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Any material with a reasonably high Melting Point can be strengthened in this fashion. It is often exploited to harden alloys that are not amenable to Heat Treatment , including low-carbon Steel . Conversely, since the low melting point of Indium makes it immune to work hardening at room temperature, it can be used as a Gasket material in high-vacuum systems.

Often, cold work is carried out by the same process that shapes the metal into its final form, including Cold Rolling (contrast Hot Rolling ) and '' Cold Drawing ''. Techniques have also been designed to maintain the general shape of the workpiece during work hardening, including '' Shot Peening '' and '' Constant Channel Angular Press ing''). A material's work hardenability can be predicted by analyzing a Stress-strain Curve , or studied in context by performing a Hardness test before and after the proposed cold work process.


MATHEMATICAL DESCRIPTIONS


There are two common mathematical descriptions of the work hardening phenomenon. Hollomon's equation is a power law relationship between the stress and the amount of plastic strain εp. Ludwik's equation is similar but includes the yield stress σy

: \sigma = K \epsilon_p ^n \,\! (Hollomon's)

: \sigma = \sigma_y + K \epsilon_p^n \,\! (Ludwik's)

where K is the strength index and n is the Strain Hardening Index .

If a material has been subjected to prior deformation (at low temperature) then the yield stress will be increased by a factor depending on the amount of prior plastic strain ε0

: \sigma = \sigma_y + K (\epsilon_0 + \epsilon_p)^n \,\!

The constant K is structure dependent and is influenced by processing while n is a material property normally lying in the range 0.2-0.5. The strain hardening index can be described by:

: n = rac{d \log(\sigma)}{d \log(\epsilon)} = rac{\epsilon}{\sigma} rac{d \epsilon}{d \sigma} \,\!

This equation can be evaluated from the slope of a log(σ) - log(ε) plot. Rearraging allows a determination of the rate of strain hardening at a given stress and strain

: rac{d \epsilon}{d \sigma} = n rac{\sigma}{\epsilon} \,\!