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1.
AN EXPERIMENTAL STUDY OF ORTHOGONAL MACHINING OF GLASS 总被引:2,自引:0,他引:2
An experimental study of machining glass with a geometrically defined cutting tool is presented. Orthogonal cutting conditions are employed to permit a focus on the fundamental modes of chip and surface formation. Analysis of the machined surfaces under an optical microscope identifies four regimes that are distinctly different with respect to either chip formation or surface formation. For a very small target uncut chip thickness, one on the order of the cutting edge radius, pure rubbing of the edge with no chip formation is observed. Edge rubbing imparts light scuffmarks on the machined surface giving it a frosted appearance. At a larger uncut chip thickness, ductile-mode chip formation occurs ahead of the cutting edge and a scuffed surface remains after the subsequent rubbing of the edge across the freshly machined surface. A further increase in uncut chip thickness maintains a ductile-mode of chip formation, but surface damage initiates in the form of surface cracks that grow down into the machined surface and ahead of the tool. The transition to this machining mode is highly dependent on rake angle. Increasing the uncut chip thickness further causes brittle spalling of chips leaving half-clamshell shaped divots on the surface. This experimental identification of the machining modes and their dependence on uncut chip thickness and rake angle supports the use of geometrically defined cutting tools to machine glass in a rough-semi-finish-finish machining strategy as is traditionally employed for machining metals. 相似文献
2.
Wei-Chong Chiu William J. Endres M. D. Thouless 《Machining Science and Technology》2013,17(2):253-275
Abstract An experimental study of machining glass with a geometrically defined cutting tool is presented. Orthogonal cutting conditions are employed to permit a focus on the fundamental modes of chip and surface formation. Analysis of the machined surfaces under an optical microscope identifies four regimes that are distinctly different with respect to either chip formation or surface formation. For a very small target uncut chip thickness, one on the order of the cutting edge radius, pure rubbing of the edge with no chip formation is observed. Edge rubbing imparts light scuffmarks on the machined surface giving it a frosted appearance. At a larger uncut chip thickness, ductile-mode chip formation occurs ahead of the cutting edge and a scuffed surface remains after the subsequent rubbing of the edge across the freshly machined surface. A further increase in uncut chip thickness maintains a ductile-mode of chip formation, but surface damage initiates in the form of surface cracks that grow down into the machined surface and ahead of the tool. The transition to this machining mode is highly dependent on rake angle. Increasing the uncut chip thickness further causes brittle spalling of chips leaving half-clamshell shaped divots on the surface. This experimental identification of the machining modes and their dependence on uncut chip thickness and rake angle supports the use of geometrically defined cutting tools to machine glass in a rough-semi-finish-finish machining strategy as is traditionally employed for machining metals. 相似文献
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Continuous, unbroken chips used to be a significant manufacturing problem, creating a hazardous situation for the operator and endangering the machine tool. This problem, however, is now largely solved. At this point, further work is needed to optimize well-broken chips. Once chip initial curl and spiral characteristics can be predicted, they can be optimized as part of the overall cutting process design. This may decrease the need for cutting fluids to flush the chips from the cutting region, thereby facilitating a more environmentally conscious process design. Analytic and experimental work is performed to investigate chip spiral morphology and develop a predictive orthogonal chip model. The analytic semi-spiral chip prediction model of Cook et al., [1] is extended to the constricted envelope case. Numerically developed chips are created to investigate the effects of generalized obstruction geometry. The process inputs that have statistically significant effects on chip morphology are determined to confirm the model. 相似文献
4.
