Mixed Mode Fracture

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Mixed mode fracture due to overload. Photo courtesy GEARTECH © 2014.

Definition: A mixed mode fracture is a combination of brittle and ductile failure modes.

Identification: Mixed mode fractures display characteristics of both ductile and brittle fractures.

Discussion: A mixed mode fracture is an intermediate case between ductile and brittle fractures.

Prevention: Mixed mode failures can be avoided by using ductile materials (high in Ni and Mo, low in Cr, Mn, C, P, and S), avoiding low temperature operating conditions, avoiding high loading rate events, using clean materials, using good heat treatment practices that result in small grain size and minimizes tensile residual stress, and not designing stress concentrating features in components.

More Information: For more information on mixed modes fracture failures, please submit a question to our “Ask an Expert” link. For assistance with a gearbox failure analysis, please visit our “Consulting” page.