Bart Raeymaekers

University of Utah | UOU

CALL FOR PAPERS Friction, a peer-reviewed journal, is calling for papers for the upcoming special issue "Artificial Intelligence and Emerging Computational Approaches for Tribology". Tribo-behavior is a complex system-based time-dependent process, and it is believed difficult to accurately model a tribo-system and predict its behavior. Hence, tribo...

Ultrasound directed self-assembly (DSA) allows organizing particles dispersed in a fluid medium into user-specified patterns, driven by the acoustic radiation force associated with a standing ultrasound wave. Accurate control of the spatial organization of the particles in the fluid medium requires accounting for medium viscosity and particle volum...

Engineered polymer matrix composite materials with designer electrical properties are important for a myriad of engineering applications including flexible electronics, electromagnetic shielding, and materials with embedded electrical wiring. However, existing fabrication methods are limited by material choice and dimensional scalability. We use th...

Ultrasound directed self-assembly (DSA) enables noninvasively aligning high aspect ratio particles in three-dimensional (3D) user-specified orientations, which finds application in a myriad of engineering applications, including manufacturing engineered materials. However, the number of ultrasound transducers and their spatial arrangement limit the...

Ultrasound-directed self-assembly (DSA) enables particles to be arranged into user-specified patterns, which finds application in a myriad of engineering applications. However, using ultrasound DSA with nonspherical particles requires the ability to explicitly control their orientation. We theoretically derive a method to determine the operating pa...

We use ultrasound directed self-assembly (DSA) to create two-dimensional patterns of high-aspect-ratio particles with user-specified orientation. We theoretically derive a method to determine the operating parameters of any arrangement of ultrasound transducers required to align high-aspect-ratio particles in any user-specified orientation. The met...

Ultrasound noncontact particle manipulation (NPM) is based on the acoustic radiation force associated with an ultrasound wave field, and enables a myriad of engineering applications with the ability to noninvasively manipulate particles in a fluid medium. We use multiple phased arrays of ultrasound transducers to dynamically move a 3D pattern of pa...

We introduce a new process to manufacture polymer nanocomposite materials reinforced with an ultra-high weight fraction of aligned carbon nanotubes. This process is based on using ultrasound directed self-assembly, which employs the force associated with a standing ultrasound wave to concentrate and align carbon nanotubes dispersed in the polymer m...

We use ultrasound directed self-assembly to organize particles dispersed in a fluid medium into a three-dimensional (3D) user-specified pattern. The technique employs ultrasound transducers that line the boundary of a fluid reservoir to create a standing ultrasound wave field. The acoustic radiation force associated with the wave field drives parti...

We employ an ultrasound wave field generated by one or more ultrasound transducers to organize large quantities of nanoparticles dispersed in a fluid medium into two-dimensional user-specified patterns. To accomplish this, we theoretically derive a direct method of calculating the ultrasound transducer parameters required to assemble a user-specifi...

We employ an ultrasoundwave field generated by one or more ultrasound transducers to organize large quantities of nanoparticles dispersed in a fluid medium into two-dimensional user-specified patterns. To accomplish this, we theoretically derive a direct method of calculating the ultrasound transducer parameters required to assemble a user-specifie...

Ultra-thin diamond-like carbon (DLC) coatings are used in hard disk drives to protect the intricate magnetic structures from wear and corrosion. The coating on the recording head consists of a hard DLC layer and a silicon (Si) layer that improves adhesion between the DLC layer and the substrate. Damage to this protective coating can expose the magn...

Ultra-thin lubricant films are essential in the design of nanoscale systems and devices as surface effects become increasingly important on the nanoscale. We have used molecular dynamics simulations to quantify terraced spreading of perfluoropolyether lubricant on a flat substrate as a function of polymer chain length, lubricant thickness, and func...

A major limiting factor to the longevity of prosthetic knee joints is fatigue crack damage of the polyethylene tibial insert. Existing methods to quantify fatigue crack damage have several shortcomings, including limited resolution, destructive testing approach, and high cost. We propose an alternative fatigue crack damage visualization and measure...

