A new testing apparatus has been made to analyze the ironing of thin metal cups. The frictional force Fp that acts axially along the punch side could be measured independently of the punch head load Pb, besides the ironing punch load P(=Fp + Pb). The frictional force Fp has two main constituents, one acting on the punch side in the deformation zone and the other on the punch side in contact with the thinned cup wall after ironing. These were separately estimated by using the measured stripping load of the ironed cup. This makes it possible to estimate accurately the axial stress acting on the ironed wall at the die exit, and to calculate the frictional coefficients at the die surface and the punch side. Thus cup fracture and friction during ironing could be analyzed quantitatively. The galling at the die-metal interface is unexpectedly enhanced with higher friction on the punch side. Cup fracture during ironing is probably affected by the galling.

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