Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Changes to operating properties.
Articles de revues sur le sujet « Changes to operating properties »
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 50 meilleurs articles de revues pour votre recherche sur le sujet « Changes to operating properties ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les articles de revues sur diverses disciplines et organisez correctement votre bibliographie.
1
Desbarats, Robert P., et Donald G. MacDiarmid. « Independent Operations : Article X of the CAPL Operating Procedure ». Alberta Law Review 34, no 3 (1 mai 1996) : 602. http://dx.doi.org/10.29173/alr658.
Texte intégralRésumé :
This article discusses independent oil and gas operations on jointly held properties, and in particular considers the application of Article X of the Operating Procedures of the Canadian Association of Petroleum Landmen. It explores the rights and obligations of both the party proposing the independent operation and the non-participating party. Recent judicial consideration of some aspects of the operating procedures is discussed. The article suggests some specific changes parties may wish to incorporate when adapting the operating procedure to their circumstances.
2
Chen, Chuan Min, Jing Zhang, Li Na Zhu et Song Tao Liu. « Research on the Changes of Physico-Chemical Properties of Lead-Acid Batteries ». Applied Mechanics and Materials 768 (juin 2015) : 197–203. http://dx.doi.org/10.4028/www.scientific.net/amm.768.197.
Texte intégralRésumé :
Lead-acid batteries were widely used in many industries as important power supply devices for military and civil industries, transport and shipment devices owing to its advantages of low cost,high performance and safety. According to statistics, most lead-acid batteries can reach 1-2 years life under operating conditions, generating millions of used lead-acid batteries each year in China, which caused economic and environmental losses if not properly treated. The changes of physico-chemical properties in the process of operation of lead-acid battery were summarized in this paper. The corrosion and deformation of grids, water loss in electrolyte, aging of separators, corrosion of plates and irreversible sulfation were the main physico-chemical properties changes resulting in battery failure. In the homogeneous acidic medium, the grid of the lead-acid battery corroded away, one side was dotted distribution, and the other side was interlaced net shape. The corrosion of grids and incomplete reaction may lead to the water loss in electrolyte. What’s more, there existed a series of chemical reactions that reducing the battery capacity and leading to the failure of batteries, such as the aging and elastic collision of separators and irreversible sulfation. By analyzing the physico-chemical properties changes in the process of operation, the study supplied the direction for the specification of operating conditions and the extending of service life of lead-acid battery. The basic theories were provided for the repair, regeneration and recovery of lead-acid batteries.
3
Packa, Juraj, Vladimir Kujan, Daniel Štrkula, Vladimír Šály et Milan Perný. « Changes of Insulation Properties of Photovoltaic Cables Caused by Ageing Treatment ». TRANSACTIONS ON ELECTRICAL ENGINEERING 6, no 1 (30 mars 2020) : 6–9. http://dx.doi.org/10.14311/tee.2017.1.006.
Texte intégralRésumé :
<span style="font-family: 'Times New Roman',serif; font-size: 10pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;" lang="EN-US">An important part of the photovoltaic power plants are cable systems. The dielectric properties of cables, reliability and durability depend on quality of production processes, operating conditions and degradation factors, as well. Expected lifetime of cable systems is more than 20-30 years in general. Their failure free operation and long-term stability of properties has a direct impact on the economic return of the investments. According to our experiences the tests in compliance with valid standards are not adequate to verify real life time during operation. Photovoltaic cables intended for use in outdoor applications for the connection between the solar panels and possible connection between panels and inverter were chosen for our experiments. <span style="-ms-layout-grid-mode: line;">The changes </span>of insulation resistance and breakdown voltage caused by some degradation factors, mainly water, are presented. This research was inspired by real failure in operation.</span>
4
Nallareddy, Suresh, Mani Sethuraman et Mohan Venkatachalam. « Changes in accrual properties and operating environment : Implications for cash flow predictability ». Journal of Accounting and Economics 69, no 2-3 (avril 2020) : 101313. http://dx.doi.org/10.1016/j.jacceco.2020.101313.
Texte intégral
5
Frankel, Richard M., et Yan Sun. « Predicting Accruals Based on Cash-Flow Properties ». Accounting Review 93, no 5 (1 janvier 2018) : 165–86. http://dx.doi.org/10.2308/accr-52001.
Texte intégralRésumé :
ABSTRACT Our goal is to understand the extent to which cash-flow properties explain accruals. Using the Dechow, Kothari, and Watts (1998) model, we derive a negative relation between accruals and cash-flow changes, and show that the strength of the relation is linked to negative serial correlation in cash-flow changes. Dechow et al. (1998) also suggest that the strength of the relation between accruals and revenue changes relates to operating cycle length. Prior accrual models have not incorporated these theoretical relations. We show that incorporating cash-flow changes, serial correlation in cash-flow changes, and operating cycle length increases explanatory power of all accrual models considered (i.e., Jones 1991; Ball and Shivakumar 2006; McNichols 2002; Jeter and Shivakumar 1999). We find that incorporating these variables in accrual models also improves specification and power, aids detection of earnings management in AAER firms, and produces a nondiscretionary accrual estimate that better predicts future cash flows and earnings. These results suggest the importance of considering the economic role of accruals when predicting accruals.
6
Merkisz, Jerzy, Jarosław Markowski, Jarosław Kaluzny et Robert Roszak. « The Numerical Analysis of Influence of Crankshaft Main Spindles Regeneration in Marine Engine on Stiffness and Eigenfrequency of the Crankshaft ». Solid State Phenomena 236 (juillet 2015) : 85–92. http://dx.doi.org/10.4028/www.scientific.net/ssp.236.85.
Texte intégralRésumé :
Engine operating conditions of the main propulsion, static in principle with steady-state rotation speed of the crankshaft and engine load, also work under dynamic load conditions. These conditions cause additional distortion of the crankshaft and changes in the operating conditions of the shaft bearings. However, the greatest impact on the long and trouble-free operation has proper engine maintenance. Variable operating conditions and engine operating errors, unfortunately, often cause damage to the main bearings of the crankshaft. Repair of the damaged main bearing spindles of the shaft involves performing the machining of the spindle surface then its re-hardening and selecting new bearing bushings with the appropriate bearing clearance. Trusting the engine manufacturer, there is no check of the influence of the machining of bearing spindles on the structural properties of the shaft. Therefore, the paper presents the model tests of the structure of medium-rev marine engine crankshaft aimed at determining the changes in the mechanical properties of the structure resulting from carrying out the regeneration of the main shaft spindles.
7
Hujo, Lubomir, Jozef Nosian, Marcin Zastempowski, Jan Kosiba, Jerzy Kaszkowiak et Matej Michalides. « Laboratory tests of the hydraulic pump operating load with monitoring of changes in the physical properties ». Measurement and Control 54, no 3-4 (2 février 2021) : 243–51. http://dx.doi.org/10.1177/0020294020983385.
