Measuring fracture toughness from machining tests

2009 ◽  
Vol 223 (12) ◽  
pp. 2861-2869 ◽  
Author(s):  
Y Patel ◽  
B R K Blackman ◽  
J G Williams
Keyword(s):  
Fracture Toughness ◽  
Aluminium Alloy ◽  
Coefficient Of Friction ◽  
Metal Cutting ◽  
Orthogonal Cutting ◽  
Shear Plane ◽  
Rake Angle ◽  
Sufficient Information ◽  
The Coefficient Of Friction ◽  
Adhesion Toughness

An analysis of the forces involved in orthogonal cutting or machining is presented in which yielding on a shear plane is assumed. The fracture toughness Gc is included and it is observed that Gc may be determined by measuring the cutting and transverse forces together with the chip thickness for a range of cutting depths. This latter measurement enabled the shear plane angle ϕ to be determined experimentally. A simplified version of the analysis is also given in which ϕ is predicted by a cutting force minimization scheme. Neither scheme requires any details of the friction condition to be known since the transverse force is sufficient information for any type to be included in the analysis. A friction model including a coefficient of friction and an adhesion toughness is also utilized. Data for both polymer and metal cutting are taken from the literature and Gc is determined. In some datasets the tool rake angle α is also varied and the values of Gc and the yield stress σY are found to be independent of α. The force minimization method gives a good estimate of ϕ for most polymers. For metals (aluminium alloy, steel, and brass) the method worked well. For aluminium alloy Gc was independent of α and the predicted and measured ϕ values agreed. For steel and brass this was not so. Gc was mostly independent of α except at low values where high values of Gc were observed. A constant value of the coefficient of friction was observed for each α value but values for both the coefficient of friction and the adhesion toughness varied significantly with increasing rake angle.

The Influence of Extreme Speeds and Rake Angles in Metal Cutting

1963 ◽  
Vol 85 (1) ◽  
pp. 49-64 ◽  
Author(s):  
W. N. Findley ◽  
R. M. Reed
Keyword(s):  
Coefficient Of Friction ◽  
Metal Cutting ◽  
Orthogonal Cutting ◽  
Shear Plane ◽  
Rake Angle ◽  
Lateral Extrusion ◽  
Tool Force ◽  
Steep Decrease ◽  
Peak Value ◽  
Antimony Alloy

A study is presented of the effect of wide variations in speed of cutting and rake angle on orthogonal cutting of several metals—mainly a lead-antimony alloy. It was observed that enormous decreases in tool forces occurred in the lead-antimony with increase in speed from 6 to 3800 fpm, and decrease in rake angle from +30° to −60°. Explanations for these variations are proposed. An unusual observation was that a transition as speed increased from continuous to discontinuous chips occurred at large negative rake angles. Possible causes of this behavior are discussed. Another unusual observation was that a steep rise in tool force occurred with increase in speed for rake angles of 0° and +30°. The rise to a peak value was followed by an equally steep decrease in tool forces. Other observations discussed include the appearance of side spikes on the chips, chip curl, lateral extrusion of chips, influence of normal stress occurring on the shear plane, and the apparent coefficient of friction.

Deformation Characteristics of Ultra-Fine Grained Al6061 Chip in Machining by Finite Element Method

2010 ◽  
Vol 44-47 ◽  
pp. 2931-2934
Author(s):  
Chun Ling Wu ◽  
Bang Yan Ye
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Coefficient Of Friction ◽  
Metal Cutting ◽  
High Hardness ◽  
Rake Angle ◽  
Fine Grained ◽  
The Coefficient Of Friction ◽  
Cutting Velocity ◽  
Element Method

Ultra-fine grained chips with higher hardness and strength than bulk can be produced by severe plastic deformation during orthogonal metal cutting. A finite element method was developed to characterize the distribution of stress, strain, strain rate and temperature in the deformation area at different rake angles and cutting velocities. The coefficient of friction in the tool-chip interface is approximately obtained according model of mean coefficient of friction which is based on experiments in any machining conditions. The formation mechanics of ultra-fine grained chip is discussed and effect of rake angle on microstructure of chips is highlighted. The results of experiment and modeling have shown that chip materials with ultra-fine grained and high hardness can be produced with more negative tool rake angle at some lower cutting velocity.

New Developments in the Theory of the Metal-Cutting Process: Part I. The Ploughing Process in Metal Cutting

1960 ◽  
Vol 82 (4) ◽  
pp. 348-357 ◽  
Author(s):  
P. Albrecht
Keyword(s):  
Coefficient Of Friction ◽  
Metal Cutting ◽  
Rake Angle ◽  
Cutting Edge ◽  
Cutting Process ◽  
Force Diagram ◽  
The Coefficient Of Friction ◽  
Cutting Velocity ◽  
Real Value ◽  
Force Components

Revelation of the significance of “ploughing” in the metal-cutting process, which occurs because of the finite sharpness of the cutting edge, leads to a better understanding of the mechanics of the metal-cutting process. The concept of the ploughing force on the extreme cutting edge allows the development of a more complete force diagram which separates the ploughing force from the chip-tool interface force. Components of this more detailed force diagram have been verified experimentally. In terms of the new force diagram the real value of the coefficient of friction on the chip-tool interface has been found and the paradox of variation of the coefficient of friction with variation of rake angle explained. The paper also contributes to a better understanding of such events as the effect of cutting velocity upon tool forces, built-up edge, chip curling, and residual stresses in the work surfaces.

