Dynamic Simulation of Cladding Thermal Stress Based on ANSYS Platform

Literature Overview and Computational Approach

Thermal stress during and after cladding operations is a primary driver of residual stress accumulation, distortion, and cracking in both the cladding layer and the substrate. This literature review examines a finite element simulation approach using the ANSYS platform to predict the dynamic evolution of thermal stress during multi-pass cladding. The study employs a coupled thermo-mechanical analysis that accounts for the transient heat transfer from arc input, the plastic deformation behavior of the weld metal and heat-affected zone, and the residual stress state after cooling. The dynamic nature of the simulation captures the sequential deposition of multiple passes and the interaction between previously deposited layers and newly formed material.

Model Configuration and Boundary Conditions

The finite element model employs a moving heat source that represents the arc energy input, with the heat flux distribution modeled as a double-elliptical or Gaussian profile calibrated to match experimental measurements of the weld bead geometry. The material properties are defined as temperature-dependent, including thermal conductivity, specific heat, density, and the elastic-plastic stress-strain relationship. The boundary conditions include convective and radiative heat loss at the free surfaces, a fixed constraint at the base of the substrate to simulate clamping, and a symmetry condition at the model boundaries where appropriate. The mesh is refined near the weld zone with element sizes of 0.5 to 1.0 millimeters, transitioning to coarser elements away from the weld to reduce computational cost.

Thermal Field Evolution and Stress Development

The simulation results show that the peak temperature during cladding reaches 1600 to 2200 degrees Celsius at the arc center, with a steep thermal gradient extending into the substrate. The cooling rate in the weld metal is typically 10 to 100 degrees Celsius per second, depending on the heat input and the thermal conductivity of the substrate. The residual stress distribution after cooling exhibits a characteristic pattern: compressive stresses in the weld metal near the surface, tensile stresses in the heat-affected zone, and a transition to near-zero stress in the far field of the substrate. The maximum residual tensile stress in the heat-affected zone can reach 400 to 600 megapascals for high-strength steel substrates, which approaches the yield strength of the material and poses a significant risk of cracking.

Multi-Pass Interaction Effects

One of the most valuable insights from the dynamic simulation is the quantification of multi-pass interaction effects. Each subsequent pass reheats the previously deposited layer, partially relieving the residual stress from the previous pass. The simulation shows that the residual stress from a single pass can be reduced by 20 to 40 percent after a subsequent pass, depending on the interpass distance and the overlap between adjacent passes. However, the cumulative effect of multiple passes also leads to a progressive increase in the heat-affected zone volume and a potential for grain coarsening in the substrate. The literature recommends an interpass distance of 0.8 to 1.2 times the bead width to achieve optimal stress relief while maintaining adequate overlap for fusion.

Comparison with Experimental Data

The simulation results are validated against experimental measurements of residual stress obtained by the hole-drilling method and X-ray diffraction. The agreement between predicted and measured stress values is generally within 15 to 20 percent for the weld metal and within 25 percent for the heat-affected zone. The larger discrepancy in the heat-affected zone is attributed to the difficulty of accurately modeling the phase transformations and plastic strain behavior in this region. The validation confirms that the simulation approach is suitable for predicting the general trend of residual stress distribution and for identifying high-stress regions that require post-weld treatment.

Stress Relief Strategies and Optimization

Based on the simulation results, several stress relief strategies are evaluated. Post-weld stress relief annealing at 550 to 650 degrees Celsius for 2 hours reduces the peak residual stress by 60 to 80 percent, but introduces the risk of grain coarsening and reduced hardness in the substrate. A more targeted approach involves applying a compressive stress overlay pass after the main cladding layer, which introduces a surface compressive stress that counteracts the tensile residual stress in the heat-affected zone. The simulation shows that a single compressive overlay pass can reduce the peak tensile stress by 30 to 50 percent without the need for a full heat treatment cycle.

Key Questions and Reflections

A significant question raised by this study is the accuracy of the simulation in predicting crack initiation and propagation under residual stress. While the stress distribution is well captured, the prediction of crack behavior requires additional material models that account for microstructural features such as grain boundaries, inclusions, and phase boundaries. The literature acknowledges this limitation and suggests that future work should integrate fracture mechanics models with the thermo-mechanical simulation to provide a more comprehensive assessment of cladding integrity. Another reflection concerns the computational efficiency: the dynamic simulation of a multi-pass cladding process with a fine mesh can require significant computational resources, and the development of surrogate models or reduced-order models could enable faster design optimization.

Study Insights and Conclusions

This literature review demonstrates that dynamic finite element simulation is a powerful tool for predicting and managing residual stress in cladding operations. The ability to simulate the sequential deposition of multiple passes and to evaluate the interaction between passes provides valuable insights that are difficult to obtain from experimental methods alone. The recommended stress relief strategies, particularly the compressive overlay pass approach, offer a practical solution for reducing cracking risk without the need for extensive post-weld heat treatment. Engineers should recognize that simulation results must be validated against experimental data for each specific application, as the accuracy depends on the quality of the material property inputs and the boundary condition assumptions. The integration of simulation-based design with experimental validation represents the most reliable approach to optimizing cladding processes for minimum residual stress.