Abstract：The critical curvature-radius as the main straightening technical parameter, decides the structure of equipment and the quality of products for straightening thin-walled tubes with equal curvature, however, it is usually carried out based on the experiential data and chart by skilled labourers, whose art is based on long experience and experiments, the special mathematical model of the critical radius is immediately necessary. But during mechanical modeling and analyzing, it is the critical curvature-radius that the cylindrical shell with the initial curvature under pure bending occurs plastic buckling, therefore, applying the general strain-displacement relations of the shell of revolution, the plastic buckling critical bending-moment model of the cylindrical shell under pure bending is presented by the Ritz method, based on the J2 deformation theory and energy method, then the critical radius is subsequently obtained and it is also shown how to solve synchronously. In order to certify whether it is correct, we have done some dynamic simulations by ANSYS/LS-DYNA, the results have shown that the model is approximate correct, by the comparison of the results of the simulations it is shown that wrinkling on the compression side of the cylindrical shell occurs before buckling due to ovalisation when the cylindrical shell occurs plastic buckling subject to pure bending.
2014, Vol. 35 
