The figure below shows the creep zirconium carbide with 10 m grains. TEMPERATURE. (C) 1500 2000 2500 3000 500 1000 10 IDEAL SHEAR STRENGTH PLASTICITY HARDNESS ZIRCONIUM CARBIDE O Zr Com d-10m 0, NORMALISED SHEAR STRESS, 10 10% OMN +ATKINS AND TABOR (1956) x LEE AND HAGGERTY (1969) LEIPOLD AND NIELSON (1960) 0.2 POWER LAW CREEP DYNAMIC RECRYSTALLISATION DIFFUSIONAL FLOW 10% 10 10 10 101 0.4 0.6 10 0.8 LO 102 +10 SHEAR STRESS AT 300K (MN/m) 10 HOMOLOGOUS TEMPERATURE, M a) Suppose that the required stead-state creep rate for a particular device is given by a maximum of 10/s at a homologous temperature of 0.8. Compute the maximum allowable shear stress. (6 pts) b) By what percentage would the creep rate at the above maximum shear stress slow down by reducing the temperature 25%? (6 pts)