Fracture toughness

Fracture toughness measures a material’s resistance to crack initiation or growth under stress. In linear-elastic fracture mechanics, it is commonly quantified by the critical stress-intensity factor at fracture.

Stress intensity factor: A parameter describing the intensity of the elastic stress field near a crack tip. Its critical value at fracture is the standard linear-elastic measure of toughness.
Fracture mechanics: The study of how cracks initiate, grow, and cause failure in materials and structures. Fracture toughness is a material property interpreted within this broader framework.
Damage tolerance: A design approach that assumes flaws exist and ensures structures remain safe until they are detected or repaired. Fracture toughness helps determine whether known flaws can grow to failure between inspections.
Tensile strength: The maximum tensile stress a material sustains before breaking in a tensile test. A strong material can still have low resistance to crack growth.
Linear-elastic fracture mechanics: A framework that analyzes cracks in materials whose deformation is predominantly elastic. It relates crack geometry and loading to the stress intensity used to characterize fracture.
Crack: A narrow discontinuity in a material that concentrates stress and can propagate under load. Toughness quantifies resistance to the growth of this defining defect.
Fitness-for-service: An engineering assessment of whether equipment with flaws or degradation can continue operating safely. Toughness is an input when evaluating crack-like defects in operating components.
Impact toughness: A material’s capacity to absorb energy during rapid loading and fracture. Impact-test energy depends on test conditions and is not equivalent to fracture toughness.
Crack-tip plasticity: Permanent deformation in the small region around a crack tip when local stresses exceed yield strength. It can blunt cracks and make measured toughness exceed purely elastic predictions.
Critical energy release rate: The energy required per unit increase in crack area at the onset of crack growth. It is an energy-based fracture criterion related to toughness under elastic conditions.

Linked from 18 pages