Fracture toughening mechanisms

Fracture toughening mechanisms

In materials science, fracture toughening mechanisms are processes that increase energy absorption during fracture, resulting in higher fracture toughness.

Intrinsic toughening mechanisms

Intrinsic toughening mechanisms involve a fundamental change of material properties like ductility and plasticity. These changes can be achieved by creating a more stable microstructure, or by increasing precipitate particle spacing to improve ductility.

Extrinsic toughening mechanisms

Extrinsic toughening mechanisms act during crack propagation at the location of the crack, and these mechanisms come in two subcategories based on where they act.

Zone shielding

Zone shielding mechanisms act the crack tip to interfere with crack propagation. The first is transformation toughening, which occurs when the crack actually changes the crystalline structure of the surrounding material to inhibit crack growth. The second and third mechanisms are microcrack toughening and crack field void formation, where either microcracks or microvoids form around the crack tip and reduce the crack tip stress concentration.

Contact shielding

Contact shielding mechanisms act behind the propagating crack. Contact shielding mechanisms often induce some sort of crack closure, either by the roughness of the fracture surface, or by unbroken fibers bridging the crack. A sliding crack surface or a wake of plasticity behind the crack are also contact shielding mechanisms.

References

*Hertzberg, Richard W. Deformation and Fracture Mechanics of Engineering Materials, Fourth Edition. John Wiley and Sons, Hoboken, NJ: 1996.


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