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Material science

34 Questions - Developed by: Gustav S - Developed on: 2015-08-12 - 5,497 taken - 3 people like it

1

Diffusion involves:

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

2

When Prince Ruperts drops fracture:

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

3

The glass used in mobile phones is treated:

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

4

Which statement is correct?

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

5

Tempering:

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

6

Aluminium cans are produced by:

Forging
Deep drawing
Extrusion
Casting

7

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

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

8

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

Toughness
Creep
Resilience
Fatigue strength

9

Most commercial glasses consist of:

Soda
All
Silica
Lime

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.
Both ductility and strength determine the fatigue strength of a material.
Upon impact, the materials toughness has to be overcome before plastic deformation and fracture begins.
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.
Some eyeglasses can change from dark to normal.
A polymer is changed from a rubbery to a rigid state.
The refractory index of glass is changed.

13

The wheels for Koenigsegg cars are made from:

Steel
CFRP (carbon-fiber)
Mg alloys
Al alloys

14

Fracture toughness determines:

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

15

Brittle fracture is more dangerous than ductile fracture because:

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

16

What is correct about atomic bondings?

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.
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.

17

The following influences deterioration of polymers:

Weather
Radiation
Temperature
All

18

Creep is:

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

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 burns readily in air/oxygen.
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.

20

Which statement is correct?

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

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
Half the bend
Twice the bend
4 times the bend

22

A crystal point defect known as a substitutional occurs when:

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

23

The structure and characteristics of a polymer is determined by:

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

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?

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

26

The crystal plane in the figure has Miller indices:

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

27

Toilets are made by:

Machining
Slip casting
3D printing
Glass blowing

28

Mechanical forming operations are often conducted at elevated temperature because:

Metals are softer at higher temperatures.
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,
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:

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

30

Ductility of a metal can be increased by:

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

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

32

Ceramics are:

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

33

The common way to protect nails from corrosion is:

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

34

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

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

Comments (1)

sb (08353)

1163 days ago

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

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