scholarly journals Substantiation of informative amplitudes during registration of acoustic emission signals from the friction zone of tribosystems

2021 ◽  
Vol 99 (1) ◽  
pp. 6-12
Author(s):  
V. Vojtov ◽  
K. Fenenko ◽  
A. Voitov ◽  
Keyword(s):  
Acoustic Emission ◽  
Steady State ◽  
Linear Relationship ◽  
Diagnostic Technique ◽  
Autocorrelation Coefficient ◽  
Recording Time ◽  
Friction Zone ◽  
Steady State Operation ◽  
Base Cluster ◽  
The Impact

In this work, the dependence of the change in the probability density of the distribution of the number of pulses and amplitudes of acoustic emission (AE) signals from the friction zone at the steady-state operation of the tribosystem is obtained. Acoustic vibrations that the tribosystem generates during operation are due to the impact interaction of the roughness of the friction surfaces of their elastoplastic deformation, processes of formation and destruction of frictional links, structural and phase rearrangement of materials, the formation and development of microcracks in the surface layers of contacting bodies, separation of wear particles. The dependence allows you to determine a sufficient number of pulses in the signal frame and their amplitude values for diagnosing tribosystems during their operation. The values of the informative amplitudes of the clusters are experimentally substantiated К2, К3, К4 in relation to the base cluster К1. It is shown that an increase in the informative frequency fAE(fix) from 250 to 500 kHz, increases the value of the informative amplitude to 17,6…43,75%. Based on the results obtained, it was concluded that this fact must be taken into account when developing methods, which will increase the accuracy of diagnosing tribosystems. The autocorrelation coefficient characterizes the closeness of the linear relationship of the current and previous frames of the series for each of the analyzed clusters. By the value of the autocorrelation coefficient, one can judge the presence of a linear relationship between the values of the recorded amplitudes, their reproducibility in terms of recording time in the steady-state operation of the tribosystem. To confirm the sufficiency of the selected number of pulses in the clusters of the AE signal frame, as well as the reproducibility of the results of the analysis of frames when they shift in time of registration, an expression is obtained for calculating the autocorrelation function, which reflects the relationship between successive levels of the time series. Based on the results of the experimental data, the values of the autocorrelation coefficients were calculated, equal to 0,82…0,92, which indicates the robustness of the chosen diagnostic technique.

The Experimental Consideration for TBM Mock-Up Effect on Plasma Performance Based on MAPES Platform in EAST

2013 ◽  
Author(s):  
Songlin Liu ◽  
Fang Ding ◽  
Xiangcun Chen ◽  
Yong Pu ◽  
Jia Li ◽  
...  
Keyword(s):  
Steady State ◽  
Plasma Physics ◽  
Evaluation System ◽  
High Performance ◽  
Martensitic Steels ◽  
Steady State Operation ◽  
Magnetic Analysis ◽  
Rafm Steel ◽  
The Impact

EAST can provide better opportunities to contribute development of ITER-relevant plasma physics and engineering because it has ITER-like configuration, and has achieved 10s H-mode plasma, and aims steady-state operation of DD high performance plasma. The impact of Test blanket module (TBM) using RAFM (reduced activation ferritic/martensitic) steels on tokomak plasma is a major concern in ITER operations. In order to assess this effect due to TBM local ripple, an experiment plan of TBM mockup using RAFM steel is being planned on MAPES (Material and Plasma Evaluation System) in EAST. This paper reports experimental consideration on MAPES based on magnetic analysis and ripple calculation at separatrix point. The relevant experiments strategy and plan in EAST are also proposed.