Texte intégralRésumé :
The present article deals with the physical properties monitoring of the transmission-hydraulic fluid, and changes of those properties due the operating load of the hydraulic pump in laboratory conditions. Tests of the transmission-hydraulic fluid were performed in laboratory conditions with the simulation of the operating load, so as to simulate the real conditions under which hydraulic circuit of the agricultural tractors operates. The universal transmission-hydraulic fluid was subjected to analysis, where the samples of the fluid were taken sequentially according to the chosen methodology at intervals of 250 and 500 h. The results of the present article include the evaluation of the physical properties of the fluid and the flow efficiency change of the hydraulic pump after 250 and 500 h of operation, while simulating the operation load. Based on a laboratory test, we found that after working for 500 h, the dynamic viscosity of the examined hydraulic fluid at 40°C decreased by 2.92 mPa.s and at 100°C decreased by 0.64 mPa.s. When determining the kinematic viscosity of the hydraulic fluid after working for 500 h, we recorded its decrease, namely, at a temperature of 40°C by a value of 3.37 mm2/s and at a temperature of 100°C, its value decreased by 0.77 mm2/s. In the analysis of the test oil samples, we found that the level of water contamination of the hydraulic fluid decreases with increasing number of hours worked. Specifically, the water concentration in the hydraulic fluid decreased by 0.031%. At the same time, we recorded a slight decrease in the flow efficiency of the hydraulic pump, specifically by a value of 0.03% after 500 h worked. After working 500 h, we found that the range of abrasion particles in the transmission-hydraulic fluid is within the prescribed range, which is determined by the standard D6595-00.
8
WOLAK, Artur, Grzegorz ZAJĄC et Magdalena ŻÓŁTY. « Changes of properties of engine oils diluted with diesel oil under real operating conditions ». Combustion Engines 173, no 2 (1 mai 2018) : 34–40. http://dx.doi.org/10.19206/ce-2018-206.
Texte intégralRésumé :
The aim of the article was to analyze changes in the trends of selected physical, chemical and functional properties of lubricating engine oil operating in a diesel-engine vehicle equipped with DPF. The vehicle was operated mainly in urban driving conditions (app. 70%), which impeded the DPF regeneration cycle and caused dilution of oil with unburned fuel. Changes in the following physical and chemical properties were assessed: the DF level in engine oil, viscosity (kinematic, dynamic HTHS and structural CCS), total base num-ber, acid number as well as the degree of oxidation, nitration and sulphonation. The tests have shown that the amount of unburned fuel that goes to the engine crankcase due to the unfinished DPF regeneration cycle is as high as 26.0–34.6%. Dilution of the lubricating oil with fuel leads to a significant reduction of its viscosity – about 30% of the fuel content causes a decrease in the kinematic viscosity measured at 100°C to the level of 7.7 mm2/s. There was also a significant decrease in total base number (TBN) < 2 mg KOH/g, and an increase in the total acid number (TAN). Moreover, the results obtained were analyzed for potential effects that could have been caused during prolonged engine operation by assessing the content of trace elements in the samples taken.
9
Смоленцев, В., V. Smolentsev, Сергей Сафонов et Sergey Safonov. « Methods and technologies for surface layer modification in metal products ». Science intensive technologies in mechanical engineering 2, no 2 (28 février 2017) : 24–30. http://dx.doi.org/10.12737/24548.
Texte intégralRésumé :
In the work it is shown that the design of combined technological processes ensuring the maximum possible operating characteristics of products assessed in a criterion way is possible. The science-based methods of choice and use of technologies created earlier, methods for the development of promising coating types, means for the modification of a surface layer and thickness changes of coatings with operating characteristics required are shown. The possibilities are considered for the creation of new methods realizing operating indices the fulfillment of which is impossible at common technologies. The well-known researches have shown that at the operation of science intensive products the mechanical characteristics including fatigue material resistance depend to a great extent upon a state and properties of a surface layer that is why there is offered a substantiated choice and design of technological processes for manufacturing products with properties corresponding most completely to operation conditions.
10
Rusin, Andrzej, Adam Wojaczek et Martyna Tomala. « Analysis and management of operating risk created by turbine operation under flexible regimes ». E3S Web of Conferences 137 (2019) : 01026. http://dx.doi.org/10.1051/e3sconf/201913701026.
Texte intégralRésumé :
The new conditions in which coal-fired power plants, especially 200 MW units, have to operate require a considerable increase in the dynamics of their operation. The power unit start-up frequency increases and so does the frequency of changes in loads. This intensifies some wear processes, such as low- cycle fatigue and crack propagation in particular. Therefore, further operation of power units which have already been in service for a long time has to be supplemented with results of analyses and tests taking account of the intensification of wear processes. The paper presents a proposal for an extension of standard diagnostic testing of turbines by adding small punch tests (SPT) of the rotor material micro specimens. The SPT method enables a fast quasi non-destructive assessment of changes in mechanical properties, especially rotor steel embrittlement due to the turbine previous operation. The other element of the proposed testing is the analysis of the propagation rate of potential cracks in the rotor and assessment of the rotor failure probability for different scenarios of the power unit further operation.
11
Szczęch, Marcin, et Wojciech Horak. « RESEARCH INTO THE INFLUENCE OF SELECTED PARAMETERS ON CRITICAL SPEED OF THRUST BEARING WITH THE MAGNETORHEOLOGICAL FLUID ». Tribologia 284, no 2 (30 avril 2019) : 125–30. http://dx.doi.org/10.5604/01.3001.0013.4158.
Texte intégralRésumé :
Magnetic fluids are substances with a complex physicochemical composition. The unique properties of these substances are based on the possibility of reversible, almost immediate, changes in their rheological parameters, as well as changes in the flow direction due to the magnetic field. These properties allow the development of machines and devices with operating parameters that can be changed by the magnetic field. The range of the fluid property changes depends on its composition, magnetic field parameters, operating conditions, and the method of fluid deformation. The paper presents the results of research into the influence of selected parameters on the critical speed of thrust sliding bearings. These parameters include the magnetic and physical properties of magnetic fluids, the value of the magnetic induction, the fluid volume in the working gap, and the temperature. The results of the conducted research indicate a significant effect of the magnetic field gradient on the critical speed value.
12
Wolak, Artur. « Changes in Lubricant Properties of Used Synthetic Oils Based on the Total Acid Number ». Measurement and Control 51, no 3-4 (avril 2018) : 65–72. http://dx.doi.org/10.1177/0020294018770916.
Texte intégralRésumé :
This article describes the processes of degradation of five engine oils belonging to the same SAE (Society of Automotive Engineers) viscosity class but launched by different manufacturers. The direction and intensity of changes in the total acid number have been analyzed. As part of the experiment, the changes in engine oils occurring during operation have been examined. The operating conditions throughout the test can be described as “severe,” that is, frequent starting of the engine, short distance driving, and extended engine idling. All engine oils were operated in passenger cars of a uniform fleet of 25 vehicles. The total acid number was determined in accordance with the ASTM D664. The obtained results have led to the development of a statistical model enabling to calculate average predictive values of the total acid number for a given mileage. The results may facilitate decision-making regarding the service life of engine oils.
13
Domantsevych, N. I., O. V. Shunkina et B. P. Yatsyshyn. « Influence of Operating Conditions on Structure and Physical Properties of Polymeric Materials ». Фізика і хімія твердого тіла 18, no 2 (28 juin 2017) : 206–10. http://dx.doi.org/10.15330/pcss.18.2.206-210.
Texte intégralRésumé :
The changes in structure and physical properties of polymeric materials that exploited in a long time with complex mechanical loads used in pipe systems for high-pressure cold water have been studied. A significant reduction in the mechanical properties of polymeric materials has been established. The most typical structural defects that occur in polymer materials during manufacture and in the exploitations, using electron microscopic studies identified.
