Lateral motion and edge wear of magnetic tapes

Lateral motion and edge wear are measured on magnetic tape, and the relationship between tape edge wear and tape lateral motion is investigated. Instrumentation for measuring tape edge force is described. Tape edge force is measured at the tape guiding position using a force-calibrated cantilever spring and a linear optical probe. Typical measurements of tape lateral motion are given as a function of tape tension, tape direction, and path position. A technique for measuring tape edge wear is introduced and wear measurements are presented as a function of load and the number of passes.     

Numerical modelling of sub-surface stress in magnetic data tape heads due to the dynamic contact with a tape

The stress field at the subsurface of the ceramic used as a tape-bearing surface (TBS) in magnetic head construction is calculated by means of numerical methods taking into account roughness and friction forces at the head to tape interface (HTI). A two-dimensional model confirms the purely elastic character of the contact. However, only a three-dimensional model allows a quantitative interpretation, and thus to estimate the real area to apparent area of contact ratio—in agreement with a previous formal calculation—as well as the depth of the maximum von Mises stress—i.e. the depth at which a crack is more likely to form and extend—near 30 nm, comparable to the pullout depth observed at the surface of the ceramic used in actual heads.     

Effect of thermal deformation on machine tool slide guide motion

This paper describes the effects on machine slide-guide contact conditions caused by thermal deformation. Since a slide guide has a large friction surface, the motion is greatly influenced by thermal distortion caused by heat generation in the ball nut and the bearing support, during machining processes. This study investigated the typical behavior of the friction coefficient in response to both the external load and the linear speed. This then led to investigating the thermal effects on the slide motion. The thermal deformation of the slide table was measured with respect to the running time and the linear motion and the frictional power were monitored and compared directly with the thermal distortion.     

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.     

Lubricant Effect on the Microtribological Behavior of Magnetic Coating Formulations 1-aliphatic Lubricants

Magnetic tape industry uses a mixture of fatty acids/fatty acid esters. This lubricant mixture transfers from the tape surface to the recording GMR head whereby they cause fouling the tape and enhances corrosion to the GMR head. The current study aims at finding a substitute lubricant that could make a bond with the binder and has no corrosive effect.     

Positioning error improvement based on ultrasonic oscillation for a linear motion rolling bearing during sinusoidal motion

Friction can be a major disturbance to precision positioning. This study presents a method for improving positioning error in a linear motion rolling bearing based on ultrasonic oscillations. Experiments were conducted in which a single-axis linear motion rolling bearing was driven in a sinusoidal motion to simulate circular motion. Two ultrasonic actuators excited both the rail and the carriage of the guide to create relative displacements between raceways and rolling elements. The carriage of the linear motion rolling bearing was driven by a frictionless voice coil motor (VCM). The displacement of the carriage and the friction force were measured by a springless linear encoder and the VCM's current, respectively. The early stages of the experiments focused on several oscillating patterns, and their consequent impacts on positioning error during sinusoidal motion were investigated. Finally, the oscillating pattern that maximally improved the positioning error was proposed and tested. By applying the proposed pattern, the maximum displacement error, exhibited just after velocity reversal, was reduced by approximately 40%, while the average error was reduced by 26%.     

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.     

The frictional sliding contact problems of rigid parabolic and cylindrical stamps on graded coatings

Graded materials, also known as functionally graded materials (FGMs), are generally two-phase composites with continuously varying volume fractions. Used as coatings and interfacial zones they can reduce thermally and mechanically induced stresses resulting from material property mismatch, increase the bonding strength and provide protection against adverse environments. In this paper, the contact problems of parabolic and cylindrical stamps on graded coatings are considered. The objective of this study is to obtain a series of analytical benchmark solutions for examining the influence of such factors as material inhomogeneity constants the coefficient of friction and various length parameters on the critical stresses that may have a bearing on the fatigue and fracture of the components with graded coatings.     

