PSI - Issue 60

Rakesh Bhadra et al. / Procedia Structural Integrity 60 (2024) 149–164 Bhadra et al. / Structural Integrity Procedia 00 (2023) 000 – 000

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(a) Only FGM

(b) Nanocomposite

Fig.2. Mesh configuration.

In the meshing process of the nanocomposite model, a 2D element called PLANE223, which is capable of thermal-structural analysis, is utilized. The top surface, where contact occurs, is meshed with CONTA172 elements, while the rigid surface in contact is meshed with TARGE169 elements. The Lagrangian contact algorithm is employed during the generation of contact pairs between the surface of the nanocomposite block and the indenter surface [Johnson (1987)]. To optimize solution time without compromising accuracy, a gradual refinement of the mesh is applied, creating a finer mesh near the contact zone and a coarser mesh away from it, as depicted in Fig. 2. Thermal analysis is conducted to incorporate the material properties of FGM. To impose the necessary structural boundary conditions, all nodes along the x-axis are constrained from moving in both x and y directions, as the base of the model is attached to the bulk material. Similarly, all nodes located along the y-axis or line of symmetry are constrained from moving in the x-direction [Brizmer et al. (2006)]. The material mechanical properties of FGM are obtained from the literature and the same equation is adopted where material mechanical property changes with the changes in elastic gradation parameter "γ e " ( or inhomogeneity parameter) [Jana et al. (2020), Giannakopoulos & Suresh (1997)]. Where γ e is the inhomogeneity parameter (gradation parameter) for an elastically graded block, R is the thickness along the direction of indentation and r is the distance from the base of the block. E 0 represented the modulus of elasticity of the material at the contact surface shown in Fig.3. The material mechanical property of FGM is considered that the Modulus of elasticity (E 0 ) at the surface of the block is 150 GPa, Poisson’s ratio is 0.3, tangent modulus is 4% of modulus of elasticity, yield strength is 750 MPa for entire block and elastic gradation parameter (γ e ) varies from -2,0 and 2 [Jana et al. (2020)]. Property of the CNTs Modulus of elasticity (E 0 ) is 1000 GPa and Poisson’s ratio is 0.27 [Ahmed et al. (2020) and Nouri et al. (2012)]. The bilinear isotropic hardening model is adopted in the present model for post-elastic behavior. The von Mises yield criterion is chosen to identify the yielding of material during the process as the rate-independent plasticity algorithm is used. As the modulus of elasticity (E) and tangent modulus (E t ) varies from the contacting surface to the base of the block this variation is achieved by the temperature-dependent material property of FGM and applied as thermal load according to the require temperature for specific properties bestowing to the coordinate location. The thermal properties conductivity and thermal expansion coefficient are set as zero which causes no structural effect during the thermal loading (boundary condition for thermal analysis). The properties of CNTs remain constant regardless of temperature when integrated into material modeling. ) ( 0 R r  e E E e   (1)