Zhuojin Pipe Fitting Co., LtdOverlay Stress and Deformation Analysis System Based on ANSYS Secondary Development
Literature Overview
This study by Deng Caiyan, Zhao Junmei, Wang Dongpo, and Gong Baoming from the College of Materials Science and Engineering, Tianjin University, published in the Journal of Tianjin University (2016, Vol. 49, No. 12, pp. 1330–1334), presents a customized overlay welding stress and deformation analysis system developed through secondary development of ANSYS using APDL (ANSYS Parametric Design Language) on a VC++ platform. The system provides parametric modeling, temperature field simulation, and residual stress analysis capabilities for overlay welding structures. Validation was performed using the case of Inconel 625 alloy overlay on X65 pipe inner wall.
System Architecture and Functionality
The developed system addresses the limitations of standard ANSYS modeling for overlay welding analysis by encapsulating common analysis procedures into parametric command stream templates. The system provides:
| Module | Function | Input Parameters |
|---|---|---|
| Parametric Modeling | Automated geometry creation | Pipe dimensions, overlay thickness, number of passes |
| Thermal Analysis | Temperature field simulation | Welding heat input, travel speed, material thermal properties |
| Stress Analysis | Residual stress calculation | Thermal expansion coefficients, yield stress vs. temperature |
| Deformation Analysis | Distortion prediction | Constraint conditions, structural geometry |
The system was validated against the Inconel 625 overlay on X65 pipe case, which is a representative application in oil and gas pipeline engineering where corrosion-resistant overlays are applied to pipeline elbows, tees, and other components subjected to erosion-corrosion damage.
Technical Approach
The overlay welding process creates complex three-dimensional thermal and mechanical fields that are difficult to model manually. The secondary development approach automates the following workflow:
- Geometry creation: Parametric generation of pipe geometry with overlay bead profiles based on user-specified dimensions and bead configurations.
- Material property definition: Automatic assignment of temperature-dependent material properties for both base metal and overlay material.
- Heat source modeling: Implementation of distributed heat source models (double-elliptical or Goldak model) with user-defined heat input parameters.
- Sequential pass simulation: Step-by-step simulation of each welding pass with proper cooling and reheating cycles.
- Stress integration: Coupled thermal-mechanical analysis to predict residual stress distribution and permanent deformation.
Validation Case: Inconel 625 on X65 Pipe
The validation case involves overlaying Inconel 625 alloy on the inner wall of an X65 carbon steel pipe. This is a common application in the oil and gas industry for protecting pipeline components from erosion-corrosion damage, particularly in sour service environments containing H₂S and CO₂.
| Parameter | Value |
|---|---|
| Base Pipe | X65 (API 5L) |
| Overlay Material | Inconel 625 |
| Application | Pipeline inner wall erosion-corrosion protection |
| Key Concern | Residual stress and distortion affecting pipe integrity |
| Welding Process | TIG or plasma arc welding |
The residual stress distribution in the overlay and base metal is critical for assessing the long-term integrity of the component. Excessive tensile residual stresses can promote stress corrosion cracking, fatigue crack initiation, and dimensional distortion of the pipe geometry.
Engineering Practice Integration
In pipeline engineering, overlay welding is used extensively for:
- Pipeline elbows and tees: Erosion-corrosion protection in high-velocity flow sections
- Wellhead components: Corrosion resistance in sour gas environments
- Subsea pipelines: Protection against marine corrosion and sand erosion
- Desulfurization equipment: Resistance to acid gas attack
The stress and deformation analysis system provides engineers with the ability to predict and mitigate welding-induced issues before they occur in production. Key design considerations include:
- Clamping and support design: Based on predicted deformation patterns, appropriate fixtures and supports can be designed to minimize distortion.
- Welding sequence optimization: The system can evaluate different welding sequences to minimize residual stress accumulation.
- Post-weld treatment planning: Predicted residual stress levels inform the need for stress relief heat treatment and the selection of appropriate PWHT parameters.
Key Questions and Reflections
The study demonstrates the value of parametric analysis systems for overlay welding, but several limitations should be acknowledged. First, the accuracy of residual stress predictions depends heavily on the quality of material property data, particularly temperature-dependent yield strength and thermal expansion coefficients. Second, the system assumes idealized welding conditions that may not represent actual production variability. Third, the validation was performed for a specific case (Inconel 625 on X65), and the system's applicability to other material combinations requires additional validation. Engineers using such systems should treat predictions as design guidance rather than absolute truth, and supplement computational results with experimental measurements where possible.
Study Insights and Implications
This research represents a significant advancement in overlay welding analysis capability. The parametric approach reduces the time and expertise required to perform stress and deformation analysis, making it accessible to a broader range of engineers. In the context of pipeline engineering, where overlay welding is used extensively for corrosion protection, the ability to predict and control residual stresses is essential for ensuring long-term component integrity. The system can be integrated into the design workflow to optimize welding parameters, sequence, and post-weld treatment before production begins, reducing the risk of in-service failures and minimizing costly rework. Future development should focus on incorporating more realistic material models, including plastic strain rate effects and anisotropic properties, to improve prediction accuracy for complex overlay geometries.