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.

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.

Investigation of Size Effect on Micro Hardness of Machined Surface in Micro Cutting

2014 ◽  
Vol 602-605 ◽  
pp. 443-446
Author(s):  
Tao Zhang ◽  
Zhen Yu Shi ◽  
Bing Yan ◽  
Hou Jun Qi
Keyword(s):  
Size Effect ◽  
Chip Thickness ◽  
Cutting Edge ◽  
Three Dimension ◽  
Micro Hardness ◽  
Uncut Chip Thickness ◽  
Machined Surface ◽  
Micro Cutting ◽  
Cutting Edge Radius ◽  
Edge Radius

Micro cutting is a promising way for manufacturing micro parts, especially micro three dimension parts. Micro hardness is an important character to evaluate surface integrity of machined surface. Micro cutting is different from macro cutting due to size effect of specific cutting energy because of the influence of the ratio of uncut chip thickness to cutting edge radius. A group of micro cutting experiments were conducted to investigate the cutting parameters on the micro hardness of machined surface. The micro hardness of machines surface decreases with the ratio of uncut chip thickness to cutting edge radius first, and then increase when the uncut chip thickness is smaller than the cutting edge radius. The micro hardness shows size effect due to the machined surface compressed twice with the round cutting edge. The micro hardness decreases with the distance increasing far away from the machined surface.

Numerical Simulations of 3D Tool Geometry Effects on Deposition Stresses in Diamond Coated Cutting Tools

2008 ◽  
Author(s):  
Anderson Renaud ◽  
Jianwen Hu ◽  
Feng Qin ◽  
Kevin Chou
Keyword(s):  
Residual Stresses ◽  
Normal Stress ◽  
Cutting Tools ◽  
Tool Geometry ◽  
Solid Model ◽  
Secondary Importance ◽  
Corner Radius ◽  
Edge Radius ◽  
Relief Angle ◽  
Geometry Effects

Diamond-coated cutting tools are attractive alternatives to polycrystalline diamond tools for machining lightweight, high-strength components made of advanced materials such as composites. However, residual stresses induced by the diamond deposition process, due to thermal mismatch between diamond and the substrate, significantly impact the coating-substrate adhesion, and thus, the tool performance in machining. Moreover, the tool geometry, particularly at the very tip, complicates the stress fields because of the sharp geometry changes. The objective of this research is to investigate the effects of critical tool geometry parameters on the residual stress augmentations in diamond coated cutting tools. In this study, computer-aided design (CAD) software was used to create the solid model of various tool geometries. It was used to create an accurate model of the tool, which emulates each aspect of the tool geometry, e.g., as small as 5-micron edge radius on a 12.7-mm tool. The solid model was then exported to finite element analysis (FEA) software for 3D simulations of residual stresses generated in the tool with given deposition conditions. The obtained stress data was transformed to evaluate the interface stress profiles around the tool edges. To systematically investigate the tool geometry effects, a test matrix, determined using the design of experiments approach, includes 4 factors (edge radius, relief angle, corner radius, and corner angle) and 2 levels with a full factorial design. Analysis of variance was performed to quantitatively reveal the significant factors and interactions between the factors that dominate the stress concentrations. Results are summarized as follows. (1) The cutting edge radius is the most significant factor to the interface stresses. (2) For a 5 μm edge radius, the radial normal stress (σΓ) increases from 0 at the top uniform surface to about 1.5 GPa in tension, and the circumferential normal stress (σθ) increases from around 3.0 GPa in compression to over 3.7 GPa. (3) The corner radius is of secondary importance to σΓ, and the relief angle is of secondary importance to σθ.

Micro Flat End Milling Simulation Model With Instantaneous Plowing Area Prediction

2016 ◽  
Vol 4 (2) ◽  
Author(s):  
Abdolreza Bayesteh ◽  
Junghyuk Ko ◽  
Martin Byung-Guk Jun
Keyword(s):  
Feed Rate ◽  
Tool Path ◽  
End Milling ◽  
Chip Thickness ◽  
Depth Of Cut ◽  
Uncut Chip Thickness ◽  
Chip Area ◽  
Edge Radius ◽  
Wide Range ◽  
Radial Depth

There is an increasing demand for product miniaturization and parts with features as low as few microns. Micromilling is one of the promising methods to fabricate miniature parts in a wide range of sectors including biomedical, electronic, and aerospace. Due to the large edge radius relative to uncut chip thickness, plowing is a dominant cutting mechanism in micromilling for low feed rates and has adverse effects on the surface quality, and thus, for a given tool path, it is important to be able to predict the amount of plowing. This paper presents a new method to calculate plowing volume for a given tool path in micromilling. For an incremental feed rate movement of a micro end mill along a given tool path, the uncut chip thickness at a given feed rate is determined, and based on the minimum chip thickness value compared to the uncut chip thickness, the areas of plowing and shearing are calculated. The workpiece is represented by a dual-Dexel model, and the simulation properties are initialized with real cutting parameters. During real-time simulation, the plowed volume is calculated using the algorithm developed. The simulated chip area results are qualitatively compared with measured resultant forces for verification of the model and using the model, effects of cutting conditions such as feed rate, edge radius, and radial depth of cut on the amount of shearing and plowing are investigated.

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.

Investigation on Mechanism of Ultra-Smoothed Surface with a Micro Slot on the Flank Face in Micro Cutting

2014 ◽  
Vol 651-653 ◽  
pp. 764-767
Author(s):  
Tao Zhang ◽  
Hou Jun Qi ◽  
Gen Li
Keyword(s):  
Surface Roughness ◽  
Chip Thickness ◽  
Cutting Edge ◽  
Back Side ◽  
Uncut Chip Thickness ◽  
Micro Cutting ◽  
Cutting Edge Radius ◽  
Edge Radius ◽  
Flank Face ◽  
Side Flow

Micro cutting is a promising manufacturing method to obtain good surface integrity. Surface roughness shows size effect when the uncut chip thickness is smaller than the cutting edge radius. A special micro slot on the flank face of cutting tools was manufactured with discharge. Two groups of micro orthogonal cutting were conducted. The surface roughness of machined surface was measured and compared to each other. The results show that surface roughness decreases first and then increases with the ratio of uncut chip thickness to cutting edge radius. The surface machined with micro slot is better than that of without micro slot due to the micro slot restrain the back side flow of work piece based on the finite element model.

A New Model and Analysis of Orthogonal Machining With an Edge-Radiused Tool

1999 ◽  
Vol 122 (3) ◽  
pp. 384-390 ◽  
Author(s):  
Jairam Manjunathaiah ◽  
William J. Endres
Keyword(s):  
Shear Stress ◽  
Deformation Zone ◽  
Lower Boundary ◽  
Chip Thickness ◽  
Rake Angle ◽  
Shear Angle ◽  
Force Model ◽  
Uncut Chip Thickness ◽  
Edge Radius ◽  
Machining Force

A new machining process model that explicitly includes the effects of the edge hone is presented. A force balance is conducted on the lower boundary of the deformation zone leading to a machining force model. The machining force components are an explicit function of the edge radius and shear angle. An increase in edge radius leads to not only increased ploughing forces but also an increase in the chip formation forces due to an average rake angle effect. Previous attempts at assessing the ploughing components as the force intercept at zero uncut chip thickness, which attribute to the ploughing mechanism all the changes in forces that occur with changes in edge radius, are seen to be erroneous in view of this model. Calculation of shear stress on the lower boundary of the deformation zone using the new machining force model indicates that the apparent size effect when cutting with edge radiused tools is due to deformation below the tool (ploughing) and a larger chip formation component due to a lower shear angle. Increases in specific energy and shear stress are also due to shear strain and strain rate increases. A consistent material behavior model that does not vary with process input conditions like uncut chip thickness, rake angle and edge radius can be developed based on the new model. [S1087-1357(00)01302-2]

Investigation of effect of uncut chip thickness to edge radius ratio on nanoscale cutting behavior of single crystal copper: MD simulation approach

2020 ◽  
pp. 251659842093763
Author(s):  
A. Sharma ◽  
P. Ranjan ◽  
R. Balasubramaniam
Keyword(s):  
Molecular Dynamics ◽  
Single Crystal ◽  
Material Removal ◽  
Chip Thickness ◽  
Cutting Process ◽  
Uncut Chip Thickness ◽  
Edge Radius ◽  
Nanoscale Cutting ◽  
Cutting Behavior ◽  
Subsurface Defects

Extremely small cutting depths in nanoscale cutting makes it very difficult to measure the thermodynamic properties and understand the underlying mechanism and behavior of workpiece material. Highly precise single-crystal Cu is popularly employed in optical and electronics industries. This study, therefore, implements the molecular dynamics technique to analyze the cutting behavior and surface and subsurface phenomenon in the nanoscale cutting of copper workpieces with a diamond tool. Molecular dynamics simulation is carried out for different ratios of uncut chip thickness ( a) to cutting edge radius ( r) to investigate material removal mechanism, cutting forces, surface and subsurface defects, material removal rate (MRR), and stresses involved during the nanoscale cutting process. Calculation of forces and amount of plowing indicate that a/ r = 0.5 is the critical ratio for which the average values of both increase to maximum. Material deformation mechanism changes from shear slip to shear zone deformation and then to plowing and elastic rubbing as the cutting depth/uncut chip thickness is reduced. The deformation during nano-cutting in terms of dislocation density changes with respect to cutting time. During the cutting process, it is observed that various subsurface defects like point defects, dislocations and dislocation loops, stacking faults, and stair-rod dislocation take place.

Analytical Prediction of the Chip Back-Flow Angle in Machining With Restricted Contact Grooved Tools

2003 ◽  
Vol 125 (2) ◽  
pp. 210-219 ◽  
Author(s):  
N. Fang ◽  
I. S. Jawahir
Keyword(s):  
High Speed ◽  
Experimental Validation ◽  
Chip Thickness ◽  
Interfacial Stress ◽  
Tool Geometry ◽  
Analytical Prediction ◽  
Flow Angle ◽  
Back Flow ◽  
Definition Of ◽  
The Given

This paper develops a new analytical model to predict the chip back-flow angle in machining with restricted contact grooved tools. The model is derived from a recently established universal slip-line model for machining with restricted contact cutaway tools. A comprehensive definition of the chip back-flow angle is presented first, and based on this, a quantitative analysis of the chip back-flow effect is established for a given set of cutting conditions, tool geometry, and variable tool-chip interfacial stress state. The model also predicts the cutting forces, the chip thickness, and the chip up-curl radius. A full experimental validation of the analytical predictive model involving the use of high speed filming technique is then presented for the chip back-flow angle. This validation provides a range of feasible/prevalent tool-chip interfacial frictional conditions for the given set of input conditions.

An Analytical Model for the Prediction of Minimum Chip Thickness in Micromachining

2005 ◽  
Vol 128 (2) ◽  
pp. 474-481 ◽  
Author(s):  
X. Liu ◽  
R. E. DeVor ◽  
S. G. Kapoor
Keyword(s):  
Analytical Model ◽  
Chip Thickness ◽  
Machining Process ◽  
Thickness Effect ◽  
Uncut Chip Thickness ◽  
Minimum Chip Thickness ◽  
Tool Edge Radius ◽  
Edge Radius ◽  
Tool Edge ◽  
Cutting Velocity

In micromachining, the uncut chip thickness is comparable or even less than the tool edge radius and as a result a chip will not be generated if the uncut chip thickness is less than a critical value, viz., the minimum chip thickness. The minimum chip thickness effect significantly affects machining process performance in terms of cutting forces, tool wear, surface integrity, process stability, etc. In this paper, an analytical model has been developed to predict the minimum chip thickness values, which are critical for the process model development and process planning and optimization. The model accounts for the effects of thermal softening and strain hardening on the minimum chip thickness. The influence of cutting velocity and tool edge radius on the minimum chip thickness has been taken into account. The model has been experimentally validated with 1040 steel and Al6082-T6 over a range of cutting velocities and tool edge radii. The developed model has then been applied to investigate the effects of cutting velocity and edge radius on the normalized minimum chip thickness for various carbon steels with different carbon contents and Al6082-T6.

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