PSI - Issue 48

Mirza Manjgo et al. / Procedia Structural Integrity 48 (2023) 161–168 Manjgo et al / Structural Integrity Procedia 00 (2023) 000 – 000

165

5

fracture surfaces.

Table 6. Percentage of ductile fractures Specimens Area of the specimen

% of ductile fracture by instrumented device

% of ductile fracture by classical measurement

500-01 500-02

32.48 32.59 32.54

31.76 31.98 31.87

64 mm 2

Average

a) b) Figure 6. Broken specimen 500-01: (a) Fracture surface side A, (b) Fracture surface side B

3.4. Fracture mechanics SENB tests

Determination of fracture toughness during plane deformation of a specimen taken from steel plate SA500 was carried out in order to determine the critical stress intensity factor, K IC , i.e., to evaluate the base material in the presence of crack-type defect as the most dangerous fault. The test was carried out according to the ASTM E1820 [11] standard, using the normalization method for obtaining the J - R curve. The specimen is shown in Figure 7.

Figure 7. Geometry of SENB specimen for fracture mechanic test In accordance with ASTM E1820, and to monitor crack growth using the normalization method, an excel file is created in which all the equations necessary to determine the fracture-mechanical parameters, force-CMOD, J -integral and CTOD-R (crack tip opening displacement) of the material are programmed. Figure 8 shows the force-CMOD diagram. This is followed by a diagram of parallels intersecting the x-axis at 0.15 mm, 0.20 mm, and 1.5 mm. The material parameter J IC is defined as the intersection of the J - R curve and the line that intersects the x-axis at 0.2 mm. The maximum value to be considered is limited to J max , since with values of J > J max the plastic deformation becomes significant so that the fracture behaviour ceases to depend only on the material, but also on the remaining ligament. The test results are given in Figure 9.