Development and validation of a meshless 3D material point method for simulating the micro-milling process

Abstract

A meshless Generalized Interpolation Material Point Method for simulating the micro-milling process was developed. This method has several advantages over well-established approaches (such as finite elements) when it comes to large plastic strains and deformations, since it inherently does not suffer from tensile instability problems. The feasibility of the developed material point model for simulating micro-milling is verified against finite element simulations and experimental data. The model is able to successfully predict experimentally measured cutting forces and determine chip temperatures in agreement with conventional finite element simulations. After having verified the approach, the model was applied to perform extensive numerical 3D simulations of the micro-milling process. The goal is to evaluate the response of the micromilling cutting forces as function of the hardening behavior of the micro-milled material. The meshless 3D simulations reveal a dependency of tool force slopes (with respect to the uncut chip thickness) on the hardening parameters. Based on these findings, a new approach is outlined to determine hardening parameters directly from two micro-milling experiments with distinct, sufficiently large uncut chip thicknesses.

Material point simulations as a basis for determining Johnson–Cook hardening parameters via instrumented scratch tests

“…The clear advantage of MPM over time explicit FEM methods lies in its nature, since the particles are discrete and interact only via their kernels, so it does not require additional separation formulations to allow fracture. MPM has been used before to simulate cutting and scratching of metals in good agreement with experiment [14,43].…”

“…The current MPM model is described in more detail in Ref. [43]. The clear advantage of MPM over time explicit FEM methods lies in its nature, since the particles are discrete and interact only via their kernels, so it does not require additional separation formulations to allow fracture.…”

“…All the simulations were carried out with the open source code LAMMPS [44], applying the MPM user package available on request from the developer Ganzenmüller [43].…”

“…Material properties for steel taken from[43] and for copper from[31]: ρ is the reference bulk density, E Young's modulus, ν the Poisson ratio, Cp the specific heat capacity at room temperature, κ the heat conductivity.…”