免费断裂韧性计算器
计算材料的断裂韧性(应力强度因子)。
Stress Intensity Factor (KI)
21.06 MPa√m
Stress Intensity Factor (KI) vs Applied Stress (sigma)
公式
## 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.
计算示例
A plate with a 5 mm edge crack under 150 MPa stress (Y=1.12, KIc=50 MPa√m).
- 01a = 5 mm = 0.005 m
- 02KI = 1.12 × 150 × sqrt(pi × 0.005)
- 03KI = 168 × sqrt(0.01571) = 168 × 0.1253 = 21.06 MPa√m
- 04Safety factor = 50 / 21.06 = 2.37 (crack is stable)
- 05Critical crack = (50 / (1.12 × 150))² / pi × 1000 = 28.2 mm
常见问题
What is the geometry factor Y?
Y accounts for the specimen shape and crack location. For a center crack in an infinite plate, Y = 1.0. For an edge crack, Y = 1.12. For specific geometries, Y can be found in fracture mechanics handbooks or by finite element analysis.
What are typical fracture toughness values?
Mild steel: 50-100 MPa√m, aluminum 2024-T3: 26 MPa√m, titanium: 55-115 MPa√m, glass: 0.7 MPa√m, concrete: 0.2-1.4 MPa√m. Higher values mean more resistance to crack growth.
How does thickness affect fracture toughness?
Thicker specimens tend toward plane strain conditions, giving the minimum (conservative) KIc value. Thin specimens experience plane stress and show higher apparent toughness. Standard tests specify minimum thickness requirements.
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