a) Ductility: the property of material which enables it to be drawn into thin wire under the action of tensile load is called as ductility. b) Toughness: The property which resists the fracture under the action of impact loading is called as toughness. Toughness is energy for failure by fracture. c) Creep: when a component is subjected to constant stress at a high temperature over a long period of time ,it will undergo a slow& permanent deformation called creep Or it is defined as “slow and progressive deformation of material with time under constant stress at elevated temperature.

Factors to be considered for selection of material for design of machine elements a) Availability: Material should be available easily in the market. b) Cost: the material should be available at cheaper rate. c) Manufacturing Consideration: the manufacturing play a vital role in selection of material and the material should suitable for required manufacturing process. d) Physical properties: like colour, density etc. f) Mechanical properties: such as strength, ductility, Malleability etc. g) Corrosion resistance: it should be corrosion resistant.

Design of Hollow shaft: Given Data: T =4750 N-m = 4750 X 103 N-mm , Ʈ = 50 N/mm2 , K=Di/Do =0.4 The hollow shaft is designed on the basis of strength from the derived torsion equation. 4750 X 103 N-mm ---- Thus Do= 79.18 mm 80 mm ( Say ) Di = 0.4 x Do = 0.4 x 80 = 32 mm

COTTER JOINT

Cotter Joint: " A cotter joint is temporary joint and used to connect two coaxial rods or bars which are subjected to axial tensile and or compressive forces."

It consist of

1) spigot : It is the male part of the joint , it has a rectangular slot for passing the cotter through it. Spigot  has a collar which rests against the socket end.

2) socket :It is the female part of the joint, it also has a rectangular slot for passing the cotter through it. It has a circular hole in which spigot fits.

1) To cushion, absorb or control energy to external load : Car springs, Railway buffers 2) To store Energy : Watches Toys 3) To Measure forces : Spring Balances, Gauges ,Engines 4) To provide clamping force in Jigs & fixtures. 5) To apply forces as in brakes, clutches & spring loaded valve.

1) The power to be transmitted 2) The velocity ration or speed of gear drive. 3) The central distance between the two shafts 4) Input speed of the driving gear. 5) Wear characteristics of the gear tooth for a long satisfactory life. 6) The use of space & material should be economical. 7) Efficiency & speed ratio 8) Cost

A) X10Cr 18 Ni9 Mo 4 Si 2 : High Alloy steel having carbon 0.10% , chromium 18%, nickel 9 % ,Molybdenum 4% & silicon 2% B) XT72W18Cr4V1: high speed tool steel having carbon 0.72% ,chromium 4% , tungsten 18% , vanadium 1%