Automotive Material UNIT-2 (4 Marks)
4 marks questions
1. Explain the properties and application of the PVC and PE materials.
A. the properties of the PVC
- Properties
- Applications
- Pipes
- Electric cables
- Unplasticized poly(vinyl chloride) (uPVC) for construction
- Signs
- Clothing and furniture
- Healthcare
- Flooring
- Other applications
- Chlorinated PVC
- Health and safety
The properties of the PE
2. What is polymerization? Describe addition polymerization and condensation polymerization.
A. polymerization is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks.There are many forms of polymerization and different systems exist to categorize them.
Refer Question No. 4 of 2 marks
3. How plastic materials are classified? Explain each classification.
A. Internet
4. What properties make carbon fiber important for reinforced plastics?
A.Carbon Fiber Properties
· High Strength to weight ratio
· Rigidity
· Corrosion resistance
· Electrical Conductivity
· Fatigue Resistance
· Good tensile strength but Brittle
· Fire Resistance/Not flammable
· High Thermal Conductivity in some forms
· Low coefficient of thermal expansion
· Non poisonous
· Biologically inert
· X-Ray Permeable
· Self Lubricating
· Excellent EMI (Electromagnetic Interference) Shielding Property
· Relatively Expensive
5. State physical and mechanical properties of plastics.
A. Mechanical Properties
· Stress/Strain relationships; tensile, flexural, compressive, shear; impact, creep, stress relaxation; temperature and strain rate effects; orientation, environmental effects; crystallinity, residual stress effects; polymer blends; composites; fracture and failure analysis; dynamic mechanical modulus
Physical Properties
· Glass transition temperature; melting and degree of crystallinity; chemical resistance, permeability; thermal properties; electrical properties; flammability; miscibility/compatibility of blends; degradation; characterization and identification of plastics
6. State chemical properties of plastics. State drawbacks of plastics.
A.
Chemical is used generally to describe the resistance of materials to the effects of chemicals.
In most cases, inadequate chemical resistance is manifested in swelling or softening of the material, which can result in loss of serviceability. The molecules of the medium diffuse into the space between the polymer chains and push them apart. As diffusion processes are temperature dependent, the specifications about chemical resistance only ever apply to the specified temperature. Primarily in the case of amorphous thermoplastic polymers, the influence of chemicals can also lead to stress crack formation. In this case, they initially form microcracks which can grow under the influence of mechanical stress to large crack networks. Consequently, temperature, the concentration of agents, exposure periods and mechanical load are all important criteria when testing for chemical resistance.
In most cases, inadequate chemical resistance is manifested in swelling or softening of the material, which can result in loss of serviceability. The molecules of the medium diffuse into the space between the polymer chains and push them apart. As diffusion processes are temperature dependent, the specifications about chemical resistance only ever apply to the specified temperature. Primarily in the case of amorphous thermoplastic polymers, the influence of chemicals can also lead to stress crack formation. In this case, they initially form microcracks which can grow under the influence of mechanical stress to large crack networks. Consequently, temperature, the concentration of agents, exposure periods and mechanical load are all important criteria when testing for chemical resistance.
Here are some of the drawbacks of plastic:
Durability Environmental Harm
Chemical Risk
Choking Hazard
7. Explain glass in detail.
A.
Glass is one of the oldest and most versatile materials known to man. The term ‘glass’ in its widest sense is used to describe a particular state of matter, known as glassy or vitreous state, which is obtained when a liquid cools without crystallisation taking place. Therefore, glass is defined as a super-cooled liquid. Glasses do not show changes like metals, ceramics or even plastics on cooling from the molten condition. Therefore, glass is considered as a very viscous liquid when it is a solid. It has apparent physical properties of a solid, such as, brittleness, hardness, transparency and chemical inertness.
Glass is manufactured by mixing the raw materials in proper proportions. The glass raw materials include sand, soda ash, limestone, dolomite, feldspar, sodium sulphate, broken glass, etc. The mixture is melted by heating upto 1500 °C. Some modifiers and refining agents are added to the melt. The melt can be cast, draWn or rolled to produce different shapes. Tubing is made by extrusion; bottles are made by a technique similar to the blowmolding techniques used to make plastic containers. Glasses are cast and ground to make precision shapes such as lenses. Sheet glass is made by casting in flat plate-type molds. The flat window glass is made by drawing a sheet out of a molten pool.
8. Explain refractory material in detail.
A.