Understanding contact between rough surfaces is of critical importance to the design of many engineering applications. Contact models rely on material properties and surface topography of the contacting surfaces as input parameters. Hence, the relevance of the contact models is dependent on their inherent assumptions and the accuracy with which the...

Metamaterials are a class of man-made materials with exotic electromagnetic properties. The ability to fabricate three-dimensional macroscale metamaterials would enable embedding these structures in engineering applications and devices, to take advantage of their unique properties. This paper reviews the implementation of optical Mie resonance-base...

With recent improvements to the properties of ultra-high molecular weight polyethylene (UHMWPE) used in joint replacements, prosthetic knee and hip longevity may extend beyond two decades. However, it is difficult and costly to replicate such a long in vivo lifetime using clinically relevant in vitro wear testing approaches such as walking gait joi...

Understanding the physical behavior of polymer-based lubricants on the nanoscale is of critical importance to a myriad of engineering applications and devices. We have used molecular dynamics simulations to quantitatively evaluate the physical mechanisms underlying perfluoropolyether lubricant spreading on a solid substrate. We quantify the effect...

We analyze the dynamic behavior of a spherical microparticle submerged in a fluid medium, driven to the node of a standing bulk acoustic wave created by two opposing transducers. We derive the dynamics of the fluid-particle system taking into account the acoustic radiation force and the time-dependent and time-independent drag force acting on the p...

It has long been known that articular cartilage exhibits a surface microtexture with shallow indentations. By contrast, prosthetic joints consist of ultra-smooth bearing surfaces, the longevity of which does not reach that of natural cartilage. We show that adding a microtexture to the smooth femoral component of a prosthetic knee joint reduces fri...

More than 285,000 total hip replacement surgeries are performed in the US each year. Most prosthetic hip joints consist of a cobalt-chromium (CoCr) femoral head that articulates with a polyethylene acetabular component, lubricated with synovial fluid. The statistical survivorship of these metal-on-polyethylene prosthetic hip joints declines signifi...

Combined normal and tangential loading of a magnetic recording head on a rigid hydrogenated diamond counterface is simulated using molecular dynamics. Deformation of the substrate, silicon interlayer and tetrahedral amorphous carbon overcoat that comprise the head is quantified as a function of operating and design parameters. We find that decreasi...

A prosthetic knee joint typically comprises a cobalt-chromium femoral component that articulates with a polyethylene tibial insert. A locking screw may be used to prevent micromotion and dislodgement of the tibial insert from the tibial tray. Screw loosening and back-out have been reported, but the mechanism that causes screw loosening is currently...

A method to increase the storage density on magnetic recording media by physically separating the individual bits from each other with a non-magnetic medium (so-called bit patterned media). This allows the bits to be closely packed together without creating magnetic “cross-talk” between adjacent bits. In one embodiment, ferromagnetic particles are...

The validity of the compressible Reynolds equation to predict the local pressure in a gas-lubricated, textured parallel slider bearing is investigated. The local bearing pressure is numerically simulated using the Reynolds equation and the Navier–Stokes equations for different texture geometries and operating conditions. The respective results are...

Bulk acoustic waves (BAWs) are used to align multi-walled carbon nanotubes (MWCNTs) in polymer composite materials. MWCNTs are first dispersed in the liquid state of a thermoset resin and aligned using standing BAWs. Cross-linking of the resin fixates the aligned MWCNTs in the polymer matrix material. We have quantified the alignment obtained with...

Approximately 285,000 total hip replacement (THR) surgeries are performed in the U.S. each year. Most prosthetic hip joints consist of a cobalt-chromium (CoCr) femoral head that articulates against a polyethylene liner (usually ultra-high molecular weight polyethylene (UHMWPE)), lubricated by joint fluid. The statistical survivorship 0f these metal...

Several methods with various levels of sophistication exist to quantify dispersion of carbon nanotubes (CNTs) in a polymer matrix, such as the ASTM D2663 standard that is often used in engineering practice. However, most methods are limited by their accuracy, complexity of implementation, and scalability. In this paper, we present a new technique a...

