A deformation mechanism map is a way of representing the dominant deformation mechanism

Deformation mechanism

In structural geology, metallurgy and materials science, deformation mechanisms refer to the various mechanisms at the grain scale that are responsible for accommodating large plastic strains in rocks, metals and other materials.-Mechanisms:...

 in a material

Material

Material is anything made of matter, constituted of one or more substances. Wood, cement, hydrogen, air and water are all examples of materials. Sometimes the term "material" is used more narrowly to refer to substances or components with certain physical properties that are used as inputs to...

 loaded under a given set of conditions and thereby its likely failure mode. Deformation mechanism maps consist of some kind of stress

Stress (physics)

In continuum mechanics, stress is a measure of the internal forces acting within a deformable body. Quantitatively, it is a measure of the average force per unit area of a surface within the body on which internal forces act. These internal forces are a reaction to external forces applied on the body...

 plotted

Graph of a function

In mathematics, the graph of a function f is the collection of all ordered pairs . In particular, if x is a real number, graph means the graphical representation of this collection, in the form of a curve on a Cartesian plane, together with Cartesian axes, etc. Graphing on a Cartesian plane is...

 against some kind of temperature axis, typically stress normalised using the shear modulus versus homologous temperature

Homologous temperature

Homologous temperature expresses the temperature of a material as a fraction of its melting point temperature using the Kelvin scale. For example, the homologous temperature of lead at room temperature is approximately 0.50 ....

. For a given set of operating conditions calculations are undergone and experiments performed to determine the predominant mechanism operative for a given material.

Constructing the Map

Repeated experiments are performed to characterize the mechanism by which the material deforms. The dominant mechanism is the one by which the material will fail, however at any given level of stress and temperature, more than one of the creep

Creep (deformation)

In materials science, creep is the tendency of a solid material to slowly move or deform permanently under the influence of stresses. It occurs as a result of long term exposure to high levels of stress that are below the yield strength of the material....

 and plasticity

Plasticity (physics)

In physics and materials science, plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces. For example, a solid piece of metal being bent or pounded into a new shape displays plasticity as permanent changes occur within the...

 mechanisms may be active. It is left to scientific experiment to determine which controls the failure of the material.

Reading the Map

For a given stress profile and temperature, the point lies in a particular "deformation field". If the values place the point near the center of a field, it is likely that the primary mechanism by which the material will fail, i.e.: the type and rate of failure expected, grain boundary diffusion, plasticity, nabarro-herring creep, etc... If however, the stress and temperature conditions place the point near the boundary between two deformation mechanism regions then the dominating mechanism is less clear. Near the boundary there are likely more than one effect that are of sufficient magnitude to affect the deformation and possible failure of the material. Deformation mechanism maps are only as accurate as the number of experiments and calculations undertaken in their creation.

Example: Creep

Creep

Creep

Creep may refer to:* CREEP, the Committee for the Re-Election of the President, associated with the Watergate scandal of U.S. president Nixon's administration....

, a mode of material failure which often requires experimental evidence to construct empirical models of its behavior, is often represented by a deformation mechanism map. Data from measurements at various levels of stress and temperature are plotted, often with constant strain rate contours included. The map may then be useful to predict one of temperature, stress, and creep strain rate, given the other two.