scholarly journals Fracture toughness, chip types and the mechanics of cutting wood. A review COST Action E35 2004–2008: Wood machining – micromechanics and fracture

Holzforschung ◽  
2009 ◽  
Vol 63 (2) ◽  
Author(s):  
David J. Wyeth ◽  
Giacomo Goli ◽  
Anthony G. Atkins
Keyword(s):  
Fracture Toughness ◽  
Chip Formation ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Surface Damage ◽  
Surface Separation ◽  
Wood Processing ◽  
Shear Yield ◽  
The Cost

Abstract Historical studies for predicting cutting forces in wood processing are based on the Piispanen/Ernst-Merchant theory employed in metal cutting where the offcut/chip is formed in shear. This analysis has been recently improved to include significant work of surface separation and formation (i.e., the fracture toughness of the workpiece, as well as the shear yield stress and friction). The new theory is applied here to wood cutting experiments. It is well known that chip formation and surface damage depend on grain orientation and chip thickness, but experiments reveal that chip formation alters with cutting speed as well. During the COST E35 action a series of experiments and special devices to orthogonally cut wood at high and low speed have been developed. In this paper, an overview of the cutting devices and the main results are given.

Process-Independent Force Characterization for Metal-Cutting Simulation

1997 ◽  
Vol 119 (1) ◽  
pp. 86-94 ◽  
Author(s):  
D. A. Stephenson ◽  
P. Bandyopadhyay
Keyword(s):  
Metal Cutting ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Rake Angle ◽  
Baseline Data ◽  
Empirical Equations ◽  
Machining Processes ◽  
Workpiece Material ◽  
Bar Turning ◽  
Force Data

Obtaining accurate baseline force data is often the critical step in applying machining simulation codes. The accuracy of the baseline cutting data determines the accuracy of simulated results. Moreover, the testing effort required to generate suitable data for new materials determines whether simulation provides a cost or time advantage over trial-and-error testing. The efficiency with which baseline data can be collected is limited by the fact that simulation programs do not use standard force or pressure equations, so that multiple sets of tests must be performed to simulate different machining processes for the same tool-workpiece material combination. Furthermore, many force and pressure equations do not include rake angle effects, so that separate tests are also required for different cutter geometries. This paper describes a unified method for simulating cutting forces in different machining processes from a common set of baseline data. In this method, empirical equations for cutting pressures or forces as a function of the cutting speed, uncut chip thickness, and tool normal rake angle are fit to baseline data from end turning, bar turning, or fly milling tests. Forces in specific processes are then calculated from the empirical equations using geometric transformations. This approach is shown to accurately predict forces in end turning, bar turning, or fly milling tests on five common tool-work material combinations. As an example application, bar turning force data is used to simulate the torque and thrust force in a combined drilling and reaming process. Extrapolation errors and corrections for workpiece hardness variations are also discussed.

New Development in the Theory of the Metal-Cutting Process: Part II—The Theory of Chip Formation

1961 ◽  
Vol 83 (4) ◽  
pp. 557-568 ◽  
Author(s):  
P. Albrecht
Keyword(s):  
Shear Zone ◽  
Tool Life ◽  
Chip Formation ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Shear Plane ◽  
Cutting Process ◽  
Chip Formation Mechanism ◽  
Bending Stresses ◽  
Set Up

Introduction of the concept of ploughing into the metal-cutting process lead to the abandoning of the assumption of collinearity of the resultant force on tool face and on the shear plane. With this understanding the tool face force is found to produce a bending effect causing bending stresses in the shear zone. Study of the chip formation mechanism when varying cutting speed showed that increased bending action reduces the shear angle and vice versa. A set-up for the development of an analytical model of the chip formation process based on the combined effect of shear and bending stresses in the shear zone has been given. Application of the gained insight to the design of the cutting tool for maximum tool life by controlling of the chip-tool contact was suggested. Brief introduction to the study of cyclic events in chip formation and their relation to the tool life is presented.