Refractory materials withstand high temperatures, possess sufficient mechanical strength heat resistance and retain a constant volume. They also possess reversible thermal expansion and resistance to thermal shock. These materials are used in furnaces either to support the heating elements or to form the linings of the inner parts of the furnace. Refractory materials which can be used at temperatures greater than 900 'C include Alundum (bonded aluminium oxide) Alumina, corundum, Al2 O3
Refractory materials are available in different shapes and sizes, some of the common shapes are dense refractory bricks, lightweight bricks, refractory tubes, protection tubes, melting crucibles, and powder form. Light weight bricks and refractory powder are used as Insulation materials.
9. Explain any one glass manufacturing process.
A. Step-by-step Manufacturing of Float Glass
Stage 1: Melting and refining
Fine-grained ingredients, closely controlled for quality, are mixed to make batch, which flows as a blanket on to molten glass at 1,500 oC in the melter.Float makes glass of near optical quality. Several processes – melting, refining, homogenising – take place simultaneously in the 2,000 tonnes of molten glass in the furnace. They occur in separate zones in a complex glass flow driven by high temperatures. It adds up to a continuous melting process, lasting as long as 50 hours, that delivers glass at 1,100oC, free from inclusions and bubbles, smoothly and continuously to the float bath. The melting process is key to glass quality; and compositions can be modified to change the properties of the finished product.
Stage 2: Float bath
Glass from the melter flows gently over a refractory spout on to the mirror-like surface of molten tin, starting at 1,100oC and leaving the float bath as a solid ribbon at 600oC.The principle of float glass is unchanged from the 1950s. But the product has changed dramatically: from a single equilibrium thickness of 6.8mm to a range from sub-millimetre to 25mm; from a ribbon frequently marred by inclusions, bubbles and striations to almost optical perfection. Float delivers what is known as fire finish, the lustre of new chinaware.
Stage 3: Coating
Coatings that make profound changes in optical properties can be applied by advanced high temperature technology to the cooling ribbon of glass.On-line chemical vapour deposition (CVD) of coatings is the most significant advance in the float process since it was invented. CVD can be used to lay down a variety of coatings, less than a micron thick, to reflect visible and infrared wavelengths, for instance. Multiple coatings can be deposited in the few seconds available as the glass ribbon flows beneath the coaters. Further development of the CVD process may well replace changes in composition as the principal way of varying the optical properties of float glass.
Stage 4: Annealing
Despite the tranquillity with which float glass is formed, considerable stresses are developed in the ribbon as it cools.Too much stress and the glass will break beneath the cutter. To relieve these stresses, the ribbon undergoes heat-treatment in a long furnace known as a lehr. Temperatures are closely controlled both along and across the ribbon. Pilkington has developed technology which automatically feeds back stress levels in the glass to control the temperatures in the lehr.
Stage 5: Inspection
The float process is renowned for making perfectly flat, flaw-free glass. But to ensure the highest quality, inspection takes place at every stage.Occasionally a bubble is not removed during refining, a sand grain refuses to melt, a tremor in the tin puts ripples into the glass ribbon. Automated on-line inspection does two things. It reveals process faults upstream that can be corrected. And it enables computers downstream to steer cutters round flaws. Flaws imply wastage; while customers press constantly for greater perfection. Inspection technology now allows more than 100 million measurements a second to be made across the ribbon, locating flaws the unaided eye would be unable to see. The data drives ‘intelligent’ cutters, further improving product quality to the customer.
Stage 6: Cutting to order
Diamond wheels trim off selvedge - stressed edges - and cut the ribbon to size dictated by computer.
Float glass is sold by the square metre. Computers translate customers’ requirements into patterns of cuts designed to minimise wastage. Increasingly, electronic systems integrate the operation of manufacturing plants with the order book.
10. Explain ceramics materials.
A.
A ceramic is a compound formed by the combination of metallic and non-metallic elements. Hence, metal oxides, carbides, nitrides, borides and silicates are considered as ceramics. Some typical examples of ceramic materials are refractories, glasses. abrasives, enamels. insulating materials, etc. There are exceptions to the above definition of a ceramic. These exceptions include elemental materials called metaloids such as boron, germanium and Silicon. Intermetallic compounds. such as, nickel aluminide, which are formed by “it combination of two metallic elements are also considered as ceramics.
Ceramic materials are generally characterised by the presence of more than one type of bond in a single material. Due to the presence of strong ionic and covalent bonds, ceramics posses high hardness, brittleness, high melting point. chemical inertness and electrical insulation.
