Tribology of metal evaporated tapes—for improvement of recording density

Increased recording density in video tape recorders and tape drives for data storage has been achieved by the increase in areal recording density and the decrease in tape thickness. Areal recording density can be increased by introducing high performance tapes, like metal evaporated tapes, with superior magnetic characteristics and smooth magnetic surfaces to reduce the spacing loss. However smoother surfaces often produce a higher friction coefficient, which could result in tape damage by the scanning heads and unstable runnability of tapes in VTRs or tape drives. Also thinner tapes show lower mechanical stiffness in general, which could result in damage of the tape edges during tape transportation. Superior durability and runnability are thus required of high performance tape in addition to magnetic characteristics, in spite of the trend towards smoother surface and thinner tapes. Therefore the development of practical new magnetic tapes requires research into their tribology. It was found that the durability and runnability of metal evaporated tapes with smoother surfaces can be improved by DLC coating, and that the edge damage of thinner tapes can be eliminated by decreasing the static friction coefficient, but not the kinetic one. Though the durability and the runnability of metal evaporated tapes themselves have been improved from the tape design point of view, as mentioned above, further improvement may be expected by integrating tape design with that of the VTR/tribo-elements tape drive design and thus further increasing recording density in the future.     

The tribology of flexible magnetic recording media—the influence of wear on signal performance

The tribology of magnetic recording systems is different to conventional tribology in many important aspects and an understanding of this branch of the science is still in its infancy. This paper presents a review of one specific aspect of the tribology of flexible tape storage systems, that is wear of heads and media and the effect on signal performance. Based on the work of this author's group and others and with reference to classical tribological principles, the various mechanisms of wear have been identified in particulate media, metal evaporated media and various recording head types and have been discussed in terms of the effect of signal degradation and error or drop out production. From this review, the wear mechanisms and surface and subsurface parameters which should have the most influence on the future development of media and systems are identified.     

Intelligent measurement — A view of the state of the art and current trends

The paper examines briefly the state of the art of intelligent measurement on the basis of the proceedings of the IMEKO 1986 Symposium on the subject. It identifies advances in computer-assisted measurement, data conditioning, measurement process control, measurement result output, and measurement data processing as well as application of machine intelligence to measurement interpretation and use in decision support. It identifies the latter as a significant area of future progress. Applications of intelligent measurement in laboratory automation, electrical measurement, mechanical manufacture and associated inspection and clinical medicine are highlighted.     

Thermal modeling of the metal cutting process — Part II: temperature rise distribution due to frictional heat source at the tool–chip interface

Heat partition and the temperature rise distribution in the moving chip as well as in the stationary tool due to frictional heat source at the chip–tool interface alone in metal cutting were determined analytically using functional analysis. An analytical model was developed that incorporates two modifications to the classical solutions of Jaeger's moving band (for the chip) and stationary rectangular (for the tool) heat sources for application to metal cutting. It takes into account appropriate boundaries (besides the tool–chip contact interface) and considers non-uniform distribution of the heat partition fraction along the tool–chip interface for the purpose of matching the temperature distribution both on the chip side and the tool side. Using the functional analysis approach, originally proposed by Chao and Trigger (Transactions of ASME, 1951; 73:57–68), a pair of functional expressions for the non-uniform heat partition fraction along the tool–chip interface — one for the moving band heat source (for the chip side) and the other for the stationary rectangular heat source (for the tool side) were developed. Using this analysis, the temperature rise distribution in the chip and the tool were determined for two cases of machining, namely, conventional machining of steel with a carbide tool at high Peclet number (N_Pe≈5–20) and ultraprecision machining of aluminum with a single-crystal diamond tool at low Peclet number (N_Pe–0.5). The calculated temperature rise distribution curves on the two sides of the tool–chip interface are found to be well matched for both cases. The analytical method developed was found to be much faster, easier to use, and more accurate than various numerical methods used earlier. Further, the model provides a better physical appreciation of the thermal aspects of the metal cutting process.     

