粉体の圧縮ならびにせん断特性について (粉体(特集))

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It is widely recognized that the three kinds of mechanism, the rearrangement, the elastic and plastic deformation and the cold working fragmentation of particles, take place during the compaction process of powder materials.Generally speaking, the compaction of powders is performed under considerably high pressure, and most reports on powder compaction refer to the results of that high pressure where plastic flow or fragmentation of particles predominats.In this paper the observation of compacting pressure P1 and of pressure on fixed piston P2 in low pressure range P1=15∼150kg/cm2 is reported, with its analysis based or these observed value according to Shaxby-Unkel equation. Shaxby-Unkel's equation P2/P1=exp[-4βμ(H/D)]is considered to be adequate for considerably high pressure as has so far been proved in many previous papers9)10)12), but it is proved that this equation is still useful if it is converted into the form P2/P1=Cexp[-4βμ(H/D)] even in the case of low pressure range where the process of rearranging particles is predominant. Moreover it depends upon the remarkable effect of internal friction and wall friction whether this equation is favorable or not.This converted Shaxby-Unkel's equation was applied to our study, and the product βμ was obtained from the slope of straight line (log P2/P1 vs. H/D) resulting from the compacting test.Accordingly, β was calculated using the valve of the product βμ from the compacting test, and the wall friction factor μ from the shearing test.β represents the ratio of radius to axial stress, and it is generally the function of internal friction factor μi and of wall friction factor μ.Here we confirmed, by substituting μi and μ from our shearing test for the formulas that have hitherto been reported, that the formula of β, derived by Unkel from the treatment using the theories of deformation, plastic and elastic, the theory of elastic deformation, is most suitable in case of graphite powder.
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粉体の圧縮ならびにせん断特性について (粉体(特集))

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