16-Mec-A4/May 2017 P 36 PART A (continued) 03 a) Assuming the cross sectional ar
ID: 2087402 • Letter: 1
Question
16-Mec-A4/May 2017 P 36 PART A (continued) 03 a) Assuming the cross sectional arcas in figure exl are the same, which eross section requires more force to extrude? Why? b) Figure ex2 shows an unbalanced cross section for a part to be extruded. What would happen if this problem is not addressed? What are other issues with this design as far as extrusion process is concerned? c) What is the cause of the defect in flat rolling process shown in: i) Figure Rol ii) Figure Ro2 harp nside otner Figure exl Figure ex2 Figure Ro2 Figure RolExplanation / Answer
a)
Besause cross section is equal, so determining factor for extrusion force will be perimeter which causes friction. Just from observation it can be concluded that figure 1 have highest perimeter so it will cause highest friction.
b)
due to non uniform wall thickness, it will be harder to maintain flatness of wall profile.
Due to sharp corners thete will be witness lines along the surface of the product.
Due to unbalanced cross section it will be harder to keep the wall of product profile straight and harder to keep it at it's place.
c)
Figure a) This defect is wavy edges. Due to roll bending middle section becomes thicker than edges.
Figure b) This defect is edge cracks. It is a result of poor ductility of material.
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