Tham khảo tài liệu 'bruhn - analysis and design of flight vehicles structures episode 3 part 11', 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 k f tan Ú s arg it ------------ LOS 3 1 The angle a must from Ref. 3 and this case for stringers satisfy the equation Is different from the hare as in equation 58 - eRG Q R tan a This formula Is similar to the one for the affective area of a single upright in a plane veb beam system Art where e - distance from . of ring to the skin p radius of gyration of the ring cross-section about an axis parallel to the skin. where as before from equation 94 r 2k z E drh sin2a or use Fig. for bracketed expression. tr . _ . _ l -jjr f from equation 104 eDrt fori from equation 103 Hti rtw Equation 103 assumes that k fg d t etc. are the same for the panels on each side of the ring. If not then some average value should be used or else fRQ must be written as the sum of 2 diagonal tension effects for each side panel as was dene for the longeron in 3 above. Equation 1ŨỔ must be solved by successive approximation as was done In the stringer system discussion. 8. Strength checks can then be made as follows using stress ratios. The maximum stress m tile ring will be as before eq. 59 . - RGTiAXi fRGTAX ÍHữ fo_ KG Where a Longerons ị where Fcc is the natural crippling i strength and F. is obtained from Fig. . L RGwiV -7- -- is obtained from Fig. . RG 7. The next problem Is the determination of the angle of diagonal tension Q. There are several ways In which d can be evaluated. Four are as follows Frequently In the case of thicker longerons the following Is used as a strength check í L _ 1 co a When there Is a significant amount of compressive strain simply assume Q 45 . b When there is no or very little axial strain present only shear use Fig. 011 45 to obtain a. That Is the primary and diagonal tension effects are simply added and checked against Fcc. b Rings frg c If sufficient tension stress or strain is present to prevent buckling from eq. 78 then of course d 0 . d Calculate a by the .
