Numerical Simulation of TIG Welding for Aviation Engine Flame筒整流罩

Literature Overview

This paper by Lei Kai, Tian Mengliang, Duan Leizhao, Tu Quan, Ao Bin, Xia Changlong, and Peng Zhenxiao, published in Hot Working Technology (2022, Vol. 51, No. 19, pp. 139–144), presents a numerical simulation study of TIG welding for the flame筒整流罩 (flame筒 straightening cover) of an aviation engine. The work was conducted at China Aero Engine Guizhou Liyang Aviation Power Co., Ltd., and addresses the practical welding challenges of joining a cylindrical component to eight support brackets.

Core Technical Approach

The study employs a thermomechanical finite element method that accounts for material nonlinearity. The methodology follows a rigorous validation-then-application approach:

1. Validation: Overlap joint welding experiments were conducted to verify the accuracy of the numerical simulation method.
2. Application: Different welding sequences and directions were simulated to predict deformation and residual stress distributions.

This validation-first approach is essential for engineering applications, as it establishes confidence in the simulation results before applying them to the actual component.

Key Findings and Technical Analysis

Welding Sequence Optimization

The study evaluated several welding sequence strategies, including interval welding (间隔焊) and symmetric welding (对称焊). The results show that:

Welding Direction Effect

A critical finding is that welding both bracket welds from top to bottom results in severe deformation of the part. This is attributed to the cumulative downward thermal force that causes the cylindrical cover to distort. In contrast, welding from bottom to top produces more manageable deformation, as the gravitational and thermal forces are more balanced.

The study also found that changing the welding sequence and direction has no significant effect on residual stress magnitude and distribution. This is an important practical insight: residual stress is primarily governed by the thermal cycle parameters (current, voltage, travel speed) rather than by the welding sequence. However, deformation is highly sensitive to welding sequence and direction, as it depends on the cumulative effect of thermal expansion and contraction forces.

Residual Stress Distribution

The residual stress in the bracket weld regions exhibits a tensile stress state along the axial direction of the cylindrical cover. This is consistent with the general behavior of residual stresses in welding, where the weld metal contracts upon cooling, pulling the surrounding material into tension. The study also found that the residual stress in the second-welded weld is higher than in the first-welded weld, which is expected because the second weld is deposited on an already-deformed and stress-relaxed structure.

Integration with Engineering Practice

For aviation engine components, dimensional accuracy and structural integrity are paramount. The flame筒整流罩 is a critical component that must maintain its geometric shape to ensure proper gas flow and engine performance. Welding distortion can lead to misalignment, increased vibration, and reduced engine life.

The recommended welding strategy of interval welding with bottom-to-top welding direction offers a practical solution for minimizing distortion while maintaining acceptable residual stress levels. This approach can be implemented with standard TIG welding equipment and does not require specialized multi-torch setups.

From a quality control perspective, the following measures should be considered:

• Pre-weld fit-up: Ensure precise alignment of the brackets before welding to minimize initial distortion.
• Welding sequence documentation: Clearly define and document the welding sequence and direction for each component.
• Post-weld inspection: Perform dimensional measurements after welding to verify that distortion is within acceptable limits.
• Residual stress assessment: Consider residual stress measurement (e.g., X-ray diffraction or hole drilling method) for critical components.

Key Questions and Reflections

The study provides valuable simulation-based guidance but has several limitations. First, the simulation is validated only for overlap joints, and the actual component involves T-joints between the cylindrical cover and the brackets. The weld geometry and thermal conditions may differ, potentially affecting the accuracy of the predictions.

Second, the study does not address the effects of welding parameters (current, voltage, travel speed) on deformation and residual stress. In practice, these parameters are critical process variables that must be optimized for each specific application. Third, the study does not consider post-weld stress relief treatment, which could significantly reduce residual stresses without affecting the component geometry.

Study Insights and Implications

This study demonstrates the value of numerical simulation in optimizing welding processes for complex aerospace components. The key findings are practical and actionable: interval welding and bottom-to-top welding direction should be adopted for the flame筒整流罩 to minimize deformation while maintaining acceptable residual stress levels.

For aerospace welding engineers, this paper reinforces the importance of welding sequence planning as a primary tool for distortion control. The simulation-based approach offers a cost-effective alternative to physical trial-and-error, particularly for components that are expensive to fabricate and difficult to repair. However, simulation results should always be validated with physical experiments before being applied to production, as demonstrated by the validation approach used in this study.