PSI - Issue 13

Primož Štefane et al. / Procedia Structural Integrity 13 (2018) 1895 – 1900 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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Table 1 List of tested SE(B) specimens with characteristic dimensions and fracture toughness values.

Specimen

Material configuration

a 0 (mm) 10.65

a 0 /W (-) 0.53 0.43 0.45 0.46 0.51 0.41 0.48

L 0 (mm)

a p (mm) 11.79 10.00 10.85 11.46 9.89

a p /W (-) 0.59 0.50 0.50 0.54 0.57 0.49 0.54

J I (kJ/m 2 )

K JI (MPa×m 1/2 )

SE(B)-02 SE(B)-38 SE(B)-40 SE(B)-27 SE(B)-58 SE(B)-11 SE(B)-52

BM OM UM

- - -

451 193 336 224 441 425 312

313.7 223.9 293.4 241.2 338.5 329.9 282.7

8.58 9.02 9.19

OM – UM OM – UM UM – OM UM – OM

0.81 0.85 0.71 0.92

10.30

8.09 9.58

9.87

10.88

All SE(B) specimens were notched in the direction of welded sample plate thickness and had a width and thickness of W=B=20 mm. Sharp fatigue cracks were introduced in SE(B) specimens through fatigue precracking with load ratio R=0.1 and applied maximum stress intensity factor (SIF) to elastic modulus ratio K max /E≤1.1×10 -4 m 2 . The distance from fusion line to crack tip was L 0 =0.5÷1 mm (Fig. 2.a and 2.b) in order to observe crack propagation through the fusion line during fracture testing. Due to uneven distribution of UM and OM material in the welded joint, the fatigue crack length a 0 varied for each SE(B) specimen. In case of SE(B) samples extracted from BM, complete UM and complete OM welds, the initial relative crack length was approx. a 0 /W=0.5. Fracture tests were conducted at room temperature under crosshead displacement control at loading rate of 1 mm/min. Crack mouth opening displacement (CMOD) was measured with a dedicated clip gauge. Development of plasticity zone and strain pattern on the surface of the specimens was monitored with 3D DIC system GOM Aramis. J-integral resistance curves (figure 3.b) were obtained by normalization data reduction technique (NDRT) in accordance to standard ASTM E1820.

a)

b)

Figure 2 Notched SE(B) specimens with sharp fatigue cracks in a) OM weld material and b) UM weld material.

a)

b)

Figure 3 Results of conducted fracture tests in form of a) load-CMOD recorded history and b) J-integral resistance curves.