PSI - Issue 33

Fuzuli Ağrı Akçay et al. / Procedia Structural Integrity 33 (2021) 279 – 286 Author name / Structural Integrity Procedia 00 (2019) 000–000

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stress conditions. However, to perform a series of reliable experiments to produce various state of stress conditions is challenging (Xin et al., 2021) as well as expensive. Therefore, a fracture criterion with a small number of calibration parameters is vital in order to identify a fracture locus with a minimum number of experiments. Ductile fracture models can be categorized as physics-based models and phenomenological models. Physics based models are generally complex with a large number of calibration parameters, whereas phenomenological models lack physical basis (Dong et al., 2020). One of the oldest phenomenological fracture model is the maximum shear stress (MSS) criterion (Bai & Wierzbicki, 2015). MSS criterion was evaluated as the most advantageous criterion with respect to accuracy and the number of calibration parameters (Wierzbicki et al., 2005), with only one parameter to be calibrated. Another one-parameter fracture criterion is the energy balance (KAEB) concept (Karr & Akçay, 2016). KAEB concept is a recently developed physics-based model and is straightforward to implement, in contrast to the most complex physics-based models. This study assesses superiorities and shortcomings of KAEB concept and MSS criterion. In this regard, fracture loci of various metallic materials are obtained and evaluated. The remainder of the article is organized as follows. Fracture criteria and materials of investigation are presented in Section 2. Results are demonstrated and discussed in Section 3 and a summary with conclusion remarks is given in Section 4. Nomenclature � specific surface energy density (of tensile mode fracture) �� specific surface energy density (of shear mode fracture) ���� calibration parameter (in hybrid model) ��� calibration parameter (in maximum shear stress criterion) n hardening exponent γ calibration parameter (in hybrid model) ε � principal strain (in the first principal direction) ε �� equivalent strain ε � � equivalent strain at failure/fracture η stress triaxiality � fracture angle θ �� ����� Lode angle parameter μ friction coefficient � , �� , ��� principal stresses �� equivalent stress Ω strength coefficient 2. Materials and Methods 2.1. Materials Two aluminum alloys (Al 2024-T351 alloy and Al 6061-T6 alloy) and two structural steels (ASTM A572 Gr. 50 steel and AISI 1045 steel) are considered in the current study. The experimental data (of the materials of interest) for the average stress triaxiality, Lode angle parameter and the fracture strain are compiled by Zhu & Engelhardt (2018) and the summary of the experimental data is presented in Table 1 and Table 2 below. Stress triaxiality ( η ), Lode angle parameter ( θ �� ����� ), and fracture strain ( ε � � ) given in Table 1 and Table 2 represents average values.