Thermal modeling of the metal cutting process — Part III: temperature rise distribution due to the combined effects of shear plane heat source and the tool–chip interface frictional heat source

This paper is Part III of a 3-part series on the Thermal Modeling of the Metal Cutting Process. In Part I (Komanduri, Hou, International Journal of Mechanical Sciences 2000;42(9):1715–1752), the temperature rise distribution in the workmaterial and the chip due to shear plane heat source alone was presented using modified Hahn's moving oblique band heat source solution with appropriate image sources for the shear plane (Hahn, Proceedings of the First US National Congress of Applied Mechanics 1951. p. 661–6). In Part II (Komanduri, Hou, International Journal of Mechanical Sciences 2000;43(1):57–88), the temperature rise distribution due to the frictional heat source at the tool–chip interface alone is considered using the modified Jaeger's moving-band (in the chip) and stationary rectangular (in the tool) heat source solutions (Jaeger, Proceedings of the Royal Society of New SouthWales, 1942;76:203–24; Carlsaw, Jaeger. Conduction of heat in solids, Oxford, UK: Oxford University Press, 1959) with appropriate image sources and non-uniform distribution of heat intensity. The matching of the temperature rise distribution at the tool–chip contact interface for a moving-band (chip) and a stationary rectangular heat source (tool) was accomplished using functional analysis technique, originally proposed by Chao and Trigger (Transactions of ASME 1955;75:1107–21). This paper (Part III) deals with the temperature rise distribution in metal cutting due to the combined effect of shear plane heat source in the primary shear zone and frictional heat source at the tool–chip interface. The basic approach is similar to that presented in Parts I and II. The model was applied to two cases of metal cutting, namely, conventional machining of steel with a carbide tool at high Peclet numbers (≈5–20) using data from Chao and Trigger (Transactions of ASME 1955;75:1107–21) and ultraprecision machining of aluminum using a single-crystal diamond at low Peclet numbers (≈0.5) using data from Ueda et al. (Annals of CIRP1998;47(1):41–4). The analytical results were found to be in good agreement with the experimental results, thus validating the model. Using relevant computer programs developed for the analytical solutions, the computation of the temperature rise distributions in the workmaterial, the chip, and the tool were found. The analytical method was found to be much easier, faster, and more accurate to use than the numerical methods used (e.g., Dutt, Brewer, International Journal of Production Research 1964;4:91–114; Tay, Stevenson, de Vahl Davis, Proceedings of the Institution of Mechanical Engineers (London) 1974;188:627). The analytical model also provides a better physical understanding of the thermal process in metal cutting.     

The ‘corpuscle’ stereological problem—re-evaluation using slab fragment volumes and application to the correction of DNA histograms from sections of spherical nuclei

A new category of stereological size distribution unfolding models is introduced. It is based on the use of the volumes of particle slab fragments, in addition to their profile dimensions. When spheres are cut by a slab of known (constant) thickness, an estimation of discrete sphere sizes from section data is then possible, as only one parent sphere solution exists for any slab fragment, given the latter's projection size and volume. The unfolding algorithm consists in sequentially testing a set of equations: only one of the solutions satisfies various constraints on bounds. A precise determination of the section thickness is required. Truncation parameters, instead of being troublesome inputs as in classical unfolding models, become valuable outputs. This model offers the first stereologically valid solution to the important problem of correcting DNA-amount histograms obtained from sectioned spherical nuclei. Under the (biologically reasonable) assumption that the nuclear volume is proportional to the DNA amount, it is possible to estimate the DNA concentration and, subsequently, compute discrete slab fragment volumes from corresponding DNA values. An application to Feulgen-stained rat liver sections is shown. Measurements of hepatocytic nuclear-profile areas and integrated optical densities are obtained by automated image analysis (IBAS), and the model is used to unfold the section-obtained DNA histogram. A maximum likelihood fitting of the final distribution with chi functions allows a parametric estimation of ploidy frequencies. This model can only be used for acceptably spherically shaped particles.