Study of Traction Properties of Three Space Lubricants Used for Rolling Bearing

2010 ◽  
Vol 136 ◽  
pp. 316-320 ◽  
Author(s):  
Jian Ping Liu ◽  
Xin Yi Zhang ◽  
Qing Xuan Jia
Keyword(s):  
Input Data ◽  
Rolling Bearing ◽  
Operating Conditions ◽  
Model Input ◽  
Traction Coefficient ◽  
Rheological Experiments ◽  
Three Space ◽  
Theoretical Results

Based on Johnson and Tevaarwerk’s model, traction coefficient was obtained for operating conditions representative of spacecraft applications. In this model input data come directly from rheological experiments or are derived from other measurements through physical relationships. Theoretical results were also compared with experimental ones which were measured for the same operating conditions.

Traction Behavior of Some Lubricants Used for Rolling Bearings in Spacecraft Applications: Experiments and Thermal Model Based on Primary Laboratory Data

2001 ◽  
Vol 124 (1) ◽  
pp. 72-81 ◽  
Author(s):  
Daniel Ne´lias ◽  
Eric Legrand ◽  
Philippe Vergne ◽  
Jean-Bernard Mondier
Keyword(s):  
Thermal Model ◽  
Laboratory Data ◽  
Rolling Bearing ◽  
Operating Conditions ◽  
Model Parameters ◽  
Rolling Bearings ◽  
Traction Coefficient ◽  
Shear Heating ◽  
Rheological Experiments

Three synthetic oils used in spacecraft mechanisms (Pennzane SHF X2000, Nye 186 A, and Fomblin Z25) have been studied. Rheological tests were performed in order to characterize the behavior of each fluid versus pressure, temperature and shear rate. That includes the determination of the WLF viscosity model parameters. Tribological tests were carried out to measure the traction coefficient for operating conditions representative of spacecraft applications. Experimental results were compared with theoretical ones obtained using a non-newtonian thermal model. The modeling of traction in EHL contact is based on the Johnson and Tevaarwerk’s model modified to account for the shear heating of the fluid. The variations of the lubricant thermal conductivity with respect to temperature and pressure are also considered. In this model, input data comes directly from rheological experiments or are derived from other measurements through physical relationships. These rheological and tribological characterizations are essential to better describe the behavior of a lubricated rolling bearing.

Failure analysis of laser-textured surfaces

2000 ◽  
Vol 214 (5) ◽  
pp. 471-483 ◽  
Author(s):  
S Chilamakuri ◽  
X Zhao ◽  
B Bhushan
Keyword(s):  
Plastic Deformation ◽  
Operating Conditions ◽  
Disk Drives ◽  
Critical Number ◽  
Textured Surfaces ◽  
Tribological Behaviour ◽  
Magnetic Disk ◽  
Size And Shape ◽  
Ultrahigh Density ◽  
Theoretical Results

Friction/stiction behaviour of ultrahigh-density magnetic disk drives can be controlled by controlling the size and shape of the laser bumps. Tribological behaviour of laser-textured disk surfaces depends on the size and shape of the laser bumps, bump density and operating conditions. In this study, theoretical and experimental analyses have been carried out on nine different laser-textured disk surfaces. Stiction and friction experiments have been carried out on sombrero, V-type and W-type laser-textured disks and these results are compared with theoretical results. A good correlation is obtained between experimental and theoretical results. The effect of laser bump uniformity on critical number of bumps required to prevent plastic deformation and stiction has also been studied.

scholarly journals Energy-Dissipation Limits in Variance-Based Computing

2018 ◽  
Vol 17 (02) ◽  
pp. 1850013
Author(s):  
Sri Harsha Kondapalli ◽  
Xuan Zhang ◽  
Shantanu chakrabartty
Keyword(s):  
Energy Dissipation ◽  
Thermal Noise ◽  
Operating Conditions ◽  
Superior Performance ◽  
Energy Scavenging ◽  
Logic Device ◽  
Additional Energy ◽  
Fundamental Limits ◽  
Bit Flip ◽  
Theoretical Results

Variance-based logic (VBL) uses the fluctuations or the variance in the state of a particle or a physical quantity to represent different logic levels. In this paper, we show that compared to the traditional bi-stable logic representation, the variance-based representation can theoretically achieve a superior performance trade-off (in terms of energy dissipation and information capacity) when operating at fundamental limits imposed by thermal noise. We show that, in addition to the universal KT ln(1/[Formula: see text]) energy dissipation required for a single bit flip, a bi-stable logic device needs to dissipate at least 4.35[Formula: see text]KT/bit of energy, whereas under similar operating conditions, a VBL device reduces the additional energy dissipation requirements down to sub-KT/bit. These theoretical results are generally enough to be applicable to different instantiations and variants of VBL ranging from digital processors based on energy-scavenging or to processors based on the emerging valleytronic devices.

scholarly journals Sensitivity of Food-Based Recommendations Developed Using Linear Programming to Model Input Data in Young Kenyan Children

