scholarly journals A Unified Treatment of Tribo-Components Degradation Using Thermodynamics Framework: A Review on Adhesive Wear

Entropy ◽  
2021 ◽  
Vol 23 (10) ◽  
pp. 1329
Author(s):  
Lijesh Koottaparambil ◽  
M. M. Khonsari
Keyword(s):  
Adhesive Wear ◽  
Operating Conditions ◽  
Variable Loading ◽  
Extensive Survey ◽  
Thermodynamic Framework ◽  
Adhesive Type

An extensive survey of open literature reveals the need for a unifying approach for characterizing the degradation of tribo-pairs. This paper focuses on recent efforts made towards developing unified relationships for adhesive-type wear under unlubricated conditions through a thermodynamic framework. It is shown that this framework can properly characterize many complex scenarios, such as degradation problems involving unidirectional, bidirectional (oscillatory and reciprocating motions), transient operating conditions (e.g., during the running-in period), and variable loading/speed sequencing.

A First Investigation on Cumulative Fatigue Life for a Type 304-L Stainless Steel Used for Pressure Water Reactor

2009 ◽  
Author(s):  
A. Fissolo ◽  
J. M. Stelmaszyk
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Fatigue Tests ◽  
Operating Conditions ◽  
Damage Effect ◽  
Final Conclusion ◽  
Variable Loading ◽  
Miner’S Rule ◽  
Miner's Rule ◽  
Type 304

In order to estimate the crack initiation damage, and also the water leakage conditions on PWR pipes, uniaxial fatigue curves are often used. They were deduced from strain or stress load control tests using normalised cylindrical specimens. However, severe thermo-mechanical loading fluctuations are observed in operating conditions. Components may also be submitted to transient loadings. The purpose of the present work is to start investigation on the fatigue life with a variable loading, in order to examine cumulative damage effect in fatigue. In this frame, multilevel strain controlled fatigue tests have been performed on a Type 304-L stainless steel (elaborated in accordance with the RCC-M specifications). The experimental results show that linear Miner’s rule is not verified in our conditions. When the strains are applied in a decreasing order (High-Low strain sequence), the summation of cycle ratios is smaller than unity, whatever the number of applied levels, whereas this summation is higher than one for an increasing order (Low-High strain sequence). A loading sequence effect is clearly evidenced. Different cumulative fatigue damage theories, proposed in literature, have been also tested. Some of them have been given better estimation than the Miner’s rule. That is the case of the so-called “Hybrid Theory” proposed and tested before by Bui Quoc on a Type 304-L steel. Extension of a model proposed by S. Taheri would seem also promising. At this stage, final conclusion cannot be yet deduced, additional investigations are needed.

scholarly journals Adaptive Scheme for Detecting Induction Motor Incipient Broken Bar Faults at Various Load and Inertia Conditions

Sensors ◽  
2022 ◽  
Vol 22 (1) ◽  
pp. 365
Author(s):  
Mohamed Esam El-Dine Atta ◽  
Doaa Khalil Ibrahim ◽  
Mahmoud Gilany ◽  
Ahmed F. Zobaa
Keyword(s):  
Main Idea ◽  
Threshold Value ◽  
Operating Conditions ◽  
Noisy Environment ◽  
Noisy Environments ◽  
Variable Loading ◽  
Protection Scheme ◽  
Stator Current ◽  
Fault Severity ◽  
Frequency Components

This paper introduces a novel online adaptive protection scheme to detect and diagnose broken bar faults (BBFs) in induction motors during steady-state conditions based on an analytical approach. The proposed scheme can detect precisely adjacent and non-adjacent BBFs in their incipient phases under different inertia, variable loading conditions, and noisy environments. The main idea of the proposed scheme is monitoring the variation in the phase angle of the main sideband frequency components by applying Fast Fourier Transform to only one phase of the stator current. The scheme does not need any predetermined settings but only one of the stator current signals during the commissioning phase. The threshold value is calculated adaptively to discriminate between healthy and faulty cases. Besides, an index is proposed to designate the fault severity. The performance of this scheme is verified using two simulated motors with different designs by applying the finite element method in addition to a real experimental dataset. The results show that the proposed scheme can effectively detect half, one, two, or three broken bars in adjacent/non-adjacent versions and also estimate their severity under different operating conditions and in a noisy environment, with accuracy reaching 100% independently from motor parameters.

