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Assignment 4 (Metal Forming)

20 Questions - Developed by: Gustav S - Developed on: 2015-10-12 - 5,456 taken

1

Which statement is correct?

Plates are normally thinner than sheets
Plates are normally thinner than 6 mm
Sheets are normally thinner than 6 mm
Sheets are normally thicker than 6 mm

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

59 kN
103 kN
157 kN
280 kN

3

What is no-slip (neutral) point in plate/sheet rolling?

None of the above
The point where the workpiece leaves the rolls
The point where the speed of the roll is equal to the speed of the workpiece being rolled; almost at the middle of the roll-strip contact length
The point where the workpiece contacts the rolls

4

Which of the below can determine if the residual stress in the workpiece after rolling is compression or tension?

The roll diameter and reduction ratio
Type of metal being rolled
None of the above
Speed of rolling

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.

3600 kN
1300 kN
5600 kN
5.6 kN

6

What is the main difference between extrusion and drawing?

They are the same
The required force in drawing is always higher than that of extrusion
In drawing we “push” the metal through the extrusion die but in extrusion the metal is “pulled” through the die
In extrusion we “push” the metal through the extrusion die but in drawing the metal is “pulled” through the die

7

What is dead-metal zone and in which process and under what conditions it is mostly seen?

A “stationary” region of the workpiece that is relatively not deformed and is mostly seen in rolling processes when the friction is very low.
A “stationary” region of the workpiece that is relatively not deformed and is mostly seen in extrusion process when the friction between the die and workpiece is high.
A “stationary” region of the workpiece that is relatively not deformed and is mostly seen in all metal forming processes when the metal is very brittle.
A “stationary” region of the workpiece that is relatively not deformed and is mostly seen in all metal forming processes when the temperature is very high.

8

What is chevron cracking and why it occurs?

Cracks at the center of the workpiece after extrusion; due to bad die design.
Cracks at the corner of the workpiece after extrusion; due to very high friction at the die.
Cracks at the edge of sheet metals after rolling process; due to inhomogeneity of the mechanical properties in the workpiece.
None of the above

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:
1 degree = 0.0175 Radian

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

1 MPa = 1 N.mm-2

2.23 N
1.68 N
2.23 kN
1.68 kN

10

In the below image, dots represent grain structure. Which component is produced by forging process?

B
C
A

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?

None of the above
Close-die forging processes
Precise forging processes
Open-die forging processes

12

Which of the below items is not a cause of defect formation in forging components?

Improper blank or die design
Microstructural changes caused by phase transformation during the process
Temperature gradient throughout the workpiece during forging
Nonuniform deformation of the material in die cavity
Using lubrication

13

What are the benefits of servo presses over other traditional forging presses?

Less material wastage and Higher energy consumption
Higher energy consumption
Less material wastage
Less noise during manufacturing and Better control over the forging speed

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.

Forging
Sand Casting
Permanent mold casting

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.

49.1 kN
70.1 kN
22.3 N
22.3 kN

16

What is the main advantage of progressive blanking process compare to normal blanking?

Higher production rate
Higher applied force
Better surface quality
Lower energy consumption

17

What is the application of Forming Limit Diagrams (FLD) in sheet metal forming?

To find out the suitable friction coefficient
It has no application in sheet metal forming
To find out the safe zone based on the major and minor strains being applied to the sheet metal
To find out the optimum sheet thickness

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).

6%
10%
8%
4%

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.

0.75
0.19
0.77
0.38

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?

Becomes half
Not enough information to answer this question
Becomes double
Thickness does not affect the minimum bend radius

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