Investigations on chip formation of turned novel AM alloy

2020 ◽  
pp. 095440892096119
Author(s):  
Sunil Dutta ◽  
Suresh Kumar Reddy Narala
Keyword(s):  
Chip Formation ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Depth Of Cut ◽  
Feed Speed ◽  
Nose Radius ◽  
Chip Shape ◽  
High Feed ◽  
Cutting Operation ◽  
On Chip

Manufacturers across varied segments look for materials having appreciable machinability and surface integrities. Machinability of Mg alloys is a vital aspect during their acceptance for different applications. The chip shape generated in the cutting operation is a crucial attribute dominating the surface roughness, besides the dimension’s precision and the tool lifespan. The study discusses the chip-formation through the dry turning of a novel AM alloy (Mg alloy with 7 wt%Al-0.9 wt%Mn) using carbide insert with a 0.4 mm nose radius. During the experiments, three chip dimensions, namely chip-thickness, chip-length, and chip-width were measured. The turning variables, namely cutting speed( v), depth of cut (DOC), and feed ( f) is altered and applied to the workpiece. The chip shape was mostly dependent on the grouping of turning parameters. It was seen that favorable continuous chip formed at high feed and low DOC. The % contribution of each turning parameter on the chip shape was calculated. The experimental results are validated with the help of analysis of variance (ANOVA). The results show that the % contribution of feed, speed, and DOC on chip-thickness is 58.49%, 28.91%, and 12.49%; the contribution on chip-length is 76.89%, 20.81%, and 2.23%; and on chip-width, it is 25.28%, 0.48%, and 74.33%, respectively. Further, the chip shapes were compared with the shapes that were predicted by FEM software. The study offers vital insights for parameter selection to improve chip shape, which, in turn, contributes to higher surface quality.

Evaluation of micro-features of chips of Inconel 825 during dry turning with uncoated and chemical vapour deposition multilayer coated tools

2016 ◽  
Vol 232 (6) ◽  
pp. 979-994 ◽  
Author(s):  
A Thakur ◽  
S Gangopadhyay
Keyword(s):  
Shear Band ◽  
Chemical Vapour Deposition ◽  
Chip Formation ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Dry Machining ◽  
Research Attention ◽  
Inconel 825

Mechanism of chip formation during dry machining of Ni-based super alloys needs considerable research attention as it directly or indirectly affects different aspects of machinability. Therefore, the present research work aims at understanding the mechanism of chip formation with the help of various chip characteristics during dry machining of Inconel 825, a nickel-based super alloy. The influence of multilayer coating deposited using chemical vapour deposition, cutting speed and machining duration has been investigated on types and form of chips, along with different characteristics of chip like shear band thickness, saw-tooth distance, equivalent chip thickness, saw-tooth angle and chip segmentation frequency. Chip–tool contact length, hardness and crystallographic orientation (through X-ray diffraction) of chip have also been studied. Furthermore, different machining characteristics such as cutting force, apparent coefficient of friction and cutting temperature have also been determined for explaining the mechanism of various aspects of chip formation. The results indicated that coated tool restricted sharp increase in shear band thickness with cutting speed and resulted in reduction in saw-tooth distance, saw-tooth angle, equivalent chip thickness, chip hardness and deformation on grains while exhibiting increase in chip segmentation frequency in comparison with its uncoated counterpart.

Numerical Analysis of Metal Cutting With Chamfered and Blunt Tools

2002 ◽  
Vol 124 (2) ◽  
pp. 178-188 ◽  
Author(s):  
M. R. Movahhedy, ◽  
Y. Altintas, ◽  
M. S. Gadala,
Keyword(s):  
Formation Process ◽  
Chip Formation ◽  
High Speed ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Cutting Edge ◽  
Hard Materials ◽  
Ale Finite Element Method ◽  
Diffusion Wear ◽  
Process Simulations

In high speed machining of hard materials, tools with chamfered edge and materials resistant to diffusion wear are commonly used. In this paper, the influence of cutting edge geometry on the chip removal process is studied through numerical simulation of cutting with sharp, chamfered or blunt edges and with carbide and CBN tools. The analysis is based on the use of ALE finite element method for continuous chip formation process. Simulations include cutting with tools of different chamfer angles and cutting speeds. The study shows that a region of trapped material zone is formed under the chamfer and acts as the effective cutting edge of the tool, in accordance with experimental observations. While the chip formation process is not significantly affected by the presence of the chamfer, the cutting forces are increased. The effect of cutting speed on the process is also studied.

