Three-body abrasion of brittle materials as studied by lapping

manufactured with a proprietary fast-tool-servo on a diamond turning lathe. For these mirrors an aspheric testing interferometer with computer generated holograms has been developed. Research work was done on the design of the optical system, the development of algorithms and software for the computation of the holograms, the techniques for manufacturing the computer generated holograms (CGH) and an appropriate strategy for adjustment of the measurement system. The hologram pattern is plotted using a CAD plotter and photographically reduced in scale. To overcome this time-consuming technique and to improve the precision of the holograms, a laser-based direct writing hologram-plotter is under development. We describe the concept of the measurement system, and discuss several systematic error sources, Some recent results are presented. 8 refs. 84. anon. A theoretical analysis of the effect of crystallographic orientation on chip formation in micromachining. International Journal of Machine Tools & Manufacture. 1993 Jun; 33(3): 439-447. The effect of crystallographic orientation on the shear zone formation in micromachining has been analyzed with a single crystal cutting model. Based on the minimum shear strength criterion, a range of shear angle values is found to exist. The most likely shear plane angle is the one that has the most negative texture softening factor among the ones with the same minimum shear strength. Theoretical findings for the shear angle and cutting force variations compare well with published experimental data. The significance of the microplasticity analysis to the understanding of chip formation in micromachining is discussed. 12 Refs. 85. Carter, G.; Nobes, M. J.; Katardjiev, I. V. The theory of ion beam polishing and machining, Vacuum Technology and Applications of Ion Beams: Conference of the Atomic Collisions in Solids Group of the Institute of Physics; 1992 Apt 7: Loughborough, UK. 1993 Mar: 303-9. The principles of wavefront propagation are employed to describe the evolution of surface topography during ion bombardment-induced sputtering erosion of solids. It is demonstrated that Huygen's wavelet or characteristics (ray) tracing methods are equally valid but that the former is preferable when multiple gradient discontinuities can develop on generally rough surfaces and the latter is preferable for more gently contoured surfaces. These concepts are elaborated in the contests of surface polishing and macro- and micro-machining and the tolerances achieved by approximation methods are evaluated. 86. Mishima, N.; Mizuhara, K.; Okazaki, Y. Thermal Properties of the Hydrostatic Air Spindle (1 st Report) Numerical Analysis and New Control Method of Thermal Deformations. 1992. 8 pages. The paper describes two topics to improve thermal properties of a thrust type hydrostatic air spindle. One is how to predict the thermal deformations of the spindle, and another topic is how to control them. Because of some advantages, such as high stability and low thermal deformations, static air spindles are often applied to ultra precision machine tools. Even air spindles, however, are not free from certain quantity of thermal deformations, and such deformations are not negligible for ultra precision machining. So, the above two topics have to be discussed. In the former part of the report, theoretical analysis based on thermo-hydrodynamic lubrication theory is conducted. Numerically calculated values of the thermal deformations fit well to the measured value. In addition, a more progressive method to control the deformations, which is to change the temperature of the supplied air with the time from the beginning of the rotation, is proposed and examined experimentally. By this method, the settling time of the thermal deformations of the spindle can be shortened and the transient hysteresis of the deformations is improved. 87. Buijs, M.; Korpel-van Houten, K. Three-body abrasion of brittle materials as studied by lapping. Wear. Jul 1; 166(2): 237-245. Lapping experiments on glass were performed to verify a model for three-body abrasion of brittle materials. The model is based on material removal by rolling abrasive particles. The particles indent the workpiece surface and remove material by lateral cracking. Median cracking introduces subsurface damage. The model leads to expressions for removal (or wear) rate, surface roughness, subsurface damage and load per particle as a function of particle shape, particle size, material parameters of workpiece and lapping plate, applied pressure and relative velocity between plate and workpiece. The model was found to give a good description of the experimental results, allowing among other things the calculation of removal rate, surface roughness or damage penetration from the measurement of either one of these parameters. 18 Refs. 88. Yao, J. J.; MacDonald, N. C. Time-resolved scanning electron microscopy analysis of nanodynamical structures. Scanning Microscopy. 1992 Dec; The authors have developed and characterized a time-resolved scanning electron microscopy (SEM) operational mode which provides non-destructive mechanical characterization of nanodynamical structures with 8-bit image resolution and 200 ns time resolution. The time-resolved SEM scheme does not require blanking plates nor does it require any hardware modification to a commercially available scanning electron microscopy. Both timeresolved images and line scan profiles of nanofabricated single crystal silicon tweezers are obtained. This time-resolved SEM operational mode can be used to evaluate a number of important mechanical properties of nanodynamical structures, including time response and resonance mode-shapes. 89. Strenkowski, J. S.; Larson, W. C. Tool flank wear in single point diamond turning. Proceedings of the International Conference on Machining of Advanced Materials - NIST Special Publication 847+ 1993 Jun: 295-302. In this paper, wear mechanisms on the flank of diamond tools are investigated. In particular, wear due to solid state diffusion of carbon atoms from the tool into the work-piece and abrasion wear are studied for their relative contribution to overall flank wear. Flank wear in single point diamond turning is of particular importance because degradation of the flank can lead to surface roughness and damage in the machined workpiece surface. The wear of diamond tools during machining is highly influenced by the temperature and velocity of the chip / tool interface. Using a 2-D Eulerian model for orthogonal cutting, the chip velocity and the temperature distribution in the chip and the tool is determined. By coupling this information with a model of wear, the relative contributions of diffusion-controlled wear and abrasion effects can be assessed, It is found that flank 78

JANUARY 1994 VOL 16 NO i