Steady-State Thermal Analysis and Structural Stress Evaluation of IC Engine Piston for Five Engineering Materials Using ANSYS Finite Element Analysis: Temperature Distribution, Thermal Stress, and Design Optimisation

Abstract

The piston is one of the most thermally and mechanically stressed components in an internal combustion engine, subjected simultaneously to high cyclic gas pressure loads of up to 6–8 MPa and steep thermal gradients arising from combustion gas temperatures exceeding 2000°C on the crown and cooling oil temperatures of 120–140°C on the underside. Piston material selection must balance conflicting requirements of low density for inertia reduction, high thermal conductivity for crown heat dissipation, adequate strength at elevated temperature, and controlled thermal expansion compatible with the cylinder bore clearance. This paper presents a comprehensive steady-state thermal and structural finite element analysis of a single-cylinder petrol engine piston (bore 87 mm, stroke 73 mm, 435 cc) for five engineering materials: aluminium alloy A2618, steel EN 8, grey cast iron G3000, titanium alloy Ti-6Al-4V, and aluminium-SiC metal matrix composite (12 wt% SiC). The analysis is conducted using ANSYS Mechanical 2024 R2 with SOLID186 elements, applying boundary conditions derived from established heat transfer correlations for the gas side, ring belt, and oil-cooled underside. A mesh convergence study confirms solution accuracy. Temperature distributions, maximum temperatures, thermal gradients, thermal stresses, combined mechanical stresses under gas pressure loading, and safety factors are compared systematically across all five materials. Topology optimisation of the aluminium piston crown is subsequently performed to reduce mass while maintaining thermal performance. Results show that Ti-6Al-4V achieves the lowest crown temperature (352°C) due to reduced heat input from its low thermal conductivity acting as an insulator, with highest safety factor (6.52 combined), but at the penalty of high cost and machining difficulty. Aluminium alloy A2618 provides the best thermal conduction and lowest thermal stress with satisfactory safety factor (1.98) and remains the most practical material choice for petrol engine pistons. The topology-optimised aluminium piston reduces mass by 11.7% while improving safety factor to 2.32.