FE analysis of the effects of process representations on the prediction of residual stresses and chip morphology in the down-milling of Ti6Al4V

2021 ◽  
pp. 1-50
Author(s):  
Nejah Tounsi ◽  
Tahany El-Wardany
Keyword(s):  
Experimental Data ◽  
Residual Stresses ◽  
Orthogonal Cutting ◽  
Chip Thickness ◽  
Chip Morphology ◽  
Milling Process ◽  
Uncut Chip Thickness ◽  
Orthogonal Machining ◽  
Cutting Length ◽  
Sequential Cuts

Abstract Part I of these two-part papers will investigate the effect of three FEM representations of the milling process on the prediction of chip morphology and residual stresses (RS), when down-milling small uncut chips with thickness in the micrometer range and finite cutting edge radius. They are: i) orthogonal cutting with the mean uncut chip thickness t, obtained by averaging the uncut chip thickness over the cutting length, ii) orthogonal cutting with variable t, which characterizes the down-milling process and which is imposed on a flat surface of the final workpiece, and iii) modelling the true kinematics of the down milling process. The appropriate constitutive model is identified through 2D FEM investigation of the effects of selected constitutive equations and failure models on the prediction of RS and chip morphology in the dry orthogonal machining of Ti6Al4V and comparison to experimental measurements. The chip morphology and RS prediction capability of these representations is assessed using the available set of experimental data. Models featuring variable chip thickness have revealed the transition from continuous chip formation to the rubbing mode and have improved the predictions of residual stresses. The use of sequential cuts is necessary to converge toward experimental data.

FE analysis of the effects of process representations on the prediction of residual stresses and chip morphology in the down-milling of Ti6Al4V

2021 ◽  
pp. 1-40
Author(s):  
Nejah Tounsi ◽  
Tahany El-Wardany
Keyword(s):  
Residual Stresses ◽  
Flank Wear ◽  
Orthogonal Cutting ◽  
Chip Thickness ◽  
Chip Morphology ◽  
Milling Process ◽  
Cutting Edge ◽  
Uncut Chip Thickness ◽  
Cutting Edge Radius ◽  
Edge Radius

Abstract In part II of these two-part papers, the effects of four FEM representations of the milling process on the prediction of chip morphology and residual stresses (RS) are investigated. Part II focuses on the milling of conventional uncut chip thickness h with finite cutting edge radius and flank wear, while part I of these two-part papers has reported on the results in the case of milling small uncut chip thickness in the micrometre range with finite cutting edge radius. Two geometric models of the flank-wear land composed of flat and curved wear land are proposed and assessed. The four process representations are: i) orthogonal cutting with flat wear land and with the mean uncut chip thickness h ¯; ii) orthogonal cutting with flat wear land and with variable h, which characterises the down-milling process and which is imposed on a flat surface of the final workpiece; iii) modelling the true kinematics of the down milling process with flat wear land and iv) modelling the true kinematics of the down milling process with curved wear land. They are designated as Cte-h, Var-h, True-h and True-h*. The effectiveness of these representations is assessed when milling Ti6Al4V with a flank-wear land of VB = 200µm.

A Metallo-Thermomechanically Coupled Analysis of Orthogonal Cutting of AISI 1045 Steel

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Hongtao Ding ◽  
Yung C. Shin
Keyword(s):  
Experimental Data ◽  
Cutting Force ◽  
Orthogonal Cutting ◽  
Cutting Temperature ◽  
Chip Morphology ◽  
Machining Process ◽  
Coupled Analysis ◽  
Aisi 1045 Steel ◽  
Aisi 1045 ◽  
1045 Steel

Materials often behave in a complicated manner involving deeply coupled effects among stress/stain, temperature, and microstructure during a machining process. This paper is concerned with prediction of the phase change effect on orthogonal cutting of American Iron and Steel Institute (AISI) 1045 steel based on a true metallo-thermomechanical coupled analysis. A metallo-thermomechanical coupled material model is developed and a finite element model (FEM) is used to solve the evolution of phase constituents, cutting temperature, chip morphology, and cutting force simultaneously using abaqus. The model validity is assessed using the experimental data for orthogonal cutting of AISI 1045 steel under various conditions, with cutting speeds ranging from 198 to 879 m/min, feeds from 0.1 to 0.3 mm, and tool rake angles from −7 deg to 5 deg. A good agreement is achieved in chip formation, cutting force, and cutting temperature between the model predictions and the experimental data.

