N Value Sheet Metal Forming

Thus as the n value increases the material s resistance to necking increases and the material can be stretched farther before necking starts.

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. Tools include punch die that are used to deform the sheets. The n value describes the hardening increase in strain during plastic deformation up to uniform elongation while the r value describes the vertical anisotropism. In order to determine whether a given region has failed a mechanical test is performed.

The larger the n value the more the material can elongate before necking. Of all the mechanical properties determined by a tensile test the plastic strain ratio is the most difficult and requires close attention to detail. 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. The strain hardening exponent plays an important role in sheet metal forming.

Sheet metal forming involves forming and cutting operations performed on metal sheets strips and coils. 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. A forming limit diagram also known as a forming limit curve is used in sheet metal forming for predicting forming behavior of sheet metal. The surface area to volume ratio of the starting metal is relatively high.

It is the ability to maintain thickness as the material is drawn. The forming limit increases due to increase the n value. The strain values that mark the forming limit is called the forming limit curve flc. Astm e517 standard test method for plastic strain ratio r for sheet metal determines the plastic strain ratio.

The constant n plays a crucial role in sheet metal forming. All you need are the sheet metal thickness and strain hardening exponent also known as the n value. If thickness is in mm. The effect of the n value in deep drawing is ambiguous.

The diagram attempts to provide a graphical description of material failure tests such as a punched dome test.