Materials also discusses the defects that distort the material

                 Materials Science And Engineering

 

 

Mohammed
Oudah Al-Harbi

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Mechanical Engineering , College of Engineering
, Majma’ah university, Saudi Arabia

[email protected]

19/10/2017

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Abstract: This
report discusses the structure, classification and the properties of the
materials also discusses the defects that distort the material and some tests
for the materials , through which the proper application of the material is
determined .The aim of this study is to design new type of material based
on  the properties and the structure of
the materials.

 

 

Key words: Materials  , Smart materials , Tensile test .

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Indexes

Table of Contents
Abstract. 2
1.Introduction           3
2.Structure of
materials         4
2.1  Atomic structure. 5
2.2  Microstructure. 5
2.3  Macrostructure. 5
3.Classification of
materials         6
4.Materials defects         7
5.Mechanical properties
of materials            8
5.1   Tensile test                  9
5.2   The process. 9
6.Recommendation         10
7.Conclusion            10
References. 11
 

 

 

Table of Figures

Figure 1. 7

Figure 2. 8

Figure 3. 10

 

 

Table of Tables

Table 1. 5

 

 

Table of Equations

 Equation 1. 9

Equation 2. 10

 

 

 

 

1.     
Introduction

Material
engineering is a subject that’s dedicated to explain the relation between
material science and its application, through Engineering point of view. Material
science, involve studying the correlation between material structure and
material property. ??1   

The purpose of
studying material engineering is to design and engineer a new type of material
based on the known structure and property .

The first educational institution that recognized the drive of
discovery and innovation in material engineering as a mean to serve social
needs was the Department of material science and engineering (DMSE) at MIT (Massachusetts
Institute of Technology). The overlook of the of social needs consist of
construction , transportation , industrialization expansion. The development of
materials through (DMSE) was recognized in the second world war, The (DMSE) assisted
in military manufacturing and development of new material.? ??5     

 

 

 

 

 

 

 

 

 

 

 

 

2.      Structure of
materials

As it is known
all matters are made of atoms , there are about 100 kinds of atoms in the
universe according to the periodic table . The properties of materials depends
on the atoms and atomic bond. Therefore, we can generally determine the
different behaviors of materials.   

The structure
of materials is classified into three types based on size:

1 – atomic structure

2 –
microstructure

3 –
macrostructure??6   

 

2.1  Atomic structure

The discovery of the inner structure of the atom is considered as a
one of the most important scientific discoveries in this century.

 All atoms are made up of
three subatomic particles : Protons , neutron and electrons.

These parts have the properties shown in Table1 :

Table 1           

Particle

Charge

Mass (g)

Mass (amu)

Proton

+1

1.6727 x 10-24 g

1.007316

Neutron

0

1.6750 x 10-24 g

1.008701

Electron

-1

9.110 x 10-28 g

0.000549

 

In Table1 the unit was used for atomic mass is (amu).It is more
appropriate than gram for describing masses of atoms . ??6   

 

 

 

 

 

 

 

 

 

2.2  Microstructure

 Microstructure
defined as the surface structure of materials such as thin foils which can be
detected after zooming 25 times at a microscopic level.

The microstructure of the material can affect the mechanical and
physical properties such as strength , ductility , hardness and corrosion
resistance. ??8   

 

2.3  Macrostructure

Macrostructure defined as The overall structure of the material and
can be seen by the naked eye. Materials behaves differently based on mass and
density that behavior can be determined based on the atomic bonding , when we
examine a material in solid state  at a
microscopic level we can notes visually the higher number of atoms in
comparison with other material with low density in liquid state . based on that
observation we can tell the differences in nature between solid and liquid.
Furthermore, at macro level liquid behaves differently than solid , for example
when you pour water out of a cup you can see the continuous flow of water. ??9   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.     
Classification of materials

Materials has been used since the dawn of human existence for
different needs.                                                  
humans life demands has been the driving force for discovering new types
of materials based on the demands such as using metals for heavy duties
machines. furthermore, humans found ways to classify materials depending on the
use and needs of the materials

The most common classification for materials is  based on atomic bonding  and atomic forces, thus,  divided the materials into four categorize:

