Tham khảo tài liệu 'bruhn - analysis and design of flight vehicles structures episode 2 part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER A13 BENDING STRESSES A13 0 Introduction. The tar AB in rig. a Is subjected to an axial compressive load p. If the compressive stresses are such that no buckling of the bar takes place then bar sections such as 1-1 and 2-2 move parallel to each other as the bar shortens under the compressive stress. lt 2 p-----1 I I H----------p A p Ij B Fig. a Shear Diagram z Moment Pia7 In Fig. b the same bar is used as a simply-supported beam with two applied loads p as shown. The shear and bending moment diagrams for the given beam loading are also shown. The portion of the beam between sections 1-1 and 2-2 under the given loading are subjected to pure bending since the shear 15 zero m this region. Experimental evidence for a beam segment 4x taken m this beam region under pure bending shows that plane sections remain plane after bending but that the plane sections rotate with respect to each other as Illustrated In Fig. c where the dashed line represents the unstressed beam segment and the heavy section the shape after pure bending takes place. Thus the top fibers are shortened and subjected to compressive stresses and the lower fibers are elongated and subjected to tensile stresses. Therefore at some plane n-n on the cross-section the fibers suffer no deformation and thus have zero stress. This location of zero stress under pure bending is referred to as the neutral axis. Location of Neutral Axis. Fig. d shows a cantilever beam subjected to a pure moment at Its free end and under this Beam Section applied moment the beam takes the exaggerated deflected shape as shown. The applied bending moment vector acts parallel to the z axis or In other words the applied bending moment acts In a plane perpendicular to the z axis. Consider a beam segment of length L. Fig. d shows the distortion of this segment when plane sections remain plane after bending of the beam. It will be assumed that the beam section Is homogeneous that is made of the same material and that the beam .
