equipment is left to stabilize for approximately one minute. The ‘zero’

button is then pressed and hold until the display readings become 0 (zero).

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6. The ‘Record Data Values’ button is clicked to record the strain readings.

7. The small weight hanger is hooked to the knife-edge hanger.

8. The weights are then added to the weight hanger according to the set values in

the table and the mass value is adjusted respectively using the software.

Experiment 2: The Torsion System

Procedure 1 (using shear and torque strain gauges)

1. The ‘Torsion System Experiment’ is selected using VDAS software. A blank


2. The blue strain gauge is connected to the strain display as a quarter bridge.

The Strain Display is adjusted to show the correct gauge factor and ACT=1.

3. The torque arm is screwed into the threaded hole at the end of the torsion

system.



5. A small weight hanger is added to the end of the torque arm.

6. 500 g load (49 weights) is added to the weight hanger. The mass value is

adjusted to 500 g using the software and the ‘Record Data Values’ button is

clicked.

7. The strain reading and its polarity are recorded.

8. Next, the weights are removed and the experiment is repeated using red,

yellow, and green gauges sequentially.

Procedure 2 (comparing strains)

1. A new data series is started using VDAS software and a blank result table is

created.


3. The torsion system red and green gauges ‘tensile twist’ is connected as

opposites. The blue and yellow gauges ‘compressive twist’ is connected as

opposites to complete a full bridge.



5. The ‘Record Data Values’ button is clicked. The strain reading is recorded in

the table.

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6. A small weight hanger is added to the end of the torque arm. 24 weights are

firstly added to the weight hanger and the mass value is adjusted to 250 g

using the software. The ‘Record Data Values’ button is then pressed.

7. More weights are added until it reaches 500 g. The mass is again adjusted to

500 g, and then the ‘Record Data Values’ button is pressed.

Experiment 3: The Tension System

Procedure 1 (tensile strains only-red and yellow gauges)

1. The ‘Tension System Experiment’ is selected using VDAS software. A blank



3. The red and yellow gauges of the Tension System are connected to the Strain

Display as a half bridge (opposite). ACT is set to be equal to 2.


button is then pressed and hold until the display readings become 0 (zero). The

‘Record Data Values’ button is clicked.

5. The large weight hanger is fitted to the bottom of the Tension System

specimen. 0.5 kg is added to the weight hanger to give a total load of 1 kg. The

mass value is then adjusted to 1 kg using the software.

6. The ‘Record Data Values’ button is clicked to obtain the strain reading.

7. More weights are added to the weight hanger in 1 kg increment, until it

eventually reaches 10kg. The mass value is then adjusted accordingly using

the software. The ‘Record Data Values’ button is again clicked to obtain the

strain reading.

Procedure 2 (compressive strain only-blue and green gauges)


created.

2. Procedure 1 (Tensile Strain Only-Red and Yellow Gauges) is repeated, but

using different gauges - the blue and the green gauges.

Procedure 3 (full bridge tensile and compressive strain)


created.

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2. Procedure 1 (Tensile Strain Only-Red and Yellow Gauges) is repeated, but all

four gauges are connected as a full bridge. The configuration control is set so

that ACT=N.

Experiment 4: The Optional Tension System Specimens

1. The ‘Tension System Experiment’ is selected using VDAS software. A blank


2. The locating pin is slide out. The standard Tension Specimen and its connector

assembly are removed from the Strain Gauge Trainer.

3. Aluminium Tension specimen is fitted to the Strain Gauge Trainer.

4. The specimen details are entered into the software (i.e Material: Aluminum)

and the dimensions are read from there.

5. Table 10 is checked and the correction number for that particular material is

entered.

6. The Tension System gauges are connected to the Strain Display as a full

bridge and the Strain display is set for Act=1 (not Act=N).


button is then pressed and hold until the display readings become 0 (zero). The

‘Record Data Values’ button is then clicked.

8. The large weight hanger is fitted to the bottom of the Tension System

specimen. 0.5 kg is added to the weight hanger to give a total load of 1 kg. The

mass value is then adjusted to 1 kg using the software. The ‘Record Data

Values’ button is clicked.

9. More weights are added to the weight hanger in 1 kg increment, until it

eventually reaches 10kg. The mass value is then adjusted accordingly using

the software. The ‘Record Data Values’ button is again clicked to obtain the

strain reading.

