An uncold-worked brass specimen of average grain size 0.008 mm has a yield strength of 160 mpa (23,500 psi). estimate the yield strength of this alloy after it has been heated to 600°c for 1000 s and has achieved grain size of 0.20 mm, if it is known that the value of ky is 12.0 mpa-mm1/2 (1740 psi-mm1/2).

Steel balls 12 mm in diameter are annealed by heating to 1150 k and then slowly cooled to 400 k in an air att 325 k and h -20 w/m2 k. assume the properties of the steel to be k- 40 w/m k,p 7800 kg/m3, and cp 600 j/kg k. a. determine whether lumped system method can be used to analyze this problem and if so why" b. determine the time required for the cooling process. c. determine the total amount of heat lost from each ball to the ambient air