Stress rupture cracks are caused by what engine condition?

• A. Over temperature
• B. High fuel flow
• C. Excessive vibration
• D. Low oil pressure

Answer: (A)

Stress rupture cracks come from creep, a time-dependent deformation that occurs when a material is under sustained stress at elevated temperature. In turbine engines, hot-section parts operate at very high temperatures, so an over-temperature condition creates the heat environment that speeds up creep. As the material slowly deforms under load over time, tiny cracks form and grow until the part ruptures. Other conditions like excessive vibration, low oil pressure, or high fuel flow can cause different failure modes (fatigue, lubrication issues, or thermal/stress effects from abnormal operation) but they don’t directly drive creep rupture the way elevated temperature does.