PSI - Issue 44

Alessia Monaco et al. / Procedia Structural Integrity 44 (2023) 806–813 A. Monaco et al. / Structural Integrity Procedia 00 (2022) 000 – 000

811

6

Table 1. Scaling coefficients k i for the CSS calibration. 0-18 kN 0-35 kN 0-55 kN

600 820

390 650

258 570

k 1 k 2 k 3

1100

1100

1100

0.10%

0.08%

nT6-cable (LVDT1) LVDT 1 nT2-cable (LVDT2) LVDT 2 nT4-cable (LVDT3) LVDT 3 strain cables avg. LVDT Avg.

0.06%

0.04%

Strain [-]

0.02%

0.00%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-0.02%

Time [s]

Fig. 6. Strain values obtained by the CSSs scaled to the LVDT measurements.

Therefore, the strain values of the CSSs scaled by means of the correlation coefficients k i are then compared with the FE strain values in the capacity sensor components. In particular, Fig. 7 reports the elastic strain in the direction of the applied load (E22) of the dielectric layer of Kapton, the external layer of copper plate and the FR4 strip. For completeness, also the strains in the mortar, corresponding to the LVDT position, are reported (LVDT FEM). These numerical strain values are compared with the average strains obtained by the CSS. As expected, it can be observed that the average strains of the sensors are closest to those recorded in the mortar in the proximity of the LVDT location, due to the scaling process adopted for the alignment of the strain records. Conversely, the model shows higher values of strains in the constituent materials of the capacity sensor and this phenomenon is also emphasised by the fact that the FE model is not affected by any imperfection present in laboratory or due to the manufacturing process of the capacity sensor.

0.14%

E22_Kapton_FEM E22_Copper_FEM E22_FR4_FEM LVDT FEM strain cables avg.

0.12%

0.10%

0.08%

0.06%

Strain [-]

0.04%

0.02%

0.00%

0

0.2

0.4

0.6

0.8

1

Time [s]

Fig. 7. Comparison between the average CSS strain measurements and the FE strain values in the capacity sensor’s components .