For the AISI 304 stainless steel of Prob.15.6, assume that only elastic strains need to be added to creep strains, and approximate Poisson’s ratio as ν = 0.3. Then answer the following:
(a) For a stress of 42 MPa applied at a temperature of 950 K for one year, what is the resulting strain?
(b) If the strain at 950 K cannot exceed 0.0015 in one year, what is the highest value of stress that can be permitted?
(c) If the strain at 42 MPa cannot exceed 0.0015 in one year, what is the highest temperature that can be permitted?
(d) Compare the results of the calculations for (a), (b), and (c), and comment on the trends seen.
For AISI 304 stainless steel with a grain size of 200μm, constants for Eq. 15.6 follow for the power-law region of the deformation mechanism map. These apply for stress σ in units of MPa, temperature T in kelvins (K), and strain rates ε˙ in s−1. (Constants based on [Frost 82] p. 62)
Here, A2 depends on the shear modulus G as it varies with temperature according to Eq. 15.11. Make a log–log plot of σ versus , showing lines for T = 900, 1200, and 1450 K, and covering strain rates in the range 10−2 to 10−8 s−1.