The stress distribution at the contact area of a machine element has a large effect on the total performance of the machine. It is one of the important factors that closely relate to the performance of the element as a gear pair, a set of bolt and nut and so on. Many theoretical studies for estimating the contact stress were published. However, their validity has not been proved by experiments, because the known measuring methods are insufficient in accuracy or resolving power. The measuring method using martensite transformation is offered in this paper. If the stress is applied to the test piece made of 18-8 stainless steel at a temperature of 198 K, the stressed part of the test piece changes its structure from austenite to martensite. The martensite structure has the nature of ferromagnetism. Therefore, the contact stress distribution in the test piece can be obtained by measuring the distribution of remaining magnetism. For confirming the practical use of the method some experiments have been done using the block type (10 mm in thickness) and the film type (5 μm in thickness) test pieces of stainless steel. It has been confirmed that at the more stressed part, the more martensite transformation is induced in the test pieces, and that the test pieces have sensitivity for the measurement of the stress distribution. A homogeneous structure in the test piece is needed for the purpose of measurement.
In order to realize higher throughput in submicron X-ray lithography, higher velocity X-Y stage studies are conducted on a completely non-contact movement using an externally pressurized air bearing guide and a moving coil linear actuator. Results are as follows: (1) Sraightness of 0.05 μm and orthogonality of 0.5 arc sec over 100×190 mm area are achieved by constructing a stage capable of X-Y movements on a base plate. (2) An X-Y stage using an air bearing guide requires long settling time due to the lack of friction. To realize high velocity positioning, a new servo feedback circuit using the horizontal acceleration signal of the base plate is developed, and maximum velocity of 150 mm/s, 0.5 s for 15 mm stroke, and positional accuracy of 0.1 μm are achieved. (3) A fine positioning mechanism using a vacuum clamp and a moving coil linear actuator demonstrates step movements of 0.01 μm.
It is well known that acoustic emission (AE) is the emission of elastic stress waves resulting from the deformation and fracture of materials. This paper deals with a monitoring technique of the friction and wear behavior applied with the AE. Moreover, investigation was carried out about the prediction of unusual phenomenon of the friction and wear. The results are summarized as follows: (1) A little discrepancy of the friction and wear behavior can be detected sensitively by AE signals. (2) AE signals are used effectively in monitoring the run out state of lubricating oil film into frictional surfaces. (3) AE signals can be used for prediction of unusual phenomenon such as seizure.
A bolted joint is often confronted with a dangerous situation of self-loosening when a slip motion on the bearing surface is brought on by transverse vibration. This paper presents the results of examination on a basic problem of the self-loosening mechanism. The purpose is to comprehend an influence of torque added externally from the bearing surface. Now, the torque mentioned above is the one caused by a slip on the bearing surface in the case of uneven distribution of bearing pressure or a circular arc slip on it. By basing on the theory of self-loosening mechanism by Yamamoto et al. and developing it, an analysis is made and experiments for examining the analysis are performed in two cases of giving tilt angle to the bearing surface and adding known torque to the nut. As the result, it is shown that the analytical results agree fairly well with the experimental ones and that this analysis can be regarded to be basically appropriate. The self-loosening mechanism under transverse vibration becomes more clear than ever.
The system has been developed to calibrate some kinds of angular encoders automatically with high accuracy. This paper describes the multi-reading-head method which is a new selfchecking method and introduces the system and the calibration results of encoders. The characteristics of the system are followings: (a) Adopting the time-conversion method, a slight angular difference is detected with high resolution and high precision. (b) Adopting the multireading-head method, the calibration of masterscale can be done without angular standard. (c) Referring to the masterscale calibrated, some kinds of angular encoders are calibrated. (d) The calibration is done automatically by the micro-computer system which controls the compiling and handling of data. The followings became clear after the calibration. (1) The relative-angleposition-errors are measured with 0.01'' resolution and their standard deviations are about 0.01''. (2) The calibration values of all graduations of masterscale and subscale are obtained with an accuracy of 0.3'' in about 5 minutes.
Diagnosis of the motion error origins in NC machine tools has been studied by using double ball bar test. Motion errors of the machine is represented by error vector, and the relation between it and motion error loci obtained at double ball bar test was theoretically analyzed. Based upon this analysis characteristic patterns of loci were defined in individual motion error origin. Diagnoses is carried on by extracting these characteristic patterns from motion error loci which were measured by double ball bar test. This diagnostic method has been tried with a lot of NC machine tools. The results show that this method has sufficient accuracy and conveniency for machine shop use.
In this method, the values of coordinates and gradients at some points on a work tooth profile are needed. These values are essential for calculating the rack and the hob tooth profile analytically. Transmissions of tooth profile errors (the deviation from the theoretical value of coordinates and gradients) from a work to a rack and a rack to a hob and their inverse transmissions are analyzed. The transmission of errors is denoted by matrices. From these results, it can be known also how much error is caused on the work tooth profile by the error of hob tooth profile.
Based on the idea that the dynamic performance of a machine-tool should be evaluated in terms of its machining accuracy, a new test method is proposed which uses the machined surface as a measure of performance evaluation. The cross sectional profile of the machined test piece surface is measured in the direction orthogonal to feed direction, and nine different indexes which characterize the profile are extracted. These indexes are then checked based on the concept of SN ratio to select "straightness error of the profile" as the best one. Finally eight different machining centers are tested by using the performance index thus determined to confirm the validity of the method.
This paper discusses the results of an investigation carried out on the effects of various working factors on cylindrical finishing, using trial equipment. The following results were obtained: (1) Stock removal increases due to magnetic flux concentration at the edges of grooves arranged on a magnetic pole. (2) Stock removal is maximum at a certain value of magnetic flux density. (3) Stock removal increases by the application of axis vibration to the cylindrical workpiece. (4) stock removal in inclination in inverse proportion to the working interval. (5) Machined surface roughness is improved with inclination of stock removal.
