A steel bolt has a modulus of 207 GPa. It holds two rigid plates together at a high temperature under conditions where the creep
of the steel is described by the equation:ε=ε0σσ0nwhere n= 3, andε=127.8 10−×/s when σ= 28 MPa. The bolt is initially tightened to a stress of 69 MPa. What is the stress in it after 1 year? (14 MPa)
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Answer:
Explanation:
Given conditions
1)The stress on the blade is 100 MPa
2)The yield strength of the blade is 175 MPa
3)The Young’s modulus for the blade is 50 GPa
4)The strain contributed by the primary creep regime (not including the initial elastic strain) was 0.25 % or 0.0025 strain, and this strain was realized in the first 4 hours.
5)The temperature of the blade is 800°C.
6)The formula for the creep rate in the steady-state regime is dε /dt = 1 x 10-5 σ4 exp (-2 eV/kT)
where: dε /dt is in cm/cm-hr σ is in MPa T is in Kelvink = 8.62 x 10-5 eV/K
Young Modulus, E = Stress, /Strain, ∈
initial Strain,
creep rate in the steady state
but Tinitial = 0
solving the above equation,
we get
Tfinal = 2459.82 hr