Abstract: | In the elementary bending theory it is usual to admit the hypothesis of small strains, small enough to neglect the transversal stresses induced by severe curvature. It is also admitted that the neutral surface coincides, during deformation, with the central plane of the plate. To carry out a mechanical modeling of heavy plates bending, for the big diameter tube, it is necessary a general theory of plate bending, without restrictions regarding the magnitude of strains and curvature; it is also necessary to determine the neutral surface movement and the movement of each fiber across the plate thickness. The paper presents a model of strains and stresses calculus for both a rigid-plastic material and for a hardenable material. An important issue of these calculi is the width determination of the zone where the material suffer, during bending, both an elongation and a compression and so, the Bauschinger effect has an important influence on the mechanical proprieties of tubes. In this zone the material strength after bending is less than the plate strength, the strength diminishing being proportional to the width of mentioned zone. |