14
Cleary, P. W., M. D. Sinnott, R. D. Morrison, S. Cummins et G. W. Delaney. « Analysis of cone crusher performance with changes in material properties and operating conditions using DEM ». Minerals Engineering 100 (janvier 2017) : 49–70. http://dx.doi.org/10.1016/j.mineng.2016.10.005.
Texte intégral
15
Pavlin, Marko, Franc Novak et Gregor Papa. « Low Power Contactless Bioimpedance Sensor for Monitoring Breathing Activity ». Sensors 21, no 6 (16 mars 2021) : 2081. http://dx.doi.org/10.3390/s21062081.
Texte intégralRésumé :
An electronic circuit for contactless detection of impedance changes in a tissue is presented. It operates on the principle of resonant frequency change of the resonator having the observed tissue as a dielectric. The operating frequency reflects the tissue dielectric properties (i.e., the tissue composition and on the tissue physiological changes). The sensor operation was tested within a medical application by measuring the breathing of a patient, which was an easy detectable physiological process. The advantage over conventional contact bioimpedance measurement methods is that no direct contact between the resonator and the body is required. Furthermore, the sensor’s wide operating range, ability to adapt to a broad range of measured materials, fast response, low power consumption, and small outline dimensions enables applications not only in the medical sector, but also in other domains. This can be extended, for example, to food industry or production maintenance, where the observed phenomena are reflected in dynamic dielectric properties of the observed object or material.
16
Lemesko, Mikhail, Inessa Deyneka et Aleksey Iliev. « Providing adaptive properties of the drive of a rotary drilling machine ». MATEC Web of Conferences 329 (2020) : 03001. http://dx.doi.org/10.1051/matecconf/202032903001.
Texte intégralRésumé :
The article is devoted to the issue of automatic adjustment of the drilling machine to operating modes close to optimal. Information about the method of automatic control of the rotational drilling process is provided. The essence of the method consists in a special design of the drive, in which the work of the hydraulic motor and the hydraulic cylinder are connected through the working process. As a result of this connection of hydraulic elements, the torque of rotation on the hydraulic motor controls the feed of the hydraulic cylinder. Tuning throttles provide adjustment of modes to the required range of drilling conditions. Depending on the strength of the rock being drilled and the operating conditions of the drilling machine, the drive automatically changes the feed rate, thus ensuring maximum productivity. Several variations of this adaptive drive of the drilling machine are described. A description of the authors development, the drive scheme, and a description of the principle of operation is given. The advantages of the adaptive drive and its disadvantages are shown.
17
Xiang, Jun Ting, Jӧrg Uwe Schlüter et Fei Duan. « CFD Validation and Analysis of a Single-Stage Axial Compressor ». Applied Mechanics and Materials 629 (octobre 2014) : 109–18. http://dx.doi.org/10.4028/www.scientific.net/amm.629.109.
Texte intégralRésumé :
The knowledge about changes of flow field properties during axial compressor operationat high and relatively low speed is limited. This work provides a numerical approach to addressthese problems. Validations about the numerical scheme and the test of compressor performance at various operating speeds are conducted. The results show that computational fluid dynamics (CFD)is capable in predicting the compressor performance. Flow property changes during the compressoroperation are discussed and explanations are proposed. This work reinforces the understanding of compressor operation and provides valid results for future reference.
18
Solís, Cecilia, María Balaguer et José M. Serra. « In Situ Raman Characterization of SOFC Materials in Operational Conditions : A Doped Ceria Study ». Membranes 10, no 7 (10 juillet 2020) : 148. http://dx.doi.org/10.3390/membranes10070148.
Texte intégralRésumé :
The particular operational conditions of electrochemical cells make the simultaneous characterization of both structural and transport properties challenging. The rapidity and flexibility of the acquisition of Raman spectra places this technique as a good candidate to measure operating properties and changes. Raman spectroscopy has been applied to well-known lanthanide ceria materials and the structural dependence on the dopant has been extracted. The evolution of Pr-doped ceria with temperature has been recorded by means of a commercial cell showing a clear increment in oxygen vacancies concentration. To elucidate the changes undergone by the electrolyte or membrane material in cell operation, the detailed construction of a homemade Raman cell is reported. The cell can be electrified, sealed and different gases can be fed into the cell chambers, so that the material behavior in the reaction surface and species evolved can be tracked. The results show that the Raman technique is a feasible and rather simple experimental option for operating characterization of solid-state electrochemical cell materials, although the treatment of the extracted data is not straightforward.
19
Hujo, Ľubomír, Juraj Jablonický, Juraj Tulík, Ján Kosiba, Jerzy Kaszkowiak et Matej Michalides. « Verification Measurement of Laboratory Test Equipment for Evaluation of Technical Properties of Automotive Oil Filters ». Applied Sciences 11, no 18 (11 septembre 2021) : 8435. http://dx.doi.org/10.3390/app11188435.
Texte intégralRésumé :
By simulating the operating conditions, it is possible to verify and evaluate the technical properties of motor vehicle oil filters and the functionality of the designed equipment. Contaminated engine oil from operation was used with MANN W950/26 oil filter and a CNH Industrial 2992242 oil filter in the test circuit. Before use, the level of engine oil contamination in the test circuit was determined by evaluating the physicochemical properties. The laboratory test equipment also allows monitoring the technical life of oil filters, with variously contaminated engine oil, with the possibility of extending engine oil change service intervals depending on changes in the physicochemical properties of engine oil and filter efficiency. These laboratory tests can be performed in parallel in two hydraulic circuits, which can significantly reduce the testing time of the filter capabilities of oil filters, without the risk of engine damage, provided that the tests were performed under operating conditions. The results of the evaluation of the filtration capacity of oil filters can be used in the design of new filter materials, but also with a suitably determined methodology of oil filter replacement and engine oil change interval, it is possible to extend replacement intervals, which has a significant benefit not only from an economic but also ecological point of view. The result of the measurements is the confirmation of the functionality of the device with the possibility of simulating the operating conditions, at different degrees of oil contamination, at different operating temperatures and using different oil filters.
20
Petzová, Jana, Martin Březina, Miloš Baľák, Mária Dománková et Ľudovít Kupča. « Application of Metallographic Methods for Thermal Ageing Evaluation on Samples from Primary Piping of NPP ». Materials Science Forum 891 (mars 2017) : 60–66. http://dx.doi.org/10.4028/www.scientific.net/msf.891.60.
Texte intégralRésumé :
During a long-term operation of nuclear power plants (NPP), the changes of structural material properties occur. To ensure the safe and reliable operation, it is necessary to monitor and evaluate these changes mainly on components from primary circuit of NPPs. One of the dominant ageing mechanisms of NPP components besides the radiation embrittlement and the fatigue loads is the thermal ageing. The thermal ageing is the temperature, material and time dependent degradation mechanisms due to long-term exposure at the operating temperature of 570 K.This paper describes the project for thermal ageing monitoring at primary piping in NPP Bohunice Unit 3. There are summarized the results obtained from evaluation of original primary piping material.
21
Yang, Lu, Dunhong Zhou et Yang Kang. « Rheological Properties of Graphene Modified Asphalt Binders ». Nanomaterials 10, no 11 (4 novembre 2020) : 2197. http://dx.doi.org/10.3390/nano10112197.
