PSI - Issue 68

Josef Arthur Schönherr et al. / Procedia Structural Integrity 68 (2025) 425–431 J. A. Scho¨nherr et al. / Structural Integrity Procedia 00 (2024) 000–000

429

5

a

b

c

P92 ICHAZC FGHAZC CGHAZC Weld Material

FGHAZB CGHAZB ICHAZB Buttering CGHAZA FGHAZA ICHAZA CB2

Stress (log) Minimal creep strain rate (log)

Stress (log) Minimal creep strain rate (log)

Stress (log) Minimal creep strain rate (log)

Fig. 3. Minimal creep strain rate vs. stress relations for the three parameter sets used in a stress range representative for the specimen’s ligament. The Norton parameter A follows as the y-axis intercept value and n follows as the slope of the straight lines in double-logarithmic representation. (a) Norton parameters A and n are equal for all regions. (b) Norton parameters A are determined per region, whereas n is equal for all regions. (c) Norton parameters A and n are determined individually for each region.

Fig. 4. Von Mises stress distribution for a crack in the interface of ICHAZ B and the buttering layer with material parameters A and n determined per region in steady state conditions. The nonhomogeneous material layup causes unsymmetric and partly discontinuous stress distribution at material boundaries.

a

b

c

1 . 2

1 . 2

1 . 2

1 . 1

1 . 1

1 . 1

1 . 0

1 . 0

1 . 0

ASTME1457 Abaqus ( r → 0 ) C ∗ / C ∗ Creep Stress Power 0 . 8 0 . 9

ASTME1457 Abaqus ( r → 0 ) C ∗ / C ∗ Creep Stress Power 0 . 8 0 . 9

ASTME1457 Abaqus ( r → 0 ) C ∗ / C ∗ Creep Stress Power 0 . 8 0 . 9

Abaqus Contour 4

Abaqus Contour 8

Abaqus Contour 4

Abaqus Contour 8

Abaqus Contour 4

Abaqus Contour 8

Creep Stress Power

Creep Stress Power

Creep Stress Power

Abaqus Contour 12

Abaqus Contour 12

Abaqus Contour 12

Fig. 5. C ∗ results for a crack in the interface ICHAZ B and buttering, normalized with the creep stress power solution given for the three material parameter sets (a) to (c) referring to Fig. 3 (a) to (c).

ASTM E1457 method and the Abaqus integral solutions, return momentously higher C ∗ values. The same applies to a crack, introduced in the center line of the ICHAZ B layer, Fig. 6. If the crack is introduced deeper inside the HAZ, such as in the interface of the FGHAZ B and ICHAZ B, Fig. 7 or in the center line of FGHAZ B, Fig. 8, the ASTM E1457 method result for the n determined per region material parameter set converges to the physically sound creep stress power solution. The results indicate that all three methods to evaluate C ∗ perform comparatively equal for materially homogeneous specimens as well as for material layups that may be described with the same Norton