Enhancing tribological performance of the magnetic tape/guide interface by laser surface texturing

The friction coefficient is an important parameter in designing magnetic tape transports. We have introduced a novel approach to reduce the friction coefficient between guides and magnetic tape by laser surface texturing the cylindrical guides. The surface features enhance the formation of an air bearing and hence reduce the friction coefficient.     

Wear of tribe-elements of video tape recorders

The helical scan magnetic recording equipment, like the video tape recorders (VTR), consist of many tribe-elements. The wear of these tribe-elements is an essential problem affecting the reliability of the equipment. The rotating magnetic head in high-speed rubbing with the magnetic tape needs a self-cleaning effect by mild wear. A simple trial of reducing the head wear often brings partial recession, friction polymer and brown stain. The summary of the current study of head wear is given by dividing it into the head factors, the tape factors, the system factors and the atmosphere factors. The computational analysis of head contour change caused by wear is compared with the experimental results. The outline of the tribology of motor, capstan and tape path in the VTR is introduced.     

Limit analysis of frictional block assemblies as a mathematical program with complementarity constraints

The computation of the collapse loads of discrete rigid block systems, characterized by frictional (nonassociative) and tensionless contact interfaces, is formulated and solved as a special constrained optimization problem known as a Mathematical Program with Equilibrium Constraints (MPEC). In the present instance, some of the essential constraints are defined by a complementarity system involving the orthogonality of two sign-constrained vectors. Due to its intrinsic complexity, MPECs are computationally very hard to solve. In this paper, we investigate a simple numerical scheme, involving appropriate relaxation of the complementarity term, to solve this nonstandard limit analysis problem. Some computational results are presented to illustrate potentialities of the method.     

Dynamic rupture at a frictional interface between dissimilar materials with asperities

A numerical investigation dealing with dynamic rupture at a frictional interface between dissimilar materials is proposed. The numerical Finite Element model is comprised of two homogeneous and isotropic elastic solids which are brought into contact with friction by remote normal compression and shear traction. The applied shear traction is less than the required one to produce overall sliding of the two solids. The rupture is nucleated by decreasing instantaneously the friction coefficient to zero at the nucleation area. A “rupture” is considered when an initially sticking zone of the interface becomes in sliding state; after nucleation two propagating ruptures appeared.The properties (velocity, generated waves, interface state …) of the obtained ruptures are here analyzed for a flat interface between dissimilar materials in function of the nucleation energy; then, the analysis of the effect of the interface roughness (sinusoidal asperities) is developed. The differentiated rupture inside the asperity and the conditions for coupling or uncoupling between the waves radiating in the two bodies, in function of the asperity dimensions, have been investigated. The aim of this work is to present the results from the non-linear finite element analysis in large transformations of the dynamic rupture at the interface with contact friction between two deformable bodies with and without roughness.     

内压作用下斜接管容器塑性极限载荷的数值研究

对三台具有斜接管的圆柱形容器(θ=30°,45°,60°)在内压作用下的塑性变形特征及塑性极限载荷进行了三维非线性有限元数值研究.结果表明:斜接管与筒体截交区纵向截面的锐角侧材料首先进入塑性状态.截交区附近出现明显的塑性变形,纵向截面内发生径向收缩,而横向截面出现明显的径向鼓胀,接管与筒体间的夹角减小.结果同时提供了三台容器的极限载荷值,为该类容器的分析设计提供了依据和参考.     

Frictional behavior of piston rings of small utility two-stroke engine under secondary motion of piston

The secondary motion of the piston head of a motorized engine is captured using two laser displacement sensors to obtain the piston motion and tilt angle. The controlled parameters of the measurement are engine speed, quantity of oil and oil-fuel mixture and its ratio. The reduction in friction force is more significant at dead center at high speed as the quantity of oil supplied increases. Changes in tilt direction of piston head occur at the inlet port. The relationship between the friction force and piston tilt angle showed weak correlation at low speed and increases with the engine speed.     

