7 Ribs and frames

Pagina 1

Aerospace Structure –Exercises 7 – 1 – Exercise #7 Ribs and frames Aerospace Structure –Exercises 7 – 2 – Exercise n. 1 Evaluate the internal forces in the rib , which is connected to the semi-monocoque section that is shown in the figure. Consider T y as the external force that is introduced by the rib in the structure. Choose the rib axis parallel to the x principal inertia axes of the section. Data: A=200 mm2 a=300 mm b=350 mm Solution 1) Evaluation of the shear flows equivalent to the force applied to the rib. - Problem set -up: stringers and panels numbering, centroid and inertia property of the section, reduction to open-path section and introduction of circulating flow q* - Evaluation of the shear flows for the open-path section Aerospace Structure –Exercises 7 – 3 – - Verification of resultant equivalence to the applied force: - Evaluation of the circulating flow by invoking the equivalence of moment: - Complete equivalent shear flow system and evaluation of equilibrating system Equivalent flows Equilibrating flows B) Evaluation of the internal forces in the rib, which is schematised as a beam -Application of the beam model to the rib: axes and conventions for internal forces Aerospace Structure –Exercises 7 – 4 – -Internal forces in the first domain: The values at the ends of the domain read: - Internal forces in the second domain: The shear force must take into account the force transmitted by the first stretch of the rib and the force transmitted by the vertical panel (q6 flow). Moment is obtained considering the contributions of concentrated moment and vertical load, which are transmitted by the first stretch of the rib, and of the horizontal panels:   222222 3 4 3 4 33 4 22 12323 4ˆ  yy y yy y yyx TbTTTbTa a TTbTM    The values at…