In some cases the optimum is the minimum of the objective function (mathematical optimum), but in other cases the optimum is given by a technical constraint (technical optimum). The present paper shows the both types in two problems. The first problem is to find the optimum dimensions of a ring-stiffened circular cylindrical shell subject to external pressure, which minimize the structural cost...

The behavior of an exponentially graded hybrid cylindrical shell subjected to an axisymmetric thermo-electro-mechanical loading placed in a constant magnetic field is investigated. The hybrid shell is consisted of a functionally graded host layer  embedded with pyroelectric layers as sensor and/or actuator  that can be imperfectly bonded to the inner and the outer surfaces of a shell. The shell...

This study aimed to investigate the effects of stiffeners on buckling of thin cylindrical shells under uniform axial compression. To this end, more than 300 finite element models of stiffened cylindrical shells were prepared. The variables considered are shell thickness, number, dimension and the location of the vertical and horizontal stiffeners as well as circular symmetrical imperfections. R...

The gravitational collapse of a cylindrical thick shell of dust matter is investigated. A spacetime singularity forms at the symmetry axis and it is necessarily naked, i.e., observable in principle. We propose a physically reasonable boundary condition at the naked singularity to construct the solution including its causal future. This boundary condition enables us to construct the unique conti...

Cardboard liners are often installed within automotive drive shafts to reduce radiated noise over a certain frequency range. However, the precise mechanisms that yield noise attenuation are not well understood. To overcome this void, a thin shell (under free boundaries) with different cardboard liner thicknesses is examined using analytical, computational and experimental methods. First, an exp...

The dynamic plastic buckling of a homogeneous and isotropic thin thermoviscoplastic cylindrical shell loaded radially is studied analytically by analyzing the stability of its stressed/deformed configuration under superimposed infinitesimal perturbations. The wave number of the perturbation that maximizes its initial growth rate is assumed to determine the buckling mode. Cubic algebraic equatio...