PSI - Issue 33

O.B. Naimark et al. / Procedia Structural Integrity 33 (2021) 1115–1122

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Naimark O.B. et al / Structural Integrity Procedia 0

2. Materials and experimental conditions

Experimental set-up. Electromechanical Testometric and Shimadzu testing machines were used to study the mechanical behavior during static tension and compression tests, Fig.3a,b. The displacement and strain fields during testing were determined using the StrainMaster system and are presented in Fig.3b. DIC study of two parameter fracture criteria was conducted for the uniaxial tension of notch VT20. The strain pattern reveals the strain localization in the area close to the notch. The pattern was studied following two methods to analyze correlated behavior of multiscale damage assuming the defects induced strain as the part of the total strain.

(a)

(b)

Fig.3. Experimental scheme and DIC strain pattern

The spatial pattern in the terms “strain” versus “strain gradient” (conventionally called as the heteroclinics) reflects the existence of two attractors: the straight lines correspond to the quasi-elastic response and the dark area to blow up damage localization set, Fig.4.

Fig.4. The spatial phase portraits of the strain field in different points from the notch

The temporal phase portraits for different strain components (Fig.5) reveal the similarity with phase portraits in Fig.2 for dynamic crack with the collapsing of the elliptical set of points into the line set, which reflects the still hyperbolicity of stress-strain field according to the Irwin self-similar singular solution. The random clouds of points corresponds to the second self-similar blow-up singular solution and represents the set of damage foci transforming into the daughter cracks. The combination of parameters (the stress intensity factor and critical stress (strain according to Fig. 5)) providing the merge of two sets can be considered as the critical values and .