The Effect of Prior Cutting Conditions on the Shear Mechanics of Orthogonal Machining

1998 ◽  
Vol 120 (1) ◽  
pp. 13-20 ◽  
Author(s):  
R. Stevenson ◽  
D. A. Stephenson
Keyword(s):  
Material Properties ◽  
Metal Cutting ◽  
Orthogonal Cutting ◽  
Rake Angle ◽  
Cnc Machining ◽  
Machining Process ◽  
Depth Of Cut ◽  
Prior History ◽  
Machining Conditions ◽  
The Difference

It has been proposed several times in the metal-cutting literature that the machining process is non-unique and that the instantaneous machining conditions depend on the prior machining conditions (e.g. depth of cut, rake angle etc.). To evaluate the validity of this concept, a series of experiments was conducted using a highly accurate CNC machining center. For these experiments, the machining conditions were changed during the course of an orthogonal cutting experiment in a repeatable manner and the measured forces compared as a function of prior history. Tests were conducted on several tempers of 1100 aluminum and commercial purity zinc to evaluate the effect of material properties on the machining response. It was found that the change in measured cutting forces which could be ascribed to prior machining history was less than 3 percent and that material properties, particularly work hardening response, had no discernible effect on the magnitude of the difference.

scholarly journals Analysis of critical negative rake angle and friction characteristics in orthogonal cutting of AL1060 and T2

2019 ◽  
Vol 103 (1) ◽  
pp. 003685041987806 ◽  
Author(s):  
Yanchun Ding ◽  
Guangfeng Shi ◽  
Hua Zhang ◽  
Guoquan Shi ◽  
Dongdong Han
Keyword(s):  
Metal Cutting ◽  
Orthogonal Cutting ◽  
Cutting Tools ◽  
Flow Characteristics ◽  
Rake Angle ◽  
Machined Surface ◽  
Friction Characteristics ◽  
Model Based ◽  
Stagnant Region ◽  
Cutting Experiments

The stagnant region often appears in front of the tool cutting edge, which is caused by mechanical inlay and excessive pressing in plastic metal cutting with large negative rake angle tools at a low speed. It results in the change of the effective negative rake angle which can affect the flow characteristics of material, the quality of machined surface and the abrasion loss of cutting tools. However, the critical negative rake angle model based on the existence of the stagnant region has not been reported yet. Therefore, in order to investigate the critical negative rake angle value considering the stagnant region, a critical negative rake angle model based on the principle of minimum required energy is established, and the correctness of the theoretical model is verified by orthogonal cutting experiments. At the same time, the influence of the critical value of the large negative rake angle tool on the machined surface quality is studied through different cutting experiments. These experimental results show that the deviations of both experimental and theoretical critical negative rake angle are less than 5% during the orthogonally cutting of the aluminium (AL1060) and copper (T2) materials by the negative rake angle tool. Meanwhile, the critical negative rake angle is related to the adhesive friction coefficient of tool–workpiece contact surface. The analysis of friction characteristics shows that the deviation values of both theoretical and experimental critical negative rake angle are proportional to the coefficient of adhesive friction and the thickness of the stagnant region. Critical negative rake angle has a significant effect on roughness and residual stress of the machined surface.

A New Analysis of the Forces in Orthogonal Metal Cutting

1965 ◽  
Vol 87 (4) ◽  
pp. 480-486 ◽  
Author(s):  
J. D. Cumming ◽  
S. Kobayashi ◽  
E. G. Thomsen
Keyword(s):  
Metal Cutting ◽  
Orthogonal Cutting ◽  
Minimum Energy ◽  
Cutting Speed ◽  
Shear Plane ◽  
Force Model ◽  
Shearing Stress ◽  
Orthogonal Metal Cutting ◽  
Linear Force ◽  
Dynamic Shearing

The mechanics of orthogonal cutting have been reexamined and for the shear-plane concept of metal cutting, linear and quadratic-force models were suggested. It was shown that for steel SAE-1213, investigated under variable cutting conditions, the dynamic shearing stress remained constant and the linear-force model correlated with those experimental data which were obtained under the absence of a BUE. The angle λ formed by the shear plane and the direction of the resultant force remained constant for each test condition but varied with cutting speed. Neither the Ernst and Merchant minimum energy, nor the Lee and Shaffer solutions are in agreement with experimental observations.

