PSI - Issue 42

Zeng Chen et al. / Procedia Structural Integrity 42 (2022) 180–188 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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2. Experiments A large number of uniaxial and biaxial bending experiments were conducted to capture solely the effect of biaxiality, uncoupled from any shallow flaw effects. The tested specimens were extracted from BS1501-224 28B steel plates. The chemical composition of the material is shown in Table 1. Before the bending experiments, 20 small Charpy V-notch specimens (55mm × 10mm × 10mm) were tested in the impact test according to BS EN ISO 148-1 (148-1, 2009). The transition curve obtained is shown in Figure 1 (Oldfield, 1975). It is found that the transition region of this steel is between -120 ℃ and -20 ℃ , above -20 ℃ is the upper shelf region where ductile fracture is the main failure mode and below -120 ℃ is the lower shelf region where the brittle fracture dominates.

Table 1. Chemical composition of BS1501-224 28B Plate (Van Gelderen, 2016). ^ŝ DŶ ů

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Figure 1. Charpy impact transition curve.

Then, 16 cruciform/ 5-Point Bend (5PB – equivalent-biaxial bend) specimens and 12 rectangular/ 3-Point Bend (3PB - uniaxially bend) specimens were tested. All specimens were designed to be 10mm thick and contain a 20mm long through-thickness notch introduced using 0.1mm EDM wire and then fatigue pre-cracked until a/W =0.5. The load and displacement values were recorded directly from the Dartech 500 kN machine. The test temperature and CMOD were measured from separate instruments and all the values are gathered using a Vishay System 5000 data acquisition system. The test temperature remained at a steady temperature of approximately -160 ℃ . Tests were conducted under displacement control at a rate of 0.2 mm/min. Figure 2 shows the test setup.

Chamber

Loading punch

Cruciform specimen

Base 4 solid cylinder support rollers

Figure 2. Experimental setup of a cruciform specimen

To obtain a more convincible result, some fracture toughness values with the standard C(T) specimens and the SEN(B) specimens were collected from Balart & Knott (Balart & Knott, 2006) to support the following study.