scholarly journals A Study on the Effect of Adhesive Cavities on the Scuffing Initiation in a Sliding Contact

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4296
Author(s):  
Grzegorz Kaczor ◽  
Magdalena Machno
Keyword(s):  
Oscillation Frequency ◽  
Sliding Contact ◽  
Ring Test ◽  
Operating Parameters ◽  
Adhesive Bonds ◽  
Before And After ◽  
New Research ◽  
Simultaneous Influence ◽  
Wear Tests ◽  
Complicated Mechanism

Scuffing is a particularly problematic wear phenomenon in sliding contact that has not yet been fully elucidated. The complicated mechanism of the development of this phenomenon results from the simultaneous influence of many factors. There is a continuous need for new research to gain a deeper understanding of the complex frictional processes that scuffing is. Components such as cams, tappets, piston rings and gears are extremely susceptible to scuffing. The idea of the research on the scuffing wear development is the study of the formation of adhesive cavities as the effects of the destruction of adhesive bonds at various operating parameters. The goal of the presented work is the analysis of the influence of the oscillation frequency on the formation of adhesive cavities leading to scuffing. The tests carried out with the use of S235 steel showed that the adhesive cavities on the surfaces of the tested components appear regardless of the adopted values of the oscillation frequency. The surfaces of the specimen and counter-specimen were analyzed before and after wear tests on the block-on-ring test stand at the different values of the oscillation frequency. The conducted research revealed that the greatest change in the values of the friction coefficient occurs with an increase in frequency from 2 to 5 Hz, and the largest change in the number of scuffing initiating cycles occurs with an increase in the oscillation frequency from 1 to 2 Hz.

News and Views

2016 ◽  
Vol 53 (1) ◽  
pp. 135
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Cell Therapy ◽  
Heart Attack ◽  
Cardiac Performance ◽  
Heart Repair ◽  
Before And After ◽  
New Research ◽  
Large Animals ◽  
The University

New research reveals combined cell therapy enhances cardiac performance following heart attack. A study by Dr. Joshua Hare, Director of Interdisciplinary Stem Cell Institute (ISCI) at the University of Miami Miller School of Medicine finds that combination stem cell therapy, using ckit+ cardiac stem cells (CSCs) and mesenchymal stem cells (MSCs) can significantly enhance cardiac performance in chronic ischemic cardiomyopathy following a heart attack. The study centered on large animals three months after experiencing a heart attack. The animals were divided into three cohorts. The first group received transendocardial injections of MSCs, while the second group received a combination of MSCs and cardiacderived CSCs. The third group acted as a controlled placebo group. Cardiac MRIs were performed to determine cardiac function before and after therapy. Both groups of cell-treated animals exhibited a significant reduction in scar size. However, the group that received the combination of MSCs and cardiacderived CSCs also demonstrated increased viable tissue, improved contractile performance and increased formation of new cardiomyocytes, which contribute to heart repair. The group that received the combination cell therapy continued to show substantial cardiac enhancement for at least three months post treatment. While further testing is needed, these findings establish the safety and efficacy of combination cell-based treatments, taking the next steps in developing stem cell-based therapies for the prevention and treatment of cardiovascular disease in humans.

Phosphorus Content Dependent Sliding Wear Behaviors of Electroless Ni-P Deposits

2010 ◽  
Vol 663-665 ◽  
pp. 1187-1191
Author(s):  
Yan Hai Cheng ◽  
Zhen Cai Zhu ◽  
Zheng Tong Han ◽  
Yong Zou
Keyword(s):  
Sliding Wear ◽  
Phosphorus Content ◽  
Adhesive Wear ◽  
Wear Behavior ◽  
High Phosphorus ◽  
Heat Treated ◽  
Before And After ◽  
Electroless Ni ◽  
Wear Tests ◽  
High Phosphorus Content

In this work, the deposits of electroless Ni-P deposits prepared by different process were studied by means of EPMA, mirohardness tester, friction-wear instrument. The experimental results showed that the microhardness of the deposits was directly affected by the phosphorus content, which was depended on the processes of electroless. The friction-wear tests showed that the Ni-P deposits composing of less phosphorus content exhibited lower friction coefficient before and after being heat treated. The conclusion was drawn that the lower phosphorus content deposits could improve the wear resistance under the condition of both as-plated and after being heat treated Ni-P deposits. The wear behavior was typical of a pure adhesive wear mechanism for the high phosphorus content deposit at as-plated and after being heat treated at 200oC. However, for the high phosphorus content deposit after being heat treated at 400oC, the alternate friction mechanisms were emerged from adhesive wear to abrasive wear with the precipitating of hard Ni3P particles during Ni-P deposits suffering friction tests

The sensory contribution of a single vibrissa's cortical barrel

1986 ◽  
Vol 56 (4) ◽  
pp. 1196-1223 ◽  
Author(s):  
K. A. Hutson ◽  
R. B. Masterton
Keyword(s):  
Oscillation Frequency ◽  
Relevant Information ◽  
Temporal Acuity ◽  
The Third ◽  
Stimulus Transduction ◽  
Before And After ◽  
Sinusoidal Oscillations ◽  
Normal Sensitivity

The sensory contribution of the cortex containing the cortical barrel of the C1 vibrissa was studied in rats using the ablation-behavior method. Three independent experiments were performed, each requiring stimulus transduction by the C1 vibrissa but varying in their perceptual demands. The first required detection of sinusoidal oscillations of the vibrissa generated by an oscillating airstream directed vertically onto the vibrissa tip. The second required detection of a change in rate of the oscillation. The third required the blinded rat to jump a gap in an elevated runway after palpating the far side with its vibrissa. Psychophysical determinations of the single vibrissa system's thresholds before and after ablation of the cortex containing its barrel show that normal sensitivity either for detecting an oscillation or for detecting a change in oscillation frequency are not dependent on either the contralateral or the ipsilateral cortical barrelfield. In contrast to the lack of effect of barrelfield ablation on the spatial and temporal acuity of the vibrissa, the third experiment shows that a rat's ability to collect situation-relevant information with the vibrissa is lost after ablation of the cortex containing its contralateral barrel but not after ablation of the cortex containing its homologous ipsilateral barrel. The results of repeated retesting of an individual rat's ability to make a jump-no jump decision on the basis of vibrissa-transduced information at each stage of a series of successive single-vibrissa removals and unilateral barrelfield ablations show that the loss of the cortex containing the vibrissa's contralateral barrel is tantamount to loss of the vibrissa itself.

EXPERIMENTAL STUDIES ON THE INFLUENCE OF ABRASIVE MATERIALS ON THE WEAR OF HARD-WEARING STEELS

Tribologia ◽  
2018 ◽  
Vol 281 (5) ◽  
pp. 133