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ENMA 300/ENME 382
HW 9
Due November 21
1.
The fatigue data for a steel alloy are given as follows:
Stress Amplitude [MPa (ksi)]
Cycles to Failure
470 (68.0)
440 (63.4)
390 (56.2)
350 (51.0)
310 (45.3)
290 (42.2)
290 (42.2)
290 (42.2)
1.0
×
10
4
3.0
×
10
4
1.0
×
10
5
3.0
×
10
5
1.0
×
10
6
3.0
×
10
6
1.0
×
10
7
10
8
a.
Make an SN plot (stress amplitude versus logarithm cycles to failure)
using these data.
b.
What is the fatigue limit for this alloy?
c.
Determine the fatigue lifetimes at stress amplitudes of 415 MPa (60,000
psi) and 275 MPa (40,000 psi).
d.
Estimate the fatigue strengths at 2 x 10
4
and 6 x 10
5
cycles.
2a. A relatively large plate of glass is subjected to a tensile stress of 40 MPa.
If the specific surface energy and modulus of elasticity for this glass are 0.3 J/m
2
and 69 GPa, respectively, determine the maximum length of surface flaw that is
possible without fracture.
b.
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This note was uploaded on 04/03/2012 for the course ENME 382 taught by Professor Christou during the Spring '12 term at Maryland.
 Spring '12
 Christou

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