What normally causes stress rupture cracks?

• A. Excessive Heat Stress or Over Temperature Conditions
• B. Corrosion
• C. Mechanical Fatigue
• D. Low Temperature

Answer: (A)

Stress rupture cracks are a time-dependent failure that occurs when a material is held under sustained stress at elevated temperature. The heat enables creep, a slow, progressive deformation, and over long periods the material accumulates damage along grain boundaries and other weaknesses until a crack forms and grows. In turbine components, overheating or over-temperature conditions push the metal beyond its creep limits, making stress rupture the common failure mode.

Corrosion-related cracking involves environmental attack, not the sustained high-temperature creep process. Mechanical fatigue requires cyclic loading to build up cracks, not a steady high-temperature stress. Low temperature tends to cause brittle fracture rather than creep-driven rupture.