Multi objective optimization of orthogonally stiffened cylindrical shells subjected to non uniform external pressure

A multi objective optimality criteria (OC) is used to obtain optimum design of metal cylindrical shells under external pressure. The objectives are to maximize the loadand minimize the mass of stiffened cylinders subject to the constraints including functions of weight and buckling load in such a way that the stiffened shell has no increase in the weight and no decrease in the buckling load with respect to the initial unstiffened shell. The optimization process contain six design variables including the shell thickness, the number of circular ring stiffeners, the number of longitudinal stringer stiffeners, the height of ring stiffeners, the width of ring stiffeners, and thelongitudinal stiffeners eccentricity from shell's centerline. In analytical solution, the Rayleigh–Ritz energy procedure is applied and the ring stiffeners are treated as discreteelements. The shapes of the ring and stringer stiffeners are assumed as rectangular and Z, respectively. The shell is subjected to the non uniform external pressure. For the practical purposes, the external pressure can linearly vary from the top to the bottom. The longitudinal stringers are placed in equal spacing, whereas, the rings can be placed in unequal space due to non-constant of external pressure over the cylinder length. The results show that we have higher buckling load when the spaces between rings at the bottom of cylinder are closer than that at the top of cylinder.

کلیدواژه ها:

stiffened cylindrical shells ، external pressure ، OC method