Jump to content
Mechanical Engineering


Root Admin
  • Content Count

  • Joined

  • Last visited

  • Days Won


admin last won the day on April 22

admin had the most liked content!

About admin

  • Rank

Recent Profile Visitors

The recent visitors block is disabled and is not being shown to other users.

  1. Dear Members, we will share quiz links, questions, and discussion topics directly with whatsapp group. Please join only 1 group as - all groups will receive same posts Only for Mechanical Engineers They will be admin only groups ... you will not be allowed to post - Marketing people should not join these groups. All interaction will take place via websites Mechanical Engineering Group 101 https://chat.whatsapp.com/GUCrHpf4igeJxRXjthnzXw Mechanical Engineering Group 102 https://chat.whatsapp.com/E7yNk8JUQEt1WMx0X4wMa5 Mechanical Engineering Group 103 https://chat.whatsapp.com/FpW53FD87QDBeHKrAiHjpf Mechanical Engineering Group 104 https://chat.whatsapp.com/IX6YNa5DKLjEsscStmsqrz Mechanical Engineering Group 105 https://chat.whatsapp.com/GSmS6JPOovk74FOS7pZBh9 Mechanical Engineering Group 106 https://chat.whatsapp.com/JqZRrIkVNVH7NV04DVKvCJ Mechanical Engineering Group 107 https://chat.whatsapp.com/DCDneEo5lEz0zGpc4HSYSG Mechanical Engineering Group 108 https://chat.whatsapp.com/JqwB5O64VMc4EhQMQ2f27E Mechanical Engineering Group 109 https://chat.whatsapp.com/G4ULDyFGZkj94ssuzJtcvx Mechanical Engineering Group 110 https://chat.whatsapp.com/HOblns1YWHzB3QtocA7v8d Mechanical Engineering Group 111 https://chat.whatsapp.com/GxGCo8asPVM2CNWgFFCfLM Mechanical Engineering Group 112 https://chat.whatsapp.com/KixunbNehYy5942lRbtaHQ Mechanical Engineering Group 113 https://chat.whatsapp.com/IZ7TYGtHjp4Ff2I7zYtmBF Mechanical Engineering Group 114 https://chat.whatsapp.com/LLRZqvgbwDP4S25BaHRJj5 Mechanical Engineering Group 115 https://chat.whatsapp.com/Exb4vVx9eGj7nxCFhw4jyr Mechanical Engineering Group 116 https://chat.whatsapp.com/HiwBwLkNhWkA2Z8ZsAZn8U Mechanical Engineering Group 117 https://chat.whatsapp.com/IZ0YqCnLlHW3lcjoICrVUM Mechanical Engineering Group 118 https://chat.whatsapp.com/FCKZps8PBxlHbqd7k9zuo2 Mechanical Engineering Group 119 https://chat.whatsapp.com/JRa1UtaXjmv6qPLFEMlPj4 Mechanical Engineering Group 120 https://chat.whatsapp.com/JLCN7NeoWOEEIVPGCW4VkO Mechanical Engineering Group 121 https://chat.whatsapp.com/FTu61h8VYUALQc0uibTAsx Mechanical Engineering Group 122 https://chat.whatsapp.com/J5fZ0tuUllI0sDLx9xIoqB Mechanical Engineering Group 123 https://chat.whatsapp.com/Ct4DGT9GGVx6QJRy3ZSQ25 Mechanical Engineering Group 124 https://chat.whatsapp.com/FNNOGrnEho9311b90EwHqq Mechanical Engineering Group 125 https://chat.whatsapp.com/LYHENL4YTu75I0IbmHXoZm Mechanical Engineering Group 126 https://chat.whatsapp.com/HFdnyhFZVvZ4qgeR31qudu Mechanical Engineering Group 127 https://chat.whatsapp.com/JyyuxSxDea2LMUtnAUAECK Mechanical Engineering Group 128 https://chat.whatsapp.com/DfHWnONH2wUBBXXfeoG3U3 Mechanical Engineering Group 129 https://chat.whatsapp.com/KCxgmcuZHhL7B35uLSdyYu Mechanical Engineering Group 130 https://chat.whatsapp.com/BV50dI8BWpC6dB4S9fhTPC Mechanical Engineering Group 131 https://chat.whatsapp.com/IFUzcriJWfn5jrKRh6DtIo
  2. 1. The characteristics of a material that are displayed when a force is applied to the material 2. The stress at which a material exhibits a specified deviation from proportionality of stress and strain. 3. The stress developed at the outer fibre when a material is loaded as a simply supported beam and deflected to a certain value of strain. 4. The serviceability factor related with the mechanical properties like impact strength, notch sensitivity. 5. The mechanical properties like bend radius, percentage elongation and percentage reduction in area are related with ...... 6. When one is interested in attribute of durability of a material, he must look for properties like hardness, wear resistance and . 7. Modulus of elasticity and flexural modulus refer to ...... of the material. 8. The material characteristics that relate to the structure of a material and its formation from other elements. 9. The structure of a polished and etched metal as revealed by microscope. 10. The ordered, repeating arrangement of atoms or molecules in a material. 