Chapter 17

Question 1

Define: Metal Forming

Answer 1

Includes a large group of manufacturing processes in which plastic deformation is used to change the shape of metal workpieces

Question 2

Define: Deformation Processes

Answer 2

Generally characterized by significant deformations and massive shape changes:

• Rolling
• Forging
• Extrusion
• Drawing

Question 3

Define: Bulk vs. Sheet

Answer 3

Bulk: the work parts that have low area-to-volume ratio

Sheet: The surface area-to-volume ratio is very high

Question 4

Define: Rolling

Answer 4

Compressive deformation process in which the thickness of a slab or plate is reduced by two opposing cylindrical tools called rolls.

Question 5

Define: Forging

Answer 5

A workpiece is compressed between two opposing dies, so that the die shapes are imparted to the work. Traditionally a hot working process, but sometimes done cold.

Question 6

Define: Extrustion

Answer 6

Compression process in which the work metal is forced to flow through a die opening, thereby taking the shape of the opening as its own cross section.

Question 7

Define: Drawing

Answer 7

The diameter of a round wire or bar is reduced by pulling it through a die opening.

Question 8

Define: Stamping

Answer 8

A part produced from from sheet metal operations (press-working)

Question 9

Define: Flow Stress

Answer 9

The strength property that determines forces and power required to accomplish a particular forming operation. Defined as the instantaneous value of stress required to continue deforming the material to keep the metal “flowing”

Question 10

Define: Average Flow Stress

Answer 10

Average value of stress over the stress-strain curve from the beginning of strain to the final (maximum) value that occurs during deformation.. (Y = Ke^n) / (1+n)

Question 11

Define: Cold vs. Warm vs Hot Working

Answer 11

Cold: is metal forming performed at room temperature or slightly above. Advantages - greater accuracy, better surface finish, high strength and hardness, no heating required

Warm: is metal forming above .3*T_melt. Advantages - lower forces and power, more intricate work geometries, and need for annealing.

Hot: Metal forming and deformation at temperatures above the re-crystallization temperature.

Question 12

Define: Strain Rate Sensitivity

Answer 12

The effect of strain rate on strength properties. Strain rate is referred to as epsilon_dot and is deformation speed divided by instantaneous height of the workpiece.