Subsurface-flow constructed wetlands treatment in the plains: five years of experience

2001 ◽  
Vol 44 (11-12) ◽  
pp. 375-380 ◽  
Author(s):  
M.F. Dahab ◽  
R.Y. Surampalli
Keyword(s):  
Constructed Wetlands ◽  
Fecal Coliform ◽  
Subsurface Flow ◽  
Operating Conditions ◽  
Cod Removal ◽  
Variable Loading ◽  
Nitrogen And Phosphorus ◽  
Removal Rates ◽  
Sand Filter ◽  
Subsurface Flow Constructed Wetlands

This paper documents the performance of a subsurface-flow constructed wetlands system during its initial five years of operation under variable loading and operating conditions associated with a northern midwestern US climate. The results indicate that effective and sufficient CW seasonal removals of TSS, VSS, CBOD5, COD, and fecal coliform were achieved. Wastewater temperatures seemed to affect CBOD5 and COD removal rates. Nitrogen and phosphorus reductions were not as effective and varied seasonally, as well as with wastewater temperature. The addition of a sand filter, to aid in further nitrification and disinfection following CW treatment, markedly improved the performance of the wetlands system. After a few years of operation, the remarkable performance of the CW system was dampened by apparent clogging and subsequent eruption of wastewater at the head-end of the treatment cells. While clogging was partially caused by biomass build-up in the wetlands substrate, visual observations suggest that excessive vegetation coupled with relaxed maintenance may also be responsible for clogging.

Modeling and Simulation of a Four-Rotor Rake Loading for Predicting Accumulated Fatigue Damage: A Markov Regime-Switching Approach

2018 ◽  
Vol 34 (2) ◽  
pp. 317-325 ◽  
Author(s):  
Dimitris S. Paraforos ◽  
Hans W. Griepentrog ◽  
Stavros G. Vougioukas
Keyword(s):  
Fatigue Life ◽  
Standard Deviation ◽  
Fatigue Damage ◽  
Regime Switching ◽  
Markov Models ◽  
Transition Probabilities ◽  
High Amplitude ◽  
Operating Conditions ◽  
Training Dataset ◽  
Variable Loading

Abstract. The prediction of agricultural machinery’s fatigue life is of increasing importance for machine developers who must produce durable and reliable machines for a globalized market with different local operating conditions. Mathematical tools that can model and simulate the variable loading of agricultural machines are necessary for fatigue life prediction. Modeling should be based on measured loads from real-world operations. In this article, the loads of a four-rotor rake were recorded during grass swathing. Markov chains were used to model the transitions between the machine’s operating conditions (in-field swathing and headland turning) and the sequences of turning points present in the load signals. The Markov transition probabilities were trained using the recoded data and then fatigue life was predicted via executing 10,000 Monte Carlo simulations based on the trained Markov models. The differences between the accumulated fatigue damage predicted from the simulations and from the measured data had mean value and standard deviation equal to -22% and 12.8%, respectively. Evaluation of the trained model on new data (not present in the training dataset) that were recorded during swathing on a different grass field resulted in fatigue damage difference with mean and standard deviation equal to 34% and 7.5%, respectively. The fatigue damage difference was in a reasonable region considering how fatigue life is affected by high-amplitude individual cycles. Keywords: Accumulated damage, Agricultural machinery, Durability, Fatigue life.

On the assessment of variable loading in adhesive wear

2019 ◽  
Vol 129 ◽  
pp. 167-176 ◽  
Author(s):  
Hossein Fereidouni ◽  
Saleh Akbarzadeh ◽  
M.M. Khonsari
Keyword(s):  
Adhesive Wear ◽  
Variable Loading

scholarly journals Effects of Microstructure Evolution on Fretting Wear Behaviors of 25CrNi2MoVE Steel under Different Tempering States

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 351
Author(s):  
Xiongfeng Hu ◽  
Fuqiang Lai ◽  
Shengguan Qu ◽  
Yalong Zhang ◽  
Haipeng Liu ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Wear Resistance ◽  
Wear Rate ◽  
Wear Mechanisms ◽  
Adhesive Wear ◽  
Operating Conditions ◽  
Fretting Wear ◽  
Fatigue Wear ◽  
Tempering Temperature ◽  
Worn Surface

Increasing load requirements and harsh operating conditions have worsened the wear of drive shafts in special field vehicles. In this paper, the evolution of the microstructure and fretting wear behaviors of 25CrNi2MoVE torsion shaft steel and their influence on the wear mechanisms were investigated as a function of tempering temperature. The results showed that the coarse grain size, low matrix hardness and non-metallic inclusions in the as-received state lead to a high wear rate and serious adhesive wear. The grain refinement after normalizing and the formed M5C2 carbide and bainite helped to improve the wear resistance and worn surface quality. Low temperature tempering is conducive to further improve the wear resistance of normalized samples, and the wear rate and worn surface roughness are increased gradually after tempering temperature increases. For quenching, although martensite structure can achieve a lower wear rate, the coefficient of friction is much higher; the wear mechanisms are primarily fatigue wear and adhesive wear. Although the adhesive wear degree and worn surface roughness were increased, the optimal anti-wear performances are obtained under tempering at 350 °C with good continuity of the surface oxide film. Excessive tempering temperature will make the softened matrix unable to form a beneficial “third-body wear”.

