University of Ontario Institute of Technology ENGR 2220A Quiz 5 1)Ceramics are: Hard and very tough Hard but not tough Brittle and soft malleable and strong   Important properties of Metals are: Strong and brittle Strong and ductile Hard and non-deformable Stiff and non-deformable   At temperatures below glass transition temperature, the polymers are Quite stiff and tough Quite stiff and brittle Exhibit large visco-elasticity Rubbery and ductile   In ceramics, point defects occur in pairs so that mass conservation is maintained charge neutrality is maintained number of positive and negative ions are not in balance   During three point loading test, the maximum tensile strength occurs at the point of maximum deflection and the outer most concave layer the point of maximum deflection and the outer most convex layer the point of maximum deflection and the central layer   Most imperfections in solid crystal structure of metals originate: When it is subjected to stress and strain During the machining process When the material is heated When the molten metals solidify   Vacancy diffusion is applicable to Substitutional impur ity atoms Covalently bonded molecules in atomic lattices Atoms present in the interstitial spaces Liquid molecules   The crystalline materials deform at a much smaller force than theoretical force required to deform crystals due to the presence of: Twin boundaries Vacancies   Impur ities Dislocations   Case hardening is an example of Brownian diffusion Interstitial diffusion Substitutional diffusion Inter-molecular diffusion   Which of the following is NOT a strengthening mechanism? Increasing the number of vacancies Formation of solid solutions Grain size reduction Inclusion of precipitates   If a material is subjected to torsion; it experiences sheer stresses it experiences tensile stresses it experiences compressive stresses   True stress on a body deformed by the application of a force is defined as: Force divided by the actual cross sectional area Force multiplied by the actual cross sectional area Force multiplied by the original cross sectional area Force divided by the original cross sectional area   Eutectic transition occurs when A solid phase changes into two solid phases A liquid phase changes into two solid phases A solid phase changes into two liquid phases Two solid phases change into another solid phase   When a HypoEutectic alloy is cooled from a liquid state to a solid state, the microstructure formed consists of Primary alpha solid granules dispersed in a eutectic microstructure Eutectic granules dispersed in a primary alpha solid microstructure Primary beta solid granules dispersed in a eutectic microstructure only an eutectic matrix   The most commonly used material for fibers used for reinforcing composites is Boron Glass Kevlar SiC and Al2O3   How are continuous fibers typically oriented in fibrous composites?   Aligned Partially oriented Randomly oriented All of the above   A big disadvantage of composites is that they are Brittle Slow and expensive to manufacture Unable to withstand high impacts Have lower strength compared to metals   For an aligned fibrous composite, when a stress is applied perpendicular to the fibers, what is the reinforcement efficiency? a

University of Ontario Institute of Technology

ENGR 2220A

Quiz 5

1)Ceramics are:

1. Hard and very tough
2. Hard but not tough
3. Brittle and soft
4. malleable and strong

2. Important properties of Metals are:

1. Strong and brittle
2. Strong and ductile
3. Hard and non-deformable
4. Stiff and non-deformable

3. At temperatures below glass transition temperature, the polymers are

1. Quite stiff and tough
2. Quite stiff and brittle
3. Exhibit large visco-elasticity
4. Rubbery and ductile

4. In ceramics, point defects occur in pairs so that

1. mass conservation is maintained
2. charge neutrality is maintained
3. number of positive and negative ions are not in balance

5. During three point loading test, the maximum tensile strength occurs at

1. the point of maximum deflection and the outer most concave layer
2. the point of maximum deflection and the outer most convex layer
3. the point of maximum deflection and the central layer

6. Most imperfections in solid crystal structure of metals originate:

1. When it is subjected to stress and strain
2. During the machining process
3. When the material is heated
4. When the molten metals solidify

7. Vacancy diffusion is applicable to

1. Substitutional impur ity atoms
2. Covalently bonded molecules in atomic lattices
3. Atoms present in the interstitial spaces
4. Liquid molecules

8. The crystalline materials deform at a much smaller force than theoretical force required to deform crystals due to the presence of:

1. Twin boundaries
2. Vacancies

3. Impur ities
4. Dislocations

9. Case hardening is an example of

1. Brownian diffusion
2. Interstitial diffusion
3. Substitutional diffusion
4. Inter-molecular diffusion

10. Which of the following is NOT a strengthening mechanism?

1. Increasing the number of vacancies
2. Formation of solid solutions
3. Grain size reduction
4. Inclusion of precipitates

11. If a material is subjected to torsion;

1. it experiences sheer stresses
2. it experiences tensile stresses
3. it experiences compressive stresses

12. True stress on a body deformed by the application of a force is defined as:

1. Force divided by the actual cross sectional area
2. Force multiplied by the actual cross sectional area
3. Force multiplied by the original cross sectional area
4. Force divided by the original cross sectional area

13. Eutectic transition occurs when

1. A solid phase changes into two solid phases
2. A liquid phase changes into two solid phases
3. A solid phase changes into two liquid phases
4. Two solid phases change into another solid phase

14. When a HypoEutectic alloy is cooled from a liquid state to a solid state, the microstructure formed consists of

1. Primary alpha solid granules dispersed in a eutectic microstructure
2. Eutectic granules dispersed in a primary alpha solid microstructure
3. Primary beta solid granules dispersed in a eutectic microstructure
4. only an eutectic matrix

15. The most commonly used material for fibers used for reinforcing composites is

1. Boron
2. Glass
3. Kevlar
4. SiC and Al₂O₃

16. How are continuous fibers typically oriented in fibrous composites?

1. Aligned
2. Partially oriented
3. Randomly oriented
4. All of the above

17. A big disadvantage of composites is that they are

1. Brittle
2. Slow and expensive to manufacture
3. Unable to withstand high impacts
4. Have lower strength compared to metals

18. For an aligned fibrous composite, when a stress is applied perpendicular to the fibers, what is the reinforcement efficiency?

a. 0

b. 1/5

c. 3/8

d. ¾

e. 1

19. For a composite material, the matrix phase is normally

1. more ductile than the dispersed phase
2. less ductile than the dispersed phase
3. as ductile as the dispersed phase

20. In composites, some times a third ingredient is used to achieve bonding of primary and secondary phases. This ingredient is called:

1. Epoxy
2. Coupling agent
3. Super glue
4. Plasticizer

21. Cermets are composites in which

1. Metals are held together in a ceramic matrix
2. Ceramics are held together in a polymeric matrix
3. ceramics are held together in a metal matrix
4. polymers are held together in a ceramic matrix

22. Ceramics exhibit poor fracture resistance due to

1. The presence of small and omnipresent flaws or cracks
2. The presence of numerous dislocations
3. The inability of dislocations to move through ceramic structure
4. High impurity content.

23. Binary isomorphous phase diagrams depict

1. The phases of multi-component systems with changing pressures and temperatures
2. The phases of two component system which have unlimited solubility in each other

3. The phases of two component system which have limited solubility in each other
4. The phases of multi component system which have limited solubility in each other

24. Binary isomorphous phase diagrams depict

1. The phase changes which occur instantaneously as temperature changes
2. The phase changes which occur instantaneously as pressure changes
3. The phase changes which occur randomly as temperature changes
4. The phase changes which occur as temperature changes very slowly