Flat Pins Research Articles

Surface Micro-texturing by Hot Sintering for Advanced Bearing Polymers for Friction Reduction Under Boundary Lubrication

Surface micro-texturing has been proven an effective way to reduce friction and wear for tribological applications. In current work, we propose a low cost hot sintering method to apply micro-texturing on an advanced bearing polymer material. In step 1 of this method, one face of the mold was micro-textured using a micro-casting method, in step 2 the cured Aromatic Thermosetting coPolyester (ATSP) powder was filled in the mold. In step 3, the filled mold was placed in a hot press for a 2-h hot sintering process, and in step 4, the final textured bulk ATSP was completed after cooling down. Subsequently, the micro-textured ATSP bulk material was machined to 6.35 mm diameter pins for pin-on-disk configuration tribologcial studies at different speeds with a contact pressure of 9.1 MPa, under boundary lubrication conditions. Compared with plain untextured flat pins, the micro-textured pins could effectively reduce friction at speeds lower than 1.90 m/s: 14% reduction in average. Scanning electron microscopy was utilized for morphological studies of the micro-textured mold, and micro-textured ATSP samples, before and after the tribological experiments.

X-ray computerized tomography for characterization of pick-up destruction and pick-up parameter optimization of tomato root lumps

This study was aimed to find the causes of pick-up destruction of tomato root lumps using X-ray microcomputed tomography, and to identify the pick-up parameters of low root lump destruction. The roots and pores were reconstructed three-dimensionally and analyzed quantitatively. It was found that the roots acted winding and wraping the root lumps and thus preventing the substrate from loosening. The major causes for root lump destruction were pore aggregation and crack formation. The apex and circumference of pick-up pins were areas where root lumps were prone to fracture and breakage, respectively. Lacunarities of these two areas were used as index to quantify the root lump destruction. Single-factor analysis of variance was conducted with pick-up pin shape (circular, flat), diameter (2, 2.5, 3 mm) and initial pick-up angle (18°, 21°, 24°) as the test factors and then the effects of these three factors on root lump destruction were studied. It was found the lacunarities at the fracturable area and breakable area both increased with the rise of pick-up pin diameter and decreased with the rise of initial pick-up angle. At the same pick-up conditions, lacunarities with the use of flat pins always surpassed that of circular pins. When circular pick-up pins with diameter of 2 mm and initial pick-up angle of 24° were used, the destruction rate of root lumps (6.63%) was smaller than under other test conditions. The optimized pick-up parameters can be used to guide gripper design and to improve the working performance of automatic transplanters.

Self-lubricating laser claddings for reducing friction and wear from room temperature to 600 °C

In this work, laser cladding has been employed for the preparation of nickel-based self-lubricating coatings featuring the addition of different combinations of soft metal solid lubricants such as Ag and Cu. Transition metal dichalcogenides (WS2, MoS2) were evaluated as precursors for encapsulating and uniformly distributing the soft metals throughout the microstructure. The tribological behaviour of the resulting claddings was evaluated under high temperature reciprocating sliding conditions, including two different counter body geometries that lead to very different ranges of contact pressures during testing. An improved tribological behaviour was observed for the self-lubricating claddings compared to the unmodified nickel-based alloy up to 600 °C, attributed to the presence of silver and the formation of lubricous sulfides during sample preparation due to the thermal degradation of the transition metal dichalcogenides precursors. Additionally, the role of the contact conditions observed when testing the self-lubricating claddings against flat pins instead of spherical counter bodies are discussed in terms of frictional and wear microstructural mechanisms.

Printed Texture With Triangle Flat Pins for Bandwidth Enhancement of the Ridge Gap Waveguide

Lately, there has been a growing interest in the ridge gap waveguide (RGW) technology as a guiding structure for high-frequency applications. Low loss and low dispersion are two major advantages of the RGW. On the other hand, the major disadvantage of this technology is the difficulty in fabrication as it requires fabrication with high precision, in particular for high-frequency applications. The operating bandwidth of the RGW is controlled by the stopband of the texture surrounding the ridge. A study to enhance the bandwidth is introduced for possible utilization of the full band achievable by the unit cell in the presence of the ridge. Modifications of the cell filling shape and the ridge structure are carried out to enhance the RGW bandwidth. We have introduced a new RGW based on mixed fabrication technology. The proposed architecture introduces adaptive and straightforward structure with improved bandwidth while keeping the characteristic impedance at the same value. The proposed structure is fabricated and measured. The measured scattering parameters are in excellent agreement with the simulated ones.