10. The aforementioned steps (1-9) are repeated, but using brass and copper

tension specimens sequentially.

DATA, OBSERVATIONS, AND RESULTS:

EXPERIMENT 1: The Bending System

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Beam’s dimension: 20mm x 5mm

Young’s Modulus for the beam: 207 GN/m2

Second Moment of Area: 208.33 mm4

Bridge Connection : Full

Load Position: 420mm

Load (g) Force (N) = Load (g) x 9.81 m/s2

Strain Reading

(µε)

Output Voltage

(µV)

Bending Moment

(Nm)

Calculated Stress

(MN/m2)

Calculated Strain

(µε)

0 0 0 0 0.00 0.00 0

50 0.49 15 164 0.20 2.40 11.6

100 0.98 28 305 0.40 4.80 23.2

150 1.47 42 447 0.60 7.20 34.8

200 1.96 55 589 0.79 9.48 45.8

250 2.45 69 732 0.99 11.88 57.4

300 2.94 83 876 1.19 14.28 69

350 3.43 96 1018 1.39 16.68 80.6

400 3.92 110 1167 1.59 19.08 92.2

450 4.41 124 1310 1.79 21.48 103.8

500 4.90 137 1453 1.98 23.76 114.8

Table 1: Result for Experiment 1 (The Bending System)

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Graph 1: Result for Experiment 1

EXPERIMENT 2: The Torsion System

Gauge Factor : 2.05

Strain Gauge Strain Reading (µε)

Polarity (+/-) Type of Strain (Compressive/Tensile

)

Green -23 - Compressive

Red 21 + Tensile

Yellow -24 - Compressive

Blue 22 + Tensile

Table 2: Result for Experiment 2 Procedure 1 (The Torsion System: Using Shear and Torque Strain Gauges)

Gauge Factor : 2.05

Beam Diameter : 10 mm

Beam Radius : 5 mm

Shear Modulus for the beam : 79.6 GN/m2


Torque Arm Length : 0.15 m

Polar Moment of Inertia : 981.75 mm4

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y= -0.101698 + 0.174122(x)Gradient, k=0.174122

Calculated Stress (σ) vs Displayed Strain (μɛ) Graph

Load (g)

Force (N)

(Load x 9.81)

Torque (Nm)

Output Voltage

(µε)

Strain Reading

(µε)

Calculated shear stress

(MN/m2)

Direct Strain

(µε)

0 0.00 0.00 0 0 0.0 0.0

250 2.45 0.37 117 11 23.6 11.8

500 4.90 0.74 247 24 47.4 23.7

Table 3: Result for Experiment 2 Procedure 2 (The Torsion System: Comparing Strains)

EXPERIMENT 3: The Tension System

Gauge Factor : 2.11

Specimen Dimensions (width and thickness) : 10mm & 2mm

Specimen cross-section: 20 mm2

Young’s Modulus: 207 GN/m2


Load (kg) Force (N) Displayed Tensile Strain

(µε)

Calculated Tensile Stress

(N/m2)

Calculated Tensile Strain

0 0.00 0 0 0.0

1 9.81 2 0.49 2.4

2 19.61 5 0.98 4.7

3 29.42 7 1.47 7.1

4 39.23 10 1.96 9.5

5 49.03 12 2.45 11.8

6 58.84 15 2.94 14.2

7 68.65 18 3.43 16.6

8 78.45 20 3.92 18.9

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9 88.26 23 4.41 21.3

10 98.07 25 4.90 23.7

Table 4: Result for Experiment 3 Procedure 1 (Tension System: Tensile Strains)

Gauge Factor : 2.11




Bridge Connection : Half


(µε)


(N/m2)


0 0.00 0 0.00 0.0

1 9.81 0 0.49 0.0

2 19.61 -1 0.98 -0.4

3 29.42 -2 1.47 -0.8

4 39.23 -3 1.96 -1.2

5 49.03 -3 2.45 -1.2

6 58.84 -4 2.94 -1.5

7 68.65 -5 3.43 -1.9

8 78.45 -6 3.92 -2.3

9 88.26 -6 4.41 -2.3

10 98.07 -7 4.90 -2.7

Table 5: Result for Experiment 3 Procedure 2 (Tension System: Compressive Strains)

