The wear process of grinding wheels is discussed by the following methods.
1) The value of tan a is calculated by measuring the normal grinding force, where a is the half apical angle of the cone assumed to keep with ability of grain tips. On the basis of this result, the variation of the mean shape of grain tips is discussed.
2) The profile curve of mild steel surface ground under constant conditions is measured by use of a tracer instrument. By measuring the Abbott's bearing curve and the maximum height of its profile, the variation of the number of grain tips in a wheel is discussed.
3) Autocorrelation function is calculated for the above profile curve. On the basis of this result, the variation of the pitch of grain tips is discussed.
4) The number of times that the above profile crosses the center line is counted. On the basis of this result, the variation of the shape and the pitch of grain tips is discussed.

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Electrolytic single diamond cutting are performed to make clear the grinding mechanism of the electromechanical grinding at high work feed rate. Single diamond tools with any wear flat area are used to simulate the wear of abrasive grains on peripheral surface area of the grinding wheel. Effects of electrolytic action on frictional components in single diamond cutting forces are investigated with reference to proposed empirical cutting force equations. Summary of results are shown below. (1) Cutting forces in a single diamond cutting with any wear flat area are confirmed experimentally to consist of three components: cutting force, ploughing force and frictional or sliding force. Frictional components contains three important factors, namely compressive yield stress K_n, friction coefficient μ and wear flat area. (2) Frictional components decrease by electrolytic action, which are mainly induced by the reduction of compressive yield stress. Friction coefficient are held constant even by the applied electrolytic action. (3) Sudden stop equipment shows the preferential dissolution of hardened second phase particles in Al-Si-Cu alloy and alloy tool steel SKD11. Preferential dissolution may cause the reduction of the compressive yield stress of workpiece and/or contact pressure between workpiece and grinding wheel.

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The relation between the residual stress and the injury on the ground surface of hardened ball bearing steel was investigated. Ring specimens were hardened and tempered to Rockwell C62. The grinding of the internal surface was worked on a Heald constant force internal grinding machine under a series of severe operating conditions. The residual stresses were measured by the X-ray method, using a Geiger counter diffractometer with CrKα radiation.
According as the normal force of grinding varied from 0.5 to 3.5kg/mm, the surface residual stress changed almost linearly from a compressive value of about 10kg/mm² to a tensile value of 90kg/mm². A marked decrease of the half-height breadth was also observed with increasing tensile stress. By macroetching with hot hydrochloric acid, etch cracks were developed on the surface where the tensile residual stress exceeded the value of 50kg/mm².
To ascertain whether the surface residual stress depends upon the cutting action or on the frictional heat, the rubbing experiment of steel was made with alumina ceramics and superfinishing stone. After rubbing 10sec. with alumina ceramics, the residual stress varied with increasing load from a compressive value of about 50kg/mm² to a tensile value of 50kg/mm², as in the case of constant force grinding. Decrease of the half-height breadth was also observed when the residual stress became tensile. On the other-hand, in the case of superfinishing stone, the compressive stresses of the order of 50kg/mm² were always obtained. No decrease of the half-height breadth was observed in the range of the experiment.
Since the cutting action is very poor in both cases, it is considered that the tensile residual stress is mainly due to the frictional heat. In case the frictional heat should be neglected, the compressive residual stress would be generated by the plastic deformation in very thin surface layers. In the case of superfinishing stone, as the abrasive grains are easily detached by a small frictional force, evolution of the frictional heat will not be enough to introduce the tensile residual stress.
Tempering above 150°C decreases the tensile residual stresses and raises somewhat the critical stress of etch cracks.

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The theoretical formula on the roughness of grinding finished surface was introduced, basing upon the fact that the roughness is proportional to the root of mean cutting area (mean chip area) of a grain of wheel. The results of experiments well agreed with this formula : the surface roughness increases with depth of cut and work surface velocity, and with the decrease of wheel surface velocity, and it also increases with the decrease of the grain size number and grade of wheel.

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The tangential grinding force, under the various conditions, was measured by a special grinding attachment, which was designed by the auther for the purpose to research the grinding mechanism without loading and glazing. From the results of experiments, the grinding force increases according to increase of depth of cut, decrease of surface velocity of wheel and increase of surface velocity of work. And the higher the grain size number and grade of wheel, the larger the force becomes. On other hand, the theoretical formula of grinding force was introduced under the hypothesis that it equals the product of the force acting on a grain and the number of cutting grains at the same time, and this formula well agreed with the experimental results.

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The object of this paper is to clarify the mechanism of an electrolytic grinding method in high work feed rate. Therefore, grinding force components and chemical electrolysis were investigated and discussed through the calculation on the basis of experimental results using alloy tool steel SKD 11 and others. Summary of the results are shown below. (1) Grinding force components in this electrolytic grinding method decrease with increasing applied voltage. Their decreasing rate depends on electric current and percent wear flat area. (2) There may be two roughly classified reasons for the decrease in grinding force components by electrolytic action. The first one is the decrease in mechanical removal volume by electrochemical dissolution. The second one which has the most effect is considered to be the loss of mechanical properties on the surface layer of SKD 11 induced by the preferential dissolution of the hardened second phase. This may cause to decrease the chip formation force and the contact pressure between the wear flats on abrasive grains and the workpiece. (3) The effectiveness of this grinding method is appeared in the suppression of the friction force between the wear flats and the workpiece, which increases in proportion to the increase in the wear flat area.

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