N Value Sheet Metal Forming

Astm e646 standard test method for tensile strain hardening exponents n values of metallic sheet materials is for determining the strain hardening exponent.

N value sheet metal forming.

Tools include punch die that are used to deform the sheets. Thus as the n value increases the material s resistance to necking increases and the material can be stretched farther before necking starts. All you need are the sheet metal thickness and strain hardening exponent also known as the n value. The strain values that mark the forming limit is called the forming limit curve flc.

The r and n values are determined in the tensile test in order to characterize the forming properties. T co 7wf19j8ofd see it on twitter 3 4 times a year we send out an email on the latest topics related to sheet metal and forming which we find interesting. Sheet metal forming involves forming and cutting operations performed on metal sheets strips and coils. Classification of basic sheet forming processes bending deep drawing shearing.

The larger the n value the more the material can elongate before necking. The constant n plays a crucial role in sheet metal forming. The shape and placement of the forming limit curve for low carbon steels have been known for decades thanks to the pioneering work of dr. The forming limit increases due to increase the n value.

The diagram attempts to provide a graphical description of material failure tests such as a punched dome test. Astm e517 standard test method for plastic strain ratio r for sheet metal determines the plastic strain ratio. It is the ability to maintain thickness as the material is drawn. The effect of the n value in deep drawing is ambiguous.

The r value the plastic strain ratio of sheet metal intended for deep drawing applications is a measure of the resistance to thinning or thickening when subjected to either tensile or compressive forces in the plane of the sheet i e. The n value describes the hardening increase in strain during plastic deformation up to uniform elongation while the r value describes the vertical anisotropism. The surface area to volume ratio of the starting metal is relatively high. If thickness is in mm.

The strain hardening exponent plays an important role in sheet metal forming.