2. (a) Describe, using illustrations the main features of sand-casting mould and explain the purpose of the gating syste

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2. (a) Describe, using illustrations the main features of sand-casting mould and explain the purpose of the gating system, cores, and vent. [5 marks) (b) A sprue is 150mm long and has a diameter of 100mm at the top, where the metal is poured. If a flow rate of 80,000 mm3/s is to be achieved, what should be the diameter of the bottom of the sprue to prevent aspiration? What is the resultant velocity and Reynold number at the bottom of sprue if the metal being cast is aluminium and has viscosity 0.004 Ns/m2? [15 marks] Total marks: 20
Formula sheet a. Casting Solidification time=0 TE Volume Area Bernoulli's Theorem ht+ P11 + =ht P2 + 12 pg 29 pg Mass continuity equation : Q = A v; = AzV2 = Area x velocity Reynold Number: Re = vDp Flow speed x Diamater x Fluid Density Dynamic viscosity of the fluid H b. Rolling Power per roll πFKN 60 where N(rpm) Roll force, approximate (frictionless condition) F = Lwo', Roll force, approximate (frictional condition) F = Lwo" (1+ ul 2h Contact Length L = VRAM Average flow stress in plain strain of material in the roll gap: 0; = 1.15 KE Average flow stress, og n+1 True strain, E = In c. Sheet metal forming Maximum punch force in shearing Fmax = 0.7SUTEL Average normal anisotropy ratio for rolled sheet R = Ro + 2R9s + Ryo D. Limited Drawing ratio, LDR Dp Springback estimation, approximate R = 4 RI ( ) - (2) - +1 Et
2R (284) + 1 af Sprinback factor, K = αι +1 = 2R () + 1 d. Generated Heat in resistance welding H = 12Rt Heat for melting certain volume of material, H = uvm