The statistical survivorship of total knee replacement (TKR) devices declines dramatically after fifteen years of use because the articulating surfaces wear, and biologically active wear particles may induce osteolysis and subsequent loosening of the implant. This lack of durability leads to revision surgery or surgery postponement. Thus, friction...

The possibility of engineering near-field thermal radiative properties is investigated by adjusting design parameters of Mie resonance-based metamaterials. The sensitivities of surface polariton resonance frequencies, in both transverse magnetic and transverse electric polarizations, to parameters such as host medium relative permittivity and parti...

Surface texturing is used to increase hydrodynamic pressure and reduce friction and wear between gas-lubricated parallel sliding surfaces in a variety of applications. The shape, geometry, and density of the patterned microtexture features ("dimples") play a key role in the tribological performance of textured slider bearings. In this paper we eval...

A method of unconstrained and continuous manipulation of micro-particles in a fluid using bulk acoustic waves is theoretically derived and experimentally demonstrated. The method is based on phase-control of standing pressure waves created by two opposing transducers. Reflections are taken into account, removing the need for complex experiments. Th...

Delamination between an ultra-thin amorphous carbon overcoat, a silicon adhesion layer, and permalloy substrate material of a hard drive recording head is studied during normal loading/unloading of the head disk interface. The effect of normal load and thickness of the silicon adhesion layer on delamination of the Si-permalloy and amorphous carbon-...

The elastic contact between two computer generated isotropic rough surfaces is studied. First the surface topography parameters including the asperity density, mean summit radius, and standard deviation of asperity heights of the equivalent rough surface are determined using an 8-nearest neighbor summit identification scheme. Second, many cross sec...

Surface texturing is used to increase hydrodynamic pressure and reduce friction and wear between gas-lubricated parallel sliding surfaces. The shape, geometry, and density of the patterned microtexture features (“dimples”) play a key role in the tribological performance of the textured slider bearings. The objective of this paper is to compare the...

The Navier-Stokes and compressible Reynolds equations are solved for gas lubricated textured parallel slider bearings under hydrodynamic lubrication for a range of realistic texture geometry parameters and operating conditions. The simplifying assumptions inherent in the Reynolds equation are validated by comparing simulation results to the solutio...

Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

We have devised a method, based on a parametric array concept, to create a low-frequency (300-500 kHz) collimated ultrasound beam in fluids highly attenuating to sound. This collimated beam serves as the basis for designing an ultrasound visualization system that can be used in the oil exploration industry for down-hole imaging in drilling fluids....

We investigate manipulating 5 nm diamond nano‐particles in a user‐defined pattern on a substrate using the acoustic radiation force associated with a bulk acoustic standing wave. Both concentric and rectangular patterns are studied and the experimental results are compared with theoretical predictions. The effect of drag force acting on a nanoparti...

We investigate the manipulation of 5 nm diamond nanoparticles in a user-defined pattern on a substrate using the acoustic radiation force associated with a bulk acoustic standing wave. Both concentric and rectangular patterns are studied and the experimental results are compared with theoretical predictions. The effect of drag force acting on a nan...

In this paper we investigate using the acoustic radiation force associated with a bulk acoustic standing wave to manipulate 5 nm diamond nano-particles in a user-defined pattern. Both concentric and rectangular patterns are studied and experimental results are compared to existing models. The effect of drag force acting on a nano-particle is evalua...

Lateral tape motion (LTM) is the time-dependent displacement of magnetic tape perpendicular to the tape transport direction. Lateral tape motion may cause track misregistration between the read/write head and a

Fretting wear between a hemisphere and a flat plate is investigated experimentally and the effect of laser polishing is studied. The energy dissipated between the hemisphere and the flat plate is determined as a function of operating conditions such as frequency and normal load and material properties such as surface roughness, and related to the w...

Fretting wear of the dimple/gimbal interface in a hard disk drive suspension is investigated. The energy dissipated between the dimple and the gimbal spring is determined as a function of operating conditions and material properties, and related to the wear observed at the interface. Abrasive, adhesive and tribo-chemical wear are found to be presen...

