The Constant Force Component due to Material Separation and Its Contribution to the Size Effect in Specific Cutting Energy

2005 ◽  
Vol 128 (3) ◽  
pp. 811-815 ◽  
Author(s):  
Sathyan Subbiah ◽  
Shreyes N. Melkote
Keyword(s):  
Size Effect ◽  
Cutting Force ◽  
Orthogonal Cutting ◽  
Chip Thickness ◽  
Constant Force ◽  
Specific Cutting Energy ◽  
Force Component ◽  
Uncut Chip Thickness ◽  
Cutting Energy ◽  
Material Separation

The contribution of material separation in cutting ductile metals to the constant force component, and, hence, to the size effect in specific cutting energy is explored in this paper. A force-decomposition-based framework is proposed to reconcile the varied reasons given in literature for the size effect. In this framework, the cutting force is broken down into three components: one that is decreasing, another that is increasing, and the third that remains constant, with decreasing uncut chip thickness. The last component is investigated by performing orthogonal cutting experiments on OFHC copper at high rake angles of up to 70deg in an attempt to isolate it. As the rake angle is increased, the resulting experimental data show a trend toward a constant cutting-force component independent of the uncut chip thickness. Visual evidence of ductile tearing ahead of the tool associated with material separation leading to chip formation is shown. The measured constant force and the force needed for ductile crack extension are then compared.

On the Size-Effect in Micro-Cutting at Low and High Rake Angles

2004 ◽  
Author(s):  
Sathyan Subbiah ◽  
Shreyes N. Melkote
Keyword(s):  
Size Effect ◽  
Cutting Force ◽  
Constant Width ◽  
Orthogonal Cutting ◽  
Chip Thickness ◽  
Cutting Condition ◽  
Specific Cutting Energy ◽  
Uncut Chip Thickness ◽  
Micro Cutting ◽  
Cutting Energy

A partial explanation of the size-effect in the specific cutting energy in micro-cutting is provided in this paper. For a simple orthogonal cutting condition, with constant width of cut, the specific cutting energy is viewed as a ratio of the cutting force and the uncut chip thickness. Size-effect, i.e., an unbounded increase in the specific cutting energy with decrease in uncut chip thickness, will occur under two conditions: one, if a component of the cutting force remains constant with uncut chip thickness and two, if some component of the cutting force increases with the uncut chip thickness. Experiments have been performed at high rake angles in an attempt to isolate and detect the presence of the constant component of the cutting force. The trend confirming the presence of this component is reported and explained.

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.

The Influence of Tool Edge Radius on Size Effect in Orthogonal Micro-Cutting Process of 7050-T7451 Aluminum Alloy

2008 ◽  
Vol 375-376 ◽  
pp. 31-35
Author(s):  
Jun Zhou ◽  
Jian Feng Li ◽  
Jie Sun ◽  
Zhi Ping Xu
Keyword(s):  
Aluminum Alloy ◽  
Size Effect ◽  
Cutting Force ◽  
Chip Thickness ◽  
Specific Cutting Energy ◽  
Uncut Chip Thickness ◽  
Tool Edge Radius ◽  
Specific Cutting Force ◽  
Cutting Energy ◽  
Tool Edge

In machining, the size effect is typically characterized by a non-linear increase in the specific cutting energy (or specific cutting force) as the uncut chip thickness is decreased. A finite element model of orthogonal micro-cutting was established to study the influence of tool edge radius on size effect when cutting 7050-T7451 aluminum alloy. Diamond cutting tool was used in the simulation. Specific cutting force and specific cutting energy are obtained through the simulation. The nonlinear scaling phenomenon is evident. The likely explanations for the size effect in small uncut chip thickness were discussed in this paper.

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

2005 ◽  
Vol 128 (3) ◽  
pp. 730-738 ◽  
Author(s):  
Kai Liu ◽  
Shreyes N. Melkote
Keyword(s):  
Size Effect ◽  
Strain Rate ◽  
Strain Gradient ◽  
Orthogonal Cutting ◽  
Chip Thickness ◽  
Material Strength ◽  
Strengthening Effect ◽  
Specific Cutting Energy ◽  
Uncut Chip Thickness ◽  
Cutting Energy

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 nonlinearly as the uncut chip thickness is reduced to a few microns. This increase in strength has been attributed in the past to various factors such as strain rate, strain gradient, and temperature effects. Given that the increase in material strength 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 with Aluminum 5083-H116, a work material with a small strain rate hardening exponent, thus minimizing strain rate effects. 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 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.

Experimental Investigations of Size Effect on Cutting Force, Specific Cutting Energy, and Surface Integrity during Micro Cutting

2012 ◽  
Vol 723 ◽  
pp. 371-376
Author(s):  
Tao Zhang ◽  
Zhan Qiang Liu ◽  
Chong Hai Xu ◽  
Ning He ◽  
Liang Li
Keyword(s):  
Size Effect ◽  
Surface Integrity ◽  
Chip Thickness ◽  
Cutting Edge ◽  
Specific Cutting Energy ◽  
Uncut Chip Thickness ◽  
Micro Cutting ◽  
Burr Height ◽  
Cutting Energy ◽  
Exit Burr

Micro cutting is a promising technology to manufacture the micro parts. The shear mechanism of micro cutting is different from the conventional cutting due to the round cutting edge. The ratio of uncut chip thickness to cutting edge radius plays an important role on the micro cutting process. This paper investigates the size effect phenomena of micro cutting. Firstly, the cutting force and size effect of specific cutting energy depending on the ratio of uncut chip thickness to cutting edge radius are analyzed according to the experimental results. Then, the size effect of surface roughness due to the size effect of specific cutting energy is explored. Lastly, the size effect of the exit burr height is depicted and the potential reason is analyzed. The paper supplies a good understanding of how to get the best surface integrity and minimize the exit burr height for micro cutting.

