A study of contact-start-stop wear tracks by TOF SIMS

In magnetic hard disk drive system, an ultra thin layer of lubricant is coated to the thin film media surface to prevent wear. Under the condition of relative motion, the displacement and replenishment of the lubricant at the head and media contact area are the factors that control the friction and wear behavior of the system. In this study, we investigate the sliding wear disk surface prepared by contact-start-stop (CSS) test using TOF SIMS (Time of Flight Secondary Ion Mass Spectrometry). TOF SIMS is a power tool for surface analysis with both high spatial and high mass resolution. Our investigations show that the lubricant thickness variation of the disk media at the contact area can be captured by sharp ion map images of TOF SIMS, and the thickness can be inferred based on the relative ion fragment intensity. In addition, the composition variation of the slider material and the magnetic layer materials can also be monitored. Finally the sliding effect is analyzed.     

Three-dimensional quantification of wear tracks on amorphous NiB coatings

The early stage of the wear process can be best investigated by means of three-dimensional profilometry. This allows not only maps to be made but also wear rates to be quantified. Linear, surface and volumetric parameters are given.An application to the wear resistance of amorphous NiB coatings (thickness, 10 μm; 26 at.% B) on iron substrates was performed. Dry sliding friction tests are carried out using a pin-on-disc system. Two specific types of behaviour (viscoplastic and plastic) are exhibited before seizure occurs.     

An investigation of the wear of abrasive grains by rubbing on diamond disks

In earlier wear studies¹ single abrasive grains were rubbed against the surfaces of metal disks under light loads. These studies have now been extended to include an examination of wear behaviour when using diamond-impregnated surfaces at lower sliding speeds and when using more accurately controlled test conditions. These wear tests provided values of wear resistance in the absence of chemical effects (i.e. at sufficiently low surface temperatures). The results are in excellent agreement with the conventional wear theory pertaining to lightly loaded sliders. The wear volumes are, however, two orders of magnitude greater than those obtained when rubbing tough grains against steel disks and three orders of magnitude greater than the results obtained when rubbing friable grains against similar metallic surfaces.     

Thermomechanical finite element analysis of slider-disk impact in magnetic storage thin film disks

Oblique impact of a slider with a rotating disk in a hard disk drive was analyzed using the finite element method. A three dimensional, thermomechanical, impact model was developed to study the mechanical and thermal response during the impact of a spherical slider corner with a rotating disk. The model was validated by comparing the finite element results with analytical solutions for a homogeneous glass substrate disk. Impact penetration, stress and incurred flash temperature were obtained for various normal impact velocities. The effects of material layers on the disk were also investigated by introducing layers with different material properties and thicknesses. It was found that for a rounded slider corner and a critical normal impact velocity of 0.03 m/s studied in this work, the layers have insignificant effects on the mechanical response and small but predictable effects on the flash temperature.     

铅同位素比值的飞行时间二次离子质谱法测量

介绍了用飞行时间二次离子质谱法对器物中的铅同位素比值的测量。在仔细地讨论了质量干扰、二次离子产额的同位素分馆效应等对测量结果的影响后，认为本工作无需标准样品，可以实现对样品无损的高质量分辨的二次离子质谱分析。铅同位素比值的测量精确度优于１％。     

The magnetic effect on the wear of metals

The effect of a magnetic field on the wear of ferromagnetic metals (nickel and iron) has been investigated. Wear tests were carried out under an external magnetic field applied horizontally or vertically to the rubbing surface in atmospheres of air, nitrogen and argon. In air a magnetic field horizontal to the surface enhances specific wear. However, a magnetic field vertical to the surface accelerates the severe-to-mild-wear transition, so that it gives a remarkable reduction in specific wear. In nitrogen or argon a vertical magnetic field does not have this effect. The reduction in specific wear is thought to be due to the chemisorption of oxygen onto the ferromagnetic metals activated by the application of a vertical magnetic field.     

