The thesis deals with problems of radial expanding of
thin-walled tubes when an unstable tool is used. The target is to considere
possibility how to use obtained results for FLD elabaration. Specimens are
cut of the ø 20 x 1 tube made of 17 248 (DIN 1.4541) stainless steel. A
polyurethane cylinder of stifness of 95 Sha is used as the unstable tool.
This tool was designed for experiments to allowed radial expanding towards
free space until the firs crack occurs. The target of this thesis is not to
produce a new part but than to consider the effecienty of Polyurethan for
radial expandig in technological tests of tubes.
During first tests it was discovered creation of an
asymmetrical shape in bulging section of the specimen. This problem was
analyzed and another experimental technique was designed. The conclusion is:
creation of asymmetry is due to swing of the Polyurethane cylinder, which is
placed in tube, during the compression. This process is not influenced even
by another construction approach or change of Polyuretane stifness.
In this work an analysis of bulging section formed on
tube is done (evolution of shape change, thickness change and maximum
strain) and influence of clamping method is researched (specimens with
strapped and free ends)
Further relevance of theoretical equations for
calculation of true wall thickness was prooved on basis of comparison
theoretical values with values from experiments. Only one equation that
takes into account specimens with strapped ends is valid for radial
expanding with Polyurethane.
There was no possibility to evaluate materail
characteristic C and n with respect to asymmetrical bulging during the
biaxial test. Position of critical formability in the Keeler-Goodwin diagram
was defined due to values of critical strain.