Single Abrasive Grain Research Articles

Model of Side Contact Layer and Wear Performance of CBN Wheel in Quick-point Grinding Process

Based on the principle and technical characteristcs of point grinding process, the function of the side contact area of the thin CBN point-grinding wheel in material removal process is discussed, and the geometry and parameters models of the side contact area are established. Mathematic modeling and analysis are carried out for the side contact layer parameters, such as the equivalent workpiece diameter, the geometric and dynamic contact arc length, cutting depth of single abrasive grain and average cross-sectional area of chips. The grinding experiment is carried out to study the mechanism of effect of side contact layer parameters on the quick point grinding process and the wear characteristic and rule of thin CBN point-grinding wheel. It is found that the material removal is mainly completed in the side contact layer and the maximum wear rate of the thin CBN point-grinding wheel occurs at the largest circumference of wheel side in the point grinding process.

Research on Microscopic Grain-Workpiece Interaction in Grinding through Micro-Cutting Simulation, Part 2: Factorial Study

The grinding process can be considered as micro-cutting processes with irregular abrasive grains on the surface of grinding wheel. Single grain cutting simulation of AISI D2 steel with a wide range of cutting parameters is carried out with AdvantEdgeTM. The effect of cutting parameters on cutting force, chip formation, material removal rate, and derived parameters such as the specific cutting force, critical depth of cut and shear angle is analyzed. The formation of chip, side burr and side flow is observed in the cutting zone. Material removal rate increases with the increase of depth of cut and cutting speed. Specific cutting force decreases with the increase of depth of cut resulting in size effect. The shear angle increases as the depth of cut and cutting speed increase. This factorial analysis of single grain cutting is adopted to facilitate the calculation of force consumption for each single abrasive grain in the grinding zone.

Numerical analysis of micromachining of C45 steel by single abrasive grain

AbstractGrinding is a very complicated processing. To increase quality of product and minimize the cost of abrasive machining, we should know physical phenomena which exist during the process. The first step to solution of this problem is analysis of machining process with a single abrasive grain. In the paper [1] the thermo–mechanical models of this process are presented, but in this work attention is concentrated on chip formation and his separation from object for different velocity of abrasive grain. The phenomena on a typical step time were described using step–by–step incremental procedure, with updated Lagrangian formulation. Then, the finite elements methods (FEM) and dynamic explicit method (DEM) were used to obtain the solution. Application was developed in the ANSYS system, which makes possible a complex time analysis of the physical phenomena – states of: displacements, strains and stress. Numerical computations of the strain have been conducted with the use of two methodologies. The first one requires an introduction of boundary conditions for displacements in the contact area determined in modeling investigation, while the second – a proper definition of the contact zone, without the necessity to introduce boundary conditions in the contact area. Examples of calculations for the intensity of stress in the surface layer zones were presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

More efficient deep grinding

Currently, abrasive machining is used to improve product quality and productivity and also for preliminary and final machining in a single pass. Deep grinding is of particular interest here. In this method, with considerable metal removal in a single pass, problems arise in preventing thermal and other damage to the part. The kinematic aspects of deep grinding were analyzed in detail over the phases of the complete cycle in [1, 2]: in tool insertion; steady grinding; and removal of the grinding wheel. The productivity of the process is evaluated in terms of the volume of the layer removed in a single turn of the wheel. In specified conditions, this allows the change in cutting rate to be taken into account; in other words, it permits quantitative analysis. The processes in the contact zone of a single abrasive grain with the metal, within the range of wheel rotation bounded by the points of the grain entry into the metal and its exit, were subjected to qualitative estimation in [3]. It was found that, within this range, the temperature and pressure vary significantly in the metal. This is associated with change in the rate of removal of microvolumes of metal as the wheel turns. It is of interest to investigate deep grinding by analysis of the rate of metal removal in the sector of the wheel whose central angle is determined by the wheel radius and the cutting depth. This approach permits study of the physics of metal dispersion at different cutting speeds and depths in the actual contact zones of a single grain (a single point of the wheel) between its entry in the blank and its subsequent exit, in both ordinary and deep grinding. For the sake of simplicity, all the calculations relate to steady grinding. The arc radius remains constant as the center of the wheel moves; the displacement l ce of the center O 0 is equal to the longitudinal supply; l ce / ϕ = const, where ϕ is the contact angle (Fig. 1). The angle ϕ = arccos[( r ‐ t )/ r ], where r is the mean radius of the wheel’s working surface; t is the grinding depth. The thickness of the cut layer at any point b = l ce sin ϕ . The volume of metal removed during the contact time is enclosed between two cylindrical surfaces (impressions of the wheel) and parallel planes: the