11. The ability of a material to resist deterioration by chemical or electrochemical reaction with its environment. 12. The properties like thermal conductivity, refractive index, specific heat, dielectric strength fall under the category of ..... 13. The temperature at which ferromagnetic materials can no longer be magnetised by outside forces. 14. The ratio of the velocity of light in vacuum to its velocity in another material. 15. The temperature at which a polymer under a specified load shows a specified amount of deflection 16. The highest voltage an insulating material of a specified thickness can withstand for a specified time without occurrence of electrical breakdown through its bulk. 17. A hard and brittle alloy of iron, carbon (between 1.8 to 3%), and silicon. 18. Material used for machine housings and frames due to its high compression strength and good vibration absorption properties. 19. Cast iron which contains carbon as free carbon in the form of graphite. 20. Cast iron in which the carbon is present in the combined form as iron carbide. 21. Cast iron which contains graphite in the form of small spheres/nodules. 22. The free carbon in grey cast iron acts as an excellent ...... during machining and offers little frictional resistance. 23. Black heart, white heart, and pearlitic cast irons fall under the category of ...... 24. Which cast iron has good ductility as cast ? 25. Spheroidal graphite iron having tensile strength of 900 N/mm' and elongation of 2% is designated as ...... 26. A mechanical mixture of pig iron and distributed silicate slag. 27. The material used for chains, crane hooks, bolts subjected to shock loads etc. because it is malleable, ductile and tough. 28. Which alloying element in cast iron improves machinability, hardness, strength and corrosion resistance ? 29. Which alloying element in cast iron checks the formation of graphite and promotes the formation of carbides? 30. Which alloying element in cast iron improves strength and wear resistance ? 31. The resistance to corrosion of steel is increased by adding ...... 32. In order to eliminate blow holes in castings, ...... is added to steel. 33. Addition of boron to steel improves ...... 34. Red hardness is imparted to steel by adding ...... 35. Which alloying element in steel removes oxygen in steel making and facilitates rolling and forging? 36. Which alloying element in steel promotes tenacious oxide film to aid atmospheric corrosion resistance ? 37. Machinability of steel is improved by adding ...... 38. Simple alloys of iron and carbon with no other alloying element. 39. A group of steels with carbon content varying upto about 1% and total alloy content below 5%. 40. A solid formed by the combination of metallic and non-metallic elements. Ans. 1. Mechanical property 2. Yield strength 3. Flexural strength 4. Toughness 5. Formability 6. Fatigue strength 7. Rigidity 8. Chemical properties 9. Microstructure 10. Crystal structure 11. Corrosion resistance 12. Physical properties 13. Curie point 14. Refractive index 15. Heat distortion temperature 16. Dielectric strength 17. Cast iron 18. Cast iron 19. Grey cast iron 20. White cast iron 21. Spheroidal or nodular graphite iron 22. Lubricant 23. Malleable cast iron 24. Spheroidal graphite 25. SG 900/2 26. Wrought iron 27. Wrought iron 28. Nickel 29. Chromium 30. Molybdenum 31. Chromium 32. Phosphorus 33. Rolling qualities 34. Tungsten 35. Silicon 36. Copper 37. Lead 38. Carbon steels 39. Alloy steels 40. Ceramic.
  3. (a) Describe the steps usually considered in the process of material selection. (b) How material selection is done using decision theory. Ans. (a) Like any other aspect of engineering design, material selection is also equally important aspect. Material of part depends on the requirements of the part, number of parts needed, and manufacturing process to be adopted to make the part. The material selection primarily depends upon its properties and several other factors like availability, economic aspects, etc. As regards properties of materials, all the following properties need to be considered, (i) chemical (characteristics that relate to the structure of a material and its formation from other elements), (ii) physical (characteristics that are determined