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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 ...
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 index n usually lies between the values of 2, for fully strain hardened materials, and 2.5, for fully annealed materials. It is roughly related to the strain hardening coefficient in the equation for the true stress-true strain curve by adding 2. [1] Note, however, that below approximately d = 0.5 mm (0.020 in) the value of n can surpass 3.
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.
Beyond the Lüders strain, the stress increases due to strain hardening until it reaches the ultimate tensile stress. During this stage, the cross-sectional area decreases uniformly along the gauge length, due to the incompressibility of plastic flow (not because of the Poisson effect , which is an elastic phenomenon).
The principle behind the test is that the mean pressure required to test the material is the measurement of the hardness of the material. Units of megapascals (MPa) are frequently used for reporting Meyer hardness, but any unit of pressure can be used.
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 ...
Hardening is a metallurgical metalworking process used to increase the hardness of a metal. The hardness of a metal is directly proportional to the uniaxial yield stress at the location of the imposed strain. A harder metal will have a higher resistance to plastic deformation than a less hard metal.