(a) if a material (such as aluminum) does not have an endurance limit, how then would you estimate its fatigue life? (b) explain briefly the conditions that induce brittle fracture in an otherwise ductile metal.

Ahe-xe mixture containing a 0.75 mole fraction of helium is used for cooling electronics in an avionics application. at a temperature of 300 k and atmospheric pressure, calculate the mass fraction of helium and the mass density, molar concentration and molecular weight of the mixture. if the cooling capacity is 10 l, what is the mass of the coolant?