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hw5.pdf
Homework 5
Fracture; Fatigue
Answers due on Week 12
1.- A cantilever beam has length L = 1, breadth b = 1 and height h = 0.1. At the
upper edge of the free end, an upward force P is applied. In the lower surface of the
beam, next to the built up end, there is a straight crack of size a perpendicular to the free
surface and running
across the breadth. The material is Ti6Al4V with a σY = 600M P a and
√
KIc = 60M P a m.
From the theory of strength of materials, the maximum tensile stress (at the built up
end) is given by
σmax =
6P L
M (h/2)
=
I
Bh2
If the crack size is is a = 0.01 m would the beam fail by yielding or by fracture?
If the crack size is is a = 0.001 m would the beam fail by yielding or by fracture?
2.- Problem 7.20 in Meyers and Chawla.
3.- Problem 14.7 in Meyers and Chawla.
1
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