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Tham khảo tài liệu 'bruhn - analysis and design of flight vehicles structures episode 2 part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | A22.2 ANALYSIS OF SPECIAL WING PROBLEMS Fig. A22.1 Fig. A22. 2 Idealization of the hah panel by use of substitute stringers The sheet-stringer panel may in general contain a large number 0a longitudinal elements stringers . The labor involved In treating this multi-element structure In detail Is prohibitive and thus an appropriate Idealization must be made. First It Is likely that the panel may be considered to be symmetric about a longitudinal axis so that only the half-panel need be handled. Second the complex multi-stringer structure is replaced by one having but three stringers. As Indicated In Fig. A22.2 these stringers are 1 a substitute stringer having for Its area all the effective area of the fully continuous members to one side of the combing stringer the stringer bordering the cutout and placed at the centroid of the area of material for which It substitutes. The stress which this stringer develops is then the average stress for the material It replaces. 2 the combing stringer being simply the main continuous stringer bordering the cutout. 3 another substitute stringer this one replacing all of the effective material made discontinuous by the cutout. It is located at the centroid of the material It replaces and Its stress Is the average stress for this same material. The sheet thicknesses used are the same as those of the actual structure. An alternate idealization in which stringers 1 and 43 are located along the lines AB and CD respectively Fig. A22.2 was used in Reference 2 for a box beam loaded In torsion. When the longitudinal members themselves contribute to the shear stiffness of the cover as is the case for hat section stringers riveted to the skin so as to form small closed cross sections an effective thickness must be used. This point is discussed in Reference 3 . In this source however the increase in shear stiffness is accounted for not by increasing skin thickness but by decreasing the panel width -an equivalent procedure. -tj. -ta b 7.56 .
