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Advances in the Bonded Composite Repair o f Metallic Aircraft Structure phần 7

Đối với các vết nứt tại các lỗ hoặc bậc, hoặc sửa chữa thiệt hại-bi ăn mòn tải axiality nên được hạch toán trong quá trình thiết kế. L. dính nhấn mạnh tối đa / năng lượng được ở dưới giá trị thiệt hại mệt mỏi tích tụ trong chất kết dính, xem 8,16,21]. Đối với FM73 này | Chapter 11. Thermal stress analysis 323 derive an expression for a in terms of these quantities. From equilibrium considerations we have E t ao Eịtị E2t2 ũt0 E li xi E2t2v.2 11.21 hence oti sa2 z. . 1L22 where 11.23 The expression for the stress state in the plate just outside the patch is given by Eq. 11.16 for r R -. J c2 c3 ơ fcl l-v l v zR2 11-24 We will now derive the expressions for the stress state in the plate beneath the patch and in the patch. From Eq. 11.15 with r Ri under a uniform temperature the displacement is given by rd .r 1 11.25 Since the displacement is the same in both the patch and plate we have 1 v aiT u 2 C -R 1 v ct2T u 2 C2 R where the displacement u corresponds to the location r Rị. The radial stresses for the plate and patch are given by ai i f qr. 21 Ũ a-iEi E2C2 Ơ2 - T rdr r2 J 1 - v 11.26 11.27 11.28 11.29 Using Eqs. 11.26-11.29 we have the expressions for the radial stresses in the plate 324 Advances in the bonded composite repair of metallic aircraft structure beneath the patch and in the patch Ex ơ 1-v El Ơ2 7Ì-- 1 - v rJ f 11.30 11-31 To obtain the residual stress in the plate beneath the patch it is necessary to sum Eqs. 11.13 and 11.30 but with Tị -Tt in Eq. 11.30 . Hence the final expression for the residual stress beneath the patch is _ l v y 77 - To _ _ 11 ơ V 2 Jt l-v r 21n Ao 2o J J 7r ãía r ì 11.32 1 - v Rif Since the initial stress in the patch is zero then the residual stress in the patch is given by Eq. 11.31 but again with T -Tị hence and the final expression for the residual stress just outside the patch is given by the summation of Eqs. 11.13 and 11.24 hence r . l v k Tị-To fRj n 2 1 v 2 n R fRo Rị T - i j 01.34 These equations now give the residual stress in terms of the cure temperature T. The displacement u at r Ri for Eqs. 11.17 11.18 and integration constants c2 Cl are given in the appendix. These equations now give the residual stress in terms of the cure temperature T. For operating temperatures different from