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The uniaxial tension test is the primary experimental method used to directly measure a material's stress–strain behavior, providing valuable insights into its strain-hardening behavior. [1] The strain hardening exponent is sometimes regarded as a constant and occurs in forging and forming calculations as well as the formula known as Hollomon ...
Thus the basic influence parameters for the forming limits are, the strain hardening exponent, n, the initial sheet thickness, t 0 and the strain rate hardening coefficient, m. The lankford coefficient, r, which defines the plastic anisotropy of the material, has two effects on the forming limit curve. On the left side there is no influence ...
Work hardening, also known as strain hardening, is the process by which a material's load-bearing capacity (strength) increases during plastic (permanent) deformation. This characteristic is what sets ductile materials apart from brittle materials. [1] Work hardening may be desirable, undesirable, or inconsequential, depending on the application.
The Ramberg–Osgood equation was created to describe the nonlinear relationship between stress and strain—that is, the stress–strain curve—in materials near their yield points. It is especially applicable to metals that harden with plastic deformation (see work hardening ), showing a smooth elastic-plastic transition.
An empirical equation is commonly used to describe the relationship between true stress and true strain. = Here, n is the strain-hardening exponent and K is the strength coefficient. n is a measure of a material's work hardening behavior.
From these measurements the following properties can also be determined: Young's modulus, Poisson's ratio, yield strength, and strain-hardening characteristics. [3] Uniaxial tensile testing is the most commonly used for obtaining the mechanical characteristics of isotropic materials.
Where is flow stress, is a strength coefficient, is the plastic strain, and is the strain hardening exponent. Note that this is an empirical relation and does not model the relation at other temperatures or strain-rates (though the behavior may be similar).
It is calculated using the following equation: ˙ = where is the mid-radius value and ˙ is the strain rate. The viscosity of the sample is then calculated using the following equation: η = F π R 2 ϵ ˙ {\displaystyle \eta ={\frac {F}{\pi R^{2}{\dot {\epsilon }}}}} where η {\displaystyle \eta } is the sample viscosity, and F {\displaystyle ...