Noise calculation method of deep groove ball bearing caused by vibration of rolling elements considering raceway waviness

Raceway waviness error is the main reason to cause rolling elements to vibrate along axial direction and emit noise. In this paper, the mechanical analysis on deep groove ball bearing is carried out. With auto-correlation function, random surface waviness of both inner and outer raceways is simulated. A contact model of rolling elements and raceways considering surface waviness is established. Combining with the theory of acoustic equation, a calculation model is established for the noise caused by vibration of rolling elements and inner ring. The results show that with the decrease of machining accuracy, the noise of rolling elements increases due to axial vibration; with the increase of rotation speed, the noise also increases. Besides, the spectrum of radiation noise of inner raceway with different waviness amplitudes is given. The results indicate that the 3-D waviness on raceway surface has an influence on the vibration and the noise emitted by both rolling elements and inner ring, and provide guidance for sound control in deep groove rolling bearing.

Air, helium and water leakage in rubber O-ring seals with application to syringes

We study the leakage of fluids (liquids or gases) in syringes with glass barrel, steel plunger and rubber O-ring stopper. The leakrate depends on the interfacial surface roughness and on the viscoelastic properties of the rubber. Random surface roughness is produced by sandblasting the rubber O-rings. We present a very simple theory for gas flow which takes into account both the diffusive and ballistic flow. The theory shows that the interfacial fluid flow (leakage) channels are so narrow that the gas flow is mainly ballistic (the so called Knudsen limit). We compare the leakrate obtained using air and helium. For barrels filled with water we observe no leakage even if leakage occurs for gases. We interpret this as resulting from capillary (Laplace pressure or surface energy) effects.

Connectivity Analysis of Underwater Optical Wireless Sensor Networks

<pre>In this paper, we analyze the connectivity in the underwater optical wireless networks in which similar nodes with a certain range and coverage angle, and random surface distribution are used. In our analysis, we first classify the nodes into two categories of nodes located in the inner area and nodes located in the border strip by defining the width of the border strip as the node range. Then, we conduct their connectivity analyses separately. Finally, by combining the mentioned analyses, we obtain closed form formulas to calculate the probability of connectivity (from orders 1 and 2). Moreover, by numerical evaluation, we will compare the results of the analyses with the results of computer simulation.</pre>

Connectivity Analysis of Underwater Optical Wireless Sensor Networks

<pre>In this paper, we analyze the connectivity in the underwater optical wireless networks in which similar nodes with a certain range and coverage angle, and random surface distribution are used. In our analysis, we first classify the nodes into two categories of nodes located in the inner area and nodes located in the border strip by defining the width of the border strip as the node range. Then, we conduct their connectivity analyses separately. Finally, by combining the mentioned analyses, we obtain closed form formulas to calculate the probability of connectivity (from orders 1 and 2). Moreover, by numerical evaluation, we will compare the results of the analyses with the results of computer simulation.</pre>

THE SIMPLE SEPARATING SYSTOLE FOR HYPERBOLIC SURFACES OF LARGE GENUS

In this note we show that the expected value of the separating systole of a random surface of genus g with respect to Weil–Petersson volume behaves like $2\log g $ as the genus goes to infinity. This is in strong contrast to the behavior of the expected value of the systole which, by results of Mirzakhani and Petri, is independent of genus.

From random matrices to random tensors

After a brief presentation of random matrices as a random surface QFT approach to 2D quantum gravity, we focus on two crucial mathematical physics results: the implementation of the large N limit (N being here the size of the matrix) and of the double-scaling mechanism for matrix models. It is worth emphasizing that, in the large N limit, it is the planar surfaces which dominate. In the third section of the chapter we introduce tensor models, seen as a natural generalization, in dimension higher than two, of matrix models. The last section of the chapter presents a potential generalisation of the Bollobás–Riordan polynomial for tensor graphs (which are the Feynman graphs of the perturbative expansion of QFT tensor models).

An Investigation into the Texture Transfer in the Process of Lubricated Skin Pass Rolling

This article investigates the surface texture transfer mechanisms in lubricated skin pass rolling of metal strips with three-dimensional rough surfaces of both regular patterns and random surface asperity distributions. Two important steps have been completed. The first is the successful establishment of an efficient numerical method for predicting the 3D texture transfer. It was identified that the new method can be used reliably with the key complex factors coupled in skin pass rolling, such as the effects of lubricant and surface roughness. The second is the exploration of the texture transfer mechanisms with the aid of this new method. In addition, the effects of hydrodynamic pressure on the texture transfer efficiency were comprehensively investigated by a dynamic explicit finite element analysis. It was found that lubrication plays a critical role in determining the surface texture transfer. The texture transfer ratio decreases with increasing the lubricant viscosity. A larger pressure coefficient brings about a lower texture transfer ratio, but a larger reduction ratio leads to a greater texture transfer.

Hybrid Sol–Gel Superhydrophobic Coatings Based on Alkyl Silane-Modified Nanosilica

Hybrid sol–gel superhydrophobic coatings based on alkyl silane-modified nanosilica were synthesized and studied. The hybrid coatings were synthesized using the classic Stöber process for producing hydrophilic silica nanoparticles (NPs) modified by the in-situ addition of long-chain alkyl silanes co-precursors in addition to the common tetraethyl orthosilicate (TEOS). It was demonstrated that the long-chain alkyl substituent silane induced a steric hindrance effect, slowing the alkylsilane self-condensation and allowing for the condensation of the TEOS to produce the silica NPs. Hence, following the formation of the silica NPs the alkylsilane reacted with the silica’s hydroxyls to yield hybrid alkyl-modified silica NPs having superhydrophobic (SH) attributes. The resulting SH coatings were characterized by contact angle goniometry, demonstrating a more than 150° water contact angle, a water sliding angle of less than 5°, and a transmittance of more than 90%. Confocal microscopy was used to analyze the micro random surface morphology of the SH surface and to indicate the parameters related to superhydrophobicity. It was found that a SH coating could be obtained when the alkyl length exceeded ten carbons, exhibiting a raspberry-like hierarchical morphology.

Analysis of bio-dynamic model of seated human subject and optimization of the passenger ride comfort for three-wheel vehicle using random search technique

Ride comfort is the major concern to the roadway vehicle passengers, travelling in as it affects their health and efficiency to work. In the present study, a 9 DoF model of a three-wheel vehicle is developed with Lagrangian approach to investigate its ride behavior when subjected to random surface irregularities. The irregularities of the track are measured with a three-wheeled setup equipped with profilometer known as opto-coupler. The present model is validated in two ways, first by comparing the vertical-lateral PSD acceleration received from simulation and actual testing and second by comparing vertical seat to head transmissibility obtained from analysis (VSTH) with past reported studies. A 7 DoF bio-dynamic model of the seated human subject is formulated and integrated with the vehicle model, ride comfort of the vehicle and human body segments are assessed based on ISO specifications. Passenger Ride Comfort is optimized through non-linear optimization using Random Search Technique. The modified values of vehicle suspension parameters are presented to obtain optimum passenger comfort based on ISO-2631-1 criteria.