Float characteristics of a squeeze-film air bearing for a linear motion guide using ultrasonic vibration

The float characteristics of a square squeeze-film air bearing using piezoelectric actuators as a vibrator are discussed. In this type of bearing, piezoelectric actuators are adhered to a flat bearing plate and vibrate the bearing plate at ultrasonic resonant frequency. The influence of various design parameters on the float characteristics of the proposed bearing, such as the vibration frequency, input voltage to the piezoelectric actuator, and imposed load were investigated theoretically and experimentally. Our proposed squeeze-film air bearing was found to be quiet, because this type of bearing uses ultrasonic vibration to generate the squeeze-film. An average film thickness of 5 μm could support an imposed load of 10 N.     

A finite element simulation of the two-dimensional head/tape interface for head contours with longitudinal bleed slots

The two-dimensional (2D) steady-state linear head/tape interface with surface asperity contacts and tape shear deformations is analyzed using the finite-element method. A non-uniform mesh is utilized to improve the computational efficiency and to simulate cylindrical heads with longitudinal slots. Numerical results for the head/tape spacing and contact pressure are obtained for 2D head/tape interfaces using cylindrical heads with longitudinal slots. In addition, numerical examples are presented for the head/tape spacing and the pressure distribution using heads consisting of triple arc elements with and without longitudinal slots.     

Application of diamond-like carbon coatings to elastomers frictional surfaces

Nitrile-butyl rubber-like materials were coated with amorphous hydrogenated diamond-like carbon (DLC) coatings in order to modify their surface and tribological properties. Measurements of water contact angle were performed by the sessile drop method and showed that the coated samples are more hydrophobic with water contact angles up to 116°. The surface free energy of the elastomers was calculated by the acid-base regression method considering polar and dispersive contributions and the results were correlated with changes in the surface chemistry measured by X-ray photoelectron spectroscopy. It has been found that the lower presence of oxygen functional groups on the elastomer surfaces led to lower surface free energies, even though the polar contribution was not predominant. We also found that the DLC coatings led to a significant decrease of the surface free energy (up to 16%) and that there is a good correlation between the surface free energy values and the corresponding water contact angle values. The coefficient of friction was also measured and presented a significant decrease after coating with DLC.     

滚动直线导轨副静刚度模型的研究

根据滚动直线导轨副的承载特性和结构特点,利用理论力学、弹性力学及其赫兹接触理论等有关方面的知识,对整个滚动直线导轨副的力学性能进行了分析,最终推导出滚动直线导轨副的静刚度力学模型.所得出的刚度模型对提高导轨副刚度、寿命以及结构改进等具有指导意义.     

Barrelling of aluminium solid cylinders during cold upsetting with differential frictional conditions at the faces

The friction forces developed between the work-piece and the forming tools are of important consideration in metalworking. In many metalworking processes friction is the pre-dominant factor. This project has been taken up to experimentally study the effect of barreling of aluminium solid cylinders during cold upsetting by introducing different lubricants at one end of the solid cylinder. Experiments were conducted for three aspect ratios. The radius of curvature of bulge measured was found to conform to the calculated one using experimental data. The calculations are made with the assumption that the curvature of the bulge followed the form of a circular arc. A relationship was established between the various bulge parameters like new hoop strain, geometrical shape factor⁽¹⁾ geometrical shape factor⁽²⁾ and stress ratio parameter.     

Investigation of adhesive and frictional behavior of GeSbTe films with AFM/FFM

Frictional force microscope (FFM) was used to investigate the nanoscale frictional behavior of GeSbTe films deposited by magnetron sputtering. The effects of relative humidity, scanning velocity and surface roughness on friction were taken into account. Besides, the frictional behavior of GeSbTe films with different compositions was analyzed. Experimental results show that the coefficient of friction of GeSbTe films is almost independent of scanning velocity, while the frictional force decreases with increasing velocity. Both the relationship of friction vs. normal load and that of friction vs. RMS keep relatively linear, and the coefficient of friction increases with the increase in RMS. The influence of humidity on adhesion between the tip and the GeSb₂Te₄ film is more significant than that between the tip and the Ge₂Sb₂Te₅ film.