*2.5. Sensitivity Study*

Simulation output depends on the mesh configuration, such as the element size and the tilt angle. The element size of 0.01 mm was selected to compromise between the computational load and convergence. A smaller mesh size of 0.005 mm was compared to the 0.01 mm mesh using the 30 pcf case and showed a similar force magnitude and chip formation, but the computation could hardly proceed after a few steps due to a large number of elements and surfaces.

For the tilt angle, although 45◦ is the theoretically preferred cracking path, different angles were also tested at 0◦ (square mesh), 30◦, and 60◦ to study the mesh sensitivity using the 30 pcf case with a scaling factor of 0.02. In the case of square mesh, the chip layer was sheared off without any cutting phenomenon due to the lack of fracture path around the theoretical shear angle. Results of the other cases are shown in Figure 5. Compared to the 45◦ mesh, the chip size is larger at 30◦ and smaller at 60◦. Consequently, the cutting force is a little smaller (about 2%) at the 30◦ mesh and larger (about 20%) at the 60◦ mesh because the work done of cutting force is proportional to the number of fractured surfaces. Therefore, although the 45◦ mesh is recommended based on the shear angle, other mesh angles may also work but would produce different results. In any case, the scaling factor needs to be adjusted to match the chip behavior to the experiment for the best outcome.

**Figure 5.** Material responses to the cutting tool with different tile angles: (**a**) 30 degrees, (**b**) 45 degrees, and (**c**) 60 degrees.
