Project
Simulation of the cutting fluid effect in the machining process by means of fluid structure interaction simulation
In machining processes, a considerable share of the mechanical energy is converted into heat in the primary shear zone and at the tool–chip interface. The resulting thermomechanical loads affect tool wear, dimensional accuracy, and surface integrity. These effects are particularly relevant when machining difficult-to-cut materials such as titanium and nickel-based alloys. Cutting fluids are therefore commonly applied to reduce thermal loads and improve process stability. The effectiveness of cutting fluids depends not only on their physical properties but also on process-related factors such as supply pressure, nozzle orientation, and accessibility of the cutting zone. Since direct experimental observation of fluid behavior in the cutting zone is limited, numerical simulation is an important approach for analyzing the influence of cutting fluids on temperature, cutting forces, and chip formation. At WZL and later MTI, different simulation approaches for machining processes have been developed, including empirical–analytical, numerical, and multiscale methods. In particular, the Coupled Eulerian–Lagrangian (CEL) method has proven suitable for describing chip formation and thermomechanical tool loads. However, transferring such models from orthogonal cutting to milling remains challenging due to intermittent engagement, complex three-dimensional tool geometries, and time-dependent chip thickness. In addition, the computational cost of coupled thermomechanical simulations is very high. For this reason, the use of high-performance computing (HPC) was essential for this project.
Project Details
Project term
December 5, 2024–March 10, 2026
Affiliations
RWTH Aachen University
Institute
Manufacturing Technology Institute
Principal Investigator
Methods
The project aimed at developing and applying simulation models for analyzing the influence of cutting fluids on thermomechanical loads in milling processes. The methodology combined detailed CEL-based finite element simulations with computationally efficient multiscale modeling approaches.
In the CEL model, the workpiece was represented as an Eulerian domain and the cutting tool as a Lagrangian body. This formulation allows the simulation of large plastic deformations and chip formation without severe mesh distortion. A fine hexahedral mesh was used in the cutting zone to resolve temperature and stress gradients. Material behavior was described by temperature- and strain-rate-dependent constitutive equations, while friction and heat transfer were modeled through contact-based formulations.
The effect of the cutting fluid was incorporated by means of convective boundary conditions and calibrated heat transfer coefficients derived either from CFD-based analyses or from inverse calibration using experimental temperature data.
To improve predictive accuracy, an automated calibration workflow was implemented. Python-based scripts linked the simulation environment to optimization algorithms, enabling systematic parameter identification on HPC systems.
In addition, a multiscale modeling approach was developed to reduce computational effort. This approach combines engagement analysis, force and temperature modeling, and regression-based parameter estimation. Compared with full 3D FEM/CEL simulations, it enables a significant reduction in computation time while retaining the relevant process trends.
All large-scale simulations were carried out on the CLAIX HPC system at RWTH Aachen University. Typical simulations used parallel CPU-based computation and required approximately 100 hours per tool revolution, depending on mesh resolution and model complexity.
Results
The simulations provided detailed insight into the thermomechanical behavior of milling processes under cutting-fluid supply. The highest temperatures were found near the cutting edge, and the temperature field was strongly influenced by cutting speed, feed, and cooling conditions. Cutting fluids reduced the thermal load on the tool, particularly under interrupted cutting conditions, where improved access of the fluid to the tool surface enhanced convective cooling.
The simulations also enabled time-resolved analysis of cutting forces and chip formation. In milling, strong fluctuations in cutting forces were observed due to the periodic variation of chip thickness. Cooling conditions additionally affected friction behavior and thereby influenced both thermal and mechanical loads.
A comparison of modeling approaches showed that the detailed FEM/CEL simulations provide high physical resolution, whereas the multiscale model offers substantially improved computational efficiency while reproducing the main process trends.
Discussion
The project demonstrated that HPC is a key prerequisite for the simulation of coupled thermomechanical machining processes with sufficient spatial and temporal resolution. Without HPC resources, the application of detailed CEL models to realistic milling operations would not have been feasible within an acceptable timeframe.
At the same time, the results confirmed that the computational cost of high-fidelity simulations remains a major limitation. This underlines the importance of the multiscale modeling strategy, which bridges the gap between physical detail and industrial applicability. While detailed FEM/CEL simulations are required for fundamental process analysis and model validation, reduced-order approaches are better suited for parameter studies and process planning.
The automated calibration workflow further improved the efficiency and reliability of the simulations and represents an important step toward robust simulation-based process prediction. Future work should focus on improved fluid modeling, adaptive discretization strategies, and the use of GPU-based HPC architectures to further enhance computational performance.
Additional Project Information
DFG classification: 401-01 Metal-Cutting Manufacturing Engineering
Software: ABAQUS, ANSYS
Cluster: CLAIX
Publications
Hui Liu, Thorsten Helmig, Nicklas Gerhard, Reinhold Kneer, Thomas Bergs,
Numerical and experimental determination of contact heat transfer during orthogonal cutting,
https://dx.doi.org/10.1016/j.procir.2023.03.056, 2023
Hui Liu, Markus Meurer, Thomas Berg,
Three-Dimensional Modeling of Thermomechanical Tool Loads During Milling Using the Coupled Eulerian-Lagrangian Formulation,
https://dx.doi.org/10.1007/978-3-031-34486-2_23, 2023
Hui Liu, Anna Kibireva, Markus Meurer, Thomas Berg,
An inverse method for automatic determination of material models for metal cutting based on multi-objective optimization,
https://dx.doi.org/10.1007/s00170-023-12346-5, October 2023
Hui Liu, Markus Meurer, Thomas Berg,
Surface Integrity Analysis in Orthogonal Milling of Inconel 718,
https://dx.doi.org/10.1016/j.procir.2024.05.035, 2024
Hui Liu, Tobias Kelliger, Markus Meurer, Thomas Berg,
Investigating Nozzle Design for Cutting Fluid Supply During Inconel 718 Turning With CBN-Tools,
https://dx.doi.org/10.1115/MSEC2024-123257, June 2024
Hui Liu, Markus Meurer, Thomas Berg,
Modeling and Monitoring of the Tool Temperature During Continuous and Interrupted Turning with Cutting Fluid,
https://dx.doi.org/10.3390/met14111292, November 2024
Hui Liu, Markus Meurer, Thomas Berg,
Hybrid Modeling Approach for Predicting Tool Temperature in Metal Cutting Processes,
https://dx.doi.org/10.1016/j.procir.2025.02.055, 2025
Hui Liu, Markus Meurer, Thomas Berg,
Experimental and Finite Element Analysis of adapted cutting fluid supply on tool temperature and wear progression in Inconel 718 turning,
https://dx.doi.org/10.1016/j.jmapro.2025.01.061, March 2025
Hui Liu, Markus Meurer, Thomas Berg,
Investigation of Tool Temperature During End Milling: Experimental and Numerical Approaches,
https://dx.doi.org/10.1115/MSEC2025-155694, June 2025
Hui Liu, Markus Meurer, Thomas Berg,
Comparative Analysis of Emulsion, Cutting Oil, and Synthetic Oil-Free Fluids on Machining Temperatures and Performance in Side Milling of Ti-6Al-4V,
https://dx.doi.org/10.3390/lubricants13090396, September 2025
Hui Liu, Junjie Zha, Markus Meurer, Thomas Berg,
Experimental and numerical analysis of the adapted high-pressure cutting fluid supply for turning AISI 1045 steel,
https://dx.doi.org/10.1016/j.procir.2026.01.075, 2026