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DESIGN FUNDAMENTALS

DESIGN FUNDAMENTALS. Prof. kiran gore. Need of design. Functional requirement User comfort Safety Modification Appearance Cost reduction. General consideration in design. Type of load Selection material shape & size Friction & lubrication Operational safety

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DESIGN FUNDAMENTALS

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  1. DESIGN FUNDAMENTALS Prof. kiran gore

  2. Need of design • Functional requirement • User comfort • Safety • Modification • Appearance • Cost reduction

  3. General consideration in design • Type of load • Selection material • shape & size • Friction & lubrication • Operational safety • Machine availability • Use of standard parts

  4. General consideration in design • Production quantity • Maintenance of element • Life of element • Capacity of element • Weight of element • Cost of element

  5. steps in design • Define the need • Synthesis (mechanism) • Analysis • Selection of material • Design of elements (size, shape) • Modification • Detailed drawing • Production

  6. Properties of material • Elasticity • Plasticity • Toughness • Resilience • Stiffness • Ductility • Brittleness • Strength • fatigue • Hardness

  7. 1. Elasticity To regains its original shape after deformation When the external applied force is removed.

  8. 2. Plasticity not regains its original shape after deformation When the external applied force is removed.

  9. 3. Toughness Capacity of material to absorb the energy before failure.

  10. Resilience Total amount of energy absorbed by material during its elastic deformation.

  11. 4. Stiffness Ability of material to resist deformation under stress.

  12. 5. Ductility The ability of material to undergo plastic deformation under tensile loading.

  13. 6. Brittleness It is the property of breaking of a material with little permanent deformation.

  14. 7. Strength Ability of material to resist the externally applied force without failure.

  15. 8. Fatigue Ability of a material to resist deformation without failure when subjected to fatigue load.

  16. 9. Hardness It is the property of a material which enables it to resist penetration, abrasion, plastic deformation is called as hardness.

  17. Classification of engineering materials

  18. Ferrous metals • Are those which contains iron as their main element or constituent.

  19. 1.Cast Iron • Cast iron are formed by melting metal and casting hence called as cast iron. • Alloy of four element • Iron • Carbon ( 2.3 to 3.7%) • Silicon • Manganese . • sometime additional alloying element are added. • Melting point is low 1140 to 1240 ⁰ C

  20. Properties of cast iron • High carbon content makes molten iron very fluid, so that it can be poured into intricate shape. • The presence of graphite in the metal provides excellent machinability, wear resistance & ability to damp vibration. • Excellent castability because of high fluidity

  21. Advantages • Low cost material • High compressive strength • Good damping capacity. • High resistance to wear and abrasion. • High hardness • Corrosion resistance is fairly good • Excellent machinability

  22. Limitations • It is brittle in nature. • Its mechanical properties like toughness, stiffness, resilience poor. • due to brittleness, it is poor against fatigue and impact loading.

  23. Applications of cast iron cast iron are used in the following machine elements: • Machine beds, columns, hammers, road-rollers. • Pipe fittings, valves, farm equipments, automotive parts. • camshafts, crank shafts, gears, pulleys , coupling • Motor covers, pump bodies, furnace parts. • Engine frames, piston and cylinder, cylinder blocks and bearing blocks, etc.

  24. 2. Alloy Cast Iron • Generally, cast iron has • - low impact resistance, • - corrosion resistance and • -temperature resistance. • nickel, chromium, copper, silicon, vanadium, molybdenum etc. are used for this purpose.

  25. Alloying element Chromium • Hardness, • harden ability, • wear resistance, • Corrosion resistance Nickel • toughness, • ductility, & • strength

  26. Alloying element Silicon • Deoxidizing agent • Improve elastic limit & resilience • Vanadium • hardness, • toughness & • fatigue strength

  27. Alloying element • Molybdenum- • hardness, • toughness, • high temperature strength Tungsten- • hardness • toughens • It maintains hardness even at red heat

  28. Properties of alloy cast iron • It has high strength. • It has high oxidation resistance. • It has high wear resistance and corrosion resistance.

  29. Applications of cast iron • Gears, automobile parts like pistons, piston rings, camshaft, crank shaft, cylinders. • Brake drum, pulleys, grinding machinery parts, etc.

  30. 3.Plain Carbon Steels • _ plain carbon steel is an alloy of • iron & • carbon ( less than 1.7%) • With • Manganese ( less than 1.5% ) • Silicon ( less than 0.5% ) • Sulphur • Phosphors

  31. The plain carbon steel with less than • 0.3% carbon – low carbon steel or MS. • 0.3 % to 0.6% - medium carbon steel. • More than 0.6% - high carbon steel • Carbon content increases the strength & hardness of steel.

  32. Properties of Plain Carbon Steel • They are ductile in nature. • They have high fatigue and impact strength. • Their mechanical properties like toughness, stiffness, resilience, etc. are high.

  33. Advantages • They have high tensile strength. • They have high resilience and toughness . • They can sustain fatigue and impact load.

  34. Limitations • The vibration damping property of steel is poor. • They cannot be cast into complicated shapes. • They have low wear resistance. • Its cost is more than cast iron.

  35. Applications • Low carbon steels- automobile body, spindles, levers, light duty gears. • Medium carbon steel-nuts & bolts, transmission shaft, axles, gears, cylinders &connecting rod. • High carbon steel-coil spring, leaf spring, washers.

  36. 4.Alloy Steel • alloy steel is an alloy of iron & carbon that contain • manganese (more than 1.5%)than specified for plain carbon steel. • silicon (more than 0.5%) than specified for plain carbon steel. • other alloying element like – nickel, chromium, molybdenum, vanadium or tungsten

  37. Properties of Alloy Steel • They are ductile in nature. • They have high corrosion resistance. • They have high strength. • They are soft and having high toughness.

  38. Advantages • They have high tensile and fatigue strength. • They have high wear resistance, corrosion resistance. • They have high toughness and resilience.

  39. Limitations • Alloy steel cannot be cast into complicated shapes. • Their vibration damping property is poor. • They are costlier than steel and cast iron.

  40. Applications • Aircraft engine parts, heat exchangers, wrist watches, sanitary fittings. • Combustion chamber, furnace parts, gas burners, screws. • Valves, pumps, surgical instruments, razor blades, turbine blades, missiles, structural components, etc.

  41. High alloy steel (stainless steel) • At leat12 % chromium are called stainless steel. • Properties- higher corrosion resistance, • Heat resisting property- nickel & molybdenum. • Used – high temperature chemical handling equipment, boiler shell, food processing equipment, springs

  42. Non-Ferrous Metals • Non-ferrous metals are those which contain a metal other than iron as their main element or constituent. • Advantages • Low density, hence light in weight. • High electrical conductivity. • Easy to fabricate. • High corrosion resistance.

  43. Copper and its Alloys

  44. Properties of Copper • high ductility. • high electrical and thermal conductivity. • non-magnetic in nature. • easily alloyed with other metals. • corrosion resistance is also high. Applications Electrical parts Heat exchangers Household utensils, etc.

  45. a. Brass • Brass is an alloy of ( copper + zinc + small • amount of other alloying elements ) • Ex. Addition of lead improves its machinability. • Zing – 5 to 45% • The ductility of brass increases with increasing zing percentage. • Beyond 37%- fall in ductility.

  46. Advantages • high corrosion resistance. • high ductility. • Low coefficient of friction. • It has high machinability. • Limitations • Low strength. • High cost.

  47. Applications • Coins, needles, jewellery, condenser tubes. • springs. • • welding rods, • machine parts. • sliding contact bearing.

  48. b. Bronze • Bronze is an alloy of ( copper + tin ) • With other alloying element like : silicon aluminum, beryllium etc. • Advantages • high corrosion resistance • low coefficient of friction, • Better strength than brass, • better wear resistance than brass, • Good machinability.

  49. Limitations • The cost of bronzes is higher than the brasses. • The strength of bronzes is lower than the ferrous metals.. Applications • Bronzes are used in the manufacturing of following parts : • Springs, gears, bearings, electrical appliances. • Bolts, rivets, pressure vessels, bells, marine containers. • Valve bodies, gun barrels, pipe fittings, etc.

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