Bulk Deformation Processes Review Questions

Question 1

What are reasons why bulk deformation processes are important commercially and technologically?

Answer 1

• Capable of significant shape change when hot working is used
• Positive effect on part shape
• Produce little material waste
• Some are net shape processes

Question 2

Name all basic bulk deformation processes

Answer 2

• rolling
• forging
• extrusion
• wire and bar drawing

Question 3

What is rolling basic bulk deformation processes

Answer 3

Deformation process in which the thickness of the workpiece is reduced by compressive forces exerted by two opposing rolls

Rolls rotate, thus pulling and simultaneously squeezing the workpiece between them

Question 4

What is a two-high rolling mill

Answer 4

COnsists of 2 opposing rolls between which the work is compressed

Question 5

What is a reversing mill in rolling

Answer 5

Two high rolling mill in which the direction of rotating rolls can be reversed to allow the work to pass through either side

Question 6

what is forging

Answer 6

deformation process in which work is compressed between two dies using either impact or gradual pressure to form part

Question 7

One way to classify forging ops is the degree to which the work is constrained in a die; by this classification, name three basic types

Answer 7

open die forging

closed die forging

flashless forging

Question 8

Why is flash desirable in impression die forging

Answer 8

As flash begins to from, friction resists continued flow of metal into gap, constraining bulk of the work material to remain in the die cavity

Question 9

fwhat are two basic types of forging equipment

Answer 9

forging hammers

forging presses

Question 10

what is isothermal forging

Answer 10

hot forging operation in which the workpart is maintained at or near its starting elevated temperature during deformation, usually by heating the forging dies to same elevated temperature

metal flows more readily and the force required to perform process is reduced

Question 11

what is extrusion

Answer 11

compression process in which work material is forced to flow through a die opening to produce desired cross sectional shape

Question 12

distinguish between direct and indirect extrusion

Answer 12

Direct extrusion / forward extrusion

metal billet loaded onto a container and a ram compresses the material, forcing it to flow through one or more openings in a die at the opposing end of the container

Indirect Extrusion

Die is located on the ram

Question 13

List some products produced on a rolling mill

Answer 13

• flat sheet and plate stock
• round bar and rod stock
• railroad track rails
• I Beams
• Channels
  
  • C-Channel
  • L-Channel

Question 14

what is draft in a rolling op

Answer 14

Difference between the starting thickness and the final thickness as the workpiece passes between the 2 rolls

Question 15

what is sticking in a hot rolling operation

Answer 15

COndition in hot rolling in which the surface of the workpiece adheres to the rolls as the piece passes between them, causing severe deformation of the metal below the surface in order to allow passage through roll gap

Question 16

Identify some of the ways in which force in flat rolling can be reduced

Answer 16

• Use hot rolling
• reduce draft in each pass
• use smaller diameter rolls

Question 17

Name some products made by extrusion

Answer 17

tubes

bars

Question 18

why is friction a factor in determining ram force in direct extrusion but not a factor in indirect extrusion

Answer 18

Problem with direct extrusion is the friction that exists between the work surface and the walls of the container as the billet is forced to slide towards the die opening on the other side of the container

Not present in indirect where die is on the ram

Question 19

what are wire and bar drawing

Answer 19

drawing

operation where cross section of a bar, rod, wire achieved by pulling it through a die opening

bar drawing

large diamater bar and rod stock

Wire drawing

Small diamatere stock

Question 20

although workpiece in a wire drawing is obviously subjected to tensile strength, how do compressive stresse also play a role in the process

Answer 20

Compressive stresses are present in wire drawing because the starting metal is compressed as it is forced through the approach of the die opening

Question 21

In a wire drawing drawing operation, why must the drawing stress never exceed yield strength of the work

Answer 21

Because if the drawing stress exceeded the yield strength, the metal on the exit side of the draw die would stretch rather than force metal to be pulled through the die opening.