Failure of metals and alloys in dentistry

Abstract

Failure of a material is generally to expect the conditions under which a solid material will fail under the action of external loads. The failure of metals is usually classified into ductile failure (yielding) or brittle failure (fracture). Metals can fail in a ductile or brittle manner or both dependent on the conditions such as temperature, type of stress, loading rate. Fracture is the separation of a body into two or more pieces in response to a stress that is static and at temperatures that are low relative to the melting temperature of the materia. In metals, there are two possible fracture modes, ductile and brittle. Fatigue failure occurs in structures subjected to dynamic and fluctuating stresses. Failure occurs at a stress level lower than the yield strength of the specimen. The term fatigue is used because this type of failure normally occurs after a long period of repeated stresses or strain cycling. Fatigue is estimated to be involved in approximately 90% of all metallic failures. Creep is a time-dependent permanent deformation of materials that are used at temperatures that are close to their melting points. creep is normally an undesirable phenomenon. for metals, it becomes important only for temperatures greater than about 0.4 of the melting temperature. In this article different types of metal failure will be discussed showing different mechanics, mechanisms and stages for fracture types, fatigue and creep.