PSI - Issue 52

Yingwu Li et al. / Procedia Structural Integrity 52 (2024) 709–718 Author name / Structural Integrity Procedia 00 (2023) 000–000

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Fig. 8. The Cumming plot of temperature-frequency shift coe ffi cients obtained from the experiments in the third group

Table 4. The consistency assessment results of the temperature-frequency shift coe ffi cients. Test scenarios Cronbach’s alpha ( α ) McDonald’s omega ( ω )

Split-half reliability coe ffi cient

First Group

0.988 0.999 0.941

0.993 0.999 0.977

0.979 0.984 0.955

Second Group Third Group

with acrylate (-1.55 ◦ C / GHz). However, it is worth noting that the maximum mean di ff erence in Figure 8 is less than 0.03 ◦ C / GHz, which is equivalent to the surface mounted sensors in the second group. This indicates that the SMF sensors with polymer coating exhibit higher stability in temperature measurement compared to those with acrylate coating.

3.2. The consistency assessment of temperature-frequency shift coe ffi cient

In this section, we employed the same procedures as in Section 2.1 to assess the consistency of the temperature frequency shift coe ffi cient across various experiments. Due to the di ff erent coe ffi cient values observed in the three groups, the consistency assessment was carried out independently within each temperature experiment group. The results of the K-S tests for the three experimental groups are presented in Figure 5(b). The p-value, indicated by the red dashed line, was set at 0.05 for characterizing the normality of measured temperature-frequency shift coe ffi cient in di ff erent experiments. It can be observed that nearly all tests exhibit conformity to the normal distribution, espe cially in the surface mounted situation within the second group. As a consequence, the consistency assessment of the temperature-frequency shift coe ffi cient was represented by Cronbach’s alpha, McDonald’s omega, and Split-half reli ability coe ffi cient, which are summarized in Table 4. The results presented in this table provide compelling evidence for the high temperature measurement consistency of distributed fibre optic sensors in composite structures under various test scenarios.