Question & Answer

For what is the bend allowance intended to compensate?

Describe each of the two types of sheet-metal-bending operations: V-bending and edge bending

What is the difference between a notching operation and a seminotching operation?

What is the difference between a cutoff operation and a parting operation?

In blanking of a circular sheet-metal part, is the clearance applied to the punch diameter or the die diameter?

In conventional sheet metalworking operations, (a) what is the name of the tooling and (b) what is the name of the machine tool used in the operations?

Identify the three basic types of sheet metalworking operations.

Wire stock of initial diameter = 0.125 in is drawn through two dies each providing a 0.20 area reduction. The starting metal has a strength coefficient = 40,000 lb/in2 and a strain hardening exponent = 0.15. Each die has an entrance angle of 12°, and the coefficient of friction at the work-die interface is estimated to be 0.10. The motors driving the capstans at the die exits can each deliver 1.50 hp at 90% efficiency. Determine the maximum possible speed of the wire as it exits the second die.

Bar stock of initial diameter = 90 mm is drawn with a draft = 15 mm. The draw die has an entrance angle = 18°, and the coefficient of friction at the work-die interface = 0.08. The metal behaves as a perfectly plastic material with yield stress = 105 MPa. Determine (a) area reduction, (b) draw stress, (c) draw force required for the operation, and (d) power to perform the operation if exit velocity = 1.0 m/min

A spool of wire has a starting diameter of 2.5 mm. It is drawn through a die with an opening that is to 2.1 mm. The entrance angel of the die is 18° degrees. Coefficient of friction at the work-die interface is 0.08. The work metal has a strength coefficient of 450 MPa and a strain hardening coefficient of 0.26. The drawing is performed at room temperature. Determine (a) area reduction, (b) draw stress, and (c) draw force required for the operation.

A direct extrusion operation produces the cross section shown in Figure P19.32(d) from an aluminum billet whose diameter = 150 mm and length = 900 mm. The flow curve parameters for the aluminum are K = 240 MPa and n = 0.16. In the Johnson strain equation, a = 0.8 and b = 1.5. Determine (a) the extrusion ratio, (b) the shape factor, (c) the force required to drive the ram forward during extrusion at the point in the process when the billet length remaining in the container = 850 mm, and (d) the length of the extruded section at the end of the operation if the volume of the butt left in the container is 600,000 mm³ .

A direct extrusion operation produces the cross section shown in Figure P19.32(c) from an aluminum billet whose diameter = 150 mm and length = 500 mm. The flow curve parameters for the aluminum are K = 240 MPa and n = 0.16. In the Johnson strain equation, a = 0.8 and b = 1.2. Determine (a) the extrusion ratio, (b) the shape factor, (c) the force required to drive the ram forward during extrusion at the point in the process when the billet length remaining in the container = 400 mm, and (d) the length of the extruded section at the end of the operation if the volume of the butt left in the container is 600,000 mm3

In a direct extrusion operation the cross section shown in Figure P19.32(b) is produced from a copper billet whose diameter = 100 mm and length = 500 mm. In the flow curve for copper, the strength coefficient = 300 MPa and strain hardening exponent = 0.50. In the Johnson strain equation, a = 0.8 and b = 1.5. Determine (a) the extrusion ratio, (b) the shape factor, (c) the force required to drive the ram forward during extrusion at the point in the process when the billet length remaining in the container = 450 mm, and (d) the length of the extruded section at the end of the operation if the volume of the butt left in the container is 350,000 mm3

A direct extrusion operation produces the cross section shown in Figure P19.32(a) from a brass billet whose diameter = 125 mm and length = 350 mm. The flow curve parameters of the brass are K = 700 MPa and n = 0.35. In the Johnson strain equation, a = 0.7 and b = 1.4. Determine (a) the extrusion ratio, (b) the shape factor, (c) the force required to drive the ram forward during extrusion at the point in the process when the billet length remaining in the container = 300 mm, and (d) the length of the extruded section at the end of the operation if the volume of the butt left in the container is 600,000 mm3 .

Determine the shape factor for each of the extrusion die orifice shapes in Figure P19.32.

A cup-shaped part is backward extruded from an aluminum slug that is 50 mm in diameter. The final dimensions of the cup are: OD = 50 mm, ID = 40 mm, height = 100 mm, and thickness of base = 5 mm. Determine (a) extrusion ratio, (b) shape factor, and (c) height of starting slug required to achieve the final dimensions. (d) If the metal has flow curve parameters K = 400 MPa and n = 0.25, and the constants in the Johnson extrusion strain equation are: a = 0.8 and b = 1.5, determine the extrusion force.