Texte intégralRésumé :
Recently, low-cost, high-quality graphene can be obtained readily, so it is potential to prepare conductive graphene modified asphalts (GMAs). In this paper, GMAs were prepared with 0%, 2%, 4%, 6%, 8%, and 10% of graphene by weight of composites. Dynamic shear rheological experiments conducted from −30 to 120 °C illustrate that elasticity at above ambient temperatures and rutting resistance at higher temperatures are enhanced and, especially, the conceived percolation of GMAs occurs at graphene contents (GC) above 8% which were verified from three changes as GC increases, i.e., the curve characteristics of complex moduli, storage moduli at temperatures over 100 °C, temperatures when the phase angle reaches 90° and the trend of TG′=G″. The modification mechanisms are different before and after percolation. Before the percolation threshold, graphene which has a molecular structure similar to asphaltene enhances asphalt, like increasing asphaltene components, and after threshold, graphene improves asphalt because of the formed graphene networks. Rotational viscosities test results show that the higher the GC is, the higher the operating temperatures are, but the operating temperatures are higher than 200 °C when GC is above 4%. The percolation helps to further develop conductive asphalt concrete for intelligence pavement, but the operating properties of GMAs need to be improved.
22
Sabau, Adrian. « Transient Regimes Analysis for a Diesel Engine ». Advanced Materials Research 837 (novembre 2013) : 471–76. http://dx.doi.org/10.4028/www.scientific.net/amr.837.471.
Texte intégralRésumé :
A computer analysis has been developed for studying the energy and exergy performance of an direct-injection, naturally-aspirated diesel engine operating under transient load or speed conditions. The model is validated at steady-state operation and incorporates many novel features for simulating the transient response and analyzing all of the engine availability terms. The analysis reveals via multiple diagrams how the exergy properties of the diesel-engine subsystems vary according to the engine cycles for various speed and load changes. The diagrams also show the current-speed response. In addition, the effects of operating parameters such as the intensity of the applied change or heat loss to the walls are described from first-and second-law.
23
Amiri, Pouya, et Robert E. Kearney. « Patterns of muscle activation and modulation of ankle intrinsic stiffness in different postural operating conditions ». Journal of Neurophysiology 123, no 2 (1 février 2020) : 743–54. http://dx.doi.org/10.1152/jn.00558.2019.
Texte intégralRésumé :
Intrinsic stiffness describes the dynamic relationship between imposed angular perturbations to a joint and the resulting torque response, due to intrinsic mechanical properties of muscles and joint, and inertia of the limbs. Recently, we showed that ankle intrinsic stiffness changes substantially with sway in normal standing. In the present study, we documented how ankle intrinsic stiffness changes with postural operating conditions. Subjects stood on an apparatus while subjected to ankle position perturbations in five conditions: normal standing, toe-up and toe-down standing, and backward and forward lean. In each condition, ankle intrinsic stiffness was estimated while its modulation with sway was accounted for. The results demonstrated that ankle intrinsic stiffness varies widely, from 0.08 to 0.75 of critical stiffness, across postural operating conditions; however, it is always smaller than the critical stiffness. Therefore, other contributions are necessary to ensure stable standing. The mean intrinsic stiffness was highest in forward lean and lowest in backward lean. Moreover, within each operating condition, the intrinsic stiffness changed with center-of-pressure position in one of three ways, each associated with a distinct muscle activation pattern; these include 1) monotonically increasing stiffness-center of pressure relation, associated with a progressive increase in triceps surae activation, 2) decreasing-increasing stiffness-center of pressure relation, associated with initial activation of tibialis anterior and later activation of triceps surae, and 3) monotonically decreasing stiffness-center of pressure relation, associated with decreasing activation of tibialis anterior. Thus intrinsic stiffness varies greatly within and across postural operating conditions, and a correct understanding of postural control requires accounting for such variations. NEW & NOTEWORTHY Ankle intrinsic stiffness changes with sway in normal standing. We quantified such changes in different postural operating conditions and demonstrated that the intrinsic stiffness changes in a manner associated with different activation patterns of ankle plantarflexors and dorsiflexors, emerging in different operating conditions. Large modulations of the intrinsic stiffness within and across postural operating conditions show that the stiffness importance and contribution change and must be accounted for in the study of postural control.
24
Halenar, Robert. « Tollerance of Linear Dynamic System Calculated in Matlab Environment ». Applied Mechanics and Materials 336-338 (juillet 2013) : 604–7. http://dx.doi.org/10.4028/www.scientific.net/amm.336-338.604.
Texte intégralRésumé :
By the influence of changes in ambient parameters and operating conditions and changing parameter values LDS is changing their properties (behavior), reflected also in changes in characteristics, it is also possible to formulate an opposite role: "To what extent can be changed system parameters, to reached its behavior (under certain criteria) remained preserved ? " The answer to this question deals with the task of determining allowable changes - tolerance parameters for the desired behavior. Criteria for the behavior may be different. We will build on the frequently used criteria for optimal module. Methodology makes use of computer simulation of classical mathematical analysis.
25
Halenar, Robert. « Tollerance Coefficients of Stability in Linear Dynamic System Calculated in Matlab Environment ». Advanced Materials Research 774-776 (septembre 2013) : 1869–72. http://dx.doi.org/10.4028/www.scientific.net/amr.774-776.1869.
Texte intégralRésumé :
By the influence of changes in ambient parameters and operating conditions and changing parameter values LDS is changing their properties (behavior), reflected also in changes in characteristics, it is also possible to formulate an opposite role: "To what extent can be changed system parameters, to reached its behavior (under certain criteria) remained preserved ? " The answer to this question deals with the task of determining allowable changes - tolerance parameters for the desired behavior. Criteria for the behavior may be different. We will build on the stability criteria by Routh - Schur. Methodology makes use of computer simulation of classical mathematical analysis.
26
Liskin, I. V., Ya P. Lobachevsky, D. A. Mironov, S. A. Sidorov et A. I. Panov. « LABORATORY STUDY RESULTS OF SOIL-CUTTING OPERATING ELEMENTS ». Agricultural Machinery and Technologies 12, no 4 (27 septembre 2018) : 41–47. http://dx.doi.org/10.22314/2073-7599-2018-12-4-41-47.
Texte intégralRésumé :
Studying the wear of soil-cutting working tools in the field conditions has certain difficulties associated with the impermanence of soil properties. The paper presents the results of a laboratory study of the power characteristics in the process of wearing of a soil-cutting wedge in an artificial abrasive soil medium. (Research purpose) To determine the nature of changes in cutting forces in vertical and horizontal planes depending on the conditions and a degree of wear of a soil-cutting wedge. (Materials and methods) For the experiment, use was made of quartz as an abrasive material, paraffin with additives of ceresin and petrolatum as binding components; cement was additionally introduced to change the granulometric composition of a soil model, and a cross-planer was used as a drive mechanism. (Results and discussion) It has been shown that the horizontal component, or traction resistance, increases linearly with increasing the depth of cutting. An increase in the soil-cutting velocity also leads to an increase in the traction resistance of the wedge, and its magnitude increases in a power-law dependence on the velocity. It has been established that the cutting angle affects not only the variation of the wedge traction resistance, but also the shearing pattern, which changes as it increases and changes from shear shavings into shift shavings, which contributes to the traction force growth. It has been found that an increase in traction resistance is affected by an increase in the hardness of abrasive material and a decrease in the distribution density of solid particles in its volume. As the width of the back chamfer and the angle of its inclination to the furrow bottom increased, the traction characteristics both in the vertical and horizontal planes increased as well, the back chamfer width having the greatest influence on the vertical component. As the blade worn out depending on the friction path, the vertical component of frictional forces increased sharply, while the horizontal component increased insignificantly. (Conclusions) The results of the conducted studies have shown that the wedge depth mainly depends on the back chamfer width. The traction resistance of the wedge is greatly influenced by physical and mechanical properties of an abrasive medium, cutting conditions and a degree of the blade blunting.