Nanolubrication: Characterization of patterned lubricant films on magnetic hard disks

Patterned lubricant films on magnetic hard disks offer potential advantages in controlled bonding sites, higher average shear strength, and longer durability. However, since the lubricant film thickness is at 1 or 2 nm, characterization of the pattern is difficult. Normal atomic force microscopic techniques can only image very small area in the nanometer range and the sharp tip can potentially modify the pattern. A wide area optical technique is needed to characterize the patterns. This paper examines patterned lubricant film using an optical surface analyzer (OSA) to image the bonded phase and mobile phase of an alcohol functionalized perfluoropolyether (PFPE) on magnetic hard disks. The phase shift signal and reflectivity intensity of the polarized light spectra provide clear optical images of the lubricant film at nanometer thickness. Optical images were successfully obtained before and after the buffing process and the ramp load and unload (L/UL) testing. Results of 100% bonded, 100% mobile, and 20% zigzag patterned lubricant films confirm that the patterned lubricant films can control the bonded/mobile ratio of such films better.     

TOF-SIMS analysis of boundary films derived from calcium sulfonates

Tribological properties of over-based and neutral calcium sulfonate were examined under boundary lubrication conditions by using a ball-on-flat type tribo-tester. It was found that over-based calcium sulfonate reduced friction and wear of steel–steel contacts, whereas the neutral calcium sulfonate did not. It was found that boundary film composed of calcium oxide plays significant role on improving the tribological properties. Surface analyses by XPS and Time-of-flight secondary mass spectroscopy (TOF-SIMS) revealed that the major component of the film on upper surfaces is calcium carbonate and that at subsurfaces are composed of calcium oxide. A depth profile of the film obtained by TOF-SIMS using an etching technique revealed that thickness of the film is up to 240 nm. A static pyrolysis of the over-based calcium sulfonate on steel surface affords a thin film composed of calcium oxide, indicating that rubbing process is essential for the formation of the boundary film.     

Wear durability studies of ultra-thin perfluoropolyether lubricant on magnetic hard disks

This paper presents wear and friction studies on ultra-thin (~2 nm) film of perfluoropolyether (PFPE) coated on glass substrate magnetic hard disks. The lubricant was coated on the disk by the dip-coating method and the tribological tests were carried out by sliding a 3 mm diameter glass ball slider (normal load=20 mN) on the rotating disk surface. Lube thickness and lube wear profile were measured using an ellipsometer whereas the worn disk surface was studied using a surface reflectivity analyzer. The sliding speed and the lube bonding conditions were varied during the test. From the results, it is concluded that about 80% bonding of the lube to the disk surface leads to an increase in the wear durability of the lubricant by a factor of 2 when compared to the as-lubed condition. Lube bonding has an effect on increasing the coefficient of friction. Initially, increasing sliding speed increases both friction and wear but for very high sliding speed these values tend to decrease. The glass ball surface showed wear due to asperity interactions as well as lube transfer from the disk to the glass surface.     

Effect of the worn status of wheel/rail profiles on wheel wear over curved tracks

Journal of Mechanical Science and Technology - The worn status of wheel/rail profiles could change the wheel-rail contact and influence the wear rates of the wheel and rail. Worn wheel profiles of...     

Chemical aspects of wear of alumina ceramics

In our investigation, the effects of the tribochemically-induced dissolution of alumina ceramics and modulation of near-surface forces (surface charge) within the tribocontact were studied. The wear and friction behaviors of alumina were investigated using a reciprocating sliding test in different chemical environments. The samples for the tests were hemispherical pins and plates of polished alumina, both prepared by a near-net-shaping method.

The sliding tests were conducted in water-based liquids with different pH values or with the addition of a polyelectrolyte to control the surface charge at solid surfaces. The coefficient of friction was continuously recorded during the tests and the wear-loss was subsequently determined for all samples. The results show a significant effect of the chemical agents on the coefficient of friction as well as on the material-removal rate in different aqueous media. The results are discussed in terms of the chemical and electrochemical properties of the materials in the tribocontact.     