Numerical analysis of chip formation during machining for different value of failure strain

AbstractGrinding is a very complicated processing. To increase quality of product and minimize the cost of abrasive machining, we should know physical phenomena which exist during the process. The first step to solution of this problem is analysis of machining process with a single abrasive grain. In the papers [1, 2] the thermo‐mechanical models of this process are presented, but in this work attention is concentrated on chip formation and his separation from object. The influence of failure strain εf on states of strain and stress in surface layer during machining is explained. The phenomena on a typical incremental step were described using step‐by‐step incremental procedure, with updated Lagrangian formulation. Then, the Finite Element Method (FEM) and Dynamic Explicit Method (DEM) were used to obtain the solution. Application was developed in the ANSYS system, which makes possible a complex time analysis of the physical phenomena: states of displacements, strains and stress. Numerical computations of the strain have been conducted with the use of two methodologies. The first one requires an introduction of boundary conditions for displacements in the contact area determined in modeling investigation, while the second – a proper definition of the contact zone through the introduction of finite elements of TARGET and CONTACT types, without the necessity to introduce boundary conditions. This model includes variational equations of the object's motion and deformation. Examples of calculations for the displacement, strain and stress field in the surface layer zones were presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Theory and Experiment Study on the Grinding Force

The grinding force was one of the most important parameters, almost related with all the parameters in grinding. In this paper, the grinding force model was established by a new method. The abrasive grains were analyzed using the statistical probability method. The abrasive grains were divided into two types, one was the cutting abrasive grain, and the other was contacting abrasive grain. The force analysis of a single abrasive grain was done. The grinding force model was established on the basis of the statistical probability method and the force analysis of a single abrasive grain. Theoretical analysis was verified by the experiment. The results indicated, the experimental results agree well with the theoretical prediction. The model can accurately predict the grinding force.

単結晶シリコンの超精密加工におけるクラック発生に及ぼす結晶方位の影響

The crack-free removal of material, known as ductile mode machining, has been achieved by a very small depth of cut. In this study, the nano-scale layers of single-crystal silicon surface are machined by micro-Vickers hardness indenter witch is assumed to be a single abrasive grain. The subsurface crack as well as the surface crack are observed by a scanning prove microscope and a scanning laser microscope. When surface cracks are not observed by decreasing the depth of cut, the machining has been commonly considered to be in ductile mode. Although crack-free machining seems to be accomplished, the subsurface crack progress under the groove. The transition point determined by the subsurface crack is found to be a more shallow depth of groove than the point by the surface crack. Therefore the evaluation of the subsurface crack is significant especially in finish machining. The dependency of the depth of the subsurface crack on crystallographic direction is revealed. This dependency is due to the fact that mechanical properties of single-crystal silicon are affected by the crystallographic direction.

Formulation for the Effect of Surface Grinding on Strength Degradation of Ceramics

Relationship between fracture strength of ground ceramics and maximum grain depth of cut, g, has been formulated. The strength was expressed by an exponential function of g. This expression is based on the assumption that the crack depth of the ground specimen is represented in terms of normal grinding force applied with a single abrasive grain of a wheel, as median crack length in indentation fracture is the function of indenting load. The four-point bending strength of sintered silicon carbide ceramics ground with 4 kinds of grit diamond wheels under various conditions showed good agreement with the approximation by the function of g. In particular, the strength decreased steeply from the inherent level with a slight increase in g.

