Why is crack length converted from mm to meters?

K is reported in MPa√m, so the square-root length in K_I = Yσ√(πa) must be in meters when σ is in MPa. The UI uses mm because cracks are usually measured on that scale.

Does KI < KIC guarantee safety?

Only within the assumptions of linear-elastic fracture mechanics and the chosen geometry factor. Real designs add safety factors and check plastic zone size, crack growth, residual stress, loading spectrum, environment, and inspection reliability.

Fracture Mechanics: Griffith / K_IC

Q: Does KI < KIC guarantee safety?

Only within the assumptions of linear-elastic fracture mechanics and the chosen geometry factor. Real designs add safety factors and check plastic zone size, crack growth, residual stress, loading spectrum, environment, and inspection reliability.

Mode-I crack: K_I = Yσ√(πa), compare with K_IC, critical crack size, critical stress, and safe/unstable crack growth.

This is a linear-elastic, mode-I fracture model. Real assessments also check crack shape, finite width, plastic zone size, fatigue crack growth, residual stress, inspection uncertainty, and code safety factors.

Live graphs

About this model

Linear-elastic fracture mechanics describes the near-tip stress field with a stress-intensity factor. For a mode-I crack under tensile stress, this simulator uses K_I = Y σ sqrt(πa), where a is crack half-length in meters and Y is a geometry correction. Comparing K_I with the material fracture toughness K_IC gives a simple Griffith/Irwin-style instability check: when K_I reaches K_IC, a crack can grow unstably. The simulator also solves the inverse questions: critical crack size a_c for the current stress and critical stress σ_c for the current crack. It is a teaching calculator, not a fitness-for-service assessment: finite-width corrections, crack-front shape, plastic-zone validity, residual stresses, fatigue crack growth, corrosion, inspection uncertainty, and code safety factors are not included.

Who it's for: Fracture mechanics, mechanics of materials, machine design, aerospace, civil, and materials engineering introductions.

Key terms

Fracture toughness
Stress intensity factor
Griffith criterion
Mode I crack
Critical crack size

How it works

Linear-elastic fracture mechanics calculator: a crack under tensile stress has KI = Yσ√(πa). Compare KI with material toughness KIC and find the critical crack size or stress.

Key equations

K_I = Y σ sqrt(π a), with a in meters and K in MPa√m

Unstable crack growth when K_I ≥ K_IC; a_c = (K_IC / (Yσ))² / π

Frequently asked questions

Why is crack length converted from mm to meters?: K is reported in MPa√m, so the square-root length in K_I = Yσ√(πa) must be in meters when σ is in MPa. The UI uses mm because cracks are usually measured on that scale.
Does KI < KIC guarantee safety?: Only within the assumptions of linear-elastic fracture mechanics and the chosen geometry factor. Real designs add safety factors and check plastic zone size, crack growth, residual stress, loading spectrum, environment, and inspection reliability.

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Key equations

Frequently asked questions

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About this model

How it works

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Frequently asked questions