Indentation Recovery of Shape Memory Foams Produced by Solid State Foaming

In this study, solid state foaming was used to produce epoxy foam samples with shape memory properties. Foams were indented at room and high temperature by using flat pins with diameter from 1 to 5 mm. Micro-indentations were performed as well only at room temperature. The indentation marks were measured before and after thermal recovery to evaluate the ability of the material to reach the initial shape. For a better understanding of the overall process, a study was made also to predict the initial precursor density as a function of the compaction parameters. This way, it was also evaluated that the effect of the compaction process is covered by the effect of the foaming step.

Shaping of the cross section of a nonrelativistic high-current electron beam by means of return current leads

Calculation results and experimental data on shaping the cross-section of a nonrelativistic (10–30 keV) high-current (up to 25 kA) electron beam are presented. A circular beam is successfully transformed into a beam with a quasi-rectangular cross section. Transformation is carried out using flat buses or circular pins as return current leads over a short (4 cm) section of the beam transport channel. The distance between the edge of the beam and the leads is comparable to its radius, and the external guiding magnetic field is comparable to the self-magnetic field of the beam. The calculation results are compared with the experimental data.

Laplace pressure measurement on laser textured thin-film disk

To increase the recording density of hard disk drives (HDD), head and disk surfaces must be very flat. This will make the friction between them large when liquid bridges are formed. This is a result of Laplace pressure in the liquid bridge. Therefore, the study of Laplace pressure in real HDD interface is of an interest for head-disk interface engineers. However, Laplace pressure of perfluoropolyether (PFPE) lubricant on carbon coated thin-film disk surface was not clear until now. We measured Laplace pressure between transparent flat pins and carbon coated thin-film disks with laser texturing. Using laser textured disks, we could control the distance between two surfaces precisely by the bump height. The friction coefficient between the pin and the disk surfaces was determined when the interface was fully wet by liquids. It was 0.16 and 0.1 for water and a PFPE lubricant. The Laplace pressure was then calculated using the friction force and liquid wet area when the interface was partially wet by a liquid. The liquid wet area was measured by the observation of the contact point through the transparent pins. The results showed that the Laplace pressure at the lowest bump height (11 nm) was about 2.8 MPa for the PFPE lubricant. Results agreed well with calculated curves. We consider that PFPE acts as liquid down to 11 nm.

Sliding-pin shapes and lubricant thickness change on a thin-film magnetic disk

In developing hard disk drives, it is necessary to keep lubricant as thick as possible during operations. For this purpose, we studied lubricant loss under different-shape contact-sliders on thin-film magnetic disks by using transparent-pin sliding tests with a built-in ellipsometer. We compared sliding pins with spherical, flat circle, flat square, and double-flat-rail surfaces. We found that lubricant loss was smaller under flat pins than under the spherical pin, and the smallest under the double-flat-rail pin among flat sliders. The results show that the horizontal and vertical shapes of sliders must carefully be selected for contact recording systems.

Sliding wear behavior of nitrided and nitrocarburized cast irons

In this work the friction and the wear resistance behavior of surface treated spheroidal and lamellar cast irons was studied. Thermochemical surface treatments included nitriding and nitrocarburizing. After characterization of the surface layers, dry sliding wear tests were performed on a prototype pin-on-disk apparatus in which cast iron disks were mated to hardened steel pins. The influence of the sliding velocity on the response of the various combinations of material and surface treatment was determined. Also, the influence of the contact geometry was investigated using hemispherical and flat pins.

Friction and adhesive wear behaviour of W-C coatings against steel and titanium nitride

Tribological characteristics of W-C coatings with high carbon content produced on tool steel substrates by plasma-assisted chemical vapour deposition (the Dimigen process) were evaluated with two different rotating pin-on-disk tribometers in dry sliding conditions. The friction coefficients measured using hemispherical pins were between 0.28 and 0.32, i.e. 2.5 times lower than with uncoated steel samples. The surface roughness of the as-deposited coating was relevant only for the run-in period. The most remarkable feature of the prolonged wear test results performed with flat pins is the negligible wear on either the W-C coating, the steel pin or the titanium nitride coated pin.

コーマ用だ円および平ピンについて

コーマ用だ円および平ピンについて