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0 5 10 15 20 25 30

-9-8-7-6-5-4-3-2-10

f(x) = − 0.293814432989691 x

Compressive Strain (μɛ) vs Tensile Strain (μɛ)

Tensile strain (μɛ)

Com

pres

sive

Stra

in (μ

ɛ)

Graph 2: Result for Experiment 3 (Procedure 1 and 2)

Gauge Factor : 2.11




Bridge Connection : Quarter


(µε)


(N/m2)


(µε)

0 0.00 0 0.00 0.0

1 9.81 2 0.49 2.4

2 19.61 5 0.98 4.7

3 29.42 7 1.47 7.1

4 39.23 10 1.96 9.5

5 49.03 12 2.45 11.8

6 58.84 15 2.94 14.2

7 68.65 18 3.43 16.6

8 78.45 20 3.92 18.9

9 88.26 23 4.41 21.3

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10 98.07 25 4.90 23.7

Table 6: Result for Experiment 3 Procedure 3 (Tension System: Full Bridge Tensile and Compressive Strains)

EXPERIMENT 4: The Optional System (Aluminium, Brass, Copper)


Material : Aluminium

Active Arms : 4.0

Load (kg) Force (N) Stress Displayed Strain (µε)

Theoretical Strain (µε)

0 0.00 0.00 0 0.0

1 9.81 0.49 5 7.1

2 19.61 0.98 10 14.2

3 29.42 1.47 16 21.3

4 39.23 1.96 21 28.4

5 49.03 2.45 26 35.6

6 58.84 2.94 30 42.7

7 68.65 3.43 34 49.8

8 78.45 3.92 38 56.9

9 88.26 4.41 42 64.0

10 98.07 4.90 45 71.1

Table 7: Result for Experiment 4 (Optional Tension System: Aluminium)

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Graph 3: Result for Experiment 4 (Aluminium)

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y= -0.38957 + 0.106661(x)Gradient, k=0.106661

Calculated Stress, σ (MN/m2) vs Corrected Strain (μɛ) for Aluminium

Table 8: Result for Experiment 4 (Optional Tension System: Aluminium Neutral Bridge)

Graph 4: Result for Experiment 4 (Aluminium Neutral Bridge)

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y= 0.120592 + 0.195599(x)Gradient, k=0.195599

Calculated Stress, σ (MN/m2) vs Corrected Strain (μɛ) for Aluminium

Bridge Connection : Neutral

Material : Aluminium

Active Arms : 2.6

Load (kg) Force (N) Stress Displayed Strain (µε)


0 0.00 0.00 0 0.0

1 9.81 0.49 2 7.1

2 19.61 0.98 4 14.2

3 29.42 1.47 7 21.3

4 39.23 1.96 9 28.4

5 49.03 2.45 12 35.6

6 58.84 2.94 14 42.7

7 68.65 3.43 17 49.8

8 78.45 3.92 19 56.9

9 88.26 4.41 22 64.0

10 98.07 4.90 25 71.1

Table 9: Result for Experiment 4 (Optional Tension System: Brass)

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Material : Brass

Active Arms : 4.0

Load (kg) Force (N) Stress

(MN/m2)

Displayed Strain (µε)


0 0.00 0.00 0 0.0

1 9.81 0.49 13 4.7

2 19.61 0.98 27 9.3

3 29.42 1.47 41 14.0

4 39.23 1.96 55 18.7

5 49.03 2.45 67 23.3

6 58.84 2.94 82 28.0

7 68.65 3.43 96 32.7

8 78.45 3.92 108 37.3

9 88.26 4.41 121 42.0

10 98.07 4.90 136 46.7

Graph 5: Result for Experiment 4 (Brass)

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Table 10: Result for Experiment 4 (Optional Tension System: Copper)

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Material : Copper

Active Arms : 4.0

Load (kg) Force (N) Stress

(MN/m2)

Displayed Strain (µε)


0 0.00 0.00 0 0.0

1 9.81 0.49 7 3.8

2 19.61 0.98 16 7.5

3 29.42 1.47 27 11.3

4 39.23 1.96 38 15.1

5 49.03 2.45 49 18.8

6 58.84 2.94 60 22.6

7 68.65 3.43 71 26.4

8 78.45 3.92 81 30.2

9 88.26 4.41 93 33.9

10 98.07 4.90 103 37.7

Graph 6: Result for Experiment 4 (Copper)

DISCUSSIONS:

The strain reading and the calculated strain reading was combined in one table

(Table 1) is because to make and check for the percentage difference. The calculated

and actual strain results in Experiment 1 are not very deviated. This difference is due

to rounding off the values which make an error of percentage differences to 15.88%.

