Abstract
The objectives of this work were to examine the tube expanding process in relation to as many variables as possible and to determine whether there would be any significant ‘size effect’. For these investigations an apparatus has been constructed which enables detailed observations to be made of the behaviour of a specimen tube-plate joint during expanding.
A typical record is given showing how the strains and mandrel torque develop during expanding. No appreciable size effect was found on the three geometrically similar systems tested. It is shown that the residual strains are much greater on the back than on the front of the plate, leading to lack of parallelism in the joint face, and that the plastic-elastic interface can extend much farther into the plate than was previously thought possible.
Comparison is made between these experimental results and the predictions of a theory proposed by the authors, and it is concluded that higher seat pressures could be obtained if axial extrusion of the tube could be restricted. This finding was confirmed by axially compressing short lengths of tube into a plate, the axial compression causing the tubes to bulge and expand themselves into the plate seat.
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