Chemical effects in sliding wear of aluminum

The mechanism of the sliding wear of metals in corrosive media was investigated. In particular, the role of chemical heterogeneities on chemical interactions between the sliding surface and its environment was studied using 2024 aluminum alloy and sodium chloride solutions of varying pH and NaCl concentration. Sliding wear tests with a cylinder-on-cylinder geometry were performed at a sliding speed of 1 m min^?1 and a normal load of 9.8 N (1 kgf). The results show that at pH = 0 and pH = 14, the wear rate is dominated by the dissolution of aluminum into the NaCl solution. In the intermediate pH range, the wear rate is shown to be controlled by the conjoint actions of corrosion and delamination wear. Microscope examination of the worn specimens by means of a scanning electron microscope further confirms that the mode of corrosion is of a localized nature.     

Evaluations of tribological characteristics of PFPE lubricants on DLC surfaces of magnetic disks

This article presents measurements of adhesion and friction of perfluoropolyether (PFPE) lubricant films dip-coated on magnetic disks covered with diamond-like carbon (DLC) film. We have developed a custom-built pin-on-disk type micro-tribotester to perform the tribological measurements. The adhesion tests were performed by pulling down/up a 1.5-mm-diameter glass ball on a stationary disk surface, and the friction tests were carried out by sliding the glass ball on a rotating disk surface without changing head-disk interface conditions from the adhesion tests. Experiments were performed for the different kinds of 2- and 6-nm-thick PFPE lubricants (polar: Zdol4000 and Zdol2000; nonpolar: Z03) under lightly loaded and slow sliding conditions to minimize disturbance against the molecular layered structure. The adhesive forces were found to decrease with increasing film thickness in the order of Z03 > Zdol2000 > Zdol4000 (decreasing rate), which closely corresponds to the order of monolayer thickness, and then to saturate to almost the same calculated values. As for the friction forces of 2-nm-thick films, Zdol2000 featured extraordinarily large friction in comparison with Zdol4000 and Z03, while Zdol4000 was slightly larger than Z03. The largest friction of Zdol2000 reveals that the 2-nm-thick Zdol2000 formed a monolayer that served as an immobile layer. With the increase in film thickness, the friction force of Zdol2000 decreased, indicating that extra lubricant molecules served as a mobile layer, while that of Z03 remained unchanged as the lowest value. By extrapolating the loading force versus friction force relationship into a negative loading force region, it is found that the friction force of Z03 tended to zero at zero net load (loading force plus adhesion force), while those for Zdol2000 and Zdol4000 exhibited finite values, indicating formation of an immobile layer, which shows similar characteristics to those of adhesive rubber material. The dewetted surface is found to feature violently changing friction force only at the first stage of sliding, and it then becomes stable after several sliding passes.     

Imaging TOF-SIMS of rat kidney prepared by high-pressure freezing

Phosphocholine, potassium ions, and sodium ions were localized in rat kidney with imaging TOF-SIMS. Tissue preparation was performed with high-pressure freezing, freeze-fracturing and freeze-drying. The distribution of sodium ions was visualized by imaging the signal at m/z 23 of positively charged secondary ions, and the distribution of potassium ions was visualized by imaging the signal at m/z 39. Potassium was found localized within cells of the proximal tubulus epithelium and within cells of the glomeruli. High signals of sodium ions were seen in the interstitial tissue and also in epithelial cells of the collecting ducts and in glomeruli. The overlay image showed that the distribution of sodium ions and potassium ions were largely complementary with color mixing in glomeruli and in the interstitium surrounding proximal tubules. The ion distribution was further analyzed by correlation analysis. Phosphocholine-containing phospholipids were visualized by imaging the phosphocholine head group at m/z 184 of positively charged ions. The m/z 184 signal shows a ubiquitous distribution with a high intensity of phosphocholine in epithelial cells. Overlay image of m/z 184, m/z 39, and m/z 23 and multivariate analysis showed that the localization of high levels of phosphocholine colocalizes with high levels of potassium ions, as expected for an ion with intracellular localization.     

