PSI - Issue 71

M. Mohan Kumar et al. / Procedia Structural Integrity 71 (2025) 333–339

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Fig. 6. Strain gauge installation on Wing top, bottom and web skins.

For displacement measurements, four Cable Displacement Sensors (CDS) were used, with two sensors positioned at the front and trailing edges of the wing tips on both the left-hand side (LHS) and right-hand side (RHS) for the maximum up-bending case. Additionally, two Linear Variable Differential Transformers (LVDTs) were placed near the main landing gear (MLG) attachment brackets for the one-wheel landing case.

D01 -LVDT

D02 - LVDT

Fig. 7. Cable Displacement Sensor (CDS) and LVDT used in the displacement measurements.

5. Results and Discussion 5.1 Static Testing and Finite Element Analysis Results

During the static strength test, the wing was subjected to 100% of the Design Limit Load (DLL) for the one-wheel landing load case. Both Z and X loads were applied at the landing gear attachment bracket holes on all four landing gear attachment points. The test began by loading the wing to 10% of the DLL, with deflection and strain readings recorded at this load level. The load was then increased incrementally by 10% of the DLL, with strains and deflections measured at each step until the load reached 100% DLL. After reaching 100% DLL, the strain and deflection readings were documented before unloading the wing in steps of 10% DLL down to zero load. After complete unloading, a check was performed to determine any permanent set based on the deflection measurements. The test results indicated a maximum compressive strain of - 810 με, closely matching the FE analysis strain of - 854 με, at the rosette gauge S5_90°, located on the left-hand side (LHS) of the wing's bottom skin. The maximum tensile strain recorded was 1369 με, compared to an FE strain of 1408 με at the strain gauge location S3_45°, situated on the wing web, as shown in Fig. 8. During the limit load case, the maximum deflection measured in the Z direction was 4.77 mm on the LHS and -4.76 mm on the right-hand side (RHS) of the wing, as measured by the displacement sensors (CDS) mounted at the leading and trailing edges (LE & TE) of the wing tips. These values were compared to the FEA-predicted deflections of 6.7 mm and -6.16 mm, respectively, as shown in Fig. 9. The deflection readings observed during the test, when compared with FEA results, are tabulated in Table 2 and plotted in Fig. 9, demonstrating linearity in the deflection values measured during the test.