Interrelation between Shearing Angles of External and Internal Friction during Chip Formation

2019 ◽  
Vol 291 ◽  
pp. 193-203 ◽  
Author(s):  
Oleksii Zhuravel ◽  
Vitalii Derbaba ◽  
Volodymyr Protsiv ◽  
Sergey Patsera
Keyword(s):  
Internal Friction ◽  
Chip Formation ◽  
Metal Cutting ◽  
Analytical Calculation ◽  
Cutting Speed ◽  
Computer Experiments ◽  
Front Surface ◽  
Practical Significance ◽  
Front Angle ◽  
Algorithmic Model

The aim of this work is to develop a methodology for graphically analytical calculation of angles of chip formation process for the case when the initial data are reliable empirical dependencies for the cutting forces’ components and value of shearing angle are obtained experimentally. The research method is based on the application of the elements of cutting theory with respect to flow chip formation scheme and the model of plastic deformation of metal with one slip surface with free cutting without a build-up on the front surface of the blade. Academic novelty is characterized by the developed algorithmic model which is based on the interrelation of shearing angles, external friction-slip chips on the front surface of the blade, internal friction-shear in the plane of shear and the front angle of the blade. The algorithmic model is implemented programmatically in the NI LabVIEW environment and graphically analytical in the KOMPAS-3D program. There were carried out computer experiments and identified the dependencies of chip formation angles on cutting speed and the front angle of the blade. The practical significance consists in the possibility to carry out an engineering analysis of the metal cutting mechanics without carrying out some valuable complex experiments.

Micro-Structural Analysis of Chip Formation During Orthogonal Machining of Al/SiCp Composites

2000 ◽  
Vol 123 (3) ◽  
pp. 315-321 ◽  
Author(s):  
S. S. Joshi ◽  
N. Ramakrishnan ◽  
P. Ramakrishnan
Keyword(s):  
Free Surface ◽  
Structural Analysis ◽  
Chip Formation ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Shear Plane ◽  
Point Of View ◽  
Unique Case ◽  
Orthogonal Machining ◽  
Cutting Point

Discontinuously Reinforced Aluminum (DRA) Composites form unique case from the research in metal cutting point of view. Reinforcement in these materials acts as “macroscopic” and “isolated” discontinuities in the path of the tool. The mechanism of chip formation for such materials is yet to be evolved completely. In this paper, the mechanism of chip formation during machining of Al/SiCp composites based on the micro-structural analysis of chips and chip roots is presented. It was evident that the mechanism involves initiation of a gross fracture on the chip free surface and its propagation toward the tool nose. The extent of propagation of gross fracture depends upon the cutting speed and volume of reinforcement in composites. A model of deformation of the material along the shear plane is presented in terms of a ratio of length of flow-type deformation on the shear plane to the total length of shear plane. Influence of volume of reinforcement in composites and cutting speed on the ratio was verified experimentally.

Rosenhain and Sturney revisited: The ‘tear’ chip in cutting interpreted in terms of modern ductile fracture mechanics

2004 ◽  
Vol 218 (10) ◽  
pp. 1181-1194 ◽  
Author(s):  
A G Atkins
Keyword(s):  
Ductile Fracture ◽  
Metal Cutting ◽  
Chip Thickness ◽  
Shear Plane ◽  
Rake Angle ◽  
Uncut Chip Thickness ◽  
General Applicability ◽  
Surface Separation ◽  
Different Types ◽  
Continuous Chip

