Numerical analysis of micro machining parameters for LDED deposited steel based on the Johnson–Cook model
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Micro milling is a key process in micro-cutting due to its ability to achieve high geometrical and dimensional precision across various materials and shapes. Understanding its behaviour when applied to Laser Direct Energy Deposition (L-DED) metals is essential, as these materials exhibit different microstructures and mechanical properties compared to conventionally wrought materials produced through forging or casting. A comprehensive approach to studying micro-cutting is through Finite Element Analysis (FEA), which enables visualization of details that are challenging to capture experimentally due to the micrometric scale. This study applies the Johnson-Cook constitutive model—widely used for processes involving plastic deformation and damage, such as machining [1]—to analyse the orthogonal cutting of L-DED ER70S-6 steel. The micro-tool was modelled with a tool tip radius of 1 µm, and the uncut chip thicknesses were set at 0.5 µm, 1.0 µm, 2.5 µm, and 5.0 µm. Material properties were derived from literature on L-DED materials, and the results were compared to AISI 1020 low-alloy steel, a widely used material with a similar composition. Findings indicate that a minimum chip thickness of 2.5 µm to 5.0 µm is required for proper chip formation. Additionally, ER70S-6 produced via L-DED exhibited less homogeneous and more fragile chips than AISI 1020, likely due to the high thermal input of the L-DED process, which can lead to microstructural variations and anisotropy. Lastly, while variations in material properties had minimal impact on Von Mises stresses, stress levels increased as the uncut chip thickness grew, as expected
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