An Experimental and Computational Study of Temperature and Strain Fields in Metal Cutting

2001 ◽  
Author(s):  
Alan T. Zehnder ◽  
Yogesh K. Potdar ◽  
Xiaomin Deng ◽  
Chandrakant Shet
Keyword(s):  
Spatial Resolution ◽  
Metal Cutting ◽  
Computational Study ◽  
Orthogonal Cutting ◽  
Critical Role ◽  
Rake Angle ◽  
General Purpose ◽  
Temperature Fields ◽  
Ir Detectors ◽  
Strain Fields

Abstract Metal cutting is a thermo-mechanically coupled process in which plasticity induced heating and friction play a critical role. In this paper, we outline a methodology that combines high resolution experiments with numerical simulations. The simulations were performed with a general purpose finite element code. With this code we evaluate the effects of chip-tool interface friction and rake angle on temperature and cutting force and show that results for residual stresses in the workpiece are consistent with experimental data. We hypothesize that by closely coupling simulations to fine scale spatial and temporal experimental measurements of temperature and strain fields, questions related to choice of parameters in FE simulations can be resolved. We have designed and conducted orthogonal cutting experiments to measure temperatures, using IR detectors, with a spatial resolution of 27 × 27 μm and time scale of 200 ns. Experimentally obtained temperature fields are compared with FE results. We also obtain deformation fields with a spatial resolution of 50 × 50 μm.

An Analysis of the Mechanism of Orthogonal Cutting and Its Application to Discontinuous Chip Formation

1961 ◽  
Vol 83 (4) ◽  
pp. 545-555 ◽  
Author(s):  
Keiji Okushima ◽  
Katsundo Hitomi
Keyword(s):  
Chip Formation ◽  
Metal Cutting ◽  
Orthogonal Cutting ◽  
Plastic Region ◽  
Flow Region ◽  
Shear Plane ◽  
Experimental Result ◽  
Conventional Theory ◽  
Boundary Lines ◽  
Continuous Chip

Instead of the conventional theory of the mechanics of metal cutting based on a process of shear confined to a single shear plane, the concept of flow region, a fairly large transitional deformation zone which exists between the rigid region of work and the plastic region of steady chip, was developed. The mechanics of orthogonal cutting was analyzed, theoretical equations for angles of boundary lines of the flow region and for strain in chip were deduced in the case of simple continuous chip formation and confirmed in cutting tests on lead. The concept of flow region was also applied to discontinuous chip formation, and theoretical expressions for angles of boundary lines of the flow region were ascertained to be in agreement with the experimental result for carbon steel.

scholarly journals Heat generated by cutting ice in deep ice-core drilling

2007 ◽  
Vol 47 ◽  
pp. 61-67 ◽  
Author(s):  
Nobuhiko Azuma ◽  
Ikuo Tanabe ◽  
Hideaki Motoyama
Keyword(s):  
Temperature Increase ◽  
Metal Cutting ◽  
Rotation Speed ◽  
Ice Core ◽  
Shear Plane ◽  
Rake Angle ◽  
Mechanical And Thermal Properties ◽  
Core Drilling ◽  
Friction Heat ◽  
Chip Temperature

AbstractIn order to understand and solve the ‘warm-ice problem’ in deep ice-core drilling, we applied the metal-cutting theory to ice and estimated the heat generated during ice coring taking into account the mechanical and thermal properties of the ice and cutters. We found that (1) most of the heat in cutting is generated by shear deformation at the shear plane of ice, and the heat could increase the chip temperature by several degrees; (2) the rake angle of the cutter has more influence on the temperature increase in chips than the barrel rotation speed and penetration pitch; (3) if the cutter is made of a material with larger thermal conductivity, the temperature increase in the chips can be reduced; and (4) if the density of the liquid is less than the density of ice, the cutting chips sink to the bottom and the friction heat generated by the drill head and slush can raise the ambient temperature of the drill head by several degrees.

Effects of Strain Rate and Temperature in Orthogonal Metal Cutting

1966 ◽  
Vol 8 (3) ◽  
pp. 264-275 ◽  
Author(s):  
G. Boothroyd ◽  
J. A. Bailey
Keyword(s):  
Theoretical Analysis ◽  
Strain Rate ◽  
Metal Cutting ◽  
Single Phase ◽  
Orthogonal Cutting ◽  
Cutting Speed ◽  
Rake Angle ◽  
Cutting Process ◽  
Strain Rates ◽  
Continuous Chip

A new theoretical analysis of the orthogonal cutting process is described which is based on the known behaviour of a single phase metal at high strains, strain rates and temperatures. The theoretical analysis applies to the case where a continuous chip is produced under non-lubricated conditions with the absence of a built-up edge on the tool face and indicates the important parameters in the cutting process. The theory is examined experimentally and its validity established. Finally, from a knowledge of the effects of strain rate and temperature on the yield stress of a single phase metal, the theory is used to predict the effects of changes in cutting speed and tool rake angle on the tool forces and geometry of the cutting process. These predictions are compared qualitatively with the results of cutting tests.

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