 1 – Metals

2 – Polymers

3 – Ceramics

4 – Composites ??7   

In addition , some new materials have been developed by changing
the crystalline structure of the material. The change yield a new material with
new  properties to suit a wanted
application.  we classify the new group
as smart material, the smart material is tailored from the four categories of
the materials.
??2    

 

Figure 1

 

Figure 1 shows the classification of material

 

 

4.      Materials
defects

 When discussing the defects of the materials we have to understand
the atomic structure of an atom. Crystalline material have atoms arrangements
over large atomic distance. The crystalline structure is defined as the
arrangements of atoms. The lattice of the crystalline structure , is the 3d
arrangements of atoms. The defects of the material can occur over the atomic
arrangement of the material, defects can be categorized based on impurity and
vacancy. ??1 ??4     

A defects can occur in into a hole between two lattice site which
is known as interstitial impurity. The second impurity  when a particle vacant other particle by
taking its spot. Dislocation are hole that is not large enough for the particle
vacancy. ??3   

 

                                                                             
Figure 2

                                                                       

Figure 2 showing point defects, vacancy, interstitial impurity,
substitutional impurities, and dislocations

 

 

 

 

 

 

 

 

5.      Mechanical
properties of materials

The mechanical properties of materials are those which affects  the strength and ability of materials.

Some of mechanical properties

Strength , Toughness , Hardness , Malleability , Brittleness ,
Ductility , Creep

There are some tests we have to do for the material to know the
mechanical properties for it and also we have to know the degree for the
mechanical property that we are testing the material for . The most
important  mechanical properties are
strength and ductility and we can test these properties by tensile test. ??3   

5.1   
 Tensile test

Is the test in which the sample is subjected to a controlled
tension force until it reaches failure. Depending on the result, the test can
determine the extent of the material’s bearing to the forces effected on it in
the application that we test the material for. ??3    

 

5.2   The process

The test is done by placing the sample on the testing machine and
slowly extend by tensile force we apply on it until it reaches the failure .
during the process we calculate the elongation and from it we can calculate the
strain by Equation 1

                              
Equation 1

 

 

 

 

 

 

The force which we apply on the sample is used to find the stress
by equation 2

         Equation 2                 ??3
  

specimen

 
Figure 4

 

extensometer

                          Figure 3

 

 

 

 

 

 

 

 

 

 

Figure 3 shows the typical tensile test machine         
 

 

 

 

 

 

 

6.      Recommendation

To choose the best material for an application we have to know the
atomic structure and the defects  that
can occur in the material , also we have to do some tests on the material to
know its limitation such as tensile testing.

For the use of smart materials , we must know their basic
classification and the changes which happened to them to know the original and
new properties of the material and this will help to know whether the material
suitable for the application that we want or not .

7.      Conclusion

Material is divided into different categorize based on their atomic
bonding. From that relation  determine
the types of the materials based on the atomic structure.

Mechanical testing can stress the materials to its limitation to
define the mechanical properties of the materials.

 By understanding the
molecular structure of materials,  the
defect at a microstructure level can be used  to engineer a new type of material  that compensate the flaws such as smart
material.

Study of nanomaterials will be the future work .   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

References

 

Books:

1    
William
Callister-David Rethwisch  , Fundamentals
of materials science and engineering an integrated approach , Wiley , 2016.

2    
M.V
Gandhi-B.S Thompson , Smart materials and structures  , Chapman and Hall ,1992 .

3    
R.
Smallman , A. Ngan, Physical metallurgy and advanced materials , Elsevier
Science , 2011.

4    
John
Hook , Henry Hal , Solid state physics , John Wiley & Sons  , 2010 .

 

 

Websites:

5    
https://dmse.mit.edu/about/history.

6    
https://cbc-wb01x.chemistry.ohio-state.edu/~woodward/ch121/ch2_atoms.htm .

7    
https://www.nde-ed.org/EducationResources/CommunityCollege/Materials/Introduction/classifications.htm .

8    
https://www.corrosionpedia.com/definition/777/microstructure .

9    
http://www.memidex.com/macrostructure.