The Griffith theory of brittle fracture, also known as the Griffith criterion or Griffith’s law, is a fundamental theory that explains how and why brittle materials such as glass and ceramics fracture under stress. The theory was first proposed by British engineer Alan Griffith in 1920.
The Griffith theory states that brittle fracture occurs when the stress at the tip of a crack exceeds the theoretical strength of the material. The theoretical strength is defined as the maximum stress that a material can withstand without breaking. According to the theory, cracks in a material act as stress concentrators, meaning that stress is amplified at the tip of the crack. As the stress at the tip of the crack increases, the crack will propagate or grow, ultimately leading to fracture.
The Griffith theory is based on the assumption that materials are homogenous, isotropic, and have no pre-existing defects. In reality, materials often have imperfections such as microcracks and voids that can influence the onset of fracture. However, the Griffith theory remains a useful tool for understanding the basic principles of brittle fracture and can be applied to materials that are close to the idealized assumptions.
The Griffith theory has also been extended to include the effect of surface energy and the presence of flaws and defects in the material. Additionally, the theory has found applications in a variety of fields, including materials science, mechanical engineering, and civil engineering.
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