Thermal-Mechanical Coupled Simulation and Parameter Optimization of Narrow-Gap TIG Oscillating Welding Sidewalls

Literature Overview

The research by Gao Hui, Qu Jiajun, and Li Xianhui, published in Ordnance Materials and Engineering (2026), presents a finite element simulation study of thermal-mechanical coupling in narrow-gap TIG oscillating welding, with emphasis on sidewall behavior and process parameter optimization. Narrow-gap welding is a highly efficient technique for thick-section fabrication where the groove is pre-formed with minimal width, enabling single-pass or few-pass welding with reduced filler metal consumption and heat input.

Core Technical Points

Narrow-Gap TIG Oscillating Welding Configuration

The narrow-gap configuration typically involves:

• Groove width: 20–40 mm (compared to 40–80 mm in conventional V-groove)
• Groove depth: 20–50 mm
• Bevel angle: 0–2° (near-parallel walls)
• Oscillation amplitude: 5–15 mm
• Oscillation frequency: 2–6 Hz
• Travel speed: 15–40 cm/min

Thermal-Mechanical Coupled Simulation Approach

The study employs a sequential coupled analysis approach:

1. Thermal analysis: Moving heat source model (double-ellipsoidal or Gaussian) representing the oscillating arc trajectory. The heat source follows a sinusoidal path within the narrow gap, creating periodic heating of the sidewalls.
2. Mechanical analysis: Elastic-plastic constitutive model with temperature-dependent material properties. Residual stresses develop from differential thermal expansion and plastic deformation during cooling.
3. Coupling strategy: Temperature field from thermal analysis serves as thermal load for mechanical analysis, accounting for thermal stresses, plastic deformation, and creep effects.

Sidewall Behavior Analysis

The simulation reveals critical insights into sidewall behavior:

1. Thermal stress distribution: Maximum tensile stresses (250–350 MPa) develop at the sidewall fusion line due to differential cooling between the weld center and base metal.
2. Residual stress pattern: Compressive stresses exist in the weld center while tensile stresses concentrate at the sidewall-to-base metal interface, creating a potential cracking path.
3. Distortion mechanism: Asymmetric heating from oscillation causes progressive angular distortion, with the leading sidewall experiencing higher temperatures than the trailing sidewall.
4. Sidewall fusion control: The oscillation amplitude and frequency must be optimized to ensure complete sidewall fusion without excessive dilution or burn-through.

Parameter Optimization Results

Through multi-objective optimization (minimizing residual stress while maintaining complete fusion):

• Optimal oscillation amplitude: 8–12 mm for 30 mm gap width
• Optimal frequency: 3–4 Hz for balanced heat distribution
• Optimal travel speed: 25–30 cm/min for controlled cooling
• Residual stress reduction: 20–35% compared to non-oscillating narrow-gap welding
• Distortion reduction: 30–50% compared to conventional V-groove welding

Engineering Practice Applications

For pressure vessel fabrication, narrow-gap TIG oscillating welding offers significant advantages:

1. Material efficiency: Filler metal consumption reduced by 50–70% compared to conventional groove preparation, particularly significant for nickel-based alloy cladding where filler costs are prohibitive.
2. Heat input control: Total heat input reduced by 40–60%, minimizing HAZ width and sensitization risk in stainless steel and nickel alloy applications.
3. Distortion control: Reduced thermal distortion simplifies subsequent machining and alignment of pressure vessel components.
4. Productivity: Single-pass or few-pass capability for thick sections dramatically reduces fabrication time.

Study Insights and Implications

This research demonstrates the value of thermal-mechanical coupled simulation in predicting and controlling sidewall behavior in narrow-gap welding. For engineers involved in pressure vessel fabrication, the parameter optimization framework provides a systematic approach to process development that reduces trial-and-error costs. The findings are particularly relevant for applications where nickel-based alloy overlay is required on thick carbon steel or low-alloy steel sections, such as hydrogenation reactor internals and high-pressure hydrogen storage vessels. The ability to control residual stress through oscillation parameters offers a practical means of improving long-term fatigue performance without additional stress relief heat treatment.