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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2.2. Methods Two fracture criteria are utilized in the current investigation: Energy balance concept and Maximum shear stress criterion. The energy balance concept is recently developed by Karr & Akçay (2016), whereas the maximum shear stress criterion has been in use for a long time. 2.2.1. Energy Balance (KAEB) Concept Energy Balance (KAEB) criterion is derived under quasi-static loading conditions assumption and temperature changes are neglected with the material is assumed to be homogeneous and isotropic. KEAB criterion is based on continuum modeling of energy release rates, and it states that the system, seeking a minimum energy state, will fracture if the rate of energy change for the system in the fracture mode becomes less than that of the un-fractured continuum system. Therefore, the critical state is reached when the rate of energy change of the bulk system is balanced by the rate of energy change of the fractured medium (Karr & Akçay, 2016) � � � � � ��� � � � � �� � � ��� � � � ��� � � � � � � �� (1) where � , �� , and ��� represents principal stresses and � denotes principal strain in the first principal direction. Additionally, � correspond to fracture angle, correspond to friction coefficient, and �� is a material constant. 2.2.2. Maximum Shear Stress (MSS) Criterion Maximum Shear Stress (MSS) criterion states that fracture occurs when the maximum shear stress reaches a critical value. This critical value is a calibration parameter and is stated as C ��� in the formulation � � ��� � ��� (2) Table 1. Experimental data of aluminum alloys (Zhu & Engelhardt, 2018). Al 2024-T351 Al 6061-T6 Test number �� ���� ε � � �� ���� ε � � 1 0.626 1.000 0.283 0.072 0.206 1.497 2 0.603 0.075 0.210 0.308 0.916 0.862 3 0.117 0.338 0.261 0.447 0.598 0.687 4 –0.278 –0.822 0.451 0.577 0.000 0.403 5 0.927 1.000 0.167 0.106 0.307 1.703 6 0.401 1.000 0.469 0.139 0.401 1.374 7 –0.234 –0.681 0.380 0.146 0.421 1.623 8 –0.233 –0.679 0.356 0.205 0.596 1.116 9 –0.224 –0.652 0.341 0.258 0.760 0.921 10 –0.248 –0.714 0.622 0.262 0.771 1.018 11 0.012 0.036 0.211 0.308 0.916 0.862 12 0.343 0.966 0.310 0.348 0.951 0.748 13 0.357 0.918 0.480 0.411 0.730 0.725 14 0.356 0.929 0.326 0.480 0.463 0.663 15 0.369 1.000 0.355 0.506 0.355 0.553 16 N/A N/A N/A 0.517 0.306 0.584