EML4321 Quiz 3

True or False? Cast parts are generally tougher than forged parts.

• True

• False

True or False? The pressure at the workpiece–die interface is maximum at the center of the workpiece and decreases outward from the center.

• True

• False

When does recovery of the metal occur: below or above the recrystallization temperature?

• Below the recrystallization temperature

• Above the recrystallization temperature

Which of the following shows the recrystallization temperature range? Tm is the melting point of the metal.

• Less than 0.3 Tm

• Between 0.3 Tm and 0.5 Tm

• Greater than 0.5 Tm

• Greater than Tm

Recrystallization decreases the density of dislocations.

• This raises the strength of the metal and raises its ductility.

• This raises the strength of the metal but lowers its ductility.

• This lowers the strength of the metal but raises its ductility.

• This lowers the strength of the metal and lowers its ductility.

Why is the shape of the top section of the specimen in Fig. 1 different from the shape of the bottom section?

• The lower portion deformed more than the upper portion because the lower portion of the specimen began to warm, which increased its strength.

• The lower portion deformed less than the upper portion because the lower portion of the specimen began to warm, which decreased its strength.

• The lower portion deformed more than the upper portion because the lower portion of the specimen began to cool, which decreased its strength.

• The lower portion deformed less than the upper portion because the lower portion of the specimen began to cool, which increased its strength.

Which of the following parameters is used in the computation of the maximum force in a forging operation of stain-hardening materials?

• average flow stress

• compression strength

• final flow stress

• tensile strength

• yield strength

True or False? In plane-strain upsetting, the frictional stress cannot be higher than the shear yield strength of the workpiece material.

• True

• Flase

True or False? The transition from dry to sticking friction moves toward the workpiece center if the die-workpiece friction increases.

• True

• False

True or False? In impression-die forging, there is a sharp increase in load when the flash begins to form.

• True

• False