Force to tear a cylinder (3.28) In the case of a thin cylinder where the inside pressure is acting outward, as shown in Fig. 3.17(a), what kind of force is required to tear this cylinder in the longitudinal direction? Now, consider the cylinder longitudinally half sectioned as shown in Fig. 3.17(b), with diameter d, length 1 and inside pressure p. The force acting on the assumed vertical centre wall ABCD is pdl which balances the force in the x direction acting outward on the cylinder wall. In other words, the force generated by the pressure in the x direction on a curved surface equals the pressure pdl, since the same pressure acts on the
(T is the force acting per unit length of wall which tears this cylinder longitudinally in halves along the lines BC and AD):
If the tensile stress due to T is lower than the allowable stress, safety is assured. By utilising this principle, a thin-walled pressure tank can be designed.