Effects of High Initial Engine Start Up Speeds in Isothermal Fluid Flow and Piston Skirts EHL

2011 ◽  
Author(s):  
Syed Adnan Qasim ◽  
M. Afzaal Malik
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Adhesive Wear ◽  
Cooling System ◽  
Cylinder Liner ◽  
Operating Conditions ◽  
Solution Technique ◽  
Start Up ◽  
Piston Skirts ◽  
Engine Start

In the medium and high speed normal engine operating conditions a fully established elastohydrodynamic lubricating (EHL) film between the piston skirts and cylinder liner surfaces reduces friction and prevents adhesive wear. In the initial engine start up the absence of EHL film causes wear of piston skirts, especially at high speeds. In a few initial cold engine start up cycles, a highly efficient cooling system may not let the temperature to rise significantly and affect the viscosity and other characteristics of a lubricant. In view of the vulnerability of piston skirts to adhesive wear at high initial engine start up speeds, the hydrodynamic and EHL of piston skirts is modeled numerically. A 2-D Reynolds equation is solved by coupling the secondary piston motion and using a finite difference scheme. Transient hydrodynamic film thickness profiles are generated at a relatively high engine start up speed. In the EHL regime, the profiles of rising hydrodynamic pressures and film thicknesses are predicted by using the inverse solution technique in fully flooded conditions. The study is extended to a range of high engine start up speeds while using a fairly viscous engine lubricant. Numerical simulations show significant changes in the piston eccentricities and film thickness profiles in the hydrodynamic and EHL regimes at different start up speeds. Such variations alter the hydrodynamic and EHL pressures and visibly affect the load carrying capacity of the lubricant. This study suggests to optimize the high engine start up speed for the given viscosity grade engine lubricant when considering the vulnerability of skirts and liner surfaces to adhesive wear in the initial engine start up.

Cathodoluminescence of Catalyst Crystallites

1982 ◽  
Vol 40 ◽  
pp. 664-665
Author(s):  
E.D. Boyes ◽  
P.L. Gai ◽  
D.B. Darby ◽  
C. Warwick
Keyword(s):  
Defect Density ◽  
Chemical Properties ◽  
Operating Conditions ◽  
Semiconductor Materials ◽  
Environmental Cell ◽  
High Resolution Structure ◽  
Commercially Important ◽  
Crystallographic Defects ◽  
Resolution Structure

The extended crystallographic defects introduced into some oxide catalysts under operating conditions may be a consequence and accommodation of the changes produced by the catalytic activity, rather than always being the origin of the reactivity. Operation without such defects has been established for the commercially important tellurium molybdate system. in addition it is clear that the point defect density and the electronic structure can both have a significant influence on the chemical properties and hence on the effectiveness (activity and selectivity) of the material as a catalyst. SEM/probe techniques more commonly applied to semiconductor materials, have been investigated to supplement the information obtained from in-situ environmental cell HVEM, ultra-high resolution structure imaging and more conventional AEM and EPMA chemical microanalysis.

Comparison of Deterministic and Linear Cosine Spatial Filtering of Transmission Electron Micrographs

1972 ◽  
Vol 30 ◽  
pp. 596-597
Author(s):  
David A. Ansley
Keyword(s):  
Spherical Aberration ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Spatial Filter ◽  
Operating Conditions ◽  
Objective Lens ◽  
List Type ◽  
Spatial Filters ◽  
Transmission Electron ◽  
Wide Range

The coherence of the electron flux of a transmission electron microscope (TEM) limits the direct application of deconvolution techniques which have been used successfully on unmanned spacecraft programs. The theory assumes noncoherent illumination. Deconvolution of a TEM micrograph will, therefore, in general produce spurious detail rather than improved resolution.A primary goal of our research is to study the performance of several types of linear spatial filters as a function of specimen contrast, phase, and coherence. We have, therefore, developed a one-dimensional analysis and plotting program to simulate a wide 'range of operating conditions of the TEM, including adjustment of the:(1) Specimen amplitude, phase, and separation(2) Illumination wavelength, half-angle, and tilt(3) Objective lens focal length and aperture width(4) Spherical aberration, defocus, and chromatic aberration focus shift(5) Detector gamma, additive, and multiplicative noise constants(6) Type of spatial filter: linear cosine, linear sine, or deterministic

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