Cup-and-Cone Fracture
Definition
The classic macroscopic appearance of ductile tensile fracture in round bar: a flat central zone (the cup) formed by void coalescence surrounded by an angled shear lip (the cone), produced as the outer annulus fails by shear.
- Fracture mode
- Ductile tensile failure
- Central zone
- Flat, formed by void coalescence
- Outer zone
- Angled shear lip (cone)
- Typical material
- Round bar or rod under axial tension
Common questions
How does this differ from a brittle fracture surface?+
A brittle fracture is flat and perpendicular to the load with little necking and a granular or crystalline sheen, while cup-and-cone shows visible necking and a fibrous, dull central zone from microvoid coalescence.
What does the shear lip angle tell an examiner?+
Its consistent roughly 45 degree angle reflects the final failure of the outer annulus in shear once the central crack has propagated, and its symmetry helps confirm a uniaxial tensile load rather than bending or torsion.
Related terms
- Brittle Fracture
- Fracture with little or no plastic deformation, occurring by rapid cleavage through grains or along grain boundaries. The surface is flat, often...
- Cleavage
- Fracture by separation along specific crystallographic planes, typically {100} planes in body-centred-cubic metals. The fracture surface is flat at the grain scale...
- Ductile Fracture
- Fracture preceded by extensive plastic deformation, in which microvoids nucleate at inclusions, grow, and coalesce to form the fracture surface. The surface...
- Intergranular Fracture
- Fracture path running along grain boundaries rather than through grains. Indicates boundary weakness from segregation, embrittlement, or environmental attack, and produces a...
- SEM Fractography
- The use of scanning electron microscopy to image fracture surfaces at magnifications beyond the optical limit, revealing dimple size and distribution in...