ie hot giVen or are not correct. Write your name on ALL the pages of the exam If
ID: 2268821 • Letter: I
Question
ie hot giVen or are not correct. Write your name on ALL the pages of the exam If you need more space, use backs of pages but clearly mark ARROW pointing to back page. Section 1 (No partial credit, 30 points) 1. (2 points) Welding never causes residual stresses in the work piece, which may result in distortion stress corrosion cracking, and reduced fatigue life. (True / False) (2 points) Drawing is a process in which the cross-sectional area of a bar or tube is re changed in shape by pulling it through a converging die. (True/ False) 2. duced or (2 points) Which fo a. Extrusion rming process is most often used to manufacture the rails for the railways? b. Rolling 3. c. Forging d. Drawing (2 points) Formation of flash results in a decrease of die force in impression die forging. (True / False) 4. S. (2 points) In direct extrusion, the friction at the billet-die interface decreases with decreasing d angle. (True / False) (2 points) Springback phenomenon in sheet metal materials is caused by remaining elastic energy after deformation. (True / False) 6. (2 points) When a specimen with a rectangular cross section is subjected to open die forging, the pressure will not be maximum at the outer edges of the cross section. (True/ False) 7. (2 points) Theoretically, the strain experienced by the sheet metal during a bending operation is influenced by several factors including the bend radius, the sheet thickness, and the tensile reduction of area of the sheet material. (True / False) 8. (2 points) Practically, the bendability of sheet metal is influenced by several factors that do not include heating, hydrostatic pressure, edge roughness, nor inclusions in the sheet material. (True / False) 9. 10. (2 points) Which is the most commonly used manufacturing process for sheet metals? 838 5 6 8Explanation / Answer
1. False. Welding is the biggest reason of residual stresses in workpiece . It is caused by incompatible internal strains
2. True. In drawing , we push the workpiece into a converging die as a result the shape gets changed or the cross section of the workpiece is reduced . Drawing uses tensile forces to strech . The 2 basic types of drawing are sheet metal drawing and tube drawing .
3. b. Rolling . The most important step in manufacturing process for rails for the railways is rolling . The suitable steel billet is choosen and is then rolled which is followed by cooling , straightening and then heating
4. False. In investment die forging , two dies are brought together and the workpiece undergoes plastic deformation until its enlarged sides touch the side walls of the die. Then, a small amount of material begins to flow outside the die impression forming flash that is gradually thinned. The force exerted by the dies after the formation of flash decreases .
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