An ultrasonic scanning tool to image objects with high-spatial resolution submerged in highly attenuating fluids is described. The attenuation coefficient of the fluids used range over two orders of magnitude. For deeper penetration into the attenuating fluids, a parametric array with a difference frequency between 200 and 500 kHz was used. The pri...

We have investigated the sliding contact between nominally flat realistic rough surfaces. Using a technique based on filtering we have created well defined non-isotropic rough surfaces with a Gaussian distribution of asperity heights. We have studied the effect of inertia on the separation between sliding rough surfaces and found that inertia due t...

As tape recording density increases, high-frequency track following capability of the tape head actuator becomes more important. This paper details the mechanical design and experimental analysis of a dual state actuator tape head. The dual stage actuator design combines a traditional voice coil motor for low frequency track following with a piezoe...

We present a data-based approach for modeling and controller design of a dual-stage tape servo actuator. Our method uses step response measurements and a generalized realization algorithm to identify a multivariable discrete-time model of the actuator. The data acquisition and modeling can be implemented in the servo firmware of a tape drive. We ha...

Lateral tape motion (LTM) is a function of tape path and tape properties, design parameters such as speed, tension, and friction between tape and tape path components. This investigation deals with the LTM of a tape moving over the surface of a cylindrical guide. Starting from the equation of motion for a moving tape on a cylindrical guide surface,...

The storage market is presently dominated by hard disk drives. However, magnetic tape has maintained its cost-per-gigabyte ad- vantage with respect to hard disk drives and remains the primary choice for backup and mass data storage applications 1,2. Tape research can be divided into four main fields 1: a head technology, b recording media technolog...

Wear particles in a hard disk drive may cause the head/disk interface to fail. We have experimentally investigated wear particle generation resulting from fretting wear between the dimple on the suspension and the gimbal spring. We have found that increasing the normal load as well as using a low friction coating reduces the formation of wear parti...

Acoustic emission transducers were used to study the brush/rotor interface of a homopolar motor as a function of design parameters such as speed and load. The results indicate that acoustic emission is well suited for in situ monitoring of brush wear and rotor conditions, and for analyzing the tribological phenomena occurring at the brush/rotor int...

Homopolar motors have been proposed as an alternative propulsion means for ships. Such motors operate in a very harsh and demanding environment, making in-situ diagnostics and fault- monitoring systems a key issue for extended operation. In a typical homopolar motor, several thousand brushes are used, which are all in sliding contact with a copper...

The lateral motion of a tape moving axially over a cylindrical guide surface is investigated. The effects of lateral bending stiffness and friction force are studied and the attenuation of lateral tape motion as a function of the guide radius and friction coefficient is determined. Good agreement between numerical predictions and experimental resul...

The friction coefficient between a magnetic tape and a guide in a tape path can be minimized by creating micro dimples on the guide surface with laser surface texturing. The dimples enhance the formation of an air bearing and reduce the friction coefficient between the tape and the guide due to the increased spacing. A model is presented to optimiz...

0. Abstract Acoustic emission sensors were used to detect contact between a moving tape and the flange of a tape guide. The influence of tape drive operating conditions on the tape edge contact force was studied. A one dimensional model was developed to predict the magnitude of tape/flange impact. The model fits the experimental data well.

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.

The classical belt drive equation is modified to obtain a more accurate model, which allows the investigation of the effect of various parameters such as sliding speed, tape tension, surface roughness, material properties and guide and tape geometry on the magnetic tape/guide friction coefficient. The friction coefficient between a guide and a tape...

Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

Non-contact tension measurement of magnetic tape is performed. Light from a focussed light source is directed at a tape surface and the light reflected from the tape is captured by a photo cell. As the tape tension varies, the divergence of the reflected light bundle changes, i.e., the amount of light seen by the photo cell is a measure for the ten...

Lateral tape motion (LTM) is the motion of a tape perpendicular to the tape transport direction. It is a problem in magnetic tape recording technology that limits the track density on a tape. To reduce LTM, it is important to characterize the main sources of LTM in tape transports. In this dissertation, the effect of tape edge contact as well as ta...