3D Simulation of Adiabatic Shear Bands in High Speed Machining

Abstract

A finite element model of three-dimensional high speed machining is developed. In order to catch Adiabatic Shear Band (ASB), which is about few microns wide, the simulation uses mesh adaptation triggered by an isotropic error estimator. An enhanced version of the Zienkiewicz and Booromand REP in Patches technique is used. As ASB is a much localized phenomenon, the adaptive procedure provides highly refined meshes with strong gradients of the element size, which makes it quite difficult to produce satisfactory 3D meshes. Furthermore, high speed machining leads to very important values of strain rate, deformation and possibly to extreme mesh distortion. So, an Arbitrary Lagrangian Eulerian (ALE) method is employed. With the utilized splitting method and linear finite element interpolation, the transport of nodal variables is based on the gradient calculated in the upwind element. For variables stored at the integration points, a remapping procedure using patch recovery techniques is preferred. Finally, because of the very strong thermo-mechanical coupling taking place in ASB, several thermo-mechanical coupling schemes are studied. Explicit and fully implicit schemes are compared, showing that the second one offers a stabilizing effect and a better accuracy. All of these ingredients provide a fully automatic and process independent procedure which allows detecting and following the formation of Adiabatic Shear Band in High Speed Machining. The creation of 3D segmented chip is observed and compared to 2D reference results obtained by Baker in [1]. The influence of numerical coefficients like the mesh size is investigated. Other application to actual 3D high speed machining such as blanking is also presented.

A 3D study of the influence of friction on the Adiabatic Shear Band formation during High Speed Machining

“…In order to evaluate our numerical model based on an adaptive ALE formulation using error estimation [2], the results have first been compared to Bäker's [6]. Figure 2 shows that they are very similar in terms of strain distribution, which has also been confirmed by analyzing the cutting force evolution in [4].…”

“…The utilized constitutive equation for the Ti6Al4V is presented in more details in [2,3,4,6] and written as:…”

“…A detailed description of the used numerical model, where no friction is taken into account can be found in [2,3]. A detailed description of the used numerical model, where no friction is taken into account can be found in [2,3].…”

“…It results from the competition between plastic hardening and strain softening. After a brief description of both physical and numerical models, the previously detailed numerical [2] and physical [3] results are recalled, before studying the actual influence of friction. In the first one, the hardening is predominant with respect to softening.…”

Parallel, second-order and consistent remeshing transfer operators for evolving meshes with superconvergence property on surface and volume

“…The interested reader can find further applications results of the EPR2 operator within an ALE formulation for numerical simulations of Friction Stir Welding [1,39], of Wire Drawing [38] and of High Speed Machining [40,41].…”