PSI - Issue 50

S.V. Panin et al. / Procedia Structural Integrity 50 (2023) 220–227

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S.V. Panin et al. / Structural Integrity Procedia 00 (2019) 000 – 000

Statistical processing of the results was carried out for at least four samples with the confidence interval calculation. Then, one value was discarded according to the accepted confidence interval. Thus, the values of three samples were used for the analysis by the Taguchi method. Fig. 2 illustrates the effect of the factor levels on shear strength, elongation at break, and work of fracture of the welded joints. Rising of the compression duration from 500 up to 1500 ms was accompanied by a minimal change in shear strength (Fig. 2, a), while both compression force and USW duration values were more significant factors for this trend. The next analyzed parameter was elongation at break (Fig. 2, b). Similarly, the USW duration and the compression force were more influencing factors, while the compression duration after the USW process had a significantly lower impact. The effect of the USW parameters on another factor, namely work of fracture, showed the same trend as in the elongation at break case (Fig. 1, a).

Fig. 2. Dependencies of the mechanical properties of the welded joints from the UWS parameters: (a) shear strength; (b) elongation at break; (c) work of fracture.

Based on the obtained results, ranking of the studied factors was carried out and their optimal values were assessed (Table 3). The factor characterized by the greatest impact was marked with the minimum number. As a result, it was determined that the USW duration mostly contributed to the improvement of the mechanical properties (its optimal value was 1200 ms). The compression force possessed a slightly lesser effect (its level was optimal at 3 atm). The compression duration after the USW process had the minimal impact, so it was decided to use its maximum value of 1500 ms for further research. Since the Taguchi method did not enable to identify any specific reasons for the observed trends in the mechanical properties of the welded joints, an analysis of the structure at their cross-section was carried out (Fig. 3).

Table 3. The thicknesses and the mechanical properties of the welded joints.

Compression duration after USW, ms

USW process duration, ms

Compression force, atm

Properties

Shear strength, MPa Elongation at break, % Work of fracture, N · m

2 1 1 4

3 3 3 9

1 2 2 5 3

Total

Optimal value

1200

1500