a) A jet turbine (shown below, not to scale) rotates at an angular velocity ? = 15,000 rpm. Estimate the stress on the turbine blade if the turbine disk radius R = 70 cm and the blade’s cross-sectional area A = 15 cm2 . The mass of the blade is 0.2 kg.
(b) The blade material has a room-temperature yield stress of 400 MPa, and the temperature-dependence of the yield stress ?y is given by
?y (T) = ?0 (1 ? (T / Tm ? T )),
where Tm = 1,700 K is the melting temperature of the material and ?0 is the yield stress at absolute zero. At what temperature will the blade deform plastically under the influence of the stress in part (a)?
(Attached the picture for the problem)