Micrographic Samples Lab

8/10/2019 Micrographic Samples Lab

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MANUKAU INSTITUTE OF TECHNOLOGY

FACULTY OF ENGINEERING AND TRADES

NEW ZEALAND DIPLOMA IN ENGINEERING &

BACHELOR OF ENGINEERING TECHNOLOGY

Student Name:

Experiment Title: FAST FRACTURE LAB

Section

Failure to attend will result in a Zero mark.

Any evidence of copying will result in a Zero mark

Weighting Scored 1- 5 Mark

Objective and Relevant theory 3

Assumptions 2

Method of data collection 2

Raw data 2

Calculations/ observations 3

Use of graphs 2Discussion 4

Conclusion 2

Marks will be deducted for;

Poor use of grammar, spelling, punctuation.

Incorrect or missing units of measure.

Unsupported arguments or conclusions.

Unstated assumptions in either data or

calculations.

Failure to present the original data collected.

Up to 10%

off

Final mark, % (total weighted mark)

Total marks /100



Micrographic samples Lab

Aim: Aim of this experiment is to understand the concept of fast fracture by calculating the

critical strain energy release rate for three different types of adhesive tapes.

Theory: A fracture is the separation of an object or material into two or more pieces under the

action of stress. Fast fracture is defined as phenomena in which a flaw (such as a crack) in a

material expands quickly, and leads to failure of the material .

GC of the material is defined as the energy absorbed in making a unit area of crack. It can also

be called toughness or critical strain energy release rate. Its units are (joule per metersquare). In this experiment GC is the measure of strength of adhesives. It is measured byhanging the weight on partly peeled length while supporting the roll so the it can rotate freely.Increasing the load causes rapid peeling.

From energy formula

For fast fracture

Mathematically

Where GC = critical strain energy release rate in

M = Load applied on the tape in kg

g = Acceleration due to gravity in

t = Thickness in meter.

Engineering materials 1 by M.F.

Ashby and D. R.H. Jones, Page 13.2



Description of Apparatus:

1. Stand

2. Three types of adhesive tapes

3. Clamps

4. Weights

5. Weigh measuring machine.

Stand Brown tape on standMIT Lab Specimen



Plastic Tape on stand Masking tape on stand

Assumptions:

1. Weight of clamp was neglected.

2. Tape was peeled at uniform speed.

3. The weight machine was working fine.

4. The friction between the cardboard tube on which the tape was wrapped and steel rod

was neglected.

5. The experiment was performed at standard atmospheric conditions.

MIT Lab Specimen



Method of data collected:

1. First of all the width of the tape was measured 2. The tape was suspended on the stand. 3. Free end of the tape was peeled and rolled so that the clamp can be attached to it.

4. Weight hanger was put at the end of the clamp. 5. Weights were applied on the hanger and were kept on increasing until the tape starts to

peel rapidly. 6. The total weight of the hanger and applied weights was measured using digital scale.

7. Critical energy release rate was measured using formula

8. The experiment was repeated two more times to find critical energy release rate of two

more tapes.

Raw data:

No Type of tape Width of tapem

Load appliedKg

1 Brown tape 0.048 0.0822 Plastic tape 0.037 1.582

3 Masking tape 0.024 0.206



Results:

No Type of tape Width of tapem

Load appliedKg

GC

1 Brown tape 0.048 0.082 16.82

2 Plastic tape 0.037 1.582 418.913 Masking tape 0.024 0.206 84.20

Chart:

Discussion:

From this experiment different strain energy rate was calculated for different tapes. Each tape

has its own characteristics and used for specific purposes. Different strain energy rate was

obtained because of various reasons

1. Relative strengths of adhesive forces between the atoms of tape and adhesive used

resulted in different values of GC.Since in plastic tape strong adhesive forces required a

lot of load to unwrap the tape.

2. The material of the tape also affects its critical strain energy rate since different materials

like plastic and paper have different microstructures and behave differently in tension or

compression.

16.82

418.91

84.2

0

50

100

150

200

250

300

350

400

450

Brown Tape Plastic tape Masking tape

E n e r g y

i n

Tape

Critical Energy Release Rate



Conclusion:

From the above experiment we can conclude that different materials react differently in fast

fracture test and it is the microstructure and the strength of adhesive used which affects Gc.

Since plastic tape and brown tape both appears to be made up of plastic but they have huge

difference in values of Gc due to different adhesive used.

Refrences:

1. Engineering materials 1: an introduction to properties, applications and design by M.F.

Ashby and D. R.H. Jones 2. Materials for engineers and technicians: Fifth edition by R. A. Higgins 3. http://en.wikipedia.org/wiki/Adhesive_tape.

4. http://en.wikipedia.org/wiki/Strain_energy_release_rate

Micrographic Samples Lab

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