Under external pressure, what is the likely failure mode if the pipe wall is not sufficiently thick?

Under external pressure, what is the likely failure mode if the pipe wall is not sufficiently thick?

• A. Elastic buckling
• B. Yielding
• C. Creep
• D. Fatigue

Answer: (A)

When a pipe is thin-walled, its behavior under external pressure is dominated by instability of the shell rather than material deformation. The compressive loads cause the cylindrical shell to buckle, and for a thin wall the critical pressure at which this instability occurs is reached while the material is still in the elastic range. In other words, the shell can lose stability and deform dramatically without yielding, so elastic buckling is the likely failure mode. Creep would require sustained high temperature or long-term loading to cause permanent deformation, and fatigue involves cyclic loading—neither is the primary concern for a thin-walled pipe under a single external pressure condition. Yielding would come into play only if the wall were thick enough that plastic deformation precedes instability.

When a pipe is thin-walled, its behavior under external pressure is dominated by instability of the shell rather than material deformation. The compressive loads cause the cylindrical shell to buckle, and for a thin wall the critical pressure at which this instability occurs is reached while the material is still in the elastic range. In other words, the shell can lose stability and deform dramatically without yielding, so elastic buckling is the likely failure mode.

Creep would require sustained high temperature or long-term loading to cause permanent deformation, and fatigue involves cyclic loading—neither is the primary concern for a thin-walled pipe under a single external pressure condition. Yielding would come into play only if the wall were thick enough that plastic deformation precedes instability.