Definition
Localized points on a part or structure where stress concentrates well above the level seen in the surrounding material, typically caused by abrupt changes in shape, surface defects, scratches, nicks, corrosion pits, or sharp internal corners. Stress risers are common starting points for cracks and fatigue failures in metal components.
Plain English
Small spots on a part where stress builds up much more than in the rest of the part — often a scratch, dent, or sharp corner — and where cracks tend to start.
Context Anchor
Seen during the before-takeoff and preflight check, especially when inspecting propeller blades and other airplane parts for nicks, cracks, dents, or other damage.
Derivation
From 'stress' (the internal force a material carries) and 'riser' (something that goes up). The term describes a spot where stress 'rises' above the level in the surrounding material.
Why Pilots Care
Unchecked stress risers accelerate fatigue cracking and can lead to structural failure in flight.
Analogy
Think of tearing open a sealed plastic package. It resists pulling until you make a tiny notch — then it tears easily right at that notch. The notch is a stress riser.
Intuition Check
Stress does not mean worry here, and a riser is not necessarily a raised bump. In this context, it means a small defect or sharp shape that makes physical force concentrate at one spot.
Example Sentence 1
During preflight, the pilot found a small nick on the propeller leading edge and had a mechanic dress it out, since nicks can act as stress risers.
Example Sentence 2
A small scratch on the wing spar was filled and smoothed because it would have acted as a stress riser in turbulence.