27
Danos, Nicole, Natalie C. Holt, Gregory S. Sawicki et Emanuel Azizi. « Modeling age-related changes in muscle-tendon dynamics during cyclical contractions in the rat gastrocnemius ». Journal of Applied Physiology 121, no 4 (1 octobre 2016) : 1004–12. http://dx.doi.org/10.1152/japplphysiol.00396.2016.
Texte intégralRésumé :
Efficient muscle-tendon performance during cyclical tasks is dependent on both active and passive mechanical tissue properties. Here we examine whether age-related changes in the properties of muscle-tendon units (MTUs) compromise their ability to do work and utilize elastic energy storage. We empirically quantified passive and active properties of the medial gastrocnemius muscle and material properties of the Achilles tendon in young (∼6 mo) and old (∼32 mo) rats. We then used these properties in computer simulations of a Hill-type muscle model operating in series with a Hookean spring. The modeled MTU was driven through sinusoidal length changes and activated at a phase that optimized muscle-tendon tuning to assess the relative contributions of active and passive elements to the force and work in each cycle. In physiologically realistic simulations where young and old MTUs started at similar passive forces and developed similar active forces, the capacity of old MTUs to store elastic energy and produce positive work was compromised. These results suggest that the observed increase in the metabolic cost of locomotion with aging may be in part due to the recruitment of additional muscles to compensate for the reduced work at the primary MTU. Furthermore, the age-related increases in passive stiffness coupled with a reduced active force capacity in the muscle can lead to shifts in the force-length and force-velocity operating range that may significantly impact mechanical and metabolic performance. Our study emphasizes the importance of the interplay between muscle and tendon mechanical properties in shaping MTU performance during cyclical contractions.
28
Jablonický, Juraj, Mirko Simikić, Juraj Tulík, Milan Tomić, Ľubomír Hujo et Ján Kosiba. « Monitoring of Selected Physical and Chemical Parameters of Test Oil in the Wet Disc Brake System ». Acta Technologica Agriculturae 23, no 1 (1 mars 2020) : 46–52. http://dx.doi.org/10.2478/ata-2020-0008.
Texte intégralRésumé :
AbstractPaper presented is focused on the operating measurements of a tractor wet disc brake system. Operating measurements were evaluated after tractor’s operation at 500 Mth on the 3rd, 4th and 5th gear. Reference fluid and ecological fluid were tested during operation. In addition, work results include the evaluation of the fluid samples taken during the operational tests to monitor the tractor braking performance with wet disc brakes. Fluid samples were also tested in order to determine the changes in their physico-chemical properties. Chemical analysis was performed for both oil samples by means of X-ray fluorescence analysis according to the DIN 51829 and DIN 51399-2. Observed physical properties of the tested oils – density, viscosity, acid number, water content – were within the appropriate ranges after the end of test. Further analysis was focused on an amount of abrasive metals, contaminants, additives, and other important elements. On the basis of analyses conducted, it can be concluded that majority of elements preserved their original level showed at the 0 reference hour sample. In terms of the abrasion metals, an increase in their presence was not found. Furthermore, analysis of the physical properties of tested fluids did not prove their negative impact on the tractor wet disc brake system. Results of the operating measurements suggest that neither the applied conference fluid nor the ecological fluid showed negative effect on the minimum braking value. The minimum braking deceleration was implemented in accordance with the Law no. 106/2018.
29
Gabelchenko, Natalya, Artem Belov, Artem Kravchenko et Oleg Kryuchkov. « Analysis of Wear-Resistant Materials of Mixer - Pneumosuperchargers Blades Operating under Conditions of Abrasive Wear ». Solid State Phenomena 316 (avril 2021) : 893–98. http://dx.doi.org/10.4028/www.scientific.net/ssp.316.893.
Texte intégralRésumé :
We conducted comparative tests of the wear resistance of metals operating under abrasive conditions. Samples were cut from the working parts of mixer-pneumosuperchargers. The chemical composition and mechanical properties were determined. To compare samples under abrasive wear conditions, we designed and assembled a carousel installation. The principle of its operation is based on mixing the abrasive medium by the samples being studied with a given speed. Wear resistance was evaluated by weight loss by samples after several test cycles. To determine changes in the structure of the metal during abrasive wear, metallographic studies of the samples were carried out before and after the tests. It is shown that the best complex of service and mechanical properties is possessed by 110G13L steel.
30
Borawski, Andrzej. « Impact of Operating Time on Selected Tribological Properties of the Friction Material in the Brake Pads of Passenger Cars ». Materials 14, no 4 (12 février 2021) : 884. http://dx.doi.org/10.3390/ma14040884.
Texte intégralRésumé :
Braking systems have a direct impact on the safety of road users. That is why it is crucial that the performance of brakes be dependable and faultless. Unfortunately, the operating conditions of brakes during their operating time are affected by many variables, which results in changes in their tribological properties. This article presents an attempt to develop a methodology for studying how the operating time affects the value of the coefficient of friction and the abrasive wear factor. The Taguchi method of process optimization was used to plan the experiment, which was based on tests using the ball-cratering method. The results clearly show that the degree of wear affects the properties of the friction material used in the production process of brakes.
31
Indacochea, J. E., G. Wang, R. Seshadri et Y. K. Oh. « Creep Rupture Properties of High-Temperature Bainitic Steels After Weld Repair ». Journal of Engineering Materials and Technology 122, no 3 (1 mars 2000) : 259–63. http://dx.doi.org/10.1115/1.482796.
Texte intégralRésumé :
Welded high-temperature power plant components can experience a greater risk of failure by creep during service, when compared to similar as-wrought components. The heat-affected zone (HAZ) of alloy steels is usually the region of a weldment exhibiting poor mechanical properties. The arc welding of an ASTM A470, Class 8-rotor steel in this study identified the intercritical heat affected zone (ICHAZ) as the weakest region in terms of creep rupture life. The type of welding procedure significantly affects this region, but most important are the welding parameters utilized. Because of the microstructural heterogeneity of the HAZ and sensitivity of these microstructures to changes when exposed to elevated temperatures, their performance at later times is difficult to predict. Extrapolation techniques are limited in value for predicting service lives of homogeneous materials, because these do not incorporate the microstructure changes of the materials during high temperature operation. They are even less useful for predicting the operating lives of weldments. This paper considers the creep performance and structure stability of the ICHAZ of 12 percent Cr and 214-1Mo vanadium modified weldments produced on a retired CrMoV rotor steel. [S0094-4289(00)00303-0]
32
Hashimoto, Keizo, et Rieko Matsumoto. « Deformation Behaviors of Nb Doped Gamma Titanium Aluminides ». Materials Science Forum 449-452 (mars 2004) : 837–40. http://dx.doi.org/10.4028/www.scientific.net/msf.449-452.837.
