Piping under external pressure typically fails due to which phenomenon?

• A. Elastic buckling
• B. Plastic yielding
• C. Fracture
• D. Thermal creep

Answer: (A)

External pressure compresses the pipe wall, and slender cylindrical shells tend to lose stability before the material yields. When the compressive stress reaches a critical level, a small imperfection can trigger a large lateral deflection, so the structure buckles elastically. This instability-driven collapse occurs at stresses below the yield strength, which is why elastic buckling is the typical failure mode under external pressure for piping.

Plastic yielding would require the material to reach and exceed its yield strength, which is not the immediate cause of collapse in many external-pressure scenarios. Fracture would need a crack and high localized stress, not the general stability loss from external compression. Thermal creep involves time-dependent deformation at high temperature, not the instantaneous instability that characterizes buckling under external pressure.