Fracture Toughness Calculator

Calculate the stress intensity factor and compare to fracture toughness to assess crack stability.

MPa
mm
MPa√m

Stress Intensity Factor (KI)

21.06 MPa√m

Fracture Safety Factor2.37
Critical Crack Length28.19 mm

Stress Intensity Factor (KI) vs Applied Stress (sigma)

Vedi formula →

Formula

## Fracture Toughness and Stress Intensity Fracture mechanics predicts whether a crack will grow catastrophically. The stress intensity factor KI characterizes the stress field near a crack tip, and fracture occurs when KI reaches the material's fracture toughness KIc. ### Formula **KI = Y × sigma × sqrt(pi × a)** where Y is a dimensionless geometry factor (1.12 for an edge crack), sigma is the remote applied stress, and a is the crack length. If KI >= KIc, the crack propagates unstably.

Esempio Risolto

A plate with a 5 mm edge crack under 150 MPa stress (Y=1.12, KIc=50 MPa√m).

  1. 01a = 5 mm = 0.005 m
  2. 02KI = 1.12 × 150 × sqrt(pi × 0.005)
  3. 03KI = 168 × sqrt(0.01571) = 168 × 0.1253 = 21.06 MPa√m
  4. 04Safety factor = 50 / 21.06 = 2.37 (crack is stable)
  5. 05Critical crack = (50 / (1.12 × 150))² / pi × 1000 = 28.2 mm