Simulation of tape edge wear of magnetic tapes

Wear of the tape edge of magnetic tape in sliding contact with a stationary guide pad is investigated numerically. The thickness profile of the tape is discretized and each node of the profile is considered to act as an independent spring compressed by the guide pad. Archard's wear equation is used to predict wear of each node as a function of nodal force and materials properties of the tape. The simulation results show the evolution of tape edge wear as a function of the number of repeated wear passes. Good qualitative agreement is found between numerical predictions and experimental measurements.     

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.     

3.5 t叉车离合器摩擦片早期磨损的原因分析及改进措施

近来有部分用户反应3．5t内燃叉车离合器摩擦片磨损严重,摩擦片寿命不足2t叉车的一半,而3t以下叉车正常。针对此问题,我们经过一段时间的用户调查和理论分析,找出了3．5t叉车摩擦片早期磨损的原因,并通过控制离合器的起步温升,增大离合器的储备系数,增加散热面积等改进措施,大大减少了离合器摩擦片的早期磨损,从而延长离合器的使用寿命。     

Network numerical analysis of hydromagnetic squeeze film flow dynamics between two parallel rotating disks with induced magnetic field effects

We study numerically the hydromagnetic squeeze film between two rotating disks using the numerical network simulation method. The external magnetic field, H, generates an induced magnetic field, B, with radial (B_r), tangential (B_θ) and axial (B_z) components between the two disks, which rotate with different angular velocities, Ω₁ and Ω₂, and at time t are separated by a distance D(1−αt)^1/2. The applied magnetic field at the lower disk is assumed to be zero. The conservation equations for mass, momentum and induced magnetic field are reduced to a set of ordinary differential equations using a series of transformations, in terms of four dependent variables, f (axial velocity), g (azimuthal velocity), m (axial magnetic field component) and n (azimuthal magnetic field component) and a single independent variable, η (dimensionless disk separation), with appropriate boundary conditions. The transformed ordinary differential equations have collective order of 10 and are shown to be controlled by rotational Reynolds number (R₁), squeeze Reynolds number (R₂=Re_m/Bt), dimensionless parameter based on the magnetic force in the axial direction (R₃), dimensionless parameter based on magnetic force strength in the azimuthal (tangential) direction (R₄), magnetic Reynolds number (Re_m), disk rotational velocity ratio (S) and Batchelor number (Bt). In the present study we examine the flow regime at various Batchelor numbers (for the case of unity value of the squeeze Reynolds number, Re_m=Bt). Excellent comparison of NSM solutions is achieved with earlier analytical and shooting solutions. The present study finds applications in hydromagnetic lubrication of braking devices, slider bearings, rotating machinery, etc. Applications also arise in hydraulic shock absorbers employing electrically conducting liquids such as sodium where electro-magnetical braking of streams can be achieved in liquid metal cooled nuclear reactors for arresting control rods. Finally in the context of astronautical vehicles, the present study has applications in electromagnetic braking for potential spacecraft in planetary orbits.     

Investigation of tape edge wear of magnetic recording tapes

Tape edge wear is studied for polyethylene naphthalate-based magnetic tape as a function of tape speed, tape tension, and tape guide surface roughness. The results show that tape edge wear is on the order of 0.04 nm per cycle at a constant force of 45 mN and that edge wear increases with increasing tape speed, tape tension and tape guide surface roughness. In addition, tape edge wear of three coated tapes with polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyaramid (PA) substrate is studied. It is found that edge wear of polyaramid based tape is similar to that of PET-based and PEN-based tapes.