PSI - Issue 25

Tiago Bento et al. / Procedia Structural Integrity 25 (2020) 234–245 Tiago Bento/ Structural Integrity Procedia 00 (2019) 000 – 000

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beyond yielding. Also, by limiting the loads, it is avoided fiber breakage (the fibers have a maximu m microstrain value of 1250 µε). With that explained, the results presented in this work are from standard Abaqus implicit simulations in which the only material parameters needed were the Young’s modulus and Poisson rati o. Results

3.7. Bragg fibers measurements in overlap joints

This lap joint was designed to simplify the loading conditions and serve as proof of concept. The readings from the Bragg sensor during the welding process are present in Fig. 7. To obtain the strain curve during the welding process for this particular fi ber it is necessary to multiply the wavelength shift by the first order sensitivity , S 1 = 823.4 [µε/nm] , and the following graphic is obtained. 2000

1500

5th degree 3rd degree Welding pin position Polinomial (5th degree) Polinomial (3rd degree) FBG sensor’s location

2

1000

-500 Microstrain ( με ) 0 500 0

3

1

50

100

150

200

250

-1000

4

-1500

-2000

Position along weld line [mm]

Fig. 7. Bragg wavelength shift during the welding process.

1

Stress direction in the joint plates caused by the tool Stress direction in the Bragg measuring location

Bragg sensor location

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3

4

Fig. 8. Local stress direction evolution during the welding process.