3D画像から亀裂の複雑さと材料靭性の関連性が明らかに(3D images reveal link between crack complexity and material toughness)


2024-03-28 スイス連邦工科大学ローザンヌ校(EPFL)

ジョン・コリンスキと彼のチームは、硬質物質内でのひび割れの形成を研究し、3次元のひび割れが材料の強靭性にどのように影響するかを明らかにした。従来の2次元ひび割れに関する理論を補完し、新たな材料設計アプローチを提案した。そのために、スイス軍ナイフと共焦点顕微鏡を用いて、材料内の3次元ひび割れをリアルタイムで観察し、ひび割れ先端の幾何学的複雑さと材料の強靭性との関連性を明らかにした。研究成果はNature Physicsに掲載された。


クラックフロント形状の複雑さが脆性固体の靭性を高める Complexity of crack front geometry enhances toughness of brittle solids

Xinyue Wei,Chenzhuo Li,Cían McCarthy & John M. Kolinski
Nature Physics  Published:22 March 2024

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Brittle solids typically fail by growth and propagation of a crack from a surface flaw. This process is modelled using linear elastic fracture mechanics, which parameterizes the toughness of a material by the critical stress intensity factor, or the prefactor of the singular stress field. This widely used theory applies for cracks that are planar, but cracks typically are not planar, and instead are geometrically complex, violating core tenets of linear elastic fracture mechanics. Here we characterize the crack tip kinematics of complex crack fronts in three dimensions using optical microscopy of several transparent, brittle materials, including hydrogels of four different chemistries and an elastomer. We find that the critical strain energy required to drive the crack is directly proportional to the geodesic length of the crack, which makes the sample effectively tougher. The connection between crack front geometry and toughness has repercussions for the theoretical modelling of three-dimensional cracks, from engineering testing of materials to ab-initio development of novel materials, and highlights an important gap in the current theory for three-dimensional cracks.