Nutrients ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 3485
Author(s):  
Karin J. Borgonjen-van den Berg ◽  
Jeanne H. M. de Vries ◽  
Prosper Chopera ◽  
Edith J. M. Feskens ◽  
Inge D. Brouwer
Keyword(s):  
Linear Programming ◽  
Dietary Intake ◽  
Selection Criteria ◽  
Input Data ◽  
Reference Scenario ◽  
Food Groups ◽  
Nutrient Requirement ◽  
Model Input ◽  
Alternative Scenarios ◽  
Selection Of

Food-based recommendations (FBR) developed using linear programming generally use dietary intake and energy and nutrient requirement data. It is still unknown to what extent the availability and selection of these data affect the developed FBR and identified problem nutrients. We used 24 h dietary recalls of 62 Kenyan children (4–6 years of age) to analyse the sensitivity of the FBR and problem nutrients to (1) dietary intake data, (2) selection criteria applied to these data and (3) energy and nutrient requirement data, using linear programming (Optifood©), by comparing a reference scenario with eight alternative scenarios. Replacing reported by estimated consumption frequencies increased the recommended frequencies in the FBR for most food groups while folate was no longer identified as a problem nutrient. Using the 10–90th instead of the 5–95th percentile of distribution to define minimum and maximum frequencies/week decreased the recommended frequencies in the FBR and doubled the number of problem nutrients. Other alternative scenarios negligibly affected the FBR and identified problem nutrients. Our study shows the importance of consumption frequencies for developing FBR and identifying problem nutrients by linear programming. We recommend that reported consumption frequencies and the 5–95th percentiles of distribution of reported frequencies be used to define the minimum and maximum frequencies.

scholarly journals PENGARUH KONDISI ATMOSFERIK TERHADAP PERHITUNGAN PROBABILISTIK DAMPAK RADIOLOGI KECELAKAAN PWR 1000-MWe

2015 ◽  
Vol 17 (3) ◽  
pp. 149
Author(s):  
Pande Made Udiyani ◽  
Sri Kuntjoro
Keyword(s):  
Input Data ◽  
Meteorological Data ◽  
Cumulative Frequency ◽  
Data Input ◽  
Atmospheric Conditions ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor ◽  
Model Input ◽  
Meteorological Input

ABSTRAK PENGARUH KONDISI ATMOSFERIK TERHADAP PERHITUNGAN PROBABILISTIK DAMPAK RADIOLOGI KECELAKAAN PWR 1000-MWe.  Perhitungan dampak kecelakaan radiologi terhadap lepasan produk fisi akibat kecelakaan potensial yang mungkin terjadi di Pressurized Water Reactor (PWR) diperlukan secara probabilistik. Mengingat kondisi atmosfer sangat berperan terhadap dispersi radionuklida di lingkungan, dalam penelitian ini akan dianalisis pengaruh kondisi atmosferik terhadap perhitungan probabilistik dari konsekuensi kecelakaan reaktor.  Tujuan penelitian adalah melakukan analisis terhadap pengaruh kondisi atmosfer berdasarkan model data input meteorologi terhadap dampak radiologi kecelakaan PWR 1000-MWe yang disimulasikan pada tapak yang mempunyai kondisi meteorologi yang berbeda. Simulasi menggunakan program PC-Cosyma dengan moda perhitungan probabilistik, dengan data input meteorologi yang dieksekusi secara cyclic dan stratified, dan disimulasikan di Tapak Semenanjung Muria dan Pesisir Serang. Data meteorologi diambil setiap jam untuk jangka waktu satu tahun. Hasil perhitungan menunjukkan bahwa frekuensi kumulatif  untuk model input yang sama untuk Tapak pesisir Serang lebih tinggi dibandingkan dengan Semenanjung Muria. Untuk tapak yang sama, frekuensi kumulatif model input cyclic lebih tinggi dibandingkan model stratified. Model cyclic memberikan keleluasan dalam menentukan tingkat ketelitian perhitungan dan tidak membutuhkan data acuan dibandingkan dengan model stratified. Penggunaan model cyclic dan stratified melibatkan jumlah data yang besar dan pengulangan perhitungan  akan meningkatkan  ketelitian nilai-nilai statistika perhitungan. Kata kunci: dampak kecelakaan, PWR 1000-MWe,  probabilistik,  atmosferik, PC-Cosyma   ABSTRACT THE INFLUENCE OF ATMOSPHERIC CONDITIONS TO PROBABILISTIC CALCULATION OF IMPACT OF RADIOLOGY ACCIDENT ON PWR-1000MWe. The calculation of the radiological impact of the fission products releases due to potential accidents that may occur in the PWR (Pressurized Water Reactor) is required in a  probabilistic. The atmospheric conditions greatly contribute to the dispersion of radionuclides in the environment, so that in this study will be analyzed the influence of atmospheric conditions on probabilistic calculation of the reactor accidents consequences. The objective of this study is to conduct an analysis of the influence of atmospheric conditions based on meteorological input data models on the radiological consequences of PWR-1000MWe accidents. Simulations using PC-Cosyma code with probabilistic calculations mode, the meteorological data input executed cyclic and stratified, the meteorological input data are executed in the cyclic and stratified, and simulated in Muria Peninsula and Serang Coastal. Meteorological data were taken every hour for the duration of the year. The result showed that the cumulative frequency for the same input models for Serang coastal is higher than the Muria Peninsula. For the same site, cumulative frequency on cyclic input models is higher than stratified models. The cyclic models provide flexibility in determining the level of accuracy of calculations and do not require reference data compared to stratified models. The use of cyclic and stratified models involving large amounts of data and calculation repetition will improve the accuracy of statistical calculation values. Keywords: accident impact, PWR 1000 MWe, probabilistic, atmospheric, PC-Cosyma