Texte intégralRésumé :
In this study, Nb doped γ-TiAl is designed and examined their tensile properties at elevated temperatures. Small compositional changes cause drastic changes of the mechanical properties at 1273K. In order to clarify the deformation mechanism at elevated temperatures, dislocation structures have been observed using transmission electron microscope (TEM). All of the specimens observed by TEM show that at least two slip systems are operating in each grain. The specimen having relatively lower strength and higher tensile elongations shows more than four operating slip systems in the grains. The specimen having a medium strength shows many super-dislocations and their dissociations that block the other dislocation motions. The specimen having the highest strength shows many deformation twins. These observations suggest that deformation twins become the strong obstacles against moving dislocations at elevated temperatures. The relationships between observed dislocation structures and mechanical properties of γ-TiAl are discussed.
33
Abakarov, A. A., Sh M. Igitov et Ali A. Abakarov. « Determination of engine oil change interval for patrol engines based on actual operating time ». Russian Automobile and Highway Industry Journal 18, no 3 (20 juillet 2021) : 274–85. http://dx.doi.org/10.26518/2071-7296-2021-18-3-274-285.
Texte intégralRésumé :
Introduction. This paper shows the results of a study of the frequency of maintenance of passenger cars in various operating conditions, and provides recommendations for replacing the engine oil of gasoline engines (category SN classification according to API) according to the actual engine operating time (moto-hours). The service book of passenger cars contains the regulations for car maintenance with a list of operations that must be performed. The oil change intervals specified in the Regulations on Maintenance and Repair of Rolling Stock of motor Transport and the factory instructions do not take into account the specifics of the operation of vehicles. Depending on the road and climatic conditions and the operating mode, the standard maintenance schedule can be adjusted, in particular, the frequency of engine oil changes. The scientific novelty of the work is to determine the intervals of car maintenance for specific operating conditions.Materials and methods. The paper presents an analysis of Russian and foreign car maintenance systems, in particular, the oil change intervals of gasoline engines in European countries, the United States and Japan.The results of operational and resource tests of motor oils of gasoline engines carried out by methods of measuring their physical and chemical properties are presented.Results. In this paper, based on the analysis of the problem, recommendations for changing oil in gasoline engines by motorcycle hours for the conditions of the Republic of Dagestan (RD) are developed.The use of external and built-in technical means for calculating the motor hours allows you to determine the recommended oil change interval.Discussion and conclusion. In this paper, on the basis of research on a certain number of vehicles operating in various (including difficult) conditions, recommendations are developed that allow you to determine the rules of car maintenance for various operating conditions.
34
Hurtalová, Lenka, Eva Tillová et Mária Chalupová. « The Changes of Fatigue Properties in Aluminium Cast Alloy during Solution Treatment ». Key Engineering Materials 592-593 (novembre 2013) : 433–36. http://dx.doi.org/10.4028/www.scientific.net/kem.592-593.433.
Texte intégralRésumé :
This paper describes the effect of solution treatment on the fatigue properties of AlSi9Cu3 cast alloy. The heat treatment consisted of a solution treatment at two different temperatures 515°C and 525°C, a holding time of 4 hours; water quenching at 40°C and natural aging at room temperature for 24 hours. Thus prepared samples were subjected to fatigue test with a rotating bending loading (testing machine ROTOFLEX operating at 30 Hz, load ratio R = -1). The fatigue fracture surfaces were observed using a scanning electron microscope (SEM) after the fatigue test. The results showed that the existence of casting defects (8.4 % of micro-shrinkage) has considerable influence on fatigue properties and can be considered as fatigue crack initiators in what leads to final fatigue damage. Apart from cast defects, the morphology of eutectic silicon and intermetallic phases (Fe- and Cu-rich phases) are also important factors which have an influence on the fatigue properties of Al-Si cast components. The solution treatment used (at 525°C/4hours) has increased fatigue properties (the fatigue lifetime increased from 49 to 76 MPa), thanks to Si particles, morphology changes, and cast defects area reduction as well as reduction Fe-rich phases.
35
Rezanov, E. A., V. I. Merkulov, K. V. Rossova et I. V. Tishchenko. « The Comparative Analysis of External Heat Transfer Calculation Methods for a Solar Aircraft Spacesuit ». MATEC Web of Conferences 324 (2020) : 03007. http://dx.doi.org/10.1051/matecconf/202032403007.
Texte intégralRésumé :
This article presents an assessment of the external thermal load on the life support system of a solar aircraft under extreme operating conditions. The calculation was carried out for the maximum and minimum possible heat flows in the key points of the aircraft flight. In this article the conditions on the Earth’s surface and at the operating altitude of the aircraft were taken as calculated. The dependence of the quantitative changes in the heat load on the aircraft from altitude was revealed, taking into account changes of thermal properties of the environment and mechanisms of heat transfer.
36
Piątkowski, Jarosław, Bożena Gajdzik et Aleksander Mesjasz. « Assessment of Material Durability of Steam Pipelines Based on Statistical Analysis of Strength Properties—Selected Models ». Energies 13, no 14 (14 juillet 2020) : 3633. http://dx.doi.org/10.3390/en13143633.
Texte intégralRésumé :
The paper presents a research method concerning the application of statistical prognostic models for assessment of material durability and operational reliability of steel for steam pipelines, whose operation has exceeded the working time of 100,000 h. Decisions on the admission of long-lived materials to work for power industry results from extensive diagnostic examinations are based on the results of tests of mechanical properties, microstructure degradation, and corrosion processes. Considering the economic reasons and available data published in diagnostic reports, the determination of failure-free operating time of steam pipelines is based on the results of static tensile tests—tensile strength (Rm); conventional yield point (Rp); elongation (A) and Vickers hardness (V), correlated with the operating time and the media type (fresh steam and secondarily super-heated steam) for the most sensitive element of a pipeline, namely the elbow. The results of changes in strength properties during operation are presented in the form of graphs of the analyzed material feature vs. operating time in the range from zero hours (for a new material) to 300,000 h, taking into account the impact of random and systematic disturbances within the adopted tolerance limits. It has been found that because of the R2 factor and significance level in the t-Student test for regression and correlation coefficients, exponential, hyperbolic and quadratic models are best fitted to empirical points. Based on the tensile strength results (Rm), it has been found that the forecast time of the steam pipeline ranges from 193,400 to 258,300 h. Taking the yield strength (Rp) into account, it has been ascertained that the time ranges from 225,000 to 293,000 h, and for the working time forecast of steam pipelines based on Vickers hardness results, it ranges from 192,100 to 246,800 h.
37
Parker, J. D., et L. H. Bisbee. « Monitoring in-Service Changes in Materials Properties ». Proceedings of the Institution of Mechanical Engineers, Part A : Journal of Power and Energy 206, no 3 (août 1992) : 209–16. http://dx.doi.org/10.1243/pime_proc_1992_206_031_02.
Texte intégralRésumé :
The safe operation of a wide range of large-scale plant depends on knowledge of component specific materials properties. Techniques that allow reliable measurement of changes in critical properties are therefore vital. The present paper describes a new procedure for removing miniature material samples. The technique can be applied even in difficult access conditions and results in minimum material removal so that sampling is effectively non-destructive. Specific case studies where this technique has been applied to the condition assessment of steam plant are described.
38
Kuleshova, E. A., B. A. Gurovich, E. V. Krikun, A. S. Frolov, D. A. Maltsev, Z. V. Bukina, M. A. Saltykov et A. G. Balikoev. « Specific Features of Structural-Phase State and Properties of Reactor Pressure Vessel Steel at Elevated Irradiation Temperature ». Science and Technology of Nuclear Installations 2017 (2017) : 1–12. http://dx.doi.org/10.1155/2017/1064182.