《Machining Science and Technology》2013,17(2):187-213
This paper presents an extended oblique machining theory applicable to the analysis of 3-D machining. Existing theories are evaluated to identify suitable formulations which are used with necessary modifications for predicting various quantities pertaining to cutting conditions of three dimensional machining. Actual chip flow angles extracted from measured forces, to account for the nose radius effect, are used, instead of available models, to predict important quantities such as shear plane angle, effective rake angle and shear flow angle. Experiments are conducted in the realms of conventional and high speed machining using AISI 4140 steel and aluminum 7075-T6 respectively with uncoated carbide inserts, and various process conditions pertaining to the cutting mechanics are calculated. The extended oblique machining theory is experimentally validated in predicting temperatures at the tool-chip interface and shear plane for conventional machining. Simulation results from the finite element modeling are used for verifying the shear stress and shear plane temperature predicted by the extended oblique machining theory. 相似文献
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This paper presents an extended oblique machining theory applicable to the analysis of 3-D machining. Existing theories are evaluated to identify suitable formulations which are used with necessary modifications for predicting various quantities pertaining to cutting conditions of three dimensional machining. Actual chip flow angles extracted from measured forces, to account for the nose radius effect, are used, instead of available models, to predict important quantities such as shear plane angle, effective rake angle and shear flow angle. Experiments are conducted in the realms of conventional and high speed machining using AISI 4140 steel and aluminum 7075-T6 respectively with uncoated carbide inserts, and various process conditions pertaining to the cutting mechanics are calculated. The extended oblique machining theory is experimentally validated in predicting temperatures at the tool-chip interface and shear plane for conventional machining. Simulation results from the finite element modeling are used for verifying the shear stress and shear plane temperature predicted by the extended oblique machining theory. 相似文献
7.
Roy J. Schimmel William J. Endres Robin Stevenson 《Machining Science and Technology》2013,17(1):101-125
Abstract It is well known that the edge geometry of a cutting tool affects the forces measured during metal cutting. Two experimental methods have been suggested in the past to extract the ploughing (non-cutting) component from the (total) measured force: (1) an extrapolation approach; and (2) a dwell force technique. However, it has been shown that no ploughing (non-cutting, parasitic) components need be considered to analyze the cutting forces obtained using tools with a honed (radiused) edge and positive clearance. This study reports the influence of varying lengths of zero-clearance flank in combination with controlled edge radii. Analysis shows that zero-clearance flanks do introduce ploughing (non-cutting, parasitic) force components and that the magnitude of the parasitic force is a function of the length of the land. If these parasitic components are subtracted from the total forces, the analysis described by Schimmel et al. (I) may then be followed, effectively reducing the analysis to consideration of the hone alone. Thus, the effect of a zero-clearance land is strictly parasitic and does not affect the chip formation mechanisms. It was also noted that, in these tests, Coulomb's Law applies at the land-workpiece interface and that the coefficient of friction is independent of edge radius and rake angle. 相似文献
8.
The paper presents slipline field solutions for metal machining assuming adhesion friction at the chip-tool interface. The field is of “indirect” type and is analyzed by the matrix method suggested by Dewhurst, Dewhurst and Collins. The range of validity of the proposed solutions is examined from the consideration of overstressing of rigid vertices in the assumed rigid regions. Rake angle and rake friction are found to be the most important variables that influence the deformation process in machining. Variation of cutting forces, chip thickness ratio, chip curvature and contact length with rake angle and friction parameters is investigated. It is observed that cutting and thrust forces and cutting ratio decrease as rake angle increases but increase as coefficient of friction increases. However, tool-chip contact length decreases as rake angle increases. As a result the average normal and shear stresses on the tool face increases as rake angle increases though, the cutting and thrust forces decrease. Results indicate that friction coefficient cannot be uniquely determined by the rake angle alone, but may have a range of allowable values for a particular value of rake angle. The theoretical results are compared with experimental data available in literature and also with those obtained by the authors from orthogonal cutting tests. 相似文献
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Roy J. Schimmel William J. Endres Robin Stevenson 《Machining Science and Technology》2000,4(1):101-125
It is well known that the edge geometry of a cutting tool affects the forces measured during metal cutting. Two experimental methods have been suggested in the past to extract the ploughing (non-cutting) component from the (total) measured force: (1) an extrapolation approach; and (2) a dwell force technique. However, it has been shown that no ploughing (non-cutting, parasitic) components need be considered to analyze the cutting forces obtained using tools with a honed (radiused) edge and positive clearance. This study reports the influence of varying lengths of zero-clearance flank in combination with controlled edge radii. Analysis shows that zero-clearance flanks do introduce ploughing (non-cutting, parasitic) force components and that the magnitude of the parasitic force is a function of the length of the land. If these parasitic components are subtracted from the total forces, the analysis described by Schimmel et al. (I) may then be followed, effectively reducing the analysis to consideration of the hone alone. Thus, the effect of a zero-clearance land is strictly parasitic and does not affect the chip formation mechanisms. It was also noted that, in these tests, Coulomb's Law applies at the land-workpiece interface and that the coefficient of friction is independent of edge radius and rake angle. 相似文献
11.
