Question 461 The Metal alloy shown in Fig6461a has the stres

Question 4-61

The Metal alloy shown in Fig.64-61a has the stress-strain diagram shown in Fig. P4-61b.

Determine;

The factor of safety if failure is by yielding (0.2% offset)

The factor of safety if failure is by fracture

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70 P = 6000 lb 60 50 40 30 20 0 0.2 0.4 0.6 0.8 0 Strain, % Figure P4-61

Solution

a) From 0.2 % offset method we get yield stress = 60 ksi

    Stress from load   = 6000 / pi * 0.5^2 / 4    = 30.55775 ksi

    Factor of safety   = 60 / 30.55775   = 1.9635

b) yield stress at fracture = 55 ksi

    Stress from load   = 6000 / pi * 0.5^2 / 4    = 30.55775 ksi

    Factor of safety   = 55 / 30.55775   = 1.8