What is the definition of a notch effect?

• A. A rapid change in cross section
• B. A gradual change in cross section
• C. A crack propagation
• D. A smooth transition

Answer: (A)

The notch effect is the rise in local stress caused by abrupt changes in geometry. When the cross section changes suddenly at a notch, groove, or sharp corner, the load that the material must carry is funneled through a smaller area, creating a high stress concentration at the notch tip. This concentrated stress can drive crack initiation and make failure more likely than in regions where the cross section changes gradually. A rapid change in cross section is the defining feature because smooth or gradual transitions spread stress more evenly and don’t create as large a local spike.