PSI - Issue 38

Isabel Huther et al. / Procedia Structural Integrity 38 (2022) 466–476 Author name / Structural Integrity Procedia 00 (2021) 000 – 000

473

8

a

b Figure 8 (a) Strain mapping and virtual gages J5b and J6b for a load of 240 kN, (b) strain gages values (ep 2). [5]

a

b Figure 9 Load-versus jack displacement, ( a) charge/discharge cycles (ep 2), ( b) at one go (ep 3).[5]

5.2.2. Residual stress results On the specimens (ep 3) and (ep 2), an important relaxation of the residual stresses was observed (see Table 1) after a pre-load of 240 kN (1.67 YS) and a modification of the metallurgical structure, work hardening, regarding the variation of the diffraction peak width (FWHM). This parameter is proportional to the rate of the work hardening. These modifications are due to a plastic deformation near the weld toe, the local stresses exceeding the yield stress of the material. For the specimen (ep 1) with an overload of 150 kN (1.05 YS), the same results are obtained.

Table 1. Residual stress measurements before and after pre-loading

before pre-loading

after pre-loading

Specimen / face / zone

transversal stress (MPa)

longitudinal stress (MPa)

transversal stress (MPa)

longitudinal stress (MPa)

FWHM (°)

FWHM(°)

2 / A / AB1 2 / A / CD1 2 / B / AB2 2 / B / CD2 3 / A / AB1 1 / A / AB1

331 318 247 214 247 277

43 33

2.0637 2.0135 2.0778 2.0777 2.1671 2.3661

-13

-73

1.9453

220

89

159

73

34

1.9156

91

-87

0

2.16