Size Effects in Cutting With a Diamond-Coated Tool

2011 ◽  
Author(s):  
Feng Qin ◽  
Xibing Gong ◽  
Kevin Chou
Keyword(s):  
Residual Stresses ◽  
Size Effect ◽  
Normal Stress ◽  
High Speed ◽  
Chip Thickness ◽  
Tool Geometry ◽  
Uncut Chip Thickness ◽  
Edge Radius ◽  
Coated Tool ◽  
Tool Stresses

In machining using a diamond-coated tool, the tool geometry and process parameters have compound effects on the thermal and mechanical states in the tools. For example, decreasing the edge radius tends to increase deposition-induced residual stresses at the tool edge interface. Moreover, changing the uncut chip thickness to a small-value range, comparable or smaller than the edge radius, will involve the so-called size effect. In this study, a developed 2D cutting simulation that incorporates deposition residual stresses was applied to evaluate the size effect, at different cutting speeds, on the tool stresses, tool temperatures, specific cutting energy as well as the interface stresses around a cutting edge. The size effect on the radial normal stress is more noticeable at a low speed. In particular, a large uncut chip thickness has a substantially lower stress. On the other hand, the size effect on the circumferential normal stress is more noticeable at a high speed. At a small uncut chip thickness, the stress is largely compressive.

Dynamic Simulation of the Micro-Milling Process Including Minimum Chip Thickness and Size Effect

2012 ◽  
Vol 504-506 ◽  
pp. 1269-1274 ◽  
Author(s):  
François Ducobu ◽  
Edouard Rivière-Lorphèvre ◽  
Enrico Filippi
Keyword(s):  
Size Effect ◽  
Cutting Forces ◽  
Mechanistic Model ◽  
Orthogonal Cutting ◽  
Chip Thickness ◽  
Milling Process ◽  
Cutting Conditions ◽  
Micro Milling ◽  
Minimum Chip Thickness ◽  
Physical Phenomena

Micro-milling with a cutting tool is a manufacturing technique that allows production of parts ranging from several millimeters to several micrometers. The technique is based on a downscaling of macroscopic milling process. Micro-milling is one of the most effective process to produce complex three-dimensional micro-parts, including sharp edges and with a good surface quality. Reducing the dimensions of the cutter and the cutting conditions requires taking into account physical phenomena that can be neglected in macro-milling. These phenomena include a size effect (nonlinear rising of specific cutting force when chip thickness decreases), the minimum chip thickness (under a given dimension, no chip can be machined) and the heterogeneity of the material (the size of the grains composing the material is significant as compared to the dimension of the chip). The aim of this paper is to introduce some phenomena, appearing in micromilling, in the mechanistic dynamic simulation software ‘dystamill’ developed for macro-milling. The software is able to simulate the cutting forces, the dynamic behavior of the tool and the workpiece and the kinematic surface finish in 2D1/2 milling operation (slotting, face milling, shoulder milling,…). It can be used to predict chatter-free cutting condition for example. The mechanistic model of the cutting forces is deduced from the local FEM simulation of orthogonal cutting. This FEM model uses the commercial software ABAQUS and is able to simulate chip formation and cutting forces in an orthogonal cutting test. This model is able to reproduce physical phenomena in macro cutting conditions (including segmented chip) as well as specific phenomena in micro cutting conditions (minimum chip thickness and size effect). The minimum chip thickness is also taken into account by the global model. The results of simulation for the machining of titanium alloy Ti6Al4V under macro and micro milling condition with the mechanistic model are presented discussed. This approach connects together local machining simulation and global models.

Residual Stresses Modelling of End Milling Process Using Numerical and Experimental Methods

2020 ◽  
Vol 978 ◽  
pp. 106-113
Author(s):  
Marimuthu K. Prakash ◽  
Kumar C.S. Chethan ◽  
Prasada H.P. Thirtha
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
End Milling ◽  
Orthogonal Cutting ◽  
Milling Process ◽  
Parent Material ◽  
Machining Processes ◽  
Element Analysis ◽  
1045 Steel ◽  
Cutting Model

Machining has been one of the most sort of process for realizing different products. It has significant role in the value additions process. Machining is one of the production process where material is removed from the parent material to realize the final part or component. Among machining, the well known machining processes are turning, milling, shaping, grinding and non-conventional machining processes like electric discharge machining, ultrasonic machining, chemical machining etc. The fundamental of all these processes being material removal in the form of chips using a tool either in contact or not in contact. In the present work, milling is being taken for study Finite element analysis is being used as a tool to understand the different phenomenon that underlies the machining processes. Of late, the machining induced residual stresses is of great interest to the researchers since the residual stresses have an impact on the functional performances. The present work is to model the milling process to predict the forces and residual stresses using finite element method. Unlike many researchers, the authors have attempted to develop oblique cutting model rather than an orthogonal cutting model. The present work was carried out on AISI 1045 steel.

Numerical Investigation of Two-Dimensional Thermally Assisted Ductile Regime Milling of Brittle Materials

2014 ◽  
Author(s):  
Jianfeng Ma ◽  
Xianchen Ge ◽  
Shuting Lei
Keyword(s):  
Chip Thickness ◽  
Rake Angle ◽  
Depth Of Cut ◽  
Critical Depth ◽  
Uncut Chip Thickness ◽  
Thermal Boundary Conditions ◽  
Orthogonal Machining ◽  
Preheating Temperature ◽  
Ductile Regime Machining ◽  
Critical Depth Of Cut

This study investigates the effects of different variables (preheating temperature, edge radius, and rake angle) on ductile regime milling of a bioceramic material known as nanohydroxyapatite (nano-HAP) using numerical simulation. AdvantEdge FEM Version 6.1 is used to conduct the simulation of 2D milling mimicked by orthogonal machining with varying uncut chip thickness. Thermal boundary conditions are specified to approximate laser preheating of the work material. Based on the pressure-based criterion for ductile regime machining, the dependence of critical depth of cut on cutting conditions is investigated using Tecplot 360. It is found that as uncut chip thickness decreases, the critical depth of cut decreases. In addition, the critical depth of cut increases as the negativity of rake angle and/or preheating temperature increase.

Material Strengthening Mechanisms and Their Contribution to Size Effect in Micro-Cutting

2005 ◽  
Author(s):  
Kai Liu ◽  
Sathyan Subbiah ◽  
Shreyes N. Melkote
Keyword(s):  
Size Effect ◽  
Strain Rate ◽  
Strain Gradient ◽  
Orthogonal Cutting ◽  
Chip Thickness ◽  
Material Strength ◽  
Specific Cutting Energy ◽  
Uncut Chip Thickness ◽  
Cutting Energy ◽  
Secondary Deformation

The specific cutting energy in machining is known to increase nonlinearly with decrease in uncut chip thickness. It has been reported in the literature that this phenomenon is dependent on several factors such as material strengthening, ploughing due to finite edge radius, and material separation effects. This paper examines the material strengthening effect where the material strength increases as the uncut chip thickness decreases down to a few microns. This increase in strength has been attributed to various factors such as strain-rate, strain gradient and temperature effects. Given that the increase in material strength in the primary and secondary deformation zones can occur due to many factors, it is important to understand the contributions of each factor to the increase in specific cutting energy and the conditions under which they are dominant. This paper analyzes two material strengthening factors: (i) the contribution of the decrease in the secondary deformation zone cutting temperature, and (ii) strain gradient strengthening, and their relative contributions to the increase in specific cutting energy as the uncut chip thickness is reduced. Finite Element (FE) based orthogonal cutting simulations are performed using aluminum 5083-H116, a work material with a small strain-rate hardening exponent, thus minimizing strain-rate effect. Suitable cutting conditions are identified under which the temperature and strain gradient effects are dominant. Orthogonal cutting experiments are used to validate the model in terms of the cutting forces. The simulation results are then analyzed to identify the contributions of the material strengthening factors to the size effect in specific cutting energy.

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