Where is the damage typically more severe on a compressor blade?

Where is the damage typically more severe on a compressor blade?

• A. Tip
• B. Root
• C. Midspan
• D. Leading edge

Answer: (B)

The blade root is where the blade is fixed to the disk, so it behaves like the end of a cantilever beam carrying the aerodynamic loads along the span. The bending moment from those loads is greatest at the fixed end, producing the highest stress there. In addition, the root region contains important stress concentrators such as the fillet and the dovetail (or fir-tree) attachment, where small flaws can initiate fatigue cracks that propagate under cyclic loading. Because of these combined factors—maximum bending stress and concentration at the root—the damage and potential cracking tend to be most severe in that area, making it the critical location to inspect and repair. Leading edge, tip, and midspan damage are more related to erosion, impacts, or wear and do not typically threaten structural integrity as quickly as root-area fatigue.

The blade root is where the blade is fixed to the disk, so it behaves like the end of a cantilever beam carrying the aerodynamic loads along the span. The bending moment from those loads is greatest at the fixed end, producing the highest stress there. In addition, the root region contains important stress concentrators such as the fillet and the dovetail (or fir-tree) attachment, where small flaws can initiate fatigue cracks that propagate under cyclic loading. Because of these combined factors—maximum bending stress and concentration at the root—the damage and potential cracking tend to be most severe in that area, making it the critical location to inspect and repair. Leading edge, tip, and midspan damage are more related to erosion, impacts, or wear and do not typically threaten structural integrity as quickly as root-area fatigue.