# Assignment 4 (Metal Forming)

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• 1
Which statement is correct?
• 2
A plate of 20 mm width is rolled from initial thickness of 2.5 mm to the final thickness of 1.25 mm. The roll diameter is 300 mm. Assume that there is no change on the width of the workpiece after rolling, and also neglect the effect of friction. Calculate the required force (approximate) for such a rolling process.

Assumptions:
Roll strip contact length can be calculated via: L = [R(h0-hf)]0.5, where R is the roll radius, h0 and hf are initial and final thicknesses, respectively.

And the true stress-strain relationship for this metal is: Stress = 690(Strain)0.5

1 MPa = 1 N.mm-2
• 3
What is no-slip (neutral) point in plate/sheet rolling?

• 4
Which of the below can determine if the residual stress in the workpiece after rolling is compression or tension?
• 5
A round billet made of Brass alloy is extruded at a temperature of 675°C. The initial billet diameter is 125 mm and the diameter of the extrusion is 50 mm. Assume that the extrusion constant for this alloy at this temperature is 250 MPa and calculate the extrusion force required. Neglect the effect of friction.
• 6
What is the main difference between extrusion and drawing?

• 7
What is dead-metal zone and in which process and under what conditions it is mostly seen?
• 8
What is chevron cracking and why it occurs?
• 9
A rod of 3 mm diameter is drawn to a wire with final diameter of 1 mm. The drawing die angle is 20°. Assume that friction coefficient is 0.2. Calculate the required force (approximate) for such a drawing process.

Assumptions:

And the average true stress of the material is 580 MPa.

1 MPa = 1 N.mm-2
• 10
In the below image, dots represent grain structure. Which component is produced by forging process?

• 11
Cogging is a type of forging process that is used for decreasing the diameter or thickness of metallic bars. To which category does the cogging process belong?
• 12
Which of the below items is not a cause of defect formation in forging components?
• 13
What are the benefits of servo presses over other traditional forging presses?
• 14
A company wants to produce a metallic component, with relative dimension of 70mm x 20 mm x 10 mm, that can be manufactured by either forging, or sand casting, or permanent mold casting. But the company only wants to produce 10 pieces of such component. Considering the setup, tooling and other costs, among the mentioned manufacturing processes which one do you recommend to the company as the process with the least total cost for the company? Assume that technically all the mentioned processes are equal for the company.
• 15
We would like to shear (blank) a circular disk out of a stainless steel sheet metal. The thickness of the sheet metal is 4 mm and the diamWe would like to shear (blank) a circular disk out of a stainless steel sheet metal. The thickness of the sheet metal is 4 mm and the diameter of the circular disk to be sheared off is 10 mm. The UTS of the stainless steel is 558 MPa. Calculate the punch force required for shearing (blanking) of the disk.eter of the circular disk to be sheared off is 10 mm. The UTS of the stainless steel is 558 MPa. Calculate the punch force required for shearing (blanking) of the disk.
• 16
What is the main advantage of progressive blanking process compare to normal blanking?

• 17
What is the application of Forming Limit Diagrams (FLD) in sheet metal forming?
• 18
It is desired to bend a stainless steel sheet metal with the thickness of 10 mm to reach to the bend radius of 1 mm before unloading. If the Yield stress of the metal is 290 MPa and the Elastic Modulus is 50 MPa, calculate the amount of spring back in percentage (Ri/Rf).
• 19
A sheet metal of 5 mm thickness has been bent to the bend radius of 4 mm. calculate the compressive strain at the outer surface of the bend.
• 20
Minimum bend radius is the radius at which a crack first appears at outer surface of the sheet metal. Assuming that the tensile reduction area of a sheet metal is constant, how the minimum bend radius of the sheet metal changes if we double the thickness of the sheet metal?