Page 455 - 04. Subyek Engineering Materials - Manufacturing, Engineering and Technology SI 6th Edition - Serope Kalpakjian, Stephen Schmid (2009)

Synthesis, Design, and Projects 435

QUANTITATIVE PROBLEMS

ll I6.33. Calculate Ravg for a metal where the R values for I6.4I. What is the minimum bend radius for a 1.5-mm-
the 0°, 45°, and 90° directions are 0.8, 1.7, and 1.8, respective- thick sheet metal with a tensile reduction of area of 30%?
ly. What is the limiting drawing ratio (LDR) for this material? Does the bend angle affect your answer? Explain.
ll |6.34. Calculate the value of AR in Problem 16.33. Will |l|6.42. Survey the technical literature and explain the
any ears form when this material is deep drawn? Explain. mechanism by which negative springback can occur in V-die
ll l6.35. Estimate the limiting drawing ratio for the mate- bending. Show that negative springback does not occur in air
rials listed in Table 16.4. bending.
l6.36. Using Eq. (16.15) and the K value for TNT, plot the l6.43. Using the data in Table 16.3 and referring to
pressure as a function of weight (W) and R, respectively. Eq. (16.5), calculate the tensile reduction of area for the
Describe your observations. materials and the conditions listed in the table.
|6.37. Section 16.5 states that the le values in bend allowance II l6.44. What is the force required to punch a square hole
depend on the relative magnitudes of R and T. Explain why 60 mm on each side in a 1-mm-thick 5052-O aluminum sheet
this relationship exists. by using flat dies? What would be your answer if beveled dies
are used?
l6.38. For explosive forming, calculate the peak pressure in
water for 1.2 N of TNT at a standoff distance of 1200 mm. l6.45. In Example 16.1, it was stated that the reason for
reducing the tops of cans (necking) is to save material for
Comment on whether or not the magnitude of this pressure is
sufficiently high to form sheet metals. making the lid. How much material will be saved if the lid
diameter is reduced by 10%? By 15%?
I6.39. Measure the respective areas of the solid outlines in
Fig. 16.14a, and compare them with the areas of the original l6.46. Assume that you are an instructor covering the top-
circles. Calculate the final thicknesses of the sheets, assuming ics described in this chapter and you are giving a quiz on
that the original sheet is 1 mm thick. the numerical aspects to test the understanding of the stu-
dents. Prepare two quantitative problems and supply the
l6.40. Plot Eq. (16.6) in terms of the elastic modulus, E,
answers.
and the yield stress, Y, of the material, and describe your
observations.

SYNTHESIS, DESIGN, AND PROJECTS

I6.47. Examine some of the products in your home or in an I6.53. The design shown in Fig. P16.53 is proposed for a
automobile that are made of sheet metal, and discuss the metal tray, the main body of which is made from cold-rolled
process or combination of processes by which you think they sheet steel. Noting its features and that the sheet is bent in
were made. two different directions, comment on various manufacturing
l6.48. Consider several shapes to be blanked from a large considerations. Include factors such as anisotropy of the
rolled sheet, its surface texture, the bend directions, the na-
sheet (such as oval, triangular, L-shaped, and so forth) by
laser-beam cutting, and sketch a nesting layout to minimize ture of the sheared edges, and the way the handle is snapped
scrap generation. in for assembly.
l6.49. Give several specific product applications for (a) hem-
ming and (b) seaming.
l6.50. Many axisymmetric missile bodies are made by spin-
ning. What other methods could you use if spinning processes
were not available? Fi
l6.5l. Give several structural designs and applications in ‘ o i
which diffusion bonding and superplastic forming can be used
jointly. Comment on whether this combination is capable of
producing parts at high volume.
|6.52. Metal cans are either two-piece (in which the bottom
and sides are integral) or three-piece (in which the sides, the
bottom, and the top are each separate pieces). For a three-piece
can, should the vertical seam in the can body be (a) in the rolling FIGURE PI6.53
direction, (b) normal to the rolling direction, or (c) oblique to
the rolling direction? Prove your answer.