Research on the Capability in Absorbing Electric Vehicles in Beijing Grid

2013 ◽  
Vol 448-453 ◽  
pp. 3189-3193
Author(s):  
Bi Bin Huang
Keyword(s):  
Steady State ◽  
Electric Vehicle ◽  
Electric Vehicles ◽  
Distribution Network ◽  
Steady State Operation ◽  
Load Rate ◽  
Voltage Deviation ◽  
Typical Distribution ◽  
Load Characteristics ◽  
The Impact

This paper analyzes the load characteristics of electric vehicle under different charging modes including disordered charging, peak shifting charging and continuous charging. Taking a typical distribution network in Beijing as the research object, the calculation of steady state operation is carried out under the three kinds of charging modes after the integration of electric vehicles at different scales. The voltage deviation and load rate are analyzed to reveal the impact of charging modes on the capability in absorbing electric vehicles in Beijing grid.

scholarly journals Advanced Constitutive Modeling of the Thixotropic Elasto-Visco-Plastic Behavior of Blood: Steady-State Blood Flow in Microtubes

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 367
Author(s):  
Konstantinos Giannokostas ◽  
Yannis Dimakopoulos ◽  
Andreas Anayiotos ◽  
John Tsamopoulos
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Constitutive Model ◽  
Blood Plasma ◽  
Constitutive Modeling ◽  
Flow Direction ◽  
Momentum Balance ◽  
Plastic Behavior ◽  
Flow Investigation ◽  
The Impact

The present work focuses on the in-silico investigation of the steady-state blood flow in straight microtubes, incorporating advanced constitutive modeling for human blood and blood plasma. The blood constitutive model accounts for the interplay between thixotropy and elasto-visco-plasticity via a scalar variable that describes the level of the local blood structure at any instance. The constitutive model is enhanced by the non-Newtonian modeling of the plasma phase, which features bulk viscoelasticity. Incorporating microcirculation phenomena such as the cell-free layer (CFL) formation or the Fåhraeus and the Fåhraeus-Lindqvist effects is an indispensable part of the blood flow investigation. The coupling between them and the momentum balance is achieved through correlations based on experimental observations. Notably, we propose a new simplified form for the dependence of the apparent viscosity on the hematocrit that predicts the CFL thickness correctly. Our investigation focuses on the impact of the microtube diameter and the pressure-gradient on velocity profiles, normal and shear viscoelastic stresses, and thixotropic properties. We demonstrate the microstructural configuration of blood in steady-state conditions, revealing that blood is highly aggregated in narrow tubes, promoting a flat velocity profile. Additionally, the proper accounting of the CFL thickness shows that for narrow microtubes, the reduction of discharged hematocrit is significant, which in some cases is up to 70%. At high pressure-gradients, the plasmatic proteins in both regions are extended in the flow direction, developing large axial normal stresses, which are more significant in the core region. We also provide normal stress predictions at both the blood/plasma interface (INS) and the tube wall (WNS), which are difficult to measure experimentally. Both decrease with the tube radius; however, they exhibit significant differences in magnitude and type of variation. INS varies linearly from 4.5 to 2 Pa, while WNS exhibits an exponential decrease taking values from 50 mPa to zero.

scholarly journals Monitoring of the Impact of Lithium Nitrate on the Alkali–aggregate Reaction Using Acoustic Emission Methods

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 20
Author(s):  
Justyna Zapała-Sławeta ◽  
Grzegorz Świt
Keyword(s):  
Acoustic Emission ◽  
Initial Reaction ◽  
Lithium Nitrate ◽  
Acoustic Emission Method ◽  
Emission Method ◽  
Acoustic Activity ◽  
Initial Stage ◽  
Chemical Admixture ◽  
Different Characteristics ◽  
The Impact

The study analyzed the possibility of using the acoustic emission method to analyse the reaction of alkali with aggregate in the presence of lithium nitrate. Lithium nitrate is a chemical admixture used to reduce adverse effects of corrosion. The tests were carried out using mortars with reactive opal aggregate, stored under the conditions defined by ASTM C227. The acoustic activity of mortars with a corrosion inhibitor was referred to linear changes and microstructure of specimens in the initial reaction stages. The study found a low acoustic activity of mortars with lithium nitrate. Analysis of characteristic parameters of acoustic emission signals, combined with the observation of changes in the microstructure, made it possible to describe the corrosion processes. As the reaction progressed, signals with different characteristics were recorded, indicating aggregate cracking at the initial stage of the reaction, followed by cracking of the cement paste. The results, which were referred to the acoustic activity of reference mortars, confirmed that the reaction of opal aggregate with alkali was mitigated in mortars with lithium nitrate, and the applied acoustic emission method enabled the detection and monitoring of ASR progress.

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