Most of the ceramic phases are crystalline in nature but the structures
involved are usually more complex than those in metallic crystals due to
the presence of atoms or ions of different size. In some ceramics. the
atoms align themselves adjacent in to each other giving rise to amorphous
polymerised structures. It is important to note that some ceramics exist in
different forms of crystal structure and their properties are significantly
changed due to the change in the crystal structure. For example, boron
nitride is a soft friable insulating material in its hexagonal crystal structure,
but in its cubic form it is one of the hardest materials known. Carbon is
an another example of a similar structure. It has a hexagonal structure in
the form of graphite and a cubic structure in the form of diamond.
The ceramic materials considered in this chapter are clays, cements, glasses, refractories and asphalt.
A ceramic is a compound formed by the combination of metallic and non-metallic elements. Hence, metal oxides, carbides, nitrides, borides and silicates are considered as ceramics. Some typical examples of ceramic materials are refractories, glasses. abrasives, enamels. insulating materials, etc. There are exceptions to the above definition of a ceramic. These exceptions include elemental materials called metaloids such as boron, germanium and Silicon. Intermetallic compounds. such as, nickel aluminide, which are formed by “it combination of two metallic elements are also considered as ceramics.
Ceramic materials are generally characterised by the presence of more than one type of bond in a single material. Due to the presence of strong ionic and covalent bonds, ceramics posses high hardness, brittleness, high melting point. chemical inertness and electrical insulation.
Most of the ceramic phases are crystalline in nature but the structures
involved are usually more complex than those in metallic crystals due to
the presence of atoms or ions of different size. In some ceramics. the
atoms align themselves adjacent in to each other giving rise to amorphous
polymerised structures. It is important to note that some ceramics exist in
different forms of crystal structure and their properties are significantly
changed due to the change in the crystal structure. For example, boron
nitride is a soft friable insulating material in its hexagonal crystal structure,
but in its cubic form it is one of the hardest materials known. Carbon is
an another example of a similar structure. It has a hexagonal structure in
the form of graphite and a cubic structure in the form of diamond.
The ceramic materials considered in this chapter are clays, cements, glasses, refractories and asphalt.
11. Explain properties and application of rubber.
A.
12. What is cermets? Explain in detail.
A. Cermets
MMC with ceramic contained in a metallic matrix
• The ceramic often dominates the mixture, sometimes up to 96% by volume
• Bonding can be enhanced by slight solubility between phases at elevated temperatures used in processing
• Cermets can be subdivided into 1. Cemented carbides –most common 2. Oxide-based cermets –less common
Cemented Carbides
One or more carbide compounds bonded in a metallic matrix
• The term cermet is not used for all of these materials, even though it is technically correct
• Common cemented carbides are based on tungsten carbide (WC), titanium carbide (TiC), and chromium carbide (Cr3C2)
• Tantalum carbide (TaC) and others are less common • Metallic binders: usually cobalt (Co) or nickel (Ni)
Applications of Cemented Carbides
• Tungsten carbide cermets (Co binder) -cutting tools are most common; other: wire drawing dies, rock drilling bits and other mining tools, dies for powder metallurgy, indenters for hardness testers
• Titanium carbide cermets (Ni binder) -high temperature applications such as gas-turbine nozzle vanes, valve seats, thermocouple protection tubes, torch tips, cutting tools for steels
• Chromium carbides cermets (Ni binder) -gage blocks, valve liners, spray nozzles, bearing seal rings
13. Explain elastomer in detail.
A. Elastomers
Elastomers are plastics with wide netlike crosslinking between the molecules. Usually, they cannot be melted without degradation of themoleculestructure. Above the glass temperature Tg, as the state of application, elastomers Ares of elastic. Below Tg they are hard elastic to brittle. The value of the glass temperature increases with increasing number of crosslinks. Examples of elastomers are butadiene resin (BR), styrene butadiene resin (SBR) or polyurethane resin (PUR) . Raising temperature affects an increase of elasticity, caused by reducing the stiffening effects of the crosslinks and increasing the mobility of the molecule chains. On exceeding the decomposition temperature Td, the atom bonding within and between the molecule chains will be broken and the material will be chemical decomposed.
14. Briefly explain metal matrix composite material.
A.
15. Briefly explain polymer matrix composite material.
A.
16. Briefly explain ceramic matrix composite material.
A.
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