Traction in EHL Line Contacts Using Free-Volume Pressure-Viscosity Relationship With Thermal and Shear-Thinning Effects

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Punit Kumar ◽  
M. M. Khonsari
Keyword(s):  
Free Volume ◽  
Elastohydrodynamic Lubrication ◽  
Approximate Equation ◽  
Shear Thinning ◽  
Operating Conditions ◽  
Limiting Shear Stress ◽  
Line Contacts ◽  
Traction Coefficient ◽  
Simulation Results ◽  
Volume Equation

This paper investigates the traction behavior in heavily loaded thermo-elastohydrodynamic lubrication (EHL) line contacts using the Doolittle free-volume equation, which closely represents the experimental viscosity-pressure-temperature relationship and has recently gained attention in the field of EHL, along with Tait’s equation of state for compressibility. The well-established Carreau viscosity model has been used to describe the simple shear-thinning encountered in EHL. The simulation results have been used to develop an approximate equation for traction coefficient as a function of operating conditions and material properties. This equation successfully captures the decreasing trend with increasing slide to roll ratio caused by the thermal effect. The traction-slip characteristics are expected to be influenced by the limiting shear stress and pressure dependence of lubricant thermal conductivity, which need to be incorporated in the future.

Rolling bearing defect severity assessment under varying operating conditions

2009 ◽  
Vol 4 (1) ◽  
pp. 37
Author(s):  
Changting Wang ◽  
Robert X. Gao ◽  
Ruqiang Yan ◽  
Arnaz Malhi
Keyword(s):  
Rolling Bearing ◽  
Operating Conditions ◽  
Severity Assessment ◽  
Bearing Defect

scholarly journals Turbulence generation from a stochastic wavelet model

2018 ◽  
Vol 474 (2217) ◽  
pp. 20180093
Author(s):  
Y. Du ◽  
G. Lin
Keyword(s):  
Input Data ◽  
Computation Cost ◽  
Fourier Methods ◽  
Numerical Examples ◽  
Scale Reduction ◽  
Inhomogeneous Turbulence ◽  
Comparable Accuracy ◽  
Turbulence Generation ◽  
Theoretical Results ◽  
Good Agreement

This research presents a new turbulence generation method based on stochastic wavelets and tests various properties of the generated turbulence field in both the homogeneous and inhomogeneous cases. Numerical results indicate that turbulence fields can be generated with much smaller bases in comparison to synthetic Fourier methods while maintaining comparable accuracy. Adaptive generation of inhomogeneous turbulence is achieved by a scale reduction algorithm, which greatly reduces the computation cost and practically introduces no error. The generating formula issued in this research could be adjusted to generate fully inhomogeneous and anisotropic turbulence with given RANS data under divergence-free constraint, which was not achieved previously in similar research. Numerical examples shows that the generated homogeneous and inhomogeneous turbulence are in good agreement with the input data and theoretical results.

scholarly journals A comparison of the discrete cosine and wavelet transforms for hydrologic model input data reduction

2017 ◽  
Vol 21 (7) ◽  
pp. 3827-3838 ◽  
Author(s):  
Ashley Wright ◽  
Jeffrey P. Walker ◽  
David E. Robertson ◽  
Valentijn R. N. Pauwels
Keyword(s):  
Parameter Estimation ◽  
Data Reduction ◽  
Wavelet Transforms ◽  
Input Data ◽  
Hydrologic Model ◽  
Data Uncertainty ◽  
Discrete Wavelet ◽  
Rainfall Time Series ◽  
Data Set ◽  
Model Input

Abstract. The treatment of input data uncertainty in hydrologic models is of crucial importance in the analysis, diagnosis and detection of model structural errors. Data reduction techniques decrease the dimensionality of input data, thus allowing modern parameter estimation algorithms to more efficiently estimate errors associated with input uncertainty and model structure. The discrete cosine transform (DCT) and discrete wavelet transform (DWT) are used to reduce the dimensionality of observed rainfall time series for the 438 catchments in the Model Parameter Estimation Experiment (MOPEX) data set. The rainfall time signals are then reconstructed and compared to the observed hyetographs using standard simulation performance summary metrics and descriptive statistics. The results convincingly demonstrate that the DWT is superior to the DCT in preserving and characterizing the observed rainfall data records. It is recommended that the DWT be used for model input data reduction in hydrology in preference over the DCT.

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