Experiment 1 - Devdev

COLLEGE OF ENGINEERING

DEPARTMENT OF MECHANICAL ENGINEERING

MEMB221 - MECHANICS OF MATERIAL LAB

SEMESTER 1 2014/2015

EX 1: Tensile Testing (Universal Tester)

SECTION : 04

GROUP : 04

Performed Date: 17/07/2014

Due Date : 24/07/2014

Instructor : Madam Siti Zubaidah

Author : Devien Raj(ME091067)

Table of Content

Title Pages

Table of content 2

Abstract 3

Objective 3

Theory 4

Equipment and Formula 5 - 7

Procedure 8

Data, Observations and Results

Tables

Sample Calculations

Graphs

9 - 12

Analysis and Discussion 13 – 17

Conclusion 18

References 18

ABSTRACT

The experiment conducted is known as the tensile test (Universal Tester) which is to

determine the relationship between the stress-strain and the materials involves: brass,

aluminum. This enables the mechanical properties to be determined.

The device used is the WP 300 which is designed specifically for this experiment. Initially,

the properties and characteristics of the materials are recorded. By using the device, readings

for the elongation and the corresponding strength are then collected and tabulated. The stress

strains are calculated by using the formulas given in the lab manual. The elongation and the

stress-strain graphs for all the materials are drawn thus enabling to obtain the strength,

elongation at fracture, and tensile modulus of elasticity limit.

OBJECTIVES

The main purpose of this experiment is conducted is to understand the principles of tensile testing. Furthermore, the stress-strain relationship for the two types of materials (brass and aluminum) needs to be determined. Not only that, the values of:

1. elongation of fracture2. tensile strength (UTS)3. yield strength4. Modulus of Elasticity

also needs to be determine and calculated.

THEORY

One of the most important mechanical property evaluation test is tensile test. If a load is

static or changed relatively slowly with time and is applied uniformly over a cross section

/surface of a member, the mechanical behaviour may be ascertained by a simple stress-strain

test. These tests are most commonly conducted for metals at room temperature. There are

three principal ways in which the load may be applied: tension, compression and shear.

Tension is one of the most common mechanical stress-strain tests. The stress-strain diagram

shows the different behaviour of the individual materials particularly clearly. Each material

has a characteristic pattern of stress and strain. A standard specimen is deformed, usually to

fracture with a gradually increasing tensile load that is applied uniaxially along the long axis

of a specimen. Fix one end of the material to the gripping head and apply force on the other

end of the material. Most of the tension tests for metals are conducted according to the

ASTM Standard E 8 and E 8M, “Standard Test Methods for Tension Testing of Metallic

Materials”.

EQUIPMENT / DESCRIPTION OF EXPERIMENTAL APPARATUS

Basic

The basic unit is essentially consists of the

following elements:

- Machine base (1) with handgrip (2)

- Support with cross-head (2)

- Load frame with upper (3) and lower cross-member (4)

- Hydraulic system consisting of a main cylinder (5) and

a master cylinder with hand wheel (6)

- Force display (7)

- Elongation display via a dial gauge (8)

- Gripping heads (9) with sample (10)

Machine Base

The rigid machine base made of cast iron forms the

foundation and ensures stability of the test unit in

connection with 4 rubber feet. The machine base

supports the hydraulics and the frame. (Figure 7)

Support

The posts (1) and cross-head (2) form fixed support of

the test unit. The various fixed sample receptacles are

fastened to the cross-head. The mobile load frame is

also mounted on its low-friction linear ball bearings.

(Figure 8)

Load Frame

The load frame consists of the upper (1) and lower

cross-member (2) and the guide rod (3). The load frame

transmits the test force from the hydraulic main cylinder

to the relevant sample. The load frame is slide-mounted

in the cross-head of the support. Tensile samples are

clamped between the upper cross-member and the

cross-head, whilst compressive samples are clamped

between the lower cross-member and the cross-head.