Rosenhain and Sturney in 1925 identified the ‘tear’ chip, in addition to the well-known types of chip found in metal cutting, namely continuous with or without a built-up edge and discontinuous. Tear chips occur at deep uncut chip thicknesses and, since their formation results in undesirable surface finish, they have been largely ignored in subsequent analyses of machining. A recent paper by Atkins shows that metal cutting is from the class of ductile fracture problems where there is complete plastic collapse in the formation of the chip. It was demonstrated that incorporation of significant work of surface separation (ductile fracture toughness), in analyses of machining with continuous chip formation, explains many features of metal cutting which traditional ‘plasticity and friction only’ treatments cannot, in particular why the primary shear plane angle is material dependent. It also explained why finite element simulations of machining have to employ a ‘separation criterion’ at the tool tip. The new model is extended in this paper to predict quantitatively the conditions under which the tear chip forms. The production of other well-known types of chip is also considered, and the results are applied to diagrams relating combinations of tool rake angle and uncut chip thickness at which different types of chip are formed. It is demonstrated that the analysis has general applicability to the cutting of other materials such as plastics and wood for which similar diagrams exist.

Analysis and Fabrication of a Mechanical Quick-Stop for Research on Chip Formation in Hard Turning Process

2019 ◽  
Vol 889 ◽  
pp. 87-94
Author(s):  
Nguyen Thi Quoc Dung
Keyword(s):  
Chip Formation ◽  
Hard Turning ◽  
Manufacturing Industry ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Cutting Process ◽  
Machining Process ◽  
Machining Parameters ◽  
Machining Processes ◽  
On Chip

Metal cutting is one of the most important machining processes in manufacturing industry. Thorough understanding of metal cutting process facilitates the optimization in selection of cutting tools and machining parameters. There are several methods used for studying phenomena in metal cutting process. Using a quick-top device is an efficient technique for investigation cutting process in which cutting action is stopped so suddenly that the “froze” specimen called the chip root honestly depicts what happened during cutting action. Design strategies of a quick-stop are accelerating cutting tool away from the workpiece or decelerating the workpiece remaining in engagement with the tool. Operation of a quick-stop device can be either mechanically or by explosive. Quick-stop devices can be utilized for various types of machining processes such as: turning, milling, drilling. This paper described the analysis, fabrication, and testing of a quick-stop device which is used for researching on chip formation in hard turning. This device has simple and safe operation which utilizes spring forces to retract the tool from workpiece during cutting. The results of performance at cutting speed of 283 m/min show that the separation distance is quite small, less than 0.2mm so that the deformations on the root chip are close to that while actual machining process. This indicates that the device has satisfied the requirements of an equipment for studying on chip formation.

Material Characterization for Metal-Cutting Force Modeling

1989 ◽  
Vol 111 (2) ◽  
pp. 210-219 ◽  
Author(s):  
D. A. Stephensen
Keyword(s):  
Shear Stress ◽  
Strain Rate ◽  
Cutting Force ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Shear Plane ◽  
Stress And Strain ◽  
Force Model ◽  
Wide Range

Widely applicable machining simulation programs require reliable cutting force estimates, which currently can be obtained only from process-dependent machinability databases. The greatest obstacle to developing a more basic, efficient approach is a lack of understanding of material yield and frictional behavior under the unique deformation and frictional conditions of cutting. This paper describes a systematic method of specifying yield stress and friction properties needed as inputs to process-independent cutting force models. Statistically designed end turning tests are used to generate cutting force and chip thickness data for a mild steel and an aluminum alloy over a wide range of cutting conditions. Empirical models are fit for the cutting force and model-independent material parameters such as the tool-chip friction coefficient and shear stress on the shear plane. Common material yield behavior assumptions are examined in light of correlations between these parameters. Results show no physically meaningful correlation between geometric shear stress and strain measures, a weak correlation between geometric stress and strain rate measures, and a strong correlation between material properties and input variables such as cutting speed and rake angle. An upper bound model is used to fit four- and five-parameter polynomial strain-rate sensitive constitutive equations to the data. Drilling torques calculated using this model and an empirical turning force model agree reasonably well with measured values for the same material combination, indicating that end turning test results can be used to estimate mean loads in a more complicated process.

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