Texte intégralRésumé :
This paper considers influence of elevated irradiation temperature on structure and properties of 15Kh2NMFAA reactor pressure vessel (RPV) steel. The steel is investigated after accelerated irradiation at 300°C (operating temperature of VVER-1000-type RPV) and 400°C supposed to be the operating temperature of advanced RPVs. Irradiation at 300°C leads to formation of radiation-induced precipitates and radiation defects-dislocation loops, while no carbide phase transformation is observed. Irradiation at a higher temperature (400°C) neither causes formation of radiation-induced precipitates nor provides formation of dislocation loops, but it does increase the number density of the main initial hardening phase—of the carbonitrides. Increase of phosphorus concentration in grain boundaries is more pronounced for irradiation at 400°C as compared to irradiation at 300°C due to influence of thermally enhanced diffusion at a higher temperature. The structural-phase changes determine the changes of mechanical properties: at both irradiation temperatures irradiation embrittlement is mainly due to the hardening mechanism with some contribution of the nonhardening one for irradiation at 400°C. Lack of formation of radiation-induced precipitates at T = 400°C provides a small ΔTK shift (17°C). The obtained results demonstrate that the investigated 15Kh2NMFAA steel may be a promising material for advanced reactors with an elevated operating temperature.
39
Louda, Petr, Artem Sharko et Dmitry Stepanchikov. « An Acoustic Emission Method for Assessing the Degree of Degradation of Mechanical Properties and Residual Life of Metal Structures under Complex Dynamic Deformation Stresses ». Materials 14, no 9 (21 avril 2021) : 2090. http://dx.doi.org/10.3390/ma14092090.
Texte intégralRésumé :
An acoustic emission method for assessing the degree of degradation of mechanical properties under conditions of complex dynamic deformation stresses is proposed. It has been shown that changing the operating conditions of metal structures, peak loads, external collisions, and thermally changing loads, which cannot be taken into account, leads to uncertainty and unpredictable structural changes in the material. This in turn makes it difficult to identify the state of the structure material to ensure trouble-free operation of the equipment. Changes in the mechanical properties under difficult loading conditions are identified by polynomial approximation of the results of AE measurements and the construction of boundary curves separating the operability region from the fracture region. This is achieved by approximating the experimental dependences of the acoustic parameters for various types of loading. This approach significantly expands the capabilities of the technical means of identification systems of metal structures, and in particular, allows the current state of the equipment and its suitability for further operation to be assessed without stopping the equipment in real time. It is of interest not only to fix the damage, but also to diagnose the processes of reducing the mechanical properties during the operation of the equipment.
40
Laptev, A. B., M. R. Pavlov, A. A. Novikov et A. V. Slavin. « CURRENT TRENDS IN THE DEVELOPMENT OF TESTING MATERIALS FOR RESISTANCE TO CLIMATIC FACTORS (review) Part 1. Testing of new materials ». Proceedings of VIAM, no 1 (2021) : 114–22. http://dx.doi.org/10.18577/2307-6046-2021-0-1-114-122.
Texte intégralRésumé :
In the first part of the review, based on the analysis of world experience in conducting climate tests, the main development trends related to the development of new materials are identified, and it is Shown that in parallel with the development of new materials, appropriate methods of climate testing should be developed taking into account previous experience. It is shown that to assess and predict changes in properties of materials over a long operating life tests of materials are required to conduct accelerated methods of building mathematical models of processes of degradation of their properties under the given climatic and operating factors.
41
Wróblewski, Roman, Piotr Osiński, Michał Stosiak et Rafał Cieślicki. « The Influence of Operating Conditions on Changes in the Properties of Ventilation Pipes Made of Self-extinguishing Polypropylene ». Engineering and Protection of Environment 20, no 1 (janvier 2017) : 121–30. http://dx.doi.org/10.17512/ios.2017.1.9.
Texte intégral
42
Sharma, A., M. Tomar, V. Gupta, A. Badola et N. Goswami. « Polyaniline/SnO2 Nanocomposite Sensor for NO2 Gas Sensing at Low Operating Temperature ». International Journal of Nanoscience 14, no 04 (28 juillet 2015) : 1550011. http://dx.doi.org/10.1142/s0219581x15500118.
Texte intégralRésumé :
In this paper gas sensing properties of 0.5–3% polyaniline (PAni) doped SnO 2 thin films sensors prepared by chemical route have been studied towards the trace level detection of NO 2 gas. The structural, optical and surface morphological properties of the PAni doped SnO 2 thin films were investigated by performing X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Raman spectroscopy measurements. A good correlation has been identified between the microstructural and gas sensing properties of these prepared sensors. Out of these films, 1% PAni doped SnO 2 sensor showed high sensitivity towards NO 2 gas along with a sensitivity of 3.01 × 102 at 40°C for 10 ppm of gas. On exposure to NO 2 gas, resistance of all sensors increased to a large extent, even greater than three orders of magnitude. These changes in resistance upon removal of NO 2 gas are found to be reversible in nature and the prepared composite film sensors showed good sensitivity with relatively faster response/recovery speeds.
43
Bollók, P., et M. Kozma. « Changes of Subsurface Structure of Materials Developed during Sliding Friction ». Materials Science Forum 537-538 (février 2007) : 315–20. http://dx.doi.org/10.4028/www.scientific.net/msf.537-538.315.
Texte intégralRésumé :
It is well known that during sliding friction the properties of rubbing surfaces are changed owing to transformations caused by applied loads, friction and wear processes. In the last years many research works were devoted to reveal the properties of the surfaces transformed during the friction and wear at the Budapest University of Technology and Economics in the Department of Machine Design. During these investigations the conditions of developing beneficial transformed surface layers and their operating boundaries were determined by experiments on metal sliding pairs in laboratory. The conditions of evolving large-scale adhesion junctions, scuffing and seizure were investigated on heavy-loaded surfaces at slow sliding velocity. During the experiments hard steel balls slid on dry or lubricated metal disks. Coefficient of friction and wear tracks were measured and structures and damages of sliding surfaces were evaluated using profilometry, SEM and normal microscope photographs, and micro-hardness measurement.
44
Fedorov, Pavel V., et Marat R. Lukmanov. « Impact of rheological properties of oil on pipeline operation energy efficiency ». SCIENCE & ; TECHNOLOGIES OIL AND OIL PRODUCTS PIPELINE TRANSPORTATION 10, no 1 (29 février 2020) : 8–16. http://dx.doi.org/10.28999/2541-9595-2020-10-1-8-16.
Texte intégralRésumé :
Variations in the performance of process modes and the efficiency of major pump units due to a mismatch between the planned and actual values of oil’s rheological properties leads to a deviation in actual electrical consumption compared to the planned level. A reduction formula makes it possible to quickly identify such deviations in the mid- and long-term (over the course of a month/year), with factor analysis determining the causes thereof. Such analysis should be carried out on the basis of variations in the properties of the materials and changes to the efficiency of pumping units due to shifts in their operating point. The role of variation of geodetic elevations at the beginning and end of process sections of major pipelines in determining the impact of changes in oil properties on consumed electrical power is considered. It has been found that the shorter the section and the greater the difference in geodetic elevations, the lower the share of energy consumed due to the changes in oil viscosity as a proportion of the total energy consumption in the pumping process mode. The experimental results point to the need to expand the list of parameters for conducting factor analysis and lead to the conclusion that a correct determination of the causes of deviation in actual power consumption from the planned values is only possible after hydraulic calculations of the process modes of the pipeline operation have been made.
