Se dice que un material es frágil cuando es muy poca la deformación que presentan antes de romperse. Para este tipo de materiales existen dos teorías, la teoría del máximo esfuerzo normal y el criterio de falla de Mohr.

Theory of maximum normal stress

Proposed by Rankine, under this criterion a fragile material will fail if at any of its points it happens that:

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Mohr failure criterion

In the laboratory, a sample of the material is formed as a rotating beam to which a pure bending moment is applied, so that the stress varies from maximum tension to maximum compression.

In civil engineering, various methods are used, also called failure methods, which consist of calculating which loads produce the failure of the structure, determining the admissible load using a safety coefficient. Note that these theories correspond to the hypothesis of static external loads; Other criteria must be applied in case the situation is quasi-static or dynamic.

Se dice que un material es frágil cuando es muy poca la deformación que presentan antes de romperse. Para este tipo de materiales existen dos teorías, la teoría del máximo esfuerzo normal y el criterio de falla de Mohr.

Theory of maximum normal stress

Proposed by Rankine, under this criterion a fragile material will fail if at any of its points it happens that:

{Equation|||left}.

Mohr failure criterion

In the laboratory, a sample of the material is formed as a rotating beam to which a pure bending moment is applied, so that the stress varies from maximum tension to maximum compression.

In civil engineering, various methods are used, also called failure methods, which consist of calculating which loads produce the failure of the structure, determining the admissible load using a safety coefficient. Note that these theories correspond to the hypothesis of static external loads; Other criteria must be applied in case the situation is quasi-static or dynamic.