The flow curve parameters for the aluminum alloy of Problem 19.29 are: K = 240 MPa and n = 0.16. If the die angle in this operation = 90°, and the corresponding Johnson strain equation has constants a = 0.8 and b = 1.5, compute the maximum force required to drive the ram forward at the start of extrusion.

An L-shaped structural section is direct extruded from an aluminum billet in which Lo = 500 mm and Do = 100 mm. Dimensions of the cross section are given in Figure P19.29. Die angle = 90°. Determine (a) extrusion ratio, (b) shape factor, and (c) length of the extruded section if the butt remaining in the container at the end of the ram stroke is 25 mm.

An indirect extrusion process starts with an aluminum billet with diameter = 2.0 in and length = 3.0 in. Final cross section after extrusion is a square with 1.0 in on a side. The die angle = 90°. The operation is performed cold and the strength coefficient of the metal K = 26,000 lb/in2 and strainhardening exponent n = 0.20. In the Johnson extrusion strain equation, a = 0.8 and b = 1.2. (a) Compute the extrusion ratio, true strain, and extrusion strain. (b) What is the shape factor of the product? (c) If the butt left in the container at the end of the stroke is 0.5 in thick, what is the length of the extruded section? (d) Determine the ram pressure in the process.

A direct extrusion operation is performed on a cylindrical billet with an initial diameter of 2.0 in and an initial length of 4.0 in. The die angle = 60° and orifice diameter is 0.50 in. In the Johnson extrusion strain equation, a = 0.8 and b = 1.5. The operation is carried out hot and the hot metal yields at 13,000 lb/in2 and does not strain harden when hot. (a) What is the extrusion ratio? (b) Determine the ram position at the point when the metal has been compressed into the cone of the die and starts to extrude through the die opening. (c) What is the ram pressure corresponding to this position? (d) Also determine the length of the final part if the ram stops its forward movement at the start of the die cone.

A 2.0-in-long billet with diameter = 1.25 in is direct extruded to a diameter of 0.50 in. The extrusion die angle = 90°. For the work metal, K = 45,000 lb/in2 , and n = 0.20. In the Johnson extrusion strain equation, a = 0.8 and b = 1.5. Determine (a) extrusion ratio, (b) true strain (homogeneous deformation), (c) extrusion strain, and (d) ram pressure at L = 2.0, 1.5, 1.0, 0.5 and zero in. Use of a spreadsheet calculator is recommended for part (d).

A billet that is 75 mm long with diameter = 35 mm is direct extruded to a diameter of 20 mm. The extrusion die has a die angle = 75°. For the work metal, K = 600 MPa and n = 0.25. In the Johnson extrusion strain equation, a = 0.8 and b = 1.4. Determine (a) extrusion ratio, (b) true strain (homogeneous deformation), (c) extrusion strain, and (d) ram pressure and force at L = 70, 60, 50, 40, 30, 20, and 10 mm. Use of a spreadsheet calculator is recommended for part (d).

A 3.0-in-long cylindrical billet whose diameter = 1.5 in is reduced by indirect extrusion to a diameter = 0.375 in. Die angle = 90°. In the Johnson equation, a = 0.8 and b = 1.5. In the flow curve for the work metal, K = 75,000 lb/in2 and n = 0.25. Determine (a) extrusion ratio, (b) true strain (homogeneous deformation), (c) extrusion strain, (d) ram pressure, (e) ram force, and (f) power if the ram speed = 20 in/min.

A cylindrical billet that is 100 mm long and 50 mm in diameter is reduced by indirect (backward) extrusion to a 20 mm diameter. The die angle is 90°. The Johnson equation has a = 0.8 and b = 1.4, and the flow curve for the work metal has a strength coefficient of 800 M_Pa and strain hardening exponent of 0.13. Determine (a) extrusion ratio, (b) true strain (homogeneous deformation), (c) extrusion strain, (d) ram pressure, and (e) ram force.

A connecting rod is designed to be hot forged in an impression die. The projected area of the part is 6,500 mm² . The design of the die will cause flash to form during forging, so that the area, including flash, will be 9,000 mm² . The part geometry is considered to be complex. As heated the work material yields at 75 M_Pa, and has no tendency to strain harden. Determine the maximum force required to perform the operation.