45
Griffiths, Malcolm. « Effect of Neutron Irradiation on the Mechanical Properties, Swelling and Creep of Austenitic Stainless Steels ». Materials 14, no 10 (17 mai 2021) : 2622. http://dx.doi.org/10.3390/ma14102622.
Texte intégralRésumé :
Austenitic stainless steels are used for core internal structures in sodium-cooled fast reactors (SFRs) and light-water reactors (LWRs) because of their high strength and retained toughness after irradiation (up to 80 dpa in LWRs), unlike ferritic steels that are embrittled at low doses (<1 dpa). For fast reactors, operating temperatures vary from 400 to 550 °C for the internal structures and up to 650 °C for the fuel cladding. The internal structures of the LWRs operate at temperatures between approximately 270 and 320 °C although some parts can be hotter (more than 400 °C) because of localised nuclear heating. The ongoing operability relies on being able to understand and predict how the mechanical properties and dimensional stability change over extended periods of operation. Test reactor irradiations and power reactor operating experience over more than 50 years has resulted in the accumulation of a large amount of data from which one can assess the effects of irradiation on the properties of austenitic stainless steels. The effect of irradiation on the intrinsic mechanical properties (strength, ductility, toughness, etc.) and dimensional stability derived from in- and out-reactor (post-irradiation) measurements and tests will be described and discussed. The main observations will be assessed using radiation damage and gas production models. Rate theory models will be used to show how the microstructural changes during irradiation affect mechanical properties and dimensional stability.
46
Naď, Milan, Ladislav Rolník et Lenka Čičmancová. « Prediction of Changes in Modal Properties of the Euler–Bernoulli Beam Structures Due to the Modification of Its Spatial Properties ». International Journal of Structural Stability and Dynamics 17, no 05 (23 janvier 2017) : 1740014. http://dx.doi.org/10.1142/s0219455417400144.
Texte intégralRésumé :
The beams can be considered as fundamental structural elements applied in many technical structures and equipment. In the operating regimes, these beam structures are very often loaded by the time-dependent forces which cause their undesirable dynamical behavior and the whole system is getting into critical resonant state. It is clear that the reduction of the level of unwanted vibrations or prevention of their occurrence should be one of the important objectives in the design of machine equipment and structures. To achieve these aims, the knowledge of modal properties of beam structures in relation to their internal structure is necessary. The insertion of reinforcing core into a beam body is one of the possible techniques to achieve the required changes in modal properties (mode shapes, natural frequencies) of the beam structure. The dependency of the modal properties of structurally modified beam structure on the geometric parameters and material properties of the inserted reinforcing core is studied in this paper.
47
El Mouhri, S., S. Ettaqi, A. Laazizi et Stephane Benayoun. « FSW of Aluminum Alloys : Effect of Operating Parameters on the Weld Quality ». Key Engineering Materials 640 (mars 2015) : 43–50. http://dx.doi.org/10.4028/www.scientific.net/kem.640.43.
Texte intégralRésumé :
The Friction Stir Welding FSW is a welding process in the solid state to join metallic alloys that is used in many industrial applications such as aerospace, automotive and shipbuilding. The process parameters such as the geometry of the tool, the speed of rotation and the speed of advance play a major role in determining the weld quality. In this work, an attempt was made to establish a relationship between the properties of the base material and FSW process parameters. Welds were made using AA1050 Aluminum alloy with different combination of parameters. Metallographic analysis was performed to verify the (faulty or fault-free) weld quality. Tests microhardness, tensile and bending were carried out to study the changes in the mechanical properties in the weld zone.
48
Gulyaev, V. P., P. P. Petrov, K. V. Stepanova, A. A. Platonov, M. I. Makarov et M. A. Platonov. « Experimental study of micro-deformation of structural steel under simulation of operating conditions ». Industrial laboratory. Diagnostics of materials 86, no 6 (22 juin 2020) : 55–61. http://dx.doi.org/10.26896/1028-6861-2020-86-6-55-61.
Texte intégralRésumé :
Diagnostics of the load bearing capacity of machines and structures, service properties of structural materials are carried out by destructive and non-destructive methods. In the system of non-destructive methods of diagnosing and monitoring of the service properties of materials and products, radiation technologies are of particular importance, since they have instrumental capabilities for diagnosing and controlling changes in the soundness of a solid body at different structural levels. The X-ray diffractometry method provided determination of the stability of the stress-strain state of structural steel samples subjected to prolonged (over 5 years) static loads not exceeding the yield strength of the material. The purpose of the study is to determine experimentally the effect of continuous (since 2013) elastic stress and climatic factors on the change in the half-width of the diffraction line profile. It is shown that the straight-line dependence of the half-width of the diffraction line profile is maintained in the range of elastic stresses not exceeding 0.5σt. The results of changes in the microstructural state (micro-strains) identified by the characteristics of the diffraction lines profile are presented and discussed. The results of the experimental study of the effect of small steady elastic stresses reveal that periodic annual fluctuation of temperatures (2013 – 2018) does not cause a significant change in the properties of the diffraction line profile of the 08ps structural steel samples. On the contrary, low climatic temperatures contributed to the elimination of individual instrumental errors attributed to design conditions of the experiment. A sharp change in the true half-width of the diffraction line profile at the stress values σ > 0.5σt, probably indicates the minimum margin of safety of 08ps structural steel when setting the permissible stress value (σ). The revealed changes in microplastic deformation observed in structural steels in the range of elastic stresses corresponding to real operational loads require further study and analysis.
49
Zieliński, A., G. Golański, J. Dobrzański et M. Sroka. « Creep Resistance of VM12 Steel ». Archives of Metallurgy and Materials 61, no 3 (1 septembre 2016) : 1635–40. http://dx.doi.org/10.1515/amm-2016-0265.
Texte intégralRésumé :
Abstract This article presents selected material characteristics of VM12 steel used for elements of boilers with super- and ultra-critical steam parameters. In particular, abridged and long-term creep tests with and without elongation measurement during testing and investigations of microstructural changes due to long-term impact of temperature and stress were carried out. The practical aspect of the use of creep test results in forecasting the durability of materials operating under creep conditions was presented. The characteristics of steels with regard to creep tests developed in this paper are used in assessment of changes in functional properties of the material of elements operating under creep conditions.
50
da Silva, Margarete Soares, Lucas L. Silva, Eliane F. Souza, Elson Longo, Maria A. Zaghete et Alberto A. Cavalheiro. « Study on the Piezoelectric Behavior and Structural Changes of Strontium Doped PZT Ceramics ». Materials Science Forum 869 (août 2016) : 13–18. http://dx.doi.org/10.4028/www.scientific.net/msf.869.13.
Texte intégralRésumé :
Some piezoelectric properties of lead zirconate titanate PbZr0.53Ti0.47O3 ceramic samples sintered at 1100oC for 3 hours has been investigated in this work and compared to the strontium modification at 0.2, 0.4, and 0.6 mol%. Polarization versus Electric Field curve and d33 and Kp piezoelectric parameters was taken at room temperature in order to investigate the correlation with phase amount and lattice parameters of crystalline phases calculated through Rietveld refinement. The results indicated the lead substitution with 0.4 mol% of strontium enhances the d33 and Kp piezoelectric parameters, but there is no systematic variation of the piezoelectric properties with strontium content. By the other hand, tetragonal phase seems plays an important rule on piezoelectric devices operating near the room temperature and some correlations could be found.