Residual Stress-Driven Fatigue Life Optimization of Medical Welded Structures via Coupled Thermo-Mechanical Modeling

Abstract

The study investigates the influence of welding-induced residual stress on the fatigue life of medical welded structures using a coupled thermo-mechanical finite element framework. A moving double-ellipsoidal heat source model was employed to simulate the welding process of stainless steel medical components. Residual stress fields were extracted and mapped into a fatigue damage model based on stress-life (S-N) curves and rainflow cycle counting. Numerical simulations were conducted on 36 welding parameter combinations, covering heat inputs from 0.8 to 1.6 kJ/mm. The predicted peak tensile residual stress ranged from 210 to 385 MPa, leading to fatigue life variations of up to 3.4 times under identical external loading. The proposed optimization strategy achieved an average fatigue life improvement of 27.6% compared with baseline welding parameters, demonstrating its effectiveness for life enhancement design in medical devices.