Meaning
Radial tension acting along the circumferential path of a cylindrical wall represents a fundamental stress state. For pressurized plastic pipes and screw bosses, hoop stress governs the resistance of the hollow structure to bursting or splitting. The material must withstand this force to ensure long-term pressure retention.
Mechanical Behavior
Internal pressure from a fluid or the radial force of an inserted fastener drives this outward deformation. If the stress exceeds the tensile yield strength of the polymer, the cylinder will deform permanently or rupture. Semicrystalline polymers exhibit higher resistance to this stress than amorphous ones due to their structured crystalline domains.
Moulding Effect
Mold design and gate placement can create a weak spot in the cylinder. When the flow of molten plastic splits around a core pin and reunites, it forms a weld line along the length of the cylinder. This weld line often possesses lower tensile strength than the surrounding material, which reduces the ability of the moulded part to withstand radial expansion and makes the cylinder highly vulnerable to premature splitting when pressurized.
Failure Resistance
Continuous pressure over years can lead to slow crack growth or creep rupture. Long-term calculations ensure the product survives its intended service life.
