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Material science

34 Questions - Developed by: Gustav S - Developed on: 2015-08-12 - 5,741 taken - 3 people like it

1

Diffusion involves:

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

2

When Prince Ruperts drops fracture:

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

3

The glass used in mobile phones is treated:

By gluing a polymer coating on one side to avoid scratching.
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.

4

Which statement is correct?

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

5

Tempering:

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

6

Aluminium cans are produced by:

Extrusion
Casting
Deep drawing
Forging

7

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

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

8

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

Fatigue strength
Creep
Toughness
Resilience

9

Most commercial glasses consist of:

All
Lime
Silica
Soda

10

Elastic deformation:

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

11

Which statement is correct?

Ductility is the ability to deform plastically.
Toughness is a measure of the load a material can withstand.
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.

12

The glass transition temperature is the temperature where:

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

13

The wheels for Koenigsegg cars are made from:

Steel
Mg alloys
Al alloys
CFRP (carbon-fiber)

14

Fracture toughness determines:

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

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?

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

17

The following influences deterioration of polymers:

All
Temperature
Radiation
Weather

18

Creep is:

Deformation at elevated temperature at increasing load.
Deformation at increasing deformation rate at low temperature.
Deformation at constant temperature and constant deformation rate.
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 burns readily in air/oxygen.
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 often contains internal cracks and flaws above a critical size, reducing the stress required for failure.

20

Which statement is correct?

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

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

22

A crystal point defect known as a substitutional occurs when:

Two atoms are coincident.
Another sort of atom occupies a position that is normally occupied by an atom of a given crystal structure.
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:

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

24

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

Tension
Neither tension or compression
Both in tension and compression
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.
Lead has a lower thermal expansion than Copper.
Tungsten has a lower thermal expansion than Copper.
Tungsten, Copper and Lead are all metals and therefore have the same thermal expansion.

26

The crystal plane in the figure has Miller indices:

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

27

Toilets are made by:

Machining
Slip casting
3D printing
Glass blowing

28

Mechanical forming operations are often conducted at elevated temperature because:

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

29

The tensile strength is the point where:

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

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

32

Ceramics are:

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

33

The common way to protect nails from corrosion is:

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

34

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

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

Comments (1)

sb (08353)

1252 days ago

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

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