Question

4 a)

Based on the following figures, the material that exhibits an endurance limit of 10 MPa is: 700 600 Ti-5A1-2.5Sn titanium alloy 4340 steel 500 400 Maximum stress, S (MPa) 1045 steel 300 Ductile cast iron 200 70Cu-30Zn brass 2014-T6 Al alloy 100 EQ21A-T6 Mg alloy 0 104 105 108 10 106 107 Cycles to failure, N

4 a) continued

b)

c)

Answer 1

a) PMMA

As we can see from graph PMMA has endurance limit of 10Mpa.

b) True

Sharper cracks are more vulnerable and hence effect K_{​​​​​​IC.}

c) 246mm

Alloy steel steel 4340 has fracture toughness nh. KIC = 87.4 Mga 100 MPa Kic aorta. a ~ 1 yo as? ? 87-4 = 100 ſaxa a=246 mm CS Scanned with CamScanner