Abstract
As a study of the deformation of visco-elasto-plastic materials under complex loadings, the deformation behaviour of a thin-walled tubular specimen of celluloid softened by heating was investigated. Creep tests and continuous loading tests under combined axial and torsional stresses were carried out along orthogonal bi-linear stress trajectories which are related each other as a mirror transformation in the deviatoric stress vector space.
The results obtained are summarized as follows:
(1) The resistance to deformation of the material became remarkably small after the corner of the stress trajectory.
(2) This decrease of the resistance to deformation appeared remarkably when the stress trajectory turned to the direction of small resistance to deformation.
(3) The resistance to deformation in the direction of post-corner of stress trajectory was smaller than that in the direction of pre-stress.
(4) After the corner, the directions of creep and inelastic strain-increment vectors did not coincide with that of stress vector. The difference of the directions of these two vectors became small with the lapse of time. This difference was influenced little by the location of stress trajectory.
