Principle of contact equilibration and the fundamentals of the consolidation of powder materials
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The principle of contact equilibration enables a powder material undergoing consolidation to be treated as a balance equilibrating consolidation stresses. The concepts of an effective critical cross sectionαef (a “reading on the scale” of the balance) and an effective critical pressure (pc)ef (a “scale division”) have been introduced. Simple formulas, Eqs. (8) and (9), have been derived for the determination of a strengthening factor.
The principle of contact equilibration is expressed also in the fact that changes in consolidation stresses brought about by an increase or decrease in the strength of powder materials, as given by Eqs. (8) and (10b), are proportional to the consolidating pressure.
From Eq. (6), it follows that, for any consolidation process, the magnitude of the critical cross section in any direction is the same (provided thatα0=0). When pressings exhibit anisotropy of critical cross section, this is due to an elastic aftereffect induced by consolidation.
The magnitude (pc)ef in the cold shaping of unwork-hardened powders is equal to (HB)min. During the re-pressing of powder materials, this magnitude tends to a value equal to the yield stress.
In certain cases, the principle of equilibration can be utilized for calculating the p vsϑ relationship even when theα=F(ϑ) function is not known.
KeywordsAnisotropy Simple Formula Powder Material Critical Pressure Consolidation Process
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