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The stress and strain can be normal, shear, or a mixture, and can also be uniaxial, biaxial, or multiaxial, and can even change with time. The form of deformation can be compression, stretching, torsion, rotation, and so on. If not mentioned otherwise, stress–strain curve typically refers to the relationship between axial normal stress and ...
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Conversely, ductile materials fail after significant plastic strain (deformation) and absorb more energy. Note that in this idealized example, the yield and ultimate tensile stresses are the same for both materials; brittle or ductile behavior is not necessarily related to strength.
As an example, the stress state of a steel beam in compression differs from the stress state of a steel axle under torsion, even if both specimens are of the same material. In view of the stress tensor, which fully describes the stress state, this difference manifests in six degrees of freedom , because the stress tensor has six independent ...
In a sufficiently ductile material, when necking becomes substantial, it causes a reversal of the engineering stress–strain curve (curve A, figure 2); this is because the engineering stress is calculated assuming the original cross-sectional area before necking. The reversal point is the maximum stress on the engineering stress–strain curve ...
Stress-strain curve for ductile materials with no well defined yield point. UTS=ultimate tensile strength. Yield stress is defined by an offset line, corresponding to a given amount of plastic deformation. Date: 23 August 2007: Source: Own work: Author: Sigmund
Plastic deformation is the permanent distortion of a material under applied stress, as opposed to elastic deformation, which is reversible upon removing the stress. Ductility is a critical mechanical performance indicator, particularly in applications that require materials to bend, stretch, or deform in other ways without breaking.
Other models may also include the effects of strain gradients. [3] Independent of test conditions, the flow stress is also affected by: chemical composition, purity, crystal structure, phase constitution, microstructure, grain size, and prior strain. [4] The flow stress is an important parameter in the fatigue failure of ductile materials.