Growth retardation and healing of cylindrical shell wall cracks under external pressure with different profiles

Cracks are the most dangerous defects of shells operating at high internal hydrostatic and/or aerodynamic pressures. Unlimited crack growth causes the shell fracture, frequently with catastrophic consequences. It is experimentally established by direct observations of crack growth that cracks respond asymmetrically to compressive and tensile stresses: they grow at tensile stresses but are conserved and even healed at compressive stresses. One of the authors of the present paper was the first who suggested to use this fundamental crack property to retard the crack growth and to harden the shell by its hooping with a stressed bandage or an armor compressing the shell from outside and inverting the tensile stress created by the internal pressure into the compressive stress. In this regard, the problem on mechanical stresses created in the cylindrical shell wall under simultaneous action of external and uniform internal pressures is solved in the present paper.