1.4 In a product design, you need to select a metal material for application tha

Question

1.4 In a product design, you need to select a metal material for application that requires a yield strength of at least 345MPa while maintaining a minimum ductility (%EL) of 20%. If the metal could be cold-worked, based on the figures below, which of the following is/are possible candidate(s)? 70 120 800 1040 Steel 700 100 600 500 60 2 400 300 40 200 1040 Steel 10 20 100 0 0 10 20 30 40 50 60 70 0 10 20 30 40 50 6070 Percent cold work Percent cold work (A) Brass (B) Brass and 1040 Steel (C) Copper and 1040 Steel (D) Brass and Copper 1.5 For metals, two facture modes are possible, i.e. ductile and brittle fractures. Which of the following statement best explains why ductile fractures is almost always preferred to brittle fracture? (A) Brittle fracture occurs suddenly and catastrophically without any warning. (B) In ductile fracture, the presence of plastic deformation gives warning that failure is imminent. (C) More strain energy is required to induce ductile fracture. (D) All of above (D) Ruby gemstone has a strong absorption peak at 0.5um

Explanation / Answer

1.4) from the given graphs , the criteria of 345 MPa and 20% of minimum ductility is fulfilled by only brass and copper. steel has minimum ductility of 20 % but for only small cold working not even 10 %.

so copper and brass is the clear choice.

1.5) brittle materials are very hard and they fracture very suddenly without any warning where as ductile materials fails with cup and cone formation and it is visible when it takes place so the harm can be avoided.

also ductile materials have high resilence that means they can absorb higher energy before breaking.

so the correct answer is option D

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