Shot peening plays a key role in surface modification technique for enhancing the fatigue resistance of gear steels. This paper establishes a finite element model for multi-shot shot peening of 18CrNiMo7-6 steel based on dislocation density evolution. Using the Johnson-Cook constitutive model, Avrami coverage control, and Python random distribution methods, it systematically investigates the effects of shot diameter (0.3–0.8 mm) and velocity (30–70 m/s) on residual stresses, dislocation cell size, and dislocation density. Results indicate residual stresses exhibit a hook-shaped distribution with depth. Increasing shot diameter or velocity enhances surface dislocation density, refines dislocation cells, and shifts maximum residual compressive stress deeper into the material. Optimal parameters exist: at 60 m/s velocity, a 0.5 mm shot yields the highest surface residual compressive stress (-464.9 MPa) and maximum residual compressive stress (-745.5 MPa). Excessively large diameters (e.g., 0.8 mm) or velocities diminish strengthening effects due to uneven coverage. X-ray testing validated the model's accuracy, providing theoretical basis for process parameter optimisation.

Hanlin Fu, Haifeng Chen. Numerical Simulation of Shot Peening for 18CrNiMo7-6 Gear Steel. Academic Journal of Engineering and Technology Science (2026), Vol. 9, Issue 2: 87-94. https://doi.org/10.25236/AJETS.2026.090212.

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