An estimation is carried out to determine a length of downward extension of a crack and an upper limit of depth of cut preventing its extension in orthogonal cutting of ceramics. Fracture mechanics is applied to solve a crack extension problem in the elasto-plastic tensile stress field which initiates and grows to some extent in a work by the tool progress. Two different values in fracture toughness of a work are used depending upon levels of pre-existed crack sizes which are appropriate for determining the length of the crack extension and the upper limit of depth of cut respectively. Estimated values of the length of the crack extension and the upper limit of depth of cut in various ceramics are very different from each other : the lengths of the crack extension in glass ceramics (Macor) and ZrO2 are considerably smaller than those in soda-lime glass, SiC and Al2O3, and the upper limit of depth of cut in Macor is extremely large (e.g. 14 μm in Macor and 1μm in SiC). The estimation concerning both the length of the crack extension in various depths of cut and the upper limit of depth of cut in Macor is confirmed to be valid by experiments.
Wheel wear equation in abrasive cutoff is identified by GMDH algorithm with successive determination of trends containing interaction terms. In the model equation, not only wheel, work material, feed and wheel speed, but grinding fluid are taken into account using input and output data obtained from wheel wear tests. The grinding ratio can be predicted for the combination of various factors using the model. With the wheel wear equation and machining cost model, for a given work material minimum cost combination of wheel, fluid, wheel speed and feed rate can be determined. And the relationship between these variables and costs is investigated.
This paper is an attempt to clarify the grinding properties of monocrystalline and microcrystalline CBN grinding wheels. The grinding performance of the microcrystalline CBN wheel is 2 to 3 times better than that of monocrystalline. In high efficiency grinding, its initial grinding force doesn't go beyond a certain level as does the monocrystalline. Its grinding force is independent of the influence of increasing stock removal, if used under optimum grinding conditions. Furthermore, it has a long service life and is free from burning even in high efficiency grinding. These and other findings indicate that the microcrystalline CBN wheel has properties that are ideal for high efficiency, accurate grinding.
Grinding performance of grinding wheel dressed with a diamond rotary dresser is experimentally investigated under various dressing conditions, analyzing size generation process, grinding force, surface finish, wheel wear and so on. Main results obtained in this paper are as follows: (1) Variation process of dressing force in rotary dressing is similar to that of grinding force in a plunge grinding cycle. (2) Wide variety of grinding performance can easily be obtained by changing dressing conditions such as infeed rate of dresser, speed ratio of dresser to wheel and relative dressing speed. (3) The integer revolution ratio of wheel to dresser should not be selected. (4) The grinding performance of wheel dressed with this technique can be kept constant longer than in any other methods, because of the remarkably less wear of rotary dresser.
This paper describes an estimation of interfacial surface energy γ0 from atomistic aspect and measurement of adhesion force, i. e. interaction between solid (Au, Ag, Cu) surfaces in an elastic contact condition in air. Assuming that chemical bonds occurs at the interface and the interatomic potential is Morse potential, surface energy and interface energy are calculated. The calculated surface energy of Au, Ag and Cu which is released at the interface between (111) and (100) lattice planes were 3.38, 2.69 and 4.20 J/m2, respectively. The interaction force required to separate the contact between the tip and flat plane were theoretically estimated using the calculated γ0. Then, the interaction force between the flat plane and the tip of radius 5-20 μm was measured by using a microelectrobalance. The contact pressure was controlled to be less than 2 μN in order to realize the elastic contact. The interfacial surface energy measured for Au, Ag and Cu were 1.57, 0.25 and 0.28 J/m2, respectively. The values for Ag and Cu seemed to be consistent with van der Waals attraction. However, the value for Au was considerably large being 1.57 J/m2 in spite of measurements in air, which was about 46% of atomistically calculated value. This suggests that the chemical bond (metallic bond) must be taken into consideration in the estimation of interfacial surface energy.
To understand the mechanism of the vibration suppression effected by alternating the running speed of the grinding wheel in cylindrical plunge-cut grinding operation, theoretical and experimental analyses have been undertaken. Based on the growing process of the vibration observed in grinding tests at constant wheel speeds, and referring to the previously proposed theoretical model, the onset and the growth of the grinding vibration is discussed in the present study. Theoretical model predicts that the method of alternating the wheel speed will be associated with two different frequencies of vibration that will appear during the periods of grinding at two pre-selected wheel speeds respectively, and they will be caused by the development of two corresponding series of asperities formed around the wheel surface. Above prediction has been confirmed by the plunge-cut cylindrical grinding experiments. Grinding vibration measured for different ranges of wheel speed variation indicates that the greater range up to ±10% around the average speed consistently reduces the growth of vibration. Another series of experiments revealed that the surfaces are finished by the alternating wheel speed to better quality in terms of the variation in light reflectivity around the circumference.
The Cell-Constructed-geometric-Model (CCM) is proposed as a new conception for the data representation of geometric model. The CCM consists of three-dimensional array of some finite Cells. The Cell means a unit volumetric solid bounded by six curved surfaces, and is regarded as an extended idea of bi-cubic parametric surface interpolation to a tri-cubic one. The interpolative method of the CCM is a rational cubic Bézier's. Therefore, with the CCM, it is possible to represent a closed volumetric solid bounded by some analytic surfaces and sculptured surfaces using the same data structure. This paper describes the mathematical formulation and the internal data structure of the CCM. Then the application of the CCM to the geometric model for CAM system, Finite-Element-Analysis, and calculation of weight and volume of a solid, are considered. Finally, developed geometric modelling system and methods of modelling to make the CCM interactively are described, and a modelling example of the CCM is shown.