PSI - Issue 62

Isabella Mazzatura et al. / Procedia Structural Integrity 62 (2024) 369–376 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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3.2. First phase – discussion of the results During the tests, the following data were collected: (i) the global force applied and recorded by a load cell, (ii) the deformation level recorded by the linear strain gauges on the wires, and (iii) the stresses measured by the X-ray diffraction method. Table 1 summarizes the main results achieved; for both new and extracted wires, the value of applied load for each step considered (Load), the value of stresses recorded by the strain gauges into the element ( _ ), the value of stresses given by the sum of the residual stress ( 0 ) measured at 0 kN load level, and the stress measured by the X-ray diffraction method at the single load level ( ) are presented. The resulting computed value of tension is given both by neglecting (thus, simply ) and considering (thus, ( + 0 ) ) the residual stresses. First elaborations of the measures, i.e. the values of relative errors ( ( ) ) between _ and and between _ and ( + 0 ) according to the equation (3), are also presented. ( )= _ − _ (3) being the computed value of tension, thus, simply or ( + 0 ) (either not considering or considering the influence of residual stresses). The average, the Standard Deviation (SD) and Coefficient of variation (CoV) values for and ( + 0 ) are given. The value of residual stresses ( 0 ), derived as measure at 0 kN Level, both in the extracted wire and in the new one, are equal to about -60 MPa (compression). The CoV achieved by the repeated measures on the wire for each single load level was not higher than 4,25% (excluding the very high CoV derived from the residual stress measures of the extracted wire), with slightly more spread values in the case of the extracted wire.

Table 1. Results of the test campaign.

Error ( σ XRD) [%]

Error ( σ XRD +σ 0)

σ mean (σXRD) [MPa]

SD (σXRD) [MPa]

CoV (σXRD) [%]

σ mean (σXRD+σ0) [MPa]

SD (σXRD+σ0) [MPa]

CoV (σXRD+σ0)

Load σ mean_SG

σ XRD

σ XRD +σ 0

Wire

[kN]

[MPa]

[MPa]

[MPa]

[%]

[%]

-68 -67 -65 -64 162 163 163 171 374 381 381 390 580 588 592 595 790 791 791 800 -60 -60 -54 -37 161 172 174 178 345 360 362 378 566 571 571 578 741 762

-68 -67 -65 -64 228 229 229 237 440 447 447 456 646 654 658 661 856 857 857 866 -60 -60 -54 -37 214 225 227 231 398 413 415 431 619 624 624 631 794 815

- - - -

- - - -

0

0

-66

1,83

-2,77%

-66

1,83

-2,77%

40% 40% 40% 37% 31% 30% 30% 29% 27% 26% 26% 25% 24% 25% 24% 24% 46% 42% 42% 40% 38% 35% 35% 32% 30% 30% 30% 29% 30% 28% - - - -

16% 16% 16% 12% 19% 18% 18% 16% 19% 18% 17% 17% 18% 19% 18% 17% 28% 25% 24% 23% 29% 26% 25% 22% 24% 23% 23% 22% 25% 23% - - - -

10

272

164,75

4,19

2,55%

230,75

4,19

1,82%

New

20

545

381,5

6,56

1,72%

447,5

6,56

1,47%

30

796

588,75

6,50

1,10%

654,75

6,50

0,99%

40

1046

793

4,69

0,59%

859

4,69

0,55%

0

0

-52,75

10,87

-20,61%

-52,75

10,87

-20,61%

10

298

171,25

7,27

4,25%

224

7,27

3,25%

Extracted

20

557

361,25

13,50

3,74%

414

13,50

3,26%

30

810

571,5

4,93

0,86%

624,25

4,93

0,79%

40

1056

759,25

12,50

1,65%

812

12,50

1,54%