PSI - Issue 79

Kazem Reza Kashyzadeh et al. / Procedia Structural Integrity 79 (2026) 65–72

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a function of temperature (from liquid to solid state). Next, green sand with the combinations of silica sand, chromite sand, bentonite (clay) 5-11%, water 2-4%, inert sludge 3-5%, and anthracite 0-1% was defined as the standard mold. Table 1 present the thermophysical properties of the mold.

Table 1. Thermophysical properties of the mold. Properties

Value 1450

Unit

Density

kg/m³

Thermal conductivity Specific heat capacity

0.5

W/m ꞏ K J/kg ꞏ K

1066

The interfacial heat transfer coefficient between the casting and the mold was set as a temperature-dependent function to accurately model the air gap formation that occurs during solidification and cooling. 2.2. Simulation Setup The entire simulation workflow for this study was performed using Altair Inspire, a powerful finite element method (FEM)-based simulation software suite developed for the analysis of casting processes. This software was selected for its robust capabilities in modeling coupled fluid dynamics, heat transfer, stress evolution, and defect prediction in a fully integrated environment. The simulation setup involved the following key steps and model configurations: 2.2.1. Geometry Import and Mesh Generation The CAD model of the steering knuckle was imported into the Altair Inspire. A fully automatic tetrahedral meshing algorithm was employed to generate a high-quality computational mesh. The final mesh consisted of approximately 3.2 million elements, with a global element size of 3 mm. Critical regions, such as the thin arms, junctions, and the gating system, were locally refined with a minimum element size of 1.2 mm to ensure sufficient resolution for accurate calculation of fluid flow, thermal gradients, and stress concentrations. A mesh sensitivity analysis was conducted to confirm that the results were independent of further mesh refinement. 2.2.2. Material Properties Assignment The information required in this section can be found in Section 2.1. In addition, extra information such as temperature-dependent graphs are available in the software library. 2.2.3. Initial and Boundary Conditions A uniform initial temperature of 25 °C (ambient temperature) for the entire sand mold was defined as the initial condition. In addition, the initial temperature of the molten metal was set to 1270 °C, a typical superheat temperature for ductile iron casting to ensure complete filling. Filling time and solidification time were considered as 2.884 and 309.20 seconds. Also, pouring molten metal velocity was set to 1.29 / . Finally, the acceleration due to gravity (9.81 m/s²) was defined in the appropriate direction for each pouring scenario to accurately model the filling process. 2.2.4. Solver Settings The Navier-Stokes equations were solved to model the turbulent flow of the molten metal during mold filling. Moreover, the k- ε turbulence model was selected for its proven accuracy in simulating high-Reynolds-number flows in casting processes. The energy equation was solved to compute the heat transfer between the casting and the mold, tracking the phase change from liquid to solid. Eventually, a coupled thermo-mechanical analysis was performed. 2.3. Experimental Design In this study, three different scenarios for the location of molten pool were considered as follows:  Case 1: Pouring the melt from the top of the hub.