Stress concentration

Stress concentration is the localized increase in stress around geometric features, material defects, or abrupt changes in a loaded body. It can make local stress substantially higher than the nominal stress calculated from overall dimensions and loading.

Stress concentration factor: The ratio of peak local stress to nominal stress under a specified loading condition. It quantifies the amplification caused by a particular feature and loading arrangement.
Normal stress: Stress acting perpendicular to a material surface or cross-section. It is a common component of the nominal stress compared with a local peak.
Fatigue (material): Progressive material damage caused by repeated or fluctuating loading. Repeated local stress peaks can initiate fatigue cracks below the material's static strength.
Stress singularity: A mathematical point or line where a modeled stress grows without bound. An ideal sharp crack has a singular stress field, unlike many finite-radius notches.
Circular hole in a plate: A circular opening in a flat plate that perturbs the stress field under applied loading. Under uniaxial tension in an infinite plate, its elastic edge stress reaches three times nominal stress.
Notch sensitivity: A measure of how strongly a material's fatigue strength responds to a notch or other stress raiser. It connects geometric stress amplification to the material's actual fatigue performance.
Shear stress: Stress acting parallel to a material surface or cross-section. Notches and holes can amplify shear stress as well as normal stress.
Notch: A geometric discontinuity, such as a groove or sharp corner, that alters stress in a loaded body. Notches are common engineered sources of stress concentration.
Stress shielding: A reduction in stress within a region caused by surrounding material or an intervention that redirects load. It describes local stress reduction, the opposite of concentration.
Fillet (mechanical engineering): A rounded transition between adjoining surfaces in a mechanical component. A fillet reduces the abruptness of a shoulder and typically lowers its stress concentration.

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