Thermal Aspects of Grinding: The Effect of the Wheel Bond on Heat Transfer to an Abrasive Grain

Heat generated during grinding can cause thermal damage to the workpiece and wheel. It is therefore important to understand the thermal aspects of grinding. This paper addresses heat conduction into the wheel, by considering a single abrasive grain in contact with the workpiece. In particular, the effect of the bond material on conduction into the grain is investigated. The results for the grain surface temperature are given in terms of parameters describing the geometry and thermal properties of the grain and bond. The beneficial effect of a high thermal conductivity for both the grain and the bond is clearly demonstrated.

硬ぜい材料の単粒研削 Ｉ 圧電素子を用いた単粒研削用動力計の出力特性

硬ぜい材料の単粒研削 Ｉ 圧電素子を用いた単粒研削用動力計の出力特性

Forces produced during cutting with single abrasive grains

The overcut fly-milling technique was employed to measure the forces produced during cutting with single abrasive grains. A specially mounted and calibrated piezoelectric accelerometer was used for the measurements. The results indicate that the tangential force on a grain varies linearly with the cross-sectional area of the chip. The specific energy and the shear force increase with decreasing chip size. However, normal or contact stress remains constant except in the range of very fine chip thicknesses where it increases with decreasing chip size.

Wear of Single Abrasive Grains against Various Hard Materials

本研究はSUJ2 (焼き入れ), ステライト, フェライト, シリコンなど種々の硬質円板材に対する定速定荷重のピンオンディスク型単粒摩耗実験を各種研磨材について行ったものである. 研磨材としてはダイヤモンド, 黒色炭化ケイ素, 標準アルミナ, ルビーアルミナ, 単結晶アルミナ, 及び25%ジルコニアが用いられ, 焼結したSi3N4粒についても試験された. 試験は荷重450g, 摩擦速度300及び600m/minで行われた. これによって各研磨材の摩耗の序列をそれぞれの円板材について調べた.ステライト板に対する研磨材の摩耗は焼き入れしたSUJ2板の場合に比べかなり多く, 更にフェライト板ではステライト板の2倍程度に多くなる. ダイヤモンド研磨材は円板材にかかわらず最も摩耗しにくく, Si3N4粒は反対にステライト以外の円板材に対し最も高い摩耗量を示す. A研磨材はC研磨材に比べ焼き入れしたSUJ2, フェライト板では摩耗量は少ないが, ステライト板では逆の結果が得られる. フェライト板では, 円板材摩耗粉のアブレージョン作用が研磨材摩耗を支配する重要な因子である.

Study on the Wear of Single Abrasive Grains

Study on the Wear of Single Abrasive Grains

高ぜい性砥粒のチッピング特性

The evaluation of single abrasive grains has attracted considerable attention in grinding industry. In the previous research the fly milling chipping characteristic has been extensively studied on various tough grain types using several work materials. In the present study the same chipping test has been made on several friable grain types such as 57 A, 38 A, and diamond, etc. Special interest was concerned with the differences in chipping fracture pattern between the 57 A and 2 A grains, and the 38 A and WA grains. The effects of cutting speed or grinding fluid on chipping performance were also discussed. The 38 A grain was seen to fracture more frequently than the WA grain, but the chipping height was less for the 38 A grain than for the WA grain, while the 57 A grain fractured more frequently than the 2 A grain. The diamond grain has the highest resistance to chipping fracture, but when fractured this grain type gives a high chipping height. Grinding fluid was shown to promote the chipping fracture of grain.

単粒切削における砥粒切れ刃の摩耗について

A new method for measuring accurately the wear depth of a single abrasive grain in the "fly-milling test" is introduced. The wear in the method was measured on the basis of the tip of a diamond tool which was mounted at a short distance away in the direction of the wheel axis. A change in shape of the cutting point was observed simultaneously with it. Cutting force pulses were furthermore measured with a piezo-electric dynamometer. The self-sharpenability of cutting points is discussed on a basis of these results. Some results obtained in this paper are summarized as follows:(1) The wear curve of cutting point is generally similar in shape to a flight of stairs with a gentle slope.(2) Wear rates of individual grains are highly variable.(3) Rate of wear by fracture of cutting points increases with increasing radial depth of cut, but rate of attritious wear is independent of it.(4) Self-sharpenability of cutting point is affected by a combination of grit and workpiece material.(5) Self-sharpenability of white aluminum oxide grits is better than that of green silicon carbide grits.

The Role of Grain Tip Radius in Fine Grinding

The scratches produced by single abrasive grains in overcut fly milling show that the transverse shape of a grain is closely approximated by an arc of a circle. This radius of curvature is found to be independent of grain type and grinding conditions but varies with the grain size. The equation for undeformed chip thickness for surface grinding is rederived in terms of this radius. The important role that the transverse curvature of the grain plays relative to surface finish is also discussed.

単粒摩耗試験における除去率

In the previous study the wear resistance of single abrasive grains was investigated by means of rubbing wear test on many metal-grain combinations, and then, the compatibility of grains to work materials was discussed. The present research has been done about the metal removal at the same wear test of single abrasive grain on four metals-five grains combinations. The abrasive grains used fall into group as follows; 2 A, 40 SH, ZS, AZ 40, and 75 A, while the disc materials are S 55 C, SKS 31, SUS 27, and MAS 1 steels. The 300 and 600 m/min constant sliding speeds were adopted, and the load was mainly 450 g. It was evident from this study that the metal removal increased in proportion to sliding distance and load, and that increased sliding speed led to lower metal removal rate. It was also found as a general rule that the grain types of higher hardness appeared to have higher metal removal rate over lower hardness grains. The grinding ratio was seen to decrease with decreasing grain hardness with an exception of the SUS 27 steel.

研削仕上面あらさの解析

This paper deals with the ground surface roughness theoretically and experimentally, which is one of the most important value in grinding technique. Basing on the results of scratch-deformation experiment using a single abrasive grain, the theoretical formula is presented on the surface roughness of metals ground by a contact wheel type belt grinder. The formula has five variables, that is, numbers of cutting edges existing in the contact area between the abrasive belt and the workpiece, normal load applied to the contact area, the hardness of the workpiece, the pointed angle of abrasives and the factor obtained from the scratch test. The formula can explain the effects of contact wheel, of grain size and of grain wear to the ground surface roughness from the standpoint of the number of cutting edges in the contact area. The adequacy of the formula is discussed by the results of the grinding test. The formula may give the approximate value which can be used in metal processing industries.

Thermal Analysis of the Wear of Single Abrasive Grains

It is shown that the wear of single abrasive grains in a simulated grinding operation (over-cut fly milling) is governed by a thermally activated mechanism. The model adopted in this theoretical treatment assumes that most of the energy expended during grinding enters the workpiece via adiabatic plastic flow. The accompanying rise in temperature at the grain-workpiece interface decreases the shear flow stress of the softer metal. This permits a greater adhesive wear rate. The predictions of the theory agree with the results of extensive experimental data.

研削過程のシミュレーション

Basing on the results of scratch-deformation experiment using a single abrasive grain, the grinding process performed by the abrasive belt involving a large number of cutting edges which differ in shape was analyzed in view of the depth of cut. This analysis was done using computer simulation and the results were examined from the grinding experiment. Regarding these results, the depth of cut which coincides with the actual value is calculated by substituting the machining conditions, the variables indicating the state of the cutting edges of the coated abrasives and the decided constant obtained from the mechanical properties of the workpiece to the simulation of the grinding process. Moreover, it may be possible to predict the life characteristic of the abrasive belt in the case of grains changing due to the wear only. The difference of the depth of cut depending on the state of contact between the belt and the workpiece is made clear systematically from the change in the number of cutting edges per contact area.