(6.2) For an elastic circular bar with homogeneous Young's modulus we know that the normal stress is given in terms of the axial force as σ = = R/A. Find the corresponding formula for a bar that has been functionally graded in the radial direction so that the Young's modulus can be expressed as E(r) = B+ Cr, where B and C are given material constants. Assume the bar has a radius a. (Hint: your answer should be equivalent to Cr)/[2π(Ba2/2+ Ca³/3)], coordinate.) σxx (r, z) = R(2)(B+ where z is the axial