Breaking stress
The maximum stress a material can withstand before breaking (fracture). It is found on a stress-strain graph as the stress at the point of fracture. For ductile materials, breaking stress equals ultimate tensile strength; for brittle materials, breaking stress and elastic limit are close.
Formula
Breaking stress = F_break / A
Real World
Engineers designing the cables of the Humber Bridge select steel with a breaking stress above 1500 MPa, ensuring cables survive far beyond their working load before fracture.
Exam Focus
On stress-strain graphs, mark breaking stress at the final fracture point, not the ultimate tensile strength point.
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