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5. (a) List the important parameters that affect the sheet metal forming process. Select 3 parameters and explain them in more detail. [6 marks] (b) A straight bead is being formed on a 1 mm thick aluminium sheet in a 24mm diameter die as shown in figure below. The yield strength is 90MPa and stiffness is 70.3 GPa. Considering springback, calculate the outside diameter of the bead after it is formed. [5 marks) (c) If the same thickness of aluminium sheet is bent to a radius 12mm, and the final bend angle after springback is 70°. What is the required bend angle? [3 marks) (d) Describe Die-cutting and Fine Blanking using appropriate diagrams [6 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