(Figure 9)

Hydraulic System

The test force is generated by hydraulic means. A piston

in the master cylinder (2) actuated via the hand wheel

(1) and the threaded spindle creates a hydrostatic

pressure which induces the test force in the main

cylinder (3). The hydraulic transmission ratio is 2.77:1,

whilst the mechanical transmission ratio hand

wheel/spindle is 503:1. Excluding friction losses, this

would correspond to a manual force of 1 N per 1.3 kN

test force. The full stroke of the main cylinder of 45 mm

requires 83 revolutions of the hand wheel. (Figure 10)

Force Display & Elongation Measurement

The force measuring device operates according to the

manometer principle. It measures the hydrostatic

pressure in the hydraulic system. The large display with

a diameter of 160 mm facilitates precise reading. A

maximum pointer stores the maximum force. The

elongation is measured via an adjustable mounted dial

gauge. The dial gauge indicates the relative

displacement between the upper cross-member and the

cross-head.

(Figure 11)

Gripping Heads

The gripping heads are designed for tensile samples

with an M10 threaded head. In addition, flat

compression pads can easily be inserted in the cross-

head and cross-member and are held by nut. (Figure 12)

Tensile Sample

Round samples with an M10 threaded head in

accordance with DIN 50125 made of aluminium,

copper, brass and steel are supplied with the machine.

Tensile sample B6 x 30 DIN 50125. This is a short

proportional test bar with a measuring length of 30 mm

and a diameter of 6 mm. Specimens used are Copper and

brass.

PROCEDURE

1. Device were set up as same as the figure shown.

- The hand wheel on the master cylinder was fully untwisted.

- Gripping head were screwed down at the bottom with short bolt and with pressure

pad.

2. Required tensile sample were inserted.

- Test length of the sample was measured and noted down.

- The sample then screwed down at the lower gripping head. Then the sample is

screwed into the upper gripping head by rotating the gripping head.

3. Dial gauge was adjusted.

- On the support bar, dial gauge were pushed upwards until the tracer pin touched

the drive.

- The force display was set to zero by rotating scale on the dial gauge and

maximum pointer.

4. By rotating the hand wheel, force was applied slowly and constantly over a time

interval of 5-10 minutes.

5. The force value for every 0.1mm extension for the first 1mm extension were

recorded.

6. The force value for every 0.2mm extension after the first 1mm extension were

recorded.

7. The sample was monitored and noted when constriction starts. The force tend to

decrease when constriction begins.

8. The sample was fracture with load bang.

9. The sample removed from the gripping heads.

10. The hand wheel on the master cylinder was untwisted fully.

11. The experiment then repeated with another sample.

DATA & OBSERVATIONS

Brass

Diameter : 6.0 mm

Lo : 40.0 mm

LU : 46.0mm

Elongation, ΔL=LU-LO (mm) Force (kN)

0.1 1.00

0.2 3.25

0.3 5.50

0.4 8.00

0.5 10.00

0.6 11.50

0.7 12.50

0.8 13.00

0.9 13.25

1.0 13.50

1.2 13.50

1.4 13.50

1.6 13.50

1.8 14.00

2.0 14.20

2.2 14.25

2.4 14.25

2.6 14.50

2.8 14.50

3.0 14.50

3.2 14.50

3.4 14.50

3.6 14.50

3.8 14.75

4.0 14.75

4.2 14.75

4.4 14.75

4.6 14.75

4.8 14.75

5.0 14.75

5.2 14.75

5.4 14.75

5.6 14.50

5.8 14.50

6.0 14.00

6.2 Fractured

Table 1 : Elongations and corresponding forces for Brass

Copper

Diameter : 6.00 mm

Lo : 40.0 mm

LU : 46.0 mm

Elongation, ΔL=LU-LO (mm) Force (kN)

0.1 2.50

0.2 4.00

0.3 6.50

0.4 8.50

0.5 9.00

0.6 9.00

0.7 9.00

0.8 9.00

0.9 9.00

1.0 9.00

1.2 9.00

1.4 9.00

1.6 9.00

1.8 9.00

2.0 9.00

2.2 9.00

2.4 9.00

2.6 9.00

2.8 9.00

3.0 9.00

3.2 9.00

3.4 9.00

3.6 8.75

3.8 8.75

4.0 8.50

4.2 8.45

4.4 8.20

4.6 8.00

4.8 7.75

5.0 7.50

5.2 7.25

5.4 6.90

5.6 6.50

5.8 6.00

6.0 5.50

6.2 Fractured

Table 2 : Elongations and corresponding forces for Copper

ANALYSIS & RESULTS

Brass

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 350

2

4

6

8

10

12

14

16

Force vs Elongation of Brass

ELONGATION(mm)

