MEC1201: Different Environmental Temperatures, Impact Testing - Engineering Assignment Help

Assignment Task:

Task:

Section A (100 Marks) (Attempt ALL questions in this section) Chose the most correct answer of the multiple choice questions, put a check mark next to the correct answer. Five marks are awarded for each correct answer.

1- At different environmental temperatures, impact testing is performed to determine one of the following:

a. Ultimate strength.

b. Endurance limit.

c. Flexural .

d. Ductile-brittle transition.

2- When a sample is subjected to bending load,

a. Tensile and compressive stresses are generated only.

b. Tensile and shear stresses are generated only

c. Compressive and shear stress are generated only

d. Compressive, tensile and shear stresses are generated.

3- The main difference between dynamic and hardness testing is that

a. dynamic testing is used for brittle materials only while hardness can be used for ductile and brittle.

b. hardness testing evaluates the surface characteristics only while dynamic testing can evaluate the bulk of the materials under fluctuating loading.

c. dynamic testing evaluates only the surface properties of the materials while hardness can evaluate the bulk of the materials.

d. Dynamic testing causes plastic deformation on the materials while hardness causes elastic deformation only.

4- In engineering applications, the brittle materials are not preferable compared to ductile materials. One of the main reason is that

a. the failure in ductile materials occurs on planes of minimum shear stress

b. the failure in ductile materials occurs before yielding

c. the failure in ductile materials is predictable and occurs after yielding

d. the fracture in ductile failure is generally normal to the axis of the applied load

5- The main difference between compressive and hardness testing is that

a. compressive testing is used for ductile materials only while hardness can be used for ductile and brittle.

b. compressive testing evaluates only the surface properties of the materials while hardness can evaluate the bulk of the materials.

c. hardness testing evaluates the surface characteristics only while compressive testing can evaluate the bulk of the materials.

d. compressive causes plastic deformation on the materials while hardness causes elastic deformation only.

6- Cold working process can be define as

a. a manufacturing process in which the metal plastically deformed above the recrystallisation temperature

b. a manufacturing process in which the metal elastically deformed above the recrystallisation temperature

c. a deformation process by external loading at room temperature.

d. a process to release the residual stresses in metals.

7- The atoms in the crystal lattice of metals are in constant state of motion, vibrating about a fixed point in the lattice. Due to that, the atoms exchange their places and move through the lattice. This is known as a. diffusion

b. interstitial defect

c. substitutional defect

d. dislocation

8- Cold working process changes the mechanical properties of the metals in which a. increase the cold working rate reduces the ductility of metals.

b. increase the cold working rate reduces the strength of metals

c. increases the cold working rate reduces the hardness of metals

d. increases the cold working rate reduces the strength , the hardness and the ductility of metals

9- In equilibrium phase diagrams, which one of the following statements is correct?

a. The amount of phases presented cannot be determined.

b. The microstructure of the alloys can be determined

c. The microstructure of the alloys can be determined when only equilibrium cooling rate takes place.

d. The morphology of the phases can be determined.

10- The main reason why methane cannot be used as the primary feedstock to form a long chain polymer is:

a. The methane molecule cannot form side-chains so cannot link together to form long chain molecules.

b. The methane molecule cannot contain carbon to carbon unsaturated double bonds necessary for the polymerisation process.

c. To form carbon to carbon saturated bonds, the methane molecule must first lose two of its hydrogen atoms. This can only be done at high temperatures in a catalytic converter.

d. Polymerisation of methane can only occur by first irradiating it to form an isotope.

11- A BLOCK copolymer has the following structure (where the dark circles represent the A mer and the light circles represent the B mer): (a) (b) (c) (d) 

12- Some polymers may be strengthened considerably by a mechanism called ‘crystallisation’. This mechanism can be described as:

a. The arrangement of the long chain molecules randomly to each other and there is no pattern in the structure of the polymer.

b. When the long chain molecules are heavily cross linked thus forming a regular arrayed within the structure.

c. Where individual mers are drawn into an ordered arrayed in a regular lattice structure within the polymer.

d. Where linear long chain molecules are drawn into close alignment with each other in regions of ordered structure.

13- The function of adding chlorine gas into the addition polymerisation process is to:

a. Control the rate of reaction by attaching themselves to each end of the mers prior to addition process.

b. Act as a catalyst by speeding up the polymerisation process.

c. By adding radicals to the side of the giant long chains in isotactic array to increase the polymerisation process.

d. To react with the hydrogen atoms bonded to the carbon atoms to form a HCl compound as a side reaction.

14- A ceramic material can be defined as:

a. A group of organic crystalline materials whose atoms are bonded together by strong covalent bonds only.

b. A group of inorganic non-metallic materials whose atoms are bonded together by a combination of ionic and covalent bonds.

c. A group of inorganic non-metallic materials whose atoms are bonded together by ionic bonds only.

d. Organic non-metallic materials made up of long chain molecules with an amorphous structure held together by strong covalent bonds.

15- Silica has the chemical of: a. SiO2 b. SiO4 c. (SiO4) -4 d. KAlSi3O8 16- Dry corrosion can be defined as:

a. Oxidation at the cathode of an electrolytic cell due to the chemical reaction of gases such as oxygen, sulphur, halogens, hydrogen and nitrogen directly in the absence of a liquid.

b. Chemical reduction of a metal in the absence of liquid

c. Oxidation at the anode of an electrolytic cell in the presence of oxygen in a liquid.

d. Oxidation of the surface of a metal due to the chemical reaction of gases such as oxygen, sulphur, halogens, hydrogen and nitrogen directly in the absence of a liquid.

17- The rate of corrosion in a galvanic cell can be reduced by:

a. Reducing the surface area of the anode in comparison to the cathode.

b. Reducing the surface area of the cathode in comparison to anode.

c. Increasing the ion concentration in the electrolyte.

d. Increasing the temperature of the galvanic cell.

18- With respect to electron energy bands in insulators, conductors and semi-conductors,

a ‘Conductor’ can be defined as: a. A material where the highest average energy level of electrons in the full valence band is well below the lowest average energy level in the conduction band.

b. A material where there is a small energy gap between the lowest average energy level in the conduction band and the highest average energy level of electrons in the valence band.

c. A material where the next available energy level of electrons is below the lowest level of the conduction band.

d. A material where there is an overlap between the average highest energy level of electrons in the valence band and the lowest average energy level of the conduction band.

19- In general, the conductivity of a metal can be increased by:

a. Increasing the number of dislocations within the crystal lattice.

b. Increasing its temperature.

c. Decreasing its temperature.

d. Increasing impurity atoms within the crystal lattice.

20- The hydration reaction of cement is:

a. An exothermic chemical reaction between the calcium silicates and water to produce a hydrated calcium silicate known as tobermorite gel.

b. An endothermic chemical reaction between the calcium silicates and water to produce a hydrated calcium silicate known as tobermorite gel.

c. An exothermic reaction between calcium silicates and water to form a glass like vitrified bond between cement particles.

d. An endothermic reaction between calcium silicates and water to form a glass like vitrified bond between cement particles.

 

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