Definition
A measure of how much a material's strength is reduced by the presence of a notch, scratch, sharp corner, or other small surface defect that concentrates stress. A material with high notch sensitivity loses a large amount of its load-carrying ability when such a defect is present; a material with low notch sensitivity tolerates these defects with little loss of strength.
Plain English
How badly a material is weakened when it has a small nick, scratch, or sharp corner in it. Some materials shrug these off; others crack or fail much sooner because of them.
Context Anchor
Seen in aircraft maintenance discussions about inspecting engine parts, propeller parts, shafts, blades, and other metal components for nicks, scratches, and sharp damage.
Derivation
From 'notch' (a small cut or groove) and 'sensitivity' (how strongly something reacts). Together: how strongly a material reacts to having a small cut in it.
Why Pilots Care
High notch sensitivity in a part can cause cracks to start at minor surface imperfections, leading to premature engine failure if not accounted for in design or inspection.
Analogy
Think of tearing open a plastic bag. Without a nick, the plastic resists pulling. Make one tiny cut in the edge and it tears open easily. The plastic is notch-sensitive. A piece of cloth with the same small cut would still hold together — it has low notch sensitivity.
Grounding Statement
A tiny nick can focus the load into one spot, and that spot can become where a crack starts.
Intuition Check
Do not read sensitivity here as an emotional or electronic response. In maintenance, notch sensitivity means how much a part’s strength is reduced by a small nick, scratch, or sharp corner.
Example Sentence 1
Because the alloy used in these turbine blades is highly notch sensitive, even a small nick on the leading edge is grounds for replacement.
Example Sentence 2
Because the crankshaft material showed high notch sensitivity, any small fillet radius damage required immediate replacement.