Fundamentals of Metal Forging Review Questions

Question 1

What are the difference between bulk deformation processes and sheet metal processes

Answer 1

Bulk deformation processes are characterized by significant deformations and massive shape changes, and surfacearea-to-volume of work is small

Sheet Metal working are formal cutting oeprations performed on metal sheets, coils, strips. Surfacearea-to-volume ratio of starting metal is high

Question 2

Describe extrusion

Answer 2

A 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 3

Why is the term pressworking often used for sheet metal processes

Answer 3

Term applied to sheetmetal working ops because the machine sused to perform these ops are presses

Question 4

Difference between deep drawing and bar drawing

Answer 4

Deep drawing is continous while bar drawing cuts the section into separate pieces

Question 5

Mathematical equation for flow curve

Answer 5

Flow stress = strength coefficient (strain) ^ strain hardening exponent

Question 6

How does increasing temeprature affect the parameters of the flow curve

Answer 6

For metals, the value of the strength coefficient and the shear exponent depend on temperature.

strength and strain hardening are reduced at higher temp, requiring lower forces and power during forming

Question 7

Indicate some advantages of cold working relative to warm and hot working

Answer 7

• greater accuracy
• better surface finish
• higher strength and hardness of part due to strain hardening
• grain flow during deformation provides oppotunity for desirbale directional properties to be obtained
• no heating required

Question 8

What is isothermal forming

Answer 8

forming oeprations that are carried out in such a way as to eliminate surface cooling and the resulting thermal gradients in the workpart

accomplished by preheating tools

Question 9

Why is friction generally undesirable in metal forming

Answer 9

• metal flow in work is retarded, casuing residual stresses amd defects
• forces and power to perform increases
• tool wear

Question 10

what os sticking friction in metalworking

Answer 10

tendency of two surfaces in relative motion to adhere to each other rather than slide

friction stress between the surfaces exceed the shear flow stress of work metal, causing metal to deform by a shear process beneath the surface rather than slip at the surface