by nature, like electrical, magnetic, thermal, etc.), (iii) mechanical (strength, ductility, toughness, rigidity and behaviour under application of force). (iv) dimensional (relating to available size, shape, microtopography and tolerances), (v) technological (machinability, weldability, castability, forgability, bendability, malleability, ductility, hardenability, etc. all relating to manufacturing process). It is essential to establish the performance requirements that the material must meet; then select the appropriate materials for evaluation, and finally select the material that best meets the performance requirements and economic constraints. It is best to consider the alternatives from a wide gambut of materials, viz. ferrous materials (cast iron, cast steel, mild steel, alloy steel, carbon steel, tool steel etc.), non-ferrous materials and their alloys, plastics, ceramics, elastomers, composite materials, etc. Having selected the material from consideration of properties, next step is to check availability, i.e. whether material is readily available, lead time for procurement, quantity required, nature of supplies, whether any special method required to manufacture. The final step is to examine economics, i.e. the cost should be minimum. Cost of a material consists of the initial cost, processing cost and maintenance cost
  4. Ans. 1. (i), 2. (e), 3. (a), 4.(j), 5. (b), 6. (h), 7. (c), 8. (f), 9. (g), 10. (d).
  5. Ans. 1. (j) 2. (f) 3. (i) 4. (a) 5. (l) 6. (d) 7. (b) 8. (k) 9. (g) 10. (c) 11. (h) 12. (e)
  6. Ans. 1. (f) 2. (i) 3. (a) 4. (g) 5. (b) 6. (h) 7. (d) 8. (c) 9. (e).
  7. Temperature has pronounced effect on the properties of zinc and zinc alloys. The creep resistance, in particular, decreases rapidly with increasing temperature. Ductility and general fabricating characteristics increase with temperature. Drawing and forming operation should never be attempted below 20°С. More severe operations can be performed readily at temperatures above 50°C. Zinc alloys become somewhat brittle below 0°C, depending on the particular composition, but recover their normal properties on reaching room temperature again.
  8. Season cracking is spontaneous cracking which occurs on exposure to atmospheric corrosion in brass objects with high residual tensile stresses at the surface. It occurs with high-zinc brasses but rarely with 15 per cent zinc or below. Alloys susceptible to spontaneous season cracking will crack when exposed to corrosive conditions under high service stress, even if they are free from internal strains. Season cracking can be prevented by avoiding the production of internal microstresses or by removing such stresses by relief annealing at 245 to 275°C without softening the work. Alloys containing more than 80% copper are highly resistant to season cracking.
  9. State, with reasons, suitable material for the manufacture of each of the following, giving the approximate composition : (a) a brass for deep pressed containers; (b) a brass for small machined bolts ; (c) a bronze for the impeller of a sea-water pump. (a) The suitable brass for deep pressed containers is the admiralty brass containing copper and zinc in the proportion of 7 to 3, with 1% of tin. The addition of tin to the basic cartridge brass (70% copper, 30% zinc), gives improved resistance to corrosion, renders the material less prone to season cracking, and could possibly lessen the number of interstage annealings. This material is very ductile. (b) The brass used for small machined bolts is free cutting brass with composition: 61.5% copper, 35.5% zinc, and 3% lead. This material is basically a leaded Muntz metal, the addition of lead imparts the highest machinability to the brass. (c) The suitable bronze for the impeller of sea water pump is admiralty gun metal having composition of 85% copper, 13% tin, and 2% zinc. It produces sound casting and has excellent resistance to salt-water corrosion. Machinability could be improved by addition of lead, but this has to be balanced against a lower resistance to corrosion.
