PSI - Issue 46

Raviraj Verma et al. / Procedia Structural Integrity 46 (2023) 175–181 Raviraj Verma/ Structural Integrity Procedia 00 (2021) 000–000 3 where, �� and ��� represent 0.2% yield strength and maximum reached load, respectively, while loading compact tension (C(T)) computational domain is shown in Fig. 1. Once the validation criteria are given in Eqs. (2) and (3) are satisfied, � value is established for critical fracture toughness under mode-I loading conditions ( Ⅰ � ). The Abaqus 19 platform is used to model the problem and appropriate boundary conditions are imposed with four-noded quadrilateral elements used for meshing the computational domain. 177

Fig. 1 . Computational model for compact tension (C(T)) specimen of Ti alloy utilized in fracture toughness evaluation. Crack initiation and propagation are made by incorporating XFEM approach via defining crack at the V-notched tip in C(T) specimen. The XFEM is defined by nodal displacement function ( � � � ) as mentioned in Eq. (4) which is governed by partition of unity (PU) method (Fischer et al. 2003; Tolochko et al. 2000). � � � � ∑ � � � ���� � � � � � � � � � �� � �∑ � � � �� ���� � � � �� �� �� (4) where, � � � , � � , � � � , � , and �� are Lagrange interpolation function, Heaviside function for crack surface, asymptotic crack enrichment function, additional degree of freedom (associated with the Heaviside function), and degree of freedom of enriched nodal (associated with crack tip enrichment function), respectively. The Heaviside function is decided based on criteria mentioned below in Eq. (5). � � � � � �� � � ∗ � �� �� ���� ���� � (5) where, , ∗ and are the Gauss point in the system, on the closet to crack, and outward unit normal to crack at ∗ , respectively. The asymptotic enrichment function in the polar coordinate system is governed through Eq. (6) mentioned below. � � � � �√ cos � � ,√ sin � � , √ cos � � sin √ sin � � sin � (6) The stress-life theory ‘Basquin’s Law’ is used to evaluate the fatigue life of AMed Ti-6Al-4V alloy, which is governed by Eq. (7) (Suresh 1998). It considers the material’s intrinsic behaviour through its exponent and proves its versatility within the elastic deformation regime. ∆ � � � � � � � � � � � (7) where, ∆ , � � , , � are stress-amplitude, fatigue strength coefficient, Basquin’s exponent, and number of reversal cycle to failure, respectively. The computational inputs are carefully taken to estimate fracture toughness and fatigue-life of LPBFedTi64 alloy.