Predicts crack growth using stress intensity factor K and fracture toughness.
Cracks concentrate stress. The stress intensity K=Yσ√(πa) compares with fracture toughness K_Ic; fracture occurs when K≥K_Ic. Paris law da/dN=C(ΔK)^m predicts crack growth, enabling inspection intervals.
A 5 mm crack in a plate at 200 MPa with Y=1 gives K≈25 MPa√m.
Fracture mechanics predicts how cracks grow, so it sets inspection intervals and tells you whether a flaw is safe to leave in service.
Predicts crack growth using stress intensity factor K and fracture toughness.
Fracture mechanics predicts how cracks grow, so it sets inspection intervals and tells you whether a flaw is safe to leave in service.
It is a measure of the stress field at a crack tip, combined with the crack size and geometry. Failure occurs when it reaches the material's fracture toughness.
Many steels become brittle at low temperatures, and their fracture toughness falls, so a crack that is harmless at room temperature can become critical.
Typical applications include deciding whether a crack found in a pressure vessel is acceptable, calculating the critical crack size for a bridge steel under cold conditions and choosing a material with high toughness for a pressure component.
Study "Fatigue" first (topic 68 of 106 in Engineering Mechanics). It covers the groundwork this topic builds on.
Brittle vs ductile fracture. Critical crack size. Leak-before-break design.
A 5 mm crack in a plate at 200 MPa with Y=1 gives K≈25 MPa√m.
The next topic is "Creep", which builds directly on this one.
It is classed as Intermediate in Engineering Mechanics (topic 69 of 106). It is an intermediate topic. Work through the beginner topics in Engineering Mechanics first.
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