Issue 76

V Auradi et alii, Fracture and Structural Integrity, 76 (2026) 223-237; DOI: 10.3221/IGF-ESIS.76.14

a        w

P f

q

IC (1) The critical load ௤ , the beginning of unstable crack growth, which is prominently identified at the peak, where a significant change in slope is observed. B is the thickness of the specimen, W is the width of the specimen and f (a/w) indicates the ratio of crack length to the specimen width. The 95% secant line method uses a reference line (which is drawn at 95% of the initial elastic slope) intersecting with the actual load-COD curve mainly to detect the critical transition from linear to nonlinear behaviour and the unstable fracture propagation. K B W  

Percentage increase in K IC relative to as-cast Al6061

Kq= K IC (MPa √ m )

Thickness (m)

P q (kN)

Pmax ( kN)

Pmax/ P q

2.5(Kq/YS) 2 (m)

Sample

Composition

1

Al6061

0.020

3.02

3.27

1.081

0.0199

7.28

-

Al6061-1%Al2O ₃ - 0.5%ZrO ₂ Al6061-1%Al2O ₃ - 0.75%ZrO ₂ Al6061-1%Al2O ₃ - 1%ZrO ₂ Al6061-1%Al2O ₃ - 1.25%ZrO ₂ Al6061-0.5%Al2O ₃ - 1%ZrO ₂ Al6061-0.75%Al2O ₃ - 1 %ZrO ₂ Al6061-1.25%Al2O ₃ - 1%ZrO ₂

2

0.020

3.83

4.17

1.089

0.0194

9.23

26.78%

3

0.020

4.04

4.34 4.83

1.073

0.0195

9.75

33.92%

4

0.020

4.43

1.091

0.0199

10.73

47.39%

5

0.020

4.26

4.55

1.068

0.0190

10.28

41.20 %

6

0.020

3.97

4.34

1.092

0.0197

9.61

32.00%

7

0.020 0.020

4.14

4.49

1.084

0.0197

10.01

37.5 %

8

4.09

4.39

1.074

0.0183

9.86

35.43%

Table 5: Fracture Toughness of Al6061 alloy reinforced with different weight fractions of nano alumina and zirconium dioxide reinforcing particulate.

Figure 14: Fracture Toughness of 6061Al reinforced with different weight fractions of nano alumina and Zirconium dioxide reinforcing particulates

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