PSI - Issue 2_A

Liviu Marsavina et al. / Procedia Structural Integrity 2 (2016) 1861–1869 Author name / Structural Integrity Procedia 00 (2016) 000–000

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tensile notched specimens. In Negru (2015) it’s defined the inherent stress for the Theory of Critical Distance (TCD), an approach based on the same theory of SED method, they belong to the linear elastic mechanic fracture theory (LEFM). For comparison it could be seen that the inherent stress in TCD method σ 0,TCD is lower than the failure stress on blunt specimens σ t used in this paper, Table 6, which can be explained that the σ t is the stress on the notch tip, while the inherent stress is determined at a critical distance L/2 from the notch tip. However, both increase with increasing density. Two different approach give values of the tensions in the same order of magnitude, this confirms that it’s possible to apply the SED method on these type of foams and the tensions σ t is valid to be used for determining the SED parameters for all type of notches and cracks.

1.2

1.4

1

1.2

1

0.8

0.8

0.6 (W/Wc) 0.5

0.6 (W/Wc) 0.5

708 300 145 100 Density [kg/m 3 ]

Rounded Vnotch

U notched plates

0.4

0.4

Circular hole, D= 10 mm

0.2

(b)

0.2

Circular hole, variable diameters

(a)

0

0

0

0.2

0.4

0.6 Me

0.8

1

1.2

0

100

200

300

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600

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800

Density [kg/m 3 ]

1.2

1.4

1.2

1

1

0.8

0.8

0.6 (W/Wc) 0.5

0.4 (W/Wc) 0.5 0.6

V notch U notched plates Circular hole, D= 10 mm Circular hole, variable diameters ASCB

708 300 145 100

0.4

0.2

0.2

(d)

(c)

0

0

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0.6 Me

0.8

1

1.2

0

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Density [kg/m 3 ]

Fig. 3. Ratio between the predictions of strain energy density: (a) notched specimens, (b) ASCB specimens under mixed mode, (c) new approach for ASCB specimens under mixed mode, (d) all notched specimens under mode I.

Table 6. Comparison between stress of TCD method and SED method. Density [kg/m 3 ] σ t [MPa]

σ 0,TCD [MPa]

100 145 300 708

3.19 4.39 6.06 26.7

2.17 3.19

5.6

23.14

1.4

1.2

1

0.4 (Wmean / Wc) 0.5 0.6 0.8

V notch U notch Circular hole, D=10 mm Circular hole, variable diameters ASCB

0.2

Fig. 4. Ratio between the predictions of mean strain energy density using the new values of critical energy density.

0

0

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Density [kg/m 3 ]