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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surface was then degreased with acetone, and AC-130, a chemical that served as substitute of PAA anodization, was applied on the surface for a period of one minute. After this process the plates were positioned in the welding fixation system. The welds were performed with a dedicated FSW ESAB®Legio 3UL numerical control machine. Strong horizontal and vertical clamping forces are fundamental not only to prevent distortion and undesired movement of the plates but also to reduce the magnitude of residual stresses which would be reflected in the fibers measurements. Once the aluminum sheets and the FBG sensors were in place, the two-part adhesive was applied with a nozzle mixer on the bottom plate already fixed in the system. The FSW process should be performed immediately following the adhesive application. The set of parameters which enabled production of reliable joints is presented in Table 4.

Table 4. Welding parameters Tool RPM

Welding speed 200 mm/min

Plunging force

Tool tilt

Plunge speed 0.1 mm/sec

Dwell time

1000

450 kgf

0º

6 sec

The three geometries of smart joints produced for this work are presented in Fig. 4.

(b)

(a)

Fig. 4. Produced specimens: (a) Primary specimen; (b) Secondary specimen; (c) T-joint.

(a)

(b) Fig. 5. (a) Milling of the fiber's channel in the primary specimen; (b) Transversal view of the channel in the T-joint

3.6. Finite element modelling The finite element Abaqus models were created based on a macrostructural analysis of the joint cross-section, like the one presented in Fig. 6 for the T-joint case, in order to keep the geometry as close to reality as possible.

Fig. 6. T joint's cross section

Only linear elastic material properties were used in the FEM models as it was not intended to model failure and as the goal of the instrumentation of the joint is to detect flaws in service (cracks) there is no need to model the behavior