Zhuojin Pipe Fitting Co., LtdABAQUS-Based Dynamic Simulation of Tube Plate Surfacing and Stress Characteristics
Literature Overview
This 2014 paper published in the journal Electric Welder by Wang Puquan, He Qingzhong, Yan Yunqi, Guo Shuai, and Duan Peng from Sichuan University of Science and Engineering presents a numerical simulation study of tube plate surfacing using the ABAQUS finite element software. The research, supported by the Sichuan Provincial Key Laboratory of Material Corrosion and Protection (2013CL05) and the Zigong Municipal Key Science and Technology Program (2013C16), addresses a practical engineering challenge: the surfacing of heat exchanger tube plates with transition alloy materials on high-strength base substrates. The paper spans pages 92–96 and provides both theoretical simulation results and experimental validation, offering a comprehensive approach to surfacing process optimization.
Technical Background and Engineering Challenge
Heat exchanger tube plates are critical components in chemical processing, petrochemical, and power generation equipment. They are typically fabricated from high-strength carbon steel or low-alloy steel (such as 16Mn or Q345R) and must accommodate hundreds or thousands of tube holes. In many service environments, the tube plate surfaces require corrosion-resistant or wear-resistant surfacing to extend service life.
The challenge lies in surfacing a transition alloy material (either a soft material for stress relief or a corrosion-resistant material) onto a high-strength base without introducing excessive residual stresses, distortion, or cracking. The thermal and mechanical mismatch between the base material and the deposit creates complex stress states that can lead to:
- Cracking: Thermal cracking in the deposit or HAZ cracking due to high carbon equivalent
- Distortion: Warping of the tube plate that affects tube insertion and sealing
- Delamination: Loss of bonding at the deposit-base interface under cyclic loading
- Residual stress-induced failure: Stress concentrations at tube holes that initiate fatigue cracks
ABAQUS Simulation Methodology
The researchers developed a 3D finite element model of the tube plate surfacing process using ABAQUS software. The simulation approach involved:
Heat Source Modeling
A moving heat source model was employed to represent the surfacing arc. The researchers evaluated different heat source formulations and determined that a double-ellipsoidal heat source model provided the best agreement with experimental temperature measurements:
| Parameter | Value |
|---|---|
| Heat source type | Double-ellipsoidal |
| Arc current | 250–350 A |
| Arc voltage | 25–35 V |
| Travel speed | 100–200 mm/min |
| Heat input | 2.5–5.0 kJ/mm |
| Thermal efficiency | 0.65–0.75 |
The double-ellipsoidal model accounts for the asymmetric heat distribution ahead of and behind the arc, which is critical for accurately predicting the temperature field evolution during multi-pass surfacing.
Material Properties and Boundary Conditions
The simulation incorporated temperature-dependent material properties for both the base steel and the surfacing alloy, including thermal conductivity, specific heat, elastic modulus, and yield strength. The tube plate geometry was modeled with representative tube holes to capture stress concentration effects.
Multi-Pass Surfacing Simulation
The researchers simulated a multi-pass surfacing sequence, accounting for:
- Thermal history from previous passes
- Plastic deformation accumulation
- Stress relaxation during interpass cooling
- Residual stress development at the deposit-base interface
Simulation Results and Experimental Validation
The simulation results were validated against experimental measurements obtained from actual tube plate surfacing trials. The key findings include:
Temperature Field Distribution
The temperature field showed the expected asymmetric distribution with higher temperatures ahead of the arc due to preheating of the material. The peak temperature at the surface reached approximately 1800–2000°C, while the base material temperature at a depth of 5 mm remained below 800°C. The temperature gradient decreased with distance from the surfacing line, indicating that the thermal influence zone extends approximately 30–50 mm from the weld centerline.
Stress Field Distribution
The residual stress distribution revealed several important features:
| Location | Residual Stress (MPa) | Stress State |
|---|---|---|
| Deposit surface | 150–250 | Compressive |
| Deposit-base interface | 200–350 | Tensile |
| Base HAZ | 100–200 | Tensile |
| Base far field | < 50 | Near-zero |
The tensile residual stress at the deposit-base interface is of particular concern, as it can promote cracking and delamination. The researchers found that the stress magnitude is influenced by several factors:
- Heat input: Higher heat input increases thermal expansion and subsequently increases residual stress upon cooling
- Number of passes: Multi-pass surfacing allows for stress redistribution through plastic deformation, generally reducing peak stresses compared to single-pass surfacing
- Travel speed: Faster travel speeds reduce heat input per unit length, decreasing residual stress but potentially increasing cracking susceptibility
- Preheating: Preheating to 150–250°C reduces thermal gradients and lowers peak residual stresses by 20–30%
Experimental Validation
The researchers conducted actual tube plate surfacing trials and measured:
- Surface temperature distributions using infrared thermography
- Residual stresses using hole-drilling strain gauge method
- Hardness profiles across the deposit and HAZ
- Metallographic examination of the deposit-base interface
The experimental results showed good agreement with the simulation predictions, with temperature measurements within 5% of predicted values and residual stress measurements within 15% of predicted values. This validation confirms the reliability of the simulation model for process optimization purposes.
Process Optimization Recommendations
Based on the simulation and experimental results, the researchers recommended the following process parameters for tube plate surfacing:
| Parameter | Recommended Value | Rationale |
|---|---|---|
| Preheat temperature | 150–250°C | Reduces thermal gradient and residual stress |
| Interpass temperature | 150–300°C | Controls heat input and prevents overheating |
| Arc current | 250–300 A | Balances deposition rate and heat input |
| Travel speed | 120–180 mm/min | Optimizes heat input per unit length |
| Number of passes | 2–3 | Allows stress redistribution |
| Post-weld stress relief | 550–650°C, 2 h | Reduces residual stress by 50–70% |
Study Insights and Reflections
This paper exemplifies the value of combining numerical simulation with experimental validation in surfacing process development. The ABAQUS-based approach allowed the researchers to explore process parameter effects systematically without the cost and time of extensive experimental trials. The validation against experimental data provides confidence in the simulation results and demonstrates the practical applicability of the approach.
The identification of tensile residual stress at the deposit-base interface as a critical concern is particularly important for engineers working with high-strength base materials. This stress state can promote interfacial cracking, particularly under cyclic loading conditions, and must be addressed through process optimization or post-weld treatment.
One limitation of the study is the relatively simple geometry modeled. The actual tube plate geometry, with its numerous tube holes and varying thickness, creates complex stress concentrations that may not be fully captured by a simplified model. Future work should incorporate more detailed geometric representations and consider the effect of tube hole spacing and diameter on residual stress distribution.
The paper also does not extensively address the metallurgical aspects of the deposit, such as phase transformation, grain structure, and dilution effects. While the stress analysis is thorough, the mechanical performance of the surfacing deposit depends on both the stress state and the microstructure, and a more comprehensive analysis would integrate both aspects.
In conclusion, this 2014 paper provides a solid foundation for the numerical simulation of tube plate surfacing processes. The ABAQUS-based approach, validated against experimental data, offers a practical tool for process optimization and stress management. The identification of key process parameters and their effects on residual stress provides directly applicable guidance for engineers working on heat exchanger tube plate surfacing applications.