Tham khảo tài liệu 'bruhn - analysis and design of flight vehicles structures episode 1 part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | ANALYSIS AND DESIGN OF FLIGHT VEHICLE STRUCTURES Icx anti ICy moment of inertia of each portion about their own X and Y centroidal axes. Location of centroidal axes - ỹ ZAy .6719 .767 ZA .675 X ZAx .3435 .392 SA .375 Transfer moment of Inertia and product of inertia from reference X and Y axes to parallel centroidal axes - ĩx Ix -Ay3 .955 - .875 X .767 .440 ĩy ly - Ax3 .291 - .375 X .3923 .157 ĩXy ZAxy - Axy .1132 - .375 X .767 X .392 - 7150 Calculate angle between centroidal X and Y axes and principal axes through centroidal as follows - tan 2 0 2 Ixv 2 ĩy-ĩx . 2 0 46 - 40 0 23 - 20 Calculate moments of Inertia about centroidal principal axes as fallows ĩXp ĩx cos 3 0 ĩy sin3 0 - 2ĨXy sin 0 cos 0 .44 X .918 3 .157x .396d 3 - 2 X .3965 X . 318 504 ini ĩyp ĩx slna 0 ĩy cos3 0 2ĨXy sin0cos 0 .44x .3965 .157 X .91d3 2 X .3965 X .918 .092 in. Fig. A3. 12 Example Problem 5. Fig. Shows a typical distributed flange - 2 cell - wing beam section. The upper and lower surface is stiffened by z and bulb angle sections. Determine the moment of inertia of the section about the principal axes. Solution The properties of the cross-section depend upon the effective material which can develop resisting axial stresses. The question of effective material Is taken up m later chapter. Table 9 shows the calculations for the moment of Inertia about the assumed rectangular reference axes XX and YY see 71g. . The cross section has been broken down Into 16 stringers as listed in column 1. For the top surface a width of 30 thicknesses of the .032 skin Is assumed to act with the stringers and a width of 25 thicknesses of the .04 skin see Col. 3 . On the lower surface the skin half way to adjacent stringers Is assumed acting with each stringer or the entire skin Is effective. Column 4 gives the combined area of each stringer unit and Is considered as concentrated at the centroid of the stringer and effective skin. All distances X and y
