The hollow-drawing behavior of tubing with γ0 values (ratio of initial wall thickness to outer radius) between 0 < γ0 < 1 was studied. The effect of various parameters on wall-thickness changes during hollow drawing through conical shaped dies was examined. The parameters which influenced the wall thickness changes were die-angle, alloy or metal, and γ0. The reduction per pass or magnitude of draft had only a slight or negligible effect. An examination of the wall-thickness changes in terms of current theories is made. The bulk true strain behavior of hollow-drawn tubing is also evaluated for several metals. These strains are the elongation, hoop, and thickness, and they are examined between the limits of a rod and an infinitely thin-wall tube. These limits and the constancy of volume principle suggest that the strains can be represented by ε = C In r/r0, where C is a coefficient peculiar to each strain.

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