Sanwu Tan

Experimental investigations of asperity compliance of flexible magnetic medium

Three-color interferometry was used to investigate the deformation of asperities on flexible medium surfaces. Elastic asperity compliance curves were obtained to evaluate changes in surface roughness due to burnishing, determine mechanical properties of flexible medium and analyze differences between single layer and dual layer metal particle tapes. Asperity compliance curves were obtained for metal particle tapes with different substrate properties and substrate thickness. A power function was used to fit the asperity compliance measurements and to calculate the contact pressure at the head/medium interface.

Head/Tape Spacing Measurements for Digital Linear Tape Drives Using Three-Color Interferometry

The spacing of the head/tape interface in a digital linear tape (DLT) drive was measured using replica glass heads and three-color interferometry. A modified load-unload method was used to calibrate the light intensity. Class heads with different island widths and zero and nine degree skew angle were used to investigate the effect of head contour on the head/tape spacing. In addition, thin and thick metal particle tapes were evaluated to study the effect of tape compliance, tape speed and tape tension. “Tape tenting” was observed for heads with a narrow center island. Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in Orlando, Florida, October 11–13, 1999

Analysis of tape surface roughness by magnetic recording and mechanical methods

Tape surface roughness noise is a large component of medium noise in high-density tape recording systems. Here, the results of tape surface roughness characterization by both mechanical and magnetic measurements are presented. The goal is to measure and compare both RMS roughness variance /spl sigma/ and roughness correlation length l. The results show that the magnetic recording determination of /spl sigma/ and l agrees extremely well with the mechanical measurements.

Numerical and Experimental Investigations of the Head/Tape Interface in a Digital Linear Tape Drive

Finite element analysis is applied to simulate the head/tape interface in a Digital Linear Tape (DLT) drive. The numerical model was verified by contact spacing measurements using a three-bump glass head and three-wavelength interferometry. The effect of tape speed, tension and head contour parameters (island width, island radius, and penetration) on the head/tape spacing is investigated numerically for a three-bump and a five-bump DLT-type head. A Local Tape Wrap Angle is defined to characterize the head/tape interface.

Investigations of nano- and macro-wear of magnetic tape head materials

The nano- and macro-wear characteristics of calcium titanate, single crystal ferrite and polycrystalline ferrite were investigated using nano-scratch testing and wear bar testing. Nano- and micro-indentations were made to determine nano- and micro-hardness, and nano-scratch testing was used to evaluate relative wear rates on the nano-scale. The macro-wear characteristics of the various head materials against metal particle tapes was investigated as a function of tape speed using wear bars mounted in a DLT tape drive. The micro-indentation method was used to investigate wear of the head/tape interface in a linear tape drive. The results from nano- and macro-wear tests were analysed and correlated with the microstructure of the materials.

Measurement of non-elastic asperity compliance of magnetic tapes

Cyclic loading and unloading is applied to investigate elastic and non-elastic effects of asperity compliance of magnetic tapes. Multi-wavelength ellipsometry is used to measure the optical constants of the magnetic tapes needed in the calculation of the contact spacing. The magnetic tapes investigated are found to be optically anisotropic along different directions. Plastic deformation of highest asperities is observed during the first load cycle. The effects of tape surface roughness on asperity compliance is investigated by analyzing the statistics of the highest asperities.

Correlation between head/tape spacing and asperity compliance of magnetic tapes

Three-wavelength inteferometry is used to measure the head/tape spacing and the contact spacing of metal particle tape as a function of contact pressure. The contact spacing obtained from tape asperity compliance measurements at low contact pressure was found to correlate well with the head/tape spacing, suggesting that asperity compliance measurements can be used to estimate the head/tape spacing under operating conditions.

Improved Method for the Measurement of Asperity Compliance of Magnetic Tapes

Asperity compliance of typical magnetic tapes is investigated as a function of contact pressure using intensity-based three-wavelength interferometry. Each spacing data is the average of 300 x 100 physical points. Asperity compliance curves for BaFe tape, MP tape, ME tape, and CrO 2 tape were obtained. The experimental data was curve-fit using a parabolic contact model and the Greenwood-Williamson contact model. In addition, a comparison of the present results with previous measurements is presented.

Effect of slot edge defects on the head/tape spacing

The effect of slot edge defects on the performance of the head/tape interface is studied for single and double module heads. A number of typical edge defects was created artificially on a glass replica of an actual head, and three-wavelength interferometry was used to study spacing changes caused by these defects. The results show that head edge defects have a small influence on the flying behavior of tape with the effects being localized to the immediate defect area.

Magnetic analysis of contact head/tape spacing

A new magnetic analysis method is used to determine the mean magnetic spacing of a contact head/tape interface. The initial part of the curve of readback signal amplitude versus recording current is measured at a low recording density and is fitted by using theoretical approximations to obtain the head/tape spacing. A tape looper test stand, inductive heads, and various high-density metal particle tapes are used in the recording measurements. The mean head/tape spacing obtained from magnetic analysis agrees well with the results from numerical analysis of mechanical measurements.