Materials for engineering, 3rd Edition - (Malestrom)

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Materials for engineering
to a Voigt model (of Young’s modulus E 1 and viscosity η) in series with
a spring of Young’s modulus E 2 . Determine the stress σ as a function of
time t when a constant strain ε is instantaneously applied to the specimen.
[Answers: σ = ε[E R + (E 2 – E R )exp(–t/τ)], where E R = 1/(1/E 1 + 1/E 2 ),
and τ = η/(E 1 + E 2 ).]
Chapter 3
1. The tensile yield strength of annealed iron (grain size 16 grains mm –2 )
is 100 MPa, and 250 MPa for a specimen with small grain size (4 096
grains mm –2 ). Determine the yield strength of iron with a grain size of
250 grains mm –2 .
[Answer: 149.4 MPa]
2. Describe how a recrystallization treatment may be used to prepare a
single-phase alloy:
(a) with a very fine grain size
(b) with a coarse grain size.
3. Aluminium containing a given volume fraction of (unshearable) oxide
particles of average diameter 200 nm has a shear yield strength of
30 MPa. What would be the shear yield strength if the microstructure
consisted of a dispersion of the same volume fraction of 40 nm diameter
oxide particles?
[Answer: 150 MPa]
4. 316 stainless steel with a grain size of 50 µm at a temperature of
1090 K deforms at a shear strain rate ˙ γ which varies with shear stress
τ as shown below. Explain this behaviour in as much detail as you can,
identifying the creep mechanisms operating.
τ (Pa) 6.1 × 10 4 6.1 × 10 5 6.1 × 10 6 3.7 × 10 7
γ (s –1 ) 10 –10 10 –9 10 –8 10 –7
5.1 × 10 7 6.6 × 10 7 9.2 × 10 7 1.2 × 10 8 1.6 × 10 8
10 –6 10 –5 10 –4 10 –3 10 –2
5. A component is exposed to fluctuating stresses in service: in order to
minimize the danger of it failing by fatigue discuss the steps that should
be taken (a) in the design of the component and (b) in the selection of
the material itself and any special treatment it may be given.
6. Compare the response to heat-treatment of a Ti–2.5Cu alloy with that of
IMI318.