A numerical investigation of mechanical response of unfilled Styrene Butadiene Rubber by static straight blade indentation

This study investigates the mechanical response of straight blade indentation on Unfilled Styrene Butadiene Rubber by Finite Element Analysis (FEA). The mechanical responses investigated were stiffness, maximum stress and indentation load. The rubber material was modeled as a hyperelastic material with the Money-Rivlin Strain Energy Function. Results were presented as a function of the blade characteristics, wedge angle and tip radius at a specified depth of indentation. Results showed that the stiffness and indenter load increase due to an increase in the wedge angle and the tip radius, on the other hand, the maximum stress decreases. Surprisingly, an approximately linear relationship between the mechanical response and the blade characteristic was found. Furthermore, the mechanical response at a specified maximum stress was also discussed

The Axis-Ratio Distribution of Galaxy Clusters in the SDSS-C4 Catalog as a New Cosmological Probe

We analyze the C4 catalog of galaxy clusters from the Sloan Digital Sky Survey (SDSS) to investigate the axis-ratio distribution of the projected two dimensional cluster profiles. We consider only those objects in the catalog whose virial mass is close to 10^{14}h^{-1}M_{sun}, with member galaxies within the scale radius 1000 kpc. The total number of such objects turns out to be 336. We also derive a theoretical distribution by incorporating the effect of projection onto the sky into the analytic formalism proposed recently by Lee, Jing, & Suto. The theoretical distribution of the cluster axis-ratios is shown to depend on the amplitude of the linear power spectrum (sigma_8) as well as the density parameter (Omega_{m}). Finally, fitting the observational data to the analytic distribution with Omega_{m} and sigma_{8} as two adjustable free parameters, we find the best-fitting value of sigma_{8}=(1.01 +/- 0.09)(Omega_{m}/0.6)^{(0.07 +/- 0.02) +0.1 Omega_{m}}$. It is a new sigma_{8}-Omega_{m} relation, different from the previous one derived from the local abundance of X-ray clusters. We expect that the axis-ratio distribution of galaxy clusters, if combined with the local abundance of clusters, may put simultaneous constraints on sigma_{8} and Omega_{m}.Comment: accepted for publication in ApJ, 17 pages, 3 figures, improved analysis, more discussion on the validity and the caveats of the mode

Modeling of repeated rolling contact of rigid ball on rough surface: residual stress and plastic strain analysis

In this paper, a three-dimensional finite element model of rigid hemisphere repeatedly rolling over a rough flat surface under constant normal load is discussed. The aim of this research is to study the von Mises residual stress and plastic strain distribution and to determine the steady-state phase of the repeated rolling contacts. The results show that the change of residual stress distribution takes place in the first-two rolling cycles and there is no significant change for the residual stress from the second to third rolling cycle, i.e. the surface is run-in after a few cycles. The increase of the contact load affects the area of the von Mises residual stress at the surface and subsurface and also the number of the deforming asperities. The residual stress distribution is getting wider as the normal force increases. The plastic strain is captured after the third cycle of rolling. Small area of plastic strain is found for the rough surface for the low forces applied which indicates the surface deformed mainly elastically. The rough surface is predicted to be plastically deformed for the highest force applie

Friction characteristics of liquid lubricated MEMS with deterministic boundary slippage

It has been proven experimentally that boundary slippage represents a viable effect on the hydrodynamic performance of lubricated sliding contacts. Along with several friction reduction mechanisms that have been explored in the literature, the slippage parameters remain an important feature. With the main objective of evaluating the effects of the slippage, a modified Reynolds equation is employed. The result shows that deterministic boundary slippage of the lubricated-MEMS with uniform film thickness has a very beneficial effect on decreasing friction force as well as coefficient of friction

Biomass-Derived Heteroatom-Doped Carbon Aerogels from a Salt Melt Sol–Gel Synthesis and their Performance in Li–S Batteries

An ionothermal sol–gel strategy to synthesize hierarchically porous carbon aerogels doped with different heteroatoms is presented by using biomass precursors in a scalable process. Morphologically similar but chemically different materials are used to study the influence of heteroatoms in Li–S batteries. The materials show capacities as high as 1290 mAh g−1 in the first cycle using 50 wt % S loading. Heteroatom doping reduces the capacity fading and the polarization throughout cycling. Zeta potential measurements reveal positive surface charges for heteroatom-doped carbons and indicate attractive interactions with polysulfides causing reduced fading. A polysulfide-selective sorption study reveals strongly different adsorption behavior depending on the carbon’s chemical composition. Interestingly, the polysulfide fraction is also crucial. The results indicate that improved adsorption of long-chain polysulfides to doped carbons is related to improved capacity retention

Optical coherence tomography guided laser cochleostomy: towards the accuracy on tens of micrometer scale

Lasers have been proven to be precise tools for bone ablation. Applying no mechanical stress to the patient, they are potentially very suitable for microsurgery on fragile structures such as the inner ear. However, it remains challenging to control the laser-bone ablation without injuring embedded soft tissue. In this work, we demonstrate a closed-loop control of a short-pulsed CO2 laser to perform laser cochleostomy under the monitoring of an optical coherence tomography (OCT) system. A foresighted detection of the bone-endosteum-perilymph boundary several hundred micrometers before its exposure has been realized. Position and duration of the laser pulses are planned based on the residual bone thickness distribution. OCT itself is also used as a highly accurate tracking system for motion compensation between the target area and the optics. During ex vivo experimental evaluation on fresh porcine cochleae, the ablation process terminated automatically when the thickness of the residual tissue layer uniformly reached a predefined value. The shape of the resulting channel bottom converged to the natural curvature of the endosteal layer without injuring the critical structure. Preliminary measurements in OCT scans indicated that the mean absolute accuracy of the shape approximation was only around 20 μm