PSI - Issue 58

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Aleksandar Grbovic et al. / Procedia Structural Integrity 58 (2024) 42–47 A. Grbovic et al. / Structural Integrity Procedia 00 (2019) 000–000

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Comparing the values of moments and forces calculated for the designed whiffle-tree (Table 1, 3 rd and 4 th column) with values in Table 1, 5 th and 6 th column, it can be seen that the total force of 15368 N (sum of all forces in ribs, 5 th column) that will be introduced by a hydraulic jack is very close to the calculated value of force at 10 th rib 15433 N, while the 11 th rib is at the position of support, Solob, (2021). At the same time, moment 22895 Nm at 10 th rib is 2.5% greater than moment 22337 Nm (Table 1). This was taken as acceptable, so the test assembly was completed with the manufactured whiffle-tree shown in Figs. 9 and 10.

Fig. 10. Manufactured whiffle-tree.

Fig. 9. Manufactured whiffle-tree

3. Wing test loading and obtained displacements at the wing tip European Aviation Safety Agency’s specifications for light aerobatic aircraft define two types of testing: 1: Load must rise up to the limit load (6g) in steps, adding 10% of the load in each step, with a pause of 3 s between steps. Once a 6g load is achieved, slow unloading is conducted. 2: A destructive test is carried out with loading rise until the limit load (6g) as described above, and after that, the incremental increase of load is applied until wing failure. Following these instructions, the load introduced by the hydraulic jack was incrementally increased to reach the maximum force of 15787 N (as measured by force transducer). Table 2 shows values of forces and displacements measured at 10 wing locations for 5 steps of loading and unloading.

Table 2. Forces and displacements measured at 10 wing locations for 5 steps of loading (and unloading)

F

W1 mm

W2 mm

W3 mm

W4 mm

W5 mm

W6 mm

W7 mm

W8 mm

W9 mm

W10 mm

kN

-0.048 12.272 15.787 12.426 -0.617

-0.215 102.06 133.43 131.16 26.958

-0.171 83.564 109.72 108.11 22.245

-0.11 57.035 74.747 74.025 15.677

-0.069 38.484 50.652 50.475 10.979

-0.029 18.557 24.371 24.449 5.364

-0.099 51.637 67.382 67.149 14.758

-0.146 84.046 109.27 109.67 24.801

-0.099 55.133 71.828 72.567 17.279

-0.056 36.335 47.308 48.357 12.12

-0.029 18.314 23.753 24.718 6.792

4. Conclusions On the basis of the results presented here one can conclude that numerical results agree well with the experimental one, so that numerical procedure is considered verified. Such a verification is crucial for reliable numerical simulation and should be performed in always when critical components are under investigation for possible structural and fatigue failure.