3.2 FEM Simulation for Force Coefficient Calculation The cutting coefficients have been evaluated through finite element simulation for orthogonal machining as shown in figure 4 by Deform D (version 10.1) software. Five layers of TiAlN coating of 0.2 m each having total coating thickness of 2 m has been applied on the tool as shown by coating window in figure 4. During simulation, work- piece and tool have been considered as visco-plastic and rigid body, respectively. To justify the effect of edge radius, the edge radius of the tool (both coated and uncoated) has been taken as 4 mas per the original dimension of the micro end mill cutter (Figure 1. b. Johnson-Cook material model [10] as given equation 7 has been used for the simulation where first bracket represents strain hardening, second bracket represents strain rate effect and third bracket indicates the flow softening. The values of the constant terms for the parametric equation has been given in table The mesh structures have been considered as tetrahedral for both tool and work piece. The total number mesh elements for workpiece is taken as 31996 having minimum size 1 m and tool has been meshed by 5266 number of elements having mesh size 0.5 m. Remeshing technique has been applied to avoid separation and distortion of the tool. Tool has been assumed to be rapidly heated having conductance coefficient in the order of 10 7 NS -1 mm -1 C -1 The
7 heat transfer between tool and workpiece with environment is associated with the convection coefficient of 0.02 NS -1 mm -1 C -1 . The remaining thermo-mechanical properties for P Steel, WC/Co and TiAlN are shown in table 2. 𝜎 𝑓𝑙𝑜𝑤 = (𝐴 + 𝐵𝜀 𝑛 ) (1 + 𝑐 𝑙𝑛 𝜀̇ 𝜀 0 ̇ ) (1 − ( 𝑇−𝑇 𝑟𝑜𝑜𝑚 𝑇 𝑚𝑒𝑙𝑡𝑖𝑛𝑔 −𝑇 𝑟𝑜𝑜𝑚 ) 𝑚 ) (7)
