DeGarmo's Materials and Processes in Manufacturing

12th Edition

ISBN: 9781118987674

Author: J. T. Black, Ronald A. Kohser

Publisher: WILEY

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Forming and Shaping

Metal forming is a category of metalworking process through which the material can be given the desired shape and size by subjecting it to plastic deformation, where the component undergoes bulk deformation process upon application of loads. Unlike the s…

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Textbook Question

Chapter 18, Problem 2P

Consider the extrusion of a cylindrical billet, and compute the following.

Assume the starting billet to have a length of 0.3 m and a diameter of 15 cm. This is extruded into a cylindrical product that is 3 cm in diameter and 7.5 m long (a reduction ratio of 25). Neglecting the areas on the two ends, compute the ratio between the product surface area (wraparound cylinder) and the surface area of the starting billet.
How would this ratio change if the product were a square with the same crossâ€�sectional area as that of the 3â€�cmâ€�diameter circle?
Consider a cylinderâ€�toâ€�cylinder extrusion with a reduction ratio ofÂ R. Derive a general expression of the relative surface areas of product to billet as a function ofÂ R. (Hint: Start with a cylinder with length and diameter both equal to 1 unit. Because the final area will be 1/RÂ times the original, the final length will beÂ RÂ units, and the final diameter will be proportional to 1/Â R).
If the final product had a more complex crossâ€�sectional shape than a cylinder. Would the final area be greater than or less than that computed in part c?
Relate your preceding answers to a consideration of lubrication during largeâ€�reduction extrusion operations.

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Chapter 18, Problem 1P

Chapter 18, Problem 3P

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A billet 100 mm long and 40 mm diameter is to be extruded in a direct extrusion with final diameter of product 32 mm. The semi die angle is 60°. The work metal has a strength coefficient 500 Map, and strain hardening 0.2 use the Johnson formula with a=0.8 and b=1.45 to estimate the extrusion strain. Determine the pressure applied to the end of the billet as the ram moves forward.

You have been asked to work on some design problems and technically support the team working on extrusion and forging operations: 1) The team are extruding a billet that is 80 mm long with diameter of 40 mm is directly to a diameter of 20 mm. The extrusion die has a die angle of 75°, see Figure 1. For the work metal, K = 600 MPa and n = 0.25. In the Johnson extrusion strain equation, a = 0.8 and b = 1.4. Remaining billet length 75 Ram pressure, p D. Dr Figure 1: Extrusion process. Determine the following design parameters: (a) Extrusion ratio. (b) True strain (homogeneous deformation). (c) Extrusion strain. (d) Ram pressure at L= 80, 40, and 10 mm. (e) Draw the relationship between the ram pressure and billet length and discuss the results. What are your recommendations to dccrcase the required ram pressure?

◆ A billet 75 mm long and 25 mm in diameter is to be extruded in a direct extrusion operation with extrusion ratio rx = 4.0. The extrudate has a round cross section. The die angle (half angle)=90. The work metal has a strength coefficient =-415 MPa, and strain-hardening exponent = 0.18. Use the Johnson formula with a = 0.8 and b = 1.5 to estimate extrusion strain. Determine the pressure applied to the end of the billet as the ram moves forward.

Chapter 18 Solutions

DeGarmo's Materials and Processes in Manufacturing

Ch. 18 - Briefly describe the evolution of forming...Ch. 18 - What are some of the possible means of classifying...Ch. 18 - How are bulk deformation processes different from...Ch. 18 - Prob. 4RQ Ch. 18 - Prob. 5RQ Ch. 18 - Prob. 6RQ Ch. 18 - Prob. 7RQ Ch. 18 - Why is it undesirable to minimize friction between...Ch. 18 - Prob. 9RQ Ch. 18 - Prob. 10RQ

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Solution Summary: The ratio between the product surface area and the surface areas of the starting billet is 4.99.

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