The error caused deviation of Young’s Modulus, E from its theoretical value.

In Experiment 2 Procedure 1 and 2, there are four gauges on the rod and the

polarity was differentiated. The values obtained are very similar to all gauges

measured. The only differences are the negative and positive sign in front of the

values which indicate whether it is compressive or tensile twisting strain. The strain

readings shown by compressive strain gauge set are small and slightly different with

below than 5% of error. Clearly observed from the data in experiment 2 (Table 3), the

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values of calculated strains recorded to be similar to the strain readings which have

proved the theory.

In Table 4 and Table 5, shows that the calculated tensile strains are very

similar to the displayed tensile strains. Proofed in Graph 2 that the relationship

between the tensile and compressive strains is 0.2938 which close to its theoretical

value of Poisson’s ratio for mild steel which is 0.3 which below than 5% of error. By

using all four gauges would bring more precise values of reading. And for

applications where strain values are small, a chart of the micro-volt output voltage can

give slightly better accuracy due to its high resolution. Table 6 shows the results for a

full bridge connection of the tensile and compressive strains.

The ACT=N setting is 2.6. Normally, ACT is set equal to 4 for four which

indicating the full bridge of equal magnitude strain reading. Following with ACT is

equal to two which indicating the half bridge gauges of equal magnitude strain

reading.

The Poisson’s ratio can be applied to most common metals but it varies

slightly according to the type of material itself. This concludes that, ACT=N setting

is not ideal for all material. From the experiment of bending system (Experiment 1),

torsion system (Experiment 2), and tension systems (Experiment 3) clearly seen that

the bending system and a full bridge configuration giving the best sensitivity among

these three systems.

The results of tension system for different materials (aluminium, brass and

copper) are shown in Table 7, 8, 9, 10 and Graph 3, 4, 5, 6. The plotted graphs show

gradient of 0.01066, and 0.0036, 0.00462 for aluminium (Full), brass and copper

which correspond to Young’s Modulus values of 195.66 GN/m2, 36.11 GN/m2 and

42.63 GN/m2 respectively. The error was very large and this results affected in 64.73%

error for aluminium, 65.61% error for brass and 67.21% error for copper based on the

comparisons of their experimental Young’s Modulus with the theoretical values.

The error especially for experiment 4, the values of experimental Young’s

Modulus with the theoretical are quick varied. These errors may due to the human

error and technical error where the students may take the readings before allowing the

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digital strain display to be stabilized. These errors, if controlled, can reduce the errors

taking place in this experiment, thus increasing the accuracy of data obtained from it.

Finally, the Young’s Modulus of material plays a vital role for the usage as a

force sensor, as it determines how much the material strains for a given amount of

stress. A higher strain for stress ratio (low Young’s Modulus) will produce better

sensitivity.

CONCLUSION:

Basically, all objectives of the Strain Gauge experiment have been achieved.

The errors for experiment 1, 2 and 3 are still within acceptable range of less than 20%.

Observed that, in experimental 4 the errors was varied when compared with values of

the theoretical of Young Modulus. The major error is a human error where the

reading might round off too big in a whole figure which will produces varied values

compared to the theoretical one. Minor error is that miscellaneous type of gross error

such as the improper use of the equipment and also systematic error while setting up

the equipment.

The relationship between the tensile and compressive strains from the tension

experiment is 0.2938 which is close enough to its theoretical value of Poisson’s ratio

for mild steel (0.3). From all the data recorded and graph shown in an analysis part, it

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can be said that the aforementioned objectives highlighted for each experiment had

been successfully achieved.

Safety precautions need to be highlighted seriously while doing the experiment.

In a nutshell, it is noticed that the bending system and a full bridge configuration

produces the best sensitivity compared to the torsion and tension systems. It is also

proven that a quarter bridge is acceptable for most strain measurements.

REFERENCES:

1. MESB333: Engineering Measurement and Lab Lab Manual (Strain

Measurement). Department of Mechanical Engineering College of

Engineering. Universiti Tenaga Nasional.2014.pp 1-53.

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LAB 1 FORMAL MEASUREMNET.docx