Recent Patent on an Energy Conserved Journal Bearing with the Slippage Sleeve Surface

Background: Energy consumption in mechanical apparatus has become a big problem in modern industry. It is very important to develop energy-conserved rotary machines, which are very promising in the future. Objective: To introduce a patented energy-conserved hydrodynamic journal bearing with low friction where the interfacial slippage is designed on the whole sleeve surface. Methods: The analytical results are presented for the carried load and friction coefficient of the introduced bearing based on the limiting interfacial shear strength model. The performance of the introduced bearing is compared with that of the conventional hydrodynamic journal bearing for the same operating condition. Results: The obtained results show that in the same operating condition, the carried load of the introduced bearing can be 35%~50% times that of the conventional journal bearing, but its friction coefficient on the shaft surface can be 30%~70% times that of the conventional journal bearing, while its friction coefficient on the sleeve surface is considerably lower and can only be 5%~20% times that of the conventional journal bearing. The friction reducing effect of the bearing depends on the eccentricity ratio and the fluid-sleeve surface interfacial shear strength; the lower the latter, the smaller the friction coefficients on both the shaft and sleeve surfaces. Conclusion: The introduced bearing is obviously of low friction and energy-conserved. It has application values especially in the condition of modest eccentricity ratios, where the loss of the loadcarrying capacity of the bearing due to the interfacial slippage is not so large.

Designing durable icephobic surfaces

Ice accretion has a negative impact on critical infrastructure, as well as a range of commercial and residential activities. Icephobic surfaces are defined by an ice adhesion strength τice < 100 kPa. However, the passive removal of ice requires much lower values of τice, such as on airplane wings or power lines (τice < 20 kPa). Such low τice values are scarcely reported, and robust coatings that maintain these low values have not been reported previously. We show that, irrespective of material chemistry, by tailoring the cross-link density of different elastomeric coatings and by enabling interfacial slippage, it is possible to systematically design coatings with extremely low ice adhesion (τice < 0.2 kPa). These newfound mechanisms allow for the rational design of icephobic coatings with virtually any desired ice adhesion strength. By using these mechanisms, we fabricate extremely durable coatings that maintain τice < 10 kPa after severe mechanical abrasion, acid/base exposure, 100 icing/deicing cycles, thermal cycling, accelerated corrosion, and exposure to Michigan wintery conditions over several months.

Effect of interfacial slippage on the near-tip fields of an interface crack between a soft elastomer and a rigid substrate

We consider the role of interfacial slippage in the deformation and stress fields near the tip of a plane interface crack occurring between a compressible hyperelastic material and a rigid substrate. Specifically, we draw comparisons between the two limiting cases of ‘no-slip’ (infinitely high friction) and ‘frictionless’ (zero friction) surfaces by performing corresponding asymptotic analyses in the crack-tip region. Our results indicate that for the no-slip case, when the body is subjected to far-field loading, the crack deforms to a wedge-like shape consistent with experimental observations reported in the literature. Moreover, in this case, the wedge angle is shown to be directly related to ratios of various Cauchy stress components on the bonded surface in the near-tip region. Finite-element simulations reveal that the wedge angle also depends on material compressibility and the far-field loading conditions. By contrast, the analysis of the frictionless case reveals that the crack consistently opens into a smooth parabolic shape with a right wedge angle and near-tip stress field dominated by the normal stress at the surface. The results established here can be used as a basis for the understanding of the role of varying degrees of slippage on interfacial cracks.