The paper presents slipline field solutions for metal machining assuming adhesion friction at the chip-tool interface. The field is of “indirect” type and is analyzed by the matrix method suggested by Dewhurst, Dewhurst and Collins. The range of validity of the proposed solutions is examined from the consideration of overstressing of rigid vertices in the assumed rigid regions. Rake angle and rake friction are found to be the most important variables that influence the deformation process in machining. Variation of cutting forces, chip thickness ratio, chip curvature and contact length with rake angle and friction parameters is investigated. It is observed that cutting and thrust forces and cutting ratio decrease as rake angle increases but increase as coefficient of friction increases. However, tool-chip contact length decreases as rake angle increases. As a result the average normal and shear stresses on the tool face increases as rake angle increases though, the cutting and thrust forces decrease. Results indicate that friction coefficient cannot be uniquely determined by the rake angle alone, but may have a range of allowable values for a particular value of rake angle. The theoretical results are compared with experimental data available in literature and also with those obtained by the authors from orthogonal cutting tests. 相似文献
12.
N. Jagannatha S. Hiremath Somashekhar K. Sadashivappa K. V. Arun 《Machining Science and Technology》2013,17(3):459-472
Abrasive Jet Machining is becoming one of the most prominent machining techniques for glass and other brittle materials. In this article, an attempt has been made to combine abrasive and hot air to form an abrasive hot air jet. Abrasive hot air jet machining can be applied to various operations such as drilling, surface etching, grooving and micro finishing on the glass and its composites. The effect of air temperature on the material removal rate applied to the process of glass etching and grooving is discussed in this article. The roughness of machined surface is also analyzed. It is found that the Material Removal Rate (MRR) increases as the temperature of carrier media (air) is increased. The results have revealed that the roughness of machined surface is reduced by increasing temperature of carrier media. The mechanism of material removal rate has been discussed with aid of SEM micrographs. 相似文献
13.
正交车铣运动的矢量建模及表面粗糙度的理论分析 总被引:13,自引:0,他引:13
通过矢量分析,建立了正交车铣运动的矢量模型,并在此基础上给出了描述正交车铣运动的矢量表达式。建立了表面粗糙度的计算公式,并对它进行了简要的分析。 相似文献
14.
External thread cutting is a complex 3-D process in which the cutting conditions vary over the thread cutter profile. It is accepted as a mature; however, heavily experience based technology and there are few academic work published. Determining the cutting forces during machining is crucial to explain formation of the surface layer, residual stresses, selection of the most appropriate machine tool and optimizing the process. This investigation is an attempt to predict thread cutting forces by dividing the thread chip into three parts, one thread root and two side faces. Variation of the cutting parameters including the shear angle, mean cutting temperature and friction force on the flank face of the tool along the thread tool root and sides are determined. In the thread root and sides, chip compression ratios for the V-shaped single piece and separately cut chip zones are measured and cutting forces are calculated and compared for precision metric thread cutting on a SAE 4340 steel bar. 相似文献
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H. A. Kishawy 《Machining Science and Technology》2002,6(1):67-79
This paper investigates experimentally the effects of different process parameters on the cutting edge temperature during high speed machining of D2 tool steel using polycrystalline cubic boron nitride (PCBN) tools. The cutting edge temperature is measured using thermocouples. The process parameters considered are cutting speed, feed rate, nose radius, rake angle, and tool wear. The effects of different edge preparations including sharp, honed and chamfered are also investigated. The results show that increasing cutting speed and feed rate increases the cutting temperature while increasing nose radius reduces the cutting edge temperature. In addition, there is an optimum rake angle value at which minimum cutting temperature is generated. 相似文献
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《Machining Science and Technology》2013,17(3):397-414
A plane-strain thermo-elasto-viscoplastic finite element model has been developed and used to simulate orthogonal machining of 304L stainless steel using a ceramic tool. Simulations were carried out employing temperature-dependent physical properties. The model is used to investigate the effect of process parameters, tool geometry and edge preparation on the contact mechanics at the chip/tool interface. Stress and strain within the chip and the elastic tool are presented. Variables at the chip/tool interface such as contact length, sticking and sliding regions, normal and shear stresses, and frictional heat are investigated. Plastic deformation beneath the machined surface is compared for sharp and chamfered tools. 相似文献