FORC

E(kN

)

Graph 1: Force vs Elongation of Brass

Stress, σ (kPa) Strain, ε (m/m)

35367.77 0.0025

114945.24 0.005

194522.71 0.0075

282942.12 0.0100

353677.65 0.0125

406729.30 0.015

442097.06 0.0175

459780.95 0.02

468622.89 0.0225

477464.83 0.025

477464.83 0.03

477464.83 0.035

477464.83 0.040

495148.71 0.045

502222.26 0.050

503832.59 0.055

503990.65 0.060

512832.59 0.065

512832.59 0.070

512832.59 0.075

512832.59 0.080

512832.59 0.085

512832.59 0.090

521674.54 0.095

521674.54 0.100

521674.54 0.105

521674.54 0.110

521674.54 0.115

521674.54 0.120

521674.54 0.125

521674.54 0.130

521674.54 0.135

512832.59 0.140

512832.59 0.145

495148.71 0.150

Table 3: Table of stress and strain for Brass

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 350

100000

200000

300000

400000

500000

600000

Stress vs Strain

Strain

Stre

ss

Graph 2: Stress vs Strain of Brass

Copper

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 350

1

2

3

4

5

6

7

8

9

10

Force vs Elongation

Elongation

Forc

e

Graph 3 : Force vs Elongation of Copper

Stress, σ (kPa) Strain, ε (m/m)

88419.41 0.0025

141471.06 0.005

229890.47 0.0075

300626.00 0.01

318309.89 0.0125

318309.89 0.015

318309.89 0.0175

318309.89 0.020

318309.89 0.022

318309.89 0.025

318309.89 0.030

318309.89 0.035

318309.89 0.040

318309.89 0.045

318309.89 0.050

318309.89 0.055

318309.89 0.060

318309.89 0.065

318309.89 0.070

318309.89 0.075

318309.89 0.080

318309.89 0.085

309467.94 0.090

309467.94 0.095

300626.00 0.100

298857.62 0.105

290015.67 0.110

282942.12 0.115

274100.18 0.120

265258.24 0.125

256416.30 0.130

244037.58 0.135

229890.47 0.140

212206.59 0.145

194522.71 0.150

Table 4: Table of stress and strain for Copper

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 350

50000

100000

150000

200000

250000

300000

350000

Stress vs Strain

Strain

Stre

ss

Graph 4 : Stress vs Strain of Copper

Sample calculation for Copper and Brass :

[Taken from first reading for Brass (Table 3)]

To calculate the engineering stress, σ:-

σ= FA0 , where

A0=πd2

4

Therefore,σ=4 F

πd2

At ΔL= 0.1 mm, F=1.00 kN

σ=4 F

πd2= 4×1

π×0 .00652=35367 .77kPa

To calculate the engineering strain, ε:-

ε=LU −LO

LO

= ΔLLO

=0 . 1 mm40 mm

=0 . 0025

To calculate Modulus of Elastisity, E :-

E=σε = 35367.77kPa

0.0025 = 14147.11MPa

DISCUSSION

There are many ways to improve mechanical properties for concrete to transmit better tensile force such as adding metal reinforcing bars. This makes the concrete stronger so the structure doesn’t fall. Polypropylene fiber also can improve durability and cracking level of concreate. Glass fiber also helps transmit better tensile force. Another example is adding plastic fiber it is cheaper alternative to transmit tensile force.

CONCLUSION

In conclusion, the concept of tensile test is now very understood after the experiment was conducted.

The stress strain relationship of the two materials was interesting as shown in the graph, and from the data that we collected from the experiment we were able to determine the value of the elongation of fracture, the tensile strength, yield strength and modulus of elasticity for both materials and according to the results, Copper seems to be more ductile than brass.

I think tensile test is a very important test in manufacturing process, because it helps the manufacturer to choose the suitable material for a specific design, and this lap helped us to have a clear understanding of strain-stress and ductile concepts.

REFERENCES

1. Laboratory Manual Mechanics of Materials Lab 2012.

2. Mechanics of Materials Global Edition.2012.6thedition.Singapore.McGraw-Hill

3. Tension of a concrete

http://wiki.answers.com/Q/Why_is_concrete_weak_in_tension#slide=5

Experiment 1 - Devdev

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