Zhuojin Pipe Fitting Co., LtdResidual Stress Measurement of Pure Aluminum Thin Plate TIG Welded Joints Using the Hole-Drilling Method
Literature Overview
This 2018 paper published in Hot Working Technology presents a systematic investigation of welding residual stresses in 3 mm thick pure aluminum thin plates welded using the TIG process. The research was conducted at Inner Mongolia University of Technology and was supported by the Inner Mongolia Autonomous Region Graduate Research Innovation Program. The study employs high-speed camera analysis of the arc morphology and the hole-drilling method for residual stress measurement, with strain data acquisition and wireless communication for data transmission, followed by MATLAB-based calculations. The work addresses a fundamental challenge in aluminum welding: the management of residual stresses that can compromise structural integrity, dimensional accuracy, and fatigue performance.
Core Technical Findings
Arc Morphology Analysis
The high-speed camera analysis of the TIG welding arc provides insight into the energy input characteristics and arc stability during the welding process. The arc morphology directly influences the heat input distribution, which in turn governs the thermal cycle experienced by the material and the resulting residual stress pattern. Understanding the arc behavior is essential for correlating process parameters with residual stress outcomes and for developing predictive models of welding-induced stress fields.
Residual Stress Distribution
The hole-drilling method results reveal a characteristic residual stress distribution pattern that is typical of thin plate welding. Perpendicular to the weld line, the longitudinal residual stress decreases from the weld center toward the base metal. A significant tensile stress exists at the weld center, with the maximum residual stress value occurring around the fusion zone. Upon reaching the base metal region, the tensile stress transitions to compressive stress. In the constraint region, the residual compressive stress gradually decreases and eventually transforms back into tensile stress. Along the weld line direction, the longitudinal residual tensile stress gradually decreases from both edges toward the center.
| Direction | Location | Residual Stress Characteristic |
|---|---|---|
| Perpendicular to weld | Weld center | High tensile stress |
| Perpendicular to weld | Fusion zone vicinity | Maximum residual stress value |
| Perpendicular to weld | Base metal region | Compressive stress |
| Perpendicular to weld | Constraint region | Compressive to tensile transition |
| Along weld line | Both edges | Higher tensile stress |
| Along weld line | Center | Lower tensile stress |
Engineering Practice Implications
The residual stress distribution observed in this study has direct implications for the design and fabrication of aluminum structures. The high tensile residual stress at the weld center and fusion zone creates a driving force for stress corrosion cracking, particularly in aluminum alloys susceptible to this degradation mechanism. The compressive stress in the base metal region represents the equilibrium counterpart to the tensile stresses near the weld, and this balance is essential for maintaining the overall force equilibrium of the welded structure.
For thin plate applications, the residual stress pattern can lead to significant post-weld distortion. The compressive stresses in the base metal can cause out-of-plane buckling or warping, which is a common problem in aluminum sheet fabrication. Understanding the stress distribution allows engineers to implement countermeasures such as back-rolling, tack welding, or sequential welding strategies to minimize distortion.
The hole-drilling method used in this study is a well-established non-destructive technique for residual stress measurement. However, it has limitations in thin plates where the stress gradient through the thickness may not be fully captured by a single hole depth. The study's approach of measuring at multiple locations and using wireless strain data acquisition represents a practical methodology that balances measurement accuracy with field applicability.
Key Questions and Reflections
The transition from tensile to compressive stress and back to tensile stress in the constraint region is an interesting feature that warrants further investigation. This pattern suggests that the welding process creates a complex stress field that cannot be described by simple analytical models. The interaction between the thermal expansion of the weld zone and the mechanical constraint imposed by the surrounding cooler material creates a multi-scale stress distribution that depends on plate thickness, constraint conditions, and welding sequence.
A practical question for engineers working with aluminum thin plates is how to reduce the peak tensile residual stress at the weld center without introducing unacceptable distortion. Options include post-weld stress relief annealing, mechanical peening, or optimization of the welding parameters to reduce heat input. Each approach has trade-offs in terms of cost, time, and potential impact on material properties. The study provides a baseline for evaluating the effectiveness of these countermeasures.
The wireless data transmission aspect of the measurement methodology is noteworthy from a practical standpoint. In industrial settings, the ability to acquire strain data without physical connections to the measurement equipment reduces the risk of interference and allows measurements to be taken in difficult-to-access locations. This represents a practical advancement in residual stress measurement technology.
Study Insights and Outlook
This study demonstrates the effectiveness of combining high-speed arc analysis with hole-drilling residual stress measurement for characterizing the welding-induced stress state in aluminum thin plates. The characteristic stress distribution pattern identified provides a useful reference for predicting distortion and evaluating stress relief strategies. For engineering practice, the key takeaway is that the peak tensile residual stress at the fusion zone represents the primary concern for structural integrity, and targeted stress relief measures should be applied to this region. Future work should explore the correlation between arc morphology parameters and residual stress magnitudes, as well as the effectiveness of various stress relief techniques in reducing the peak tensile stresses without introducing additional distortion. The methodology presented here offers a practical framework for residual stress assessment in aluminum welding applications.