A3 [3 Marks) The blades in one stage of a gas turbine engine are subjected to normal stresses up to 150 MPa and temperat
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- A3 3 Marks The Blades In One Stage Of A Gas Turbine Engine Are Subjected To Normal Stresses Up To 150 Mpa And Temperat 1 (288.8 KiB) Viewed 41 times
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A3 [3 Marks) The blades in one stage of a gas turbine engine are subjected to normal stresses up to 150 MPa and temperatures that range from 550 to 750°C. To avoid excessive deformation, the creep strain should nowhere exceed 1.5 % in 1000 hours. Consider the two materials given in the figure as candidates for these turbine blades. (a) What is the maximum strain rate, and what is the creep mechanism, for nickel material? Is it suitable for this use? [1 Mark] (b) What is the maximum strain rate, and what is the creep mechanism, for MAR-M200, and is it suitable? [1 Mark] (c) Either material can be differently processed to achieve a grain size anywhere in the range 10 um to 1 cm. Should this be done? What would be your final choice of a material and a grain size? [1 Mark] TEMPERATURE, (C) 400 600 800 T("C1 206 406 600 IDEAL SHEAR STRENGTH 800 1000 1200 200 DLA STRENGTH 10 1000 1200 MAR-M200 d = 100 m PURE NICKEL 4.0.1 mm PLASTICITY 10 DYNAMIC RECHYSTALLISATION DISLOCATION GLIDE POWER-LAW CREEP 1. LT CREEP o I see 10 NORMALIZED SHEAR STRESS NORMALISED SHEAR STRESS, s/ SHEAR STRESS (AT 27°C) MN/ SHEAR STRESS AT 300 K (MN/m) ? +10 HT CREEP 10 10% DIFFUSIONAL FLOW a 0 DIFFUSIONAL FLOW (BOUNDARY) Αιται BOUNDARY VOLUME 0.4 4.1 HOMOLOGOUS TEMPERATURE / LO 0.6 1.0 0.2 0.4 0.8 HOMOLOGOUS TEMPERATURE, Y Deformation mechanism maps giving shear strain rates y for nickel (left) and a nickel-base superalloy (right), both having the same grain size. Shear stresses t are normalized to the temperature-varying shear modulus G, so that the left-hand vertical axis is t/G. For the homologous temperature scale T/T m. the quantity Tim is the melting temperature, and absolute temperatures in degrees K are used.