PSI- Issue 9

Amal Saoud et al. / Procedia Structural Integrity 9 (2018) 235–242 Saoud Amal/ Structural Integrity Procedia 00 (2018) 000–000

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Table 3: Evolution of the maximum load for each test.

The critical load EUCALYPTUS GRANDIS (kN)

Standard deviation (kN)

Average (kN)

Standard deviation (kN)

Notch length a (mm) The critical load THUYA (kN)

Average (kN)

1

1.98 1.61 1.61 1.64 1.28 1.64 1.75 1.25 1.8

0.81 1.14 0.98 0.80 0.90 0.85 0.57 0.59 0.60 0.60 0.57 0.54 0.54 0.54 0.55 0.57 0.51 0.40 0.47 0.54 0.61 1

a =4

0.95

0.13

1.728

0.16

0.882

a =6

0.88

0.07

1.484

0.21

0.801

1.5 0.9 1.2

1.038

0.10

a =8

0.59

0.01

1.04

1

1.05 0.73 0.84 0.72 0.82

0.7644

0.06

a =10

0.55

0.01

0.712

0.64

0.7124

0.68

0.03

a =12

0.51

0.07

0.72

0.675

0.7

3.2. Application of the energy criterion to Thuja wood and Eucalyptus Grandis Our experimental approach helped us to determine an important parameter namely the rate of restitution of energy. To do this, we started by determining the compliance as a function of the crack size. The set of load-displacement curves provides several values of the compliance Ci (ai), defined by the slope of the load-displacement curve C = δ/P, where δ and P represent the displacement and the applied load, respectively. The experimental points were smoothed using a polynomial of order 3. To perform the calculations, the following assumptions were assumed: ・ Wood is a homogeneous material because the dimensions of the specimen are large compared to the difference between the diameters of two consecutive rings. ・ The elastic behavior is valid. ・ The orthotropic stiffness matrix is known. The G IIC mode II initiation fracture toughness G, the initiation fracture toughness corresponding to a small crack increment can be computed using the analytical form according to IRWIN-KIES:

2 B a   P C 2

(1)

G



IIc