HW _3 - Fracture and Fatigue

# HW _3 - Fracture and Fatigue - 2 Pascal Pa = N/m 2 Y = 1.00...

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CEE 3020 Civil Engineering Materials Question 1 Determine the mode I fracture stress ( σ f ) for: (a) a wide glass plate containing a crack 2 mm long; Assume shape factor Y=1, and K Ic =0.7 MPa for glass. (b) a flaw-free glass fiber Assume shape factor Y=1, and K Ic =0.7 MPa for glass. Question 2 You are offered an opportunity to earn \$10 million by simply hanging from a rope for one minute. Complicating the situation are these facts: (1) The rope is attached to a glass sheet (300 cm long by 10 cm wide by 0.127 cm thick). (2) The glass sheet contains a central crack with total length (2 a ) of 1.62 cm (3) The rope is suspended 3m above a pit of hungry alligators. Would you go for it? Could you hang from the glass successfully for one minute? Remember: the fracture toughness of glass is 0.83 MPa m 1 lb= 0.454 kg acceleration due to gravity is 9.81 m/s 2 newton, N = kg m/s

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Unformatted text preview: 2 Pascal, Pa = N/m 2 Y = 1.00 for a center cracked plate 1 min. = 60s L=300cm w=10 cm t=0.127cm Question 3 A fatigue test is made with a mean stress of 15,000 psi and a stress amplitude of 20,000 psi. Calculate the maximum and minimum stresses. Question 4 An iron alloy for a bridge deck component was tested in the laboratory under applied cyclic stresses. The S-N curve generated for the alloy is shown below. During each year of service, the bridge deck and its components are expected to experience 100,000 cycles under a 40 ksi amplitude stress and 20,000 cycles under a 60 ksi amplitude stress. Using the S-N data below and Miner’s Law for cumulative fatigue damage, calculate the expected service life (in years) for the iron alloy component in the bridge deck. 20 40 60 80 100 10 4 10 5 10 6 10 7 10 8 10 9 Number of cycles to failure (Nf)...
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HW _3 - Fracture and Fatigue - 2 Pascal Pa = N/m 2 Y = 1.00...

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