1.8 PRACTICE PROBLEMS
1. TRUE / FALSE - Electroforming removes metal from a mandrel.
2. TRUE / FALSE - Titanium can undergo superplastic deformation to be fully shaped by mating molds.
3. The part below is to be made from sheet metal. The dimensions specified are for the final part. The aluminum sheet metal has a thickness of 1/16”, and all radii are 1/16”
a) Using allowances for bend radii, determine the actual size of the blank for this piece. Draw a dimensioned sketch.
b) Create a complete process plan for this part, from sheet metal on a roll, to a final part.
c) What is the largest force required to a) bend the part? b) to shear the part? State your assumptions.
d) Give an example (and short reason) of a part best suited for production by,
4. If we can reduce sheet thickness by rolling, could this also be done by stretching the sheet? State the relative benefits of each method.
5. Spreading in rolled sheets increases as friction decreases, the material becomes thicker relative to width, and the roller radius becomes smaller. Describe why all three cases are true.
6. We are given a 1020 steel strip that is 1.0m wide, and 6mm thick. It is rolled to a thickness of 4mm. If the rollers are rotating at 300rpm and have a radius of 15cm, what is the roll force?
7. A sheet is being rolled in a set of tandem rollers. The original sheet thickness is 5mm, at the following stages it is rolled to 3.5mm, 2.8mm, 2.4mm and finally to 2.1mm. If the speed of the sheet entering the first rollers is 20m/s, calculate the drafts for each set of rollers, and the velocity of the sheet after each set of rollers.
8. Name 5 components that would be suitable to manufacturing with spinning.
9. a) Derive the equation for the tensile stress in the outermost fibers of a sheet of thickness ‘T’ that has been bent to a radius ‘r’.
10. Sheet metal is bent to have the profile below. The steel sheet thickness is 1/16”, and the bend radii are both 1/8”. (Note: Assume K = 0.5)
a) Do appropriate calculations to determine the length of the sheet metal before bending.
b) If the steel cannot be elongated more than 10%, can this part be made?
11. List and briefly describe 10 different processes for working and forming sheet metals.
12. From your own experiences describe a part that would be good to make with super plastic forming.
13. What is unique about diffusion bonding?
14. Design a die for hydroforming a barbecue propane tank.
15. How can you visually determine if a thread has been rolled or cut on a lathe?
16. We are rolling a 72” wide 9/64” thick aluminum sheet to 7/64” thick. If the roller has a diameter of 10”, and is rotating at 500RPM, What is the roll force and torque?
17. Show with figures how the mannesman process creates a hole in the center of a round piece.
18. What is the difference between punching and blanking?
19. What manufactured components could be made by spinning?
20. Step 1. Locate a sheet metal part of reasonable complexity. Show the part to me to verify that it is a good complexity.
Step 2. Develop a process plan for the part. The plan should consider a reasonable operation sequence, as well as suitable machines. This must include estimation of press tonnage, bend allowances, spring-back allowances, punch/shear clearances.
Step 3. Make a mock-up of the part by drawing the part on a computer. Print the drawing, and glue it to a thicker paper or plastic backing. Bend/shear/punch/etc the backing to get the desired shapes.
21. How could a long piece with cross section shape shown below be made by rolling?
22. Describe three different methods for making the following round part with sheet metal. Recall that we saw a similar part at MetalFlow.
23. The following piece has been made with 1/16” sheet steel and has the given dimensions.
a) What are the dimensions of the unbent piece? Draw a simple sketch.
b) What will the maximum strain be on the outermost fibers?
c) Is the piece likely to break?
d) What force will be required to shear the four sides of the piece (one at a time) if the UTS of the material is 300MPa?