  10. (a) What is the main difference between a brass and a bronze ? (b) State the composition, and two common uses of a bronze commonly used in engineering. (c) What is the general effect of adding a small proportion of (1) phosphorus, (ii) lead, to a bronze ? (a) A brass is an alloy of copper and zinc, the major constituent being copper. A bronze is an alloy of copper and tin, the major constituent being copper. (6) A bronze commonly used in engineering and commonly known as 'eighty-fives', three fives' consists of 85% of copper, with 5% each of tin, zinc and lead. Because of its improved machining qualities, it has replaced the traditionally used admiralty gun metal, It is used for low pressure pipe fittings and small pump castings where reasonable corrosion resistance is desired. (c) (i) If phosphorus is added in very small quantities, often only a trace, improves fluidity of casting. If the phosphorus ranges from about 0.05 to 0.25% as in a phosphor-bronze, it forms cuboids which resist wear and can carry heavy loads. It thus becomes an excellent bearing material. (ii) Lead is distributed throughout a bronze as globules. It allows chip cracks to propagate easily and hence the addition of lead improves machining qualities.
  11. (a) Which two elements are alloyed to form a brass ? (b) What are the differences (i) in composition, (ii) in uses, of an 'alpha' and an 'alpha-beta' brass ? (a) A brass is essentially an alloy having major constituents as copper and zinc. Minor proportions of elements such as lead and tin may be included to promote special properties. (b) An alpha brass is an alloy in which zinc does not exceed by 38%. This brass is ductile and, therefore, used for cold-rolled sheets, wire, tube and cold pressing. Cartridge brass contains 70% copper, 30% zinc and is a very suitable material for deep-drawing cartridge cases. An alpha-beta brass is an alloy of copper and zinc containing zinc between about 38% and 47%. The appearance of the beta constituent is associated with increased strength at the expense of ductility. An alpha-beta brass does not lend itself to cold-working, but is readily hot-worked by rolling, extrusion and hot-pressing. It is readily machined, the machinability being even more improved by the addition of lead. A typical alpha-beta brass is Muntz metal (60% copper, 40% zinc), which is used for the production of low pressure water fittings by hot-pressing.
  12. What do you understand by a free-cutting steel? What elements are usually added to make a steel free cutting, and how they make the steel free. cutting? A free-cutting steel is one in which an element like lead or sulphur is deliberately added to promote rapid machining When sulphur is added to steel, it forms a brittle constituent with manganese, known as manganese sulphide, which being brittle, allows chip cracks to propagate and breaks chips into easily handled lengths. The lead does not chemically combine with the other elements. It gets distributed throughout the mass as minute droplets, and thus chip cracks are propagated easily and the chips come out in easily handled lengths.
  13. (i) Permalloy, (ii) Invar, (iii) Elinvar, (iv) Platinite, (v) Dumet wire. Ans. (i) Permalloy has 78.5% nickel. It has a high permeability and low hysteresis loss. (i) Invar contains 36% nickel and has an exceedingly low coefficient of linear expansion. Since its expansion is proportional to the temperature within limits of atmospheric temperature change, it is used for secondary standards of length. (ii) Elinvar contains 32% nickel with small percentage of Cr, W, Mn, Si and C. In addition to a low coefficient of expansion, it also has a constant modulus of elasticity over the temperature range of 0 to 38°C and is thus used for hair springs for watches and springs for other precision instruments. (iv) Platinite contains 46% nickel. It has the same thermal coefficient of expansion as platinum and thus is used as a substitute for platinum. (v) Dumet wire contains 42% nickel. It is covered with copper to prevent degassing at the seal and is used to replace platinum as the "seal in" wire in incandescent lamps and vacuum tubes.
  14. Music wire is a previously treated steel wire used for small helical springs. It requires no heat-treatment except a low-temperature anneal to relieve the forming strains. Such a wire is given a special heat treatment called patenting and then cold-rolled to develop a high yield strength.
  • Create New...