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Maximum distortion energy theory (von Mises yield criterion) also referred to as octahedral shear stress theory. [4] – This theory proposes that the total strain energy can be separated into two components: the volumetric (hydrostatic) strain energy and the shape (distortion or shear) strain energy. It is proposed that yield occurs when the ...
However, by means of the von Mises yield criterion, which depends solely on the value of the scalar von Mises stress, i.e., one degree of freedom, this comparison is straightforward: A larger von Mises value implies that the material is closer to the yield point.
Figure 3 shows the von Mises yield surface in the three-dimensional space of principal stresses. It is a circular cylinder of infinite length with its axis inclined at equal angles to the three principal stresses. Figure 4 shows the von Mises yield surface in two-dimensional space compared with Tresca–Guest criterion.
The point in the stress-strain curve at which the curve levels off and plastic deformation begins to occur. [13] Offset yield point (proof stress) When a yield point is not easily defined on the basis of the shape of the stress-strain curve an offset yield point is arbitrarily defined.
In continuum mechanics, stress triaxiality is the relative degree of hydrostatic stress in a given stress state. [1] It is often used as a triaxiality factor, T.F, which is the ratio of the hydrostatic stress, , to the Von Mises equivalent stress, . [2] [3] [4].
The earliest version was a straightforward extension of the von Mises yield criterion and had a quadratic form. This model was later generalized by allowing for an exponent m. Variations of these criteria are in wide use for metals, polymers, and certain composites.
Plastic deformation of a thin metal sheet. Flow plasticity is a solid mechanics theory that is used to describe the plastic behavior of materials. [1] Flow plasticity theories are characterized by the assumption that a flow rule exists that can be used to determine the amount of plastic deformation in the material.
It is commonly used to demonstrate the pressure dependence of a yield surface or the pressure-shear trajectory of a stress path. Because r {\displaystyle r} is non-negative the plot usually omits the negative portion of the r {\displaystyle r} -axis, but can be included to illustrate effects at opposing Lode angles (usually triaxial extension ...