Simulation of cutting processes

In industrial series production of complex sheet metal components, cutting and forming operations are almost always combined. As a result, each sheet metal part must be trimmed one or several times during the manufacturing process. Using numerical simulation for these cutting operations significantly expands process understanding. Investigating the influence of key process parameters is an essential step in the development of new processes and cutting tools – enabling, for example, highly accurate predictions of tool wear on active cutting elements and of final part quality.

Cutting process simulation is particularly valuable for visualizing and analyzing process data that cannot be measured experimentally – or only with considerable effort. Of special interest are the detailed local distributions and time evolution of strains and strain rates within the workpiece. The stress distribution and the relative contributions of compressive and tensile stresses in the shear zone are also highly relevant for understanding separation behavior and cut edge characteristics.

A special application area for numerical simulation is high-speed shear cutting (HGSS). In this process, the material is first subjected to severe localized shear deformation and then separated. For many materials, the combination of very high local strains and extremely short process times leads to pronounced heating in the shear zone and the formation of an adiabatic shear band (ASB). This strong temperature rise makes it necessary to apply strain-rate-dependent and thermomechanically coupled material models with high spatial resolution.

Selecting the appropriate material model and parameter set is therefore crucial. In cutting operations, it is essential to use not only a strain-rate- and temperature-dependent plasticity model, but also a suitable damage model. Depending on process geometry and analysis objectives, axisymmetric 2D models with shell elements or full 3D solid-element models (e.g., for specific asymmetric punch geometries) can be applied.

Regardless of the modeling approach, sufficiently fine elements in the shear zone are critical. This ensures high spatial resolution of the temperature field and an accurate representation of the resulting cut surface. Material separation is governed by the fracture criteria implemented in the chosen damage model. The most commonly used approaches include GISSMO and Johnson–Cook.
At Fraunhofer IWU, experimental material testing is also carried out to identify the parameters required for these damage models across a wide range of strain rates and temperatures. 

Added value

• Deeper process insight through access to otherwise hard-to-measure local quantities
• Robust process and tool design through systematic parameter studies
• Reliable prediction of tool wear and cut edge / component quality
• Increased confidence in simulations through experimentally identified model parameters