Stress rupture cracks on turbine blades typically appear

Stress rupture cracks on turbine blades typically appear

• A. Along the root
• B. At the blade tip
• C. Across the leading or trailing edge at a right angle to the edge length
• D. In the middle of the blade

Answer: (C)

Stresses that cause rupture often start at surfaces where the material is most stressed under the combined thermal and mechanical loads. In turbine blades, the leading and trailing edges are the thinnest, experience strong thermal gradients from hot gases, and face high bending and pressure forces. This combination creates high surface stress concentrations that favor crack initiation at these edges. Once a crack forms, the driving force for growth is greatest perpendicular to the edge, so it tends to propagate across the edge length into the blade rather than along the edge. That’s why stress rupture cracks are typically seen crossing the leading or trailing edge, at a right angle to the edge length. Other locations, like the root, tip, or mid-span, don’t routinely present the same edge-driven stress conditions, so edge-crossing cracks are the most characteristic pattern.

Stresses that cause rupture often start at surfaces where the material is most stressed under the combined thermal and mechanical loads. In turbine blades, the leading and trailing edges are the thinnest, experience strong thermal gradients from hot gases, and face high bending and pressure forces. This combination creates high surface stress concentrations that favor crack initiation at these edges. Once a crack forms, the driving force for growth is greatest perpendicular to the edge, so it tends to propagate across the edge length into the blade rather than along the edge. That’s why stress rupture cracks are typically seen crossing the leading or trailing edge, at a right angle to the edge length. Other locations, like the root, tip, or mid-span, don’t routinely present the same edge-driven stress conditions, so edge-crossing cracks are the most characteristic pattern.