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Material science

34 Questions - Developed by: - Developed on: 2015-08-12 - 6,038 taken - 3 people like it

1

Diffusion involves:

A mechanism which causes thermal expansion of the material during heating.
Migration of species to reduce differences in concentration.
A mechanism which causes differences in concentration.
Crack growth during fatigue.

2

When Prince Ruperts drops fracture:

The drops bounce back because these droplets do not break.
The fracture starts from the thickest section because it is brittle.
The fracture only occurs in the thinnest section.
They shatter into many pieces because of a lot of stored energy.

3

The glass used in mobile phones is treated:

With a special coating to allow the electric signals to pass through.
With special amorphous layers in order to reduce the reflectivity of the screen.
In a molten salt bath at high temperature to put the surfaces in compression.
By gluing a polymer coating on one side to avoid scratching.

4

Which statement is correct?

Impact toughness of ceramics is high.
Ceramics are strongly bonded.
Ceramics are normally very ductile.
Mechanical forming is the main processing method for ceramics.

5

Tempering:

Is a heat treatment process to improve ductility.
Is a process used to assemble composites.
Is a heat treatment process to make polymers stronger.
Is a heat treatment process to reduce toughness.

6

Aluminium cans are produced by:

Extrusion
Deep drawing
Forging
Casting

7

If a material is deformed plastically, the yield stress will:

Decrease
None of the above, the material will break
Not change
Increase

8

The ability of a material to absorb energy in the plastic range is called:

Creep
Fatigue strength
Resilience
Toughness

9

Most commercial glasses consist of:

Soda
Lime
All
Silica

10

Elastic deformation:

Does not occur in ceramics because they are brittle.
Occurs by movement of dislocations.
Increases with decreasing yield strength.
Is determined by the stiffness of the bonds.

11

Which statement is correct?

Ductility is the ability to deform plastically.
Upon impact, the materials toughness has to be overcome before plastic deformation and fracture begins.
Both ductility and strength determine the fatigue strength of a material.
Toughness is a measure of the load a material can withstand.

12

The glass transition temperature is the temperature where:

Glass changes from solid to liquid and is therefore critical for the processing of glassware.
A polymer is changed from a rubbery to a rigid state.
Some eyeglasses can change from dark to normal.
The refractory index of glass is changed.

13

The wheels for Koenigsegg cars are made from:

CFRP (carbon-fiber)
Steel
Mg alloys
Al alloys

14

Fracture toughness determines:

The critical stress when fracture will occur.
The combination of critical stress and crack size.
The critical crack size when fracture will occur.
None of the above.

15

Brittle fracture is more dangerous than ductile fracture because:

No warning sign
No need for extra stress during crack propagation
Crack propagates at very high speeds
All

16

What is correct about atomic bondings?

Atoms with covalent bonds share electrons.
At equilibrium the potential energy of the bond is zero and the net force is equal to the stiffness of the bond.
A fully ionic character of a bond (100% ionic) can only develop between two metals.
Bonds with strong ionic character develops between atoms with hogh electronegativity.

17

The following influences deterioration of polymers:

Radiation
All
Temperature
Weather

18

Creep is:

Deformation at constant temperature and constant deformation rate.
Deformation at increasing deformation rate at low temperature.
Deformation at elevated temperature at increasing load.
Deformation at elevated temperatures at constant load.

19

Magnesium is currently receiving enormous interest for development and use in automotive components. One challenge with magnesium is the limitation in creep strength for "under bonnet" applications.
This is because:

Magnesium often contains internal cracks and flaws above a critical size, reducing the stress required for failure.
Magnesium has a hexagonal crystal structure which is unstable at higher temperature.
Magnesium undergoes significant time-dependent deformation when subjected to a constant load at moderate temperatures.
Magnesium burns readily in air/oxygen.

20

Which statement is correct?

Strength is increased when the dislocation density is reduced.
Strength increased when the distance between particles is reduced.
Particles do not affect the strength of a material.
Pure metals are always stronger than alloys.

21

According to Hooke's law, if you hang by a tree branch and note how much it bends, then hanging with twice the weight produces:

The same bend if the branch doesn't break
4 times the bend
Twice the bend
Half the bend

22

A crystal point defect known as a substitutional occurs when:

Another sort of atom occupies a position that is normally occupied by an atom of a given crystal structure.
Two atoms are coincident.
The atom occupies a position in the crystal structure not normally occupies by an atom.
The atom leaves vacant the position it would normally occupy.

23

The structure and characteristics of a polymer is determined by:

All of these together
The shape of the molecules
The arrangement of the molecules
Molecular weight

24

When you bend a tree branch by hanging on its end, the top side of the branch is under:

Tension
Compression
Both in tension and compression
Neither tension or compression

25

Tungsten is stiffer than Copper and Copper is stiffer than Lead. (Tungsten has a higher Young's modulus than Copper and Copper has a higher Young's modulus than Lead).
What statement is correct?

Copper has a higher melting point than Tungsten.
Tungsten has a lower thermal expansion than Copper.
Tungsten, Copper and Lead are all metals and therefore have the same thermal expansion.
Lead has a lower thermal expansion than Copper.

26

The crystal plane in the figure has Miller indices:

(221)
(100)
(111)
(110)

27

Toilets are made by:

Machining
Glass blowing
Slip casting
3D printing

28

Mechanical forming operations are often conducted at elevated temperature because:

The products that are formed at higher temperature are stronger than those formed at low temperature.
Alloys fracture if they are formed at room temperature,
Metals are softer at higher temperatures.
It prevents friction between the metal and the tool during forming by increasing the temperature in the metal and the tool.

29

The tensile strength is the point where:

None of the above
Dislocations start to move
The material fractures
Necking begins

30

Ductility of a metal can be increased by:

Heat treatment
Adding ceramic fibres (ie. making a fibre-reinforced composite)
None of the above
Increasing the amount of work hardening

31

If the surface crack causing fracture in a brittle material is made twice as deep, the fracture strength will:

Decrease by a factor of 2
Decrease by a factor of √2
Decrease by a factor of 4
Not change

32

Ceramics are:

Often manufactured into components by extrusion
Covalently bonded
Generally brittle because of limited slip systems for dislocation motion
Always non-crystalline compounds between non-metallic and metallic elements.

33

The common way to protect nails from corrosion is:

Do nothing - aluminium doesn't corrode
Paint it
Anodise it
Galvanise it

34

In which of the following applications is fatigue a critical design parameter?

A plane
A lap-top computer
A cup
A liquid nitrogen containment vessel

Comments (1)

sb (08353)

2211 days ago

Good experience by test .. My knowledge to exam to protect . have an a idea .. 😃

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