Variables
Description
What is this formula?
The Fracture Toughness Criterion determines whether a crack will remain stable or propagate catastrophically. Failure is expected when the applied stress intensity factor reaches or exceeds the material fracture toughness.
When to use it
Use this criterion when evaluating cracked structures, pressure vessels, aircraft components, pipelines, welded structures, and safety-critical engineering systems.
Example
A component has:
KI = 25 MPa·√m
KIC = 60 MPa·√m
Formula:
SFf = KIC / KI
Substitution:
SFf = 60 / 25
Result:
SFf = 2.4
The component has a fracture safety factor of 2.4 and is expected to operate safely under the specified loading conditions.
Applications
- Fracture mechanics assessments
- Fitness-for-service evaluations
- Pipeline integrity analysis
- Pressure vessel inspections
- Aerospace structural certification
- Failure prevention programs
Note
The actual fracture criterion is KI ≥ KIC. Since fCalc requires explicit equations, the fracture safety factor is used as a practical engineering indicator. Values greater than 1 generally indicate acceptable conditions, while values approaching or below 1 indicate increasing fracture risk. The criterion is valid under Linear Elastic Fracture Mechanics assumptions.