Brittle failures
Introduction
The criteria used to determine the allowable static stresses in structures or machine components are known as elastic failure theories or elastic failure criteria. Various formulations are used, depending on the type of material used.
More precisely, a machine working in reversible cycles must be designed in such a way that its stresses do not leave the elastic domain. The elastic failure criteria establish different approximations for different materials that allow the design to be carried out correctly. In many cases, the occurrence of elastic failure does not imply the breakage of the piece; that other case requires a study through fracture mechanics.
Ductile materials
Contenido
Se considera materiales dúctiles a aquellos que pueden deformarse considerablemente antes de llegar a rotura. Para este tipo de materiales existen dos teorías, la teoría de la máxima tensión cortante y la teoría de la máxima energía de distorsión.
Theory of maximum tangential stress (Tresca Criterion)
This theory was proposed by Henri Tresca, under this criterion a resistant piece or structural element fails when at one of its points it happens that:
being.
Maximum Distortion Energy Theory (Von Mises Criterion)
This criterion can be considered a refinement of the Tresca criterion. The maximum distortion energy criterion was first formulated by Maxwell in 1865[1] and later also mentioned by Huber[2] (1904). However, it was with the work of Richard Edler von Mises (1913) that the criterion achieved notoriety; This Von Mises stress-based theory of elastic failure is sometimes known as the James Clerk Maxwell|Maxwell-Tytus Maksymilian Huber|Huber-Hencky-Von Mises theory. The expression proposed by Von Mises and Hencky, according to this criterion, a resistant part or structural element fails when at any of its points the distortion energy per unit volume exceeds a certain threshold: