Which three factors control fracture behavior?

• A. Temperature, Corrosion, Degree of Constraint
• B. Temperature, Loading rate, Degree of Constraint
• C. Temperature, Loading rate, Surface finish
• D. Loading rate, Degree of Constraint, Residual stress

Answer: (B)

Fracture behavior is largely determined by how the material at the crack tip responds to stress under different conditions. Temperature changes the balance between ductility and brittleness: at low temperatures many materials lose ductility and become prone to brittle fracture, while higher temperatures tend to make them more ductile and tough. The rate at which load is applied also matters because materials react differently to fast versus slow loading; rapid loading can suppress plastic flow near the crack tip and promote brittle-like failure, whereas slower loading allows more time for plastic deformation and energy absorption. The degree of constraint describes how the surrounding geometry and boundary conditions limit plastic blunting at the crack tip; high constraint increases triaxial stresses and reduces the plastic zone, steering failure toward brittle fracture, while low constraint permits more plastic relaxation and typically tougher behavior. Other factors like surface finish or residual stresses influence specific cases, but they don’t govern fracture behavior as broadly across materials and conditions as temperature, loading rate, and constraint do.