Size Effect in Machining on Initial Tool Wear in Heat-Resistant Alloy Cutting

2015 ◽  
Vol 656-657 ◽  
pp. 357-362
Author(s):  
Hiroki Hayama ◽  
Hiroki Kiyota ◽  
Fumihiro Itoigawa ◽  
Takashi Nakamura
Keyword(s):  
Grain Size ◽  
Tool Wear ◽  
Size Effect ◽  
Orthogonal Cutting ◽  
Cutting Tools ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Uncut Chip Thickness ◽  
Heat Resistant ◽  
Average Grain Size

Ni based heat-resistant alloys have high strength at high temperature. In addition, they have low thermal conductivity and work-hardening properties. Therefore, Ni based heat-resistant alloys are known as a difficult-to-cut material. The final goal of our study is to develop a cutting method for extending the life of cutting tools for Ni based heat-resistant alloys. As a first step, this study investigated the size effect in machining on initial tool wear in Ni based heat-resistant alloys cutting. Using two types of Ni based heat-resistant alloys with different average grain size, orthogonal cutting tests were performed under changing uncut chip thickness from 12.5 to 200 μm. The cutting speed and width of cut were 30 m/min and 1 mm, respectively. As a result, it was found that when the uncut chip thickness is less than the average grain size, the initial tool wear strongly depends on the average grain size. In contrast, when the uncut chip thickness is sufficiently larger than the average grain size, the initial tool wear does not depend on the average grain size. These results indicate that the ratio of the uncut chip thickness to the average grain size is an important factor to extend the life of cutting tools for Ni based heat-resistant alloys.

SLIP-LINE MODELING OF MACHINING AND DETERMINE THE INFLUENCE OF RAKE ANGLE ON THE CUTTING FORCE

2012 ◽  
Vol 36 (1) ◽  
pp. 23-35 ◽  
Author(s):  
Sabri Ozturk
Keyword(s):  
Cutting Force ◽  
Slip Line ◽  
Cutting Forces ◽  
Orthogonal Cutting ◽  
Chip Thickness ◽  
Cutting Parameters ◽  
Rake Angle ◽  
Uncut Chip Thickness ◽  
Thrust Forces ◽  
Model Approach

In this study, the effects of the rake angle on main cutting force (Fc), and thrust forces (Ft) was investigated. A new slip line model approach for modelling the orthogonal cutting process was proposed. This model was applied at negative rake angles from 0° to –60° and consists of three regions. The main forces were measured with a computer aided quick stop device. Variance Analysis (ANOVA) was utilized to analyze the effects of the cutting parameters on cutting and thrust forces accordingly. Multi-variable regression analysis was also employed to determine the correlations between the factors and the cutting forces. The cutting forces could be calculated by equation parameters which are the rake angle and the uncut chip thickness.

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.

scholarly journals Prediction of Nonlinear Micro-Milling Force with a Novel Minimum Uncut Chip Thickness Model

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1495
Author(s):  
Tongshun Liu ◽  
Kedong Zhang ◽  
Gang Wang ◽  
Chengdong Wang
Keyword(s):  
Cutting Force ◽  
Chip Thickness ◽  
Micro Milling ◽  
Force Model ◽  
Force Coefficient ◽  
Uncut Chip Thickness ◽  
Milling Force ◽  
Minimum Uncut Chip Thickness ◽  
Cutting Force Coefficient ◽  
Milling Force Model

The minimum uncut chip thickness (MUCT), dividing the cutting zone into the shear region and the ploughing region, has a strong nonlinear effect on the cutting force of micro-milling. Determining the MUCT value is fundamental in order to predict the micro-milling force. In this study, based on the assumption that the normal shear force and the normal ploughing force are equivalent at the MUCT point, a novel analytical MUCT model considering the comprehensive effect of shear stress, friction angle, ploughing coefficient and cutting-edge radius is constructed to determine the MUCT. Nonlinear piecewise cutting force coefficient functions with the novel MUCT as the break point are constructed to represent the distribution of the shear/ploughing force under the effect of the minimum uncut chip thickness. By integrating the cutting force coefficient function, the nonlinear micro-milling force is predicted. Theoretical analysis shows that the nonlinear cutting force coefficient function embedded with the novel MUCT is absolutely integrable, making the micro-milling force model more stable and accurate than the conventional models. Moreover, by considering different factors in the MUCT model, the proposed micro-milling force model is more flexible than the traditional models. Micro-milling experiments under different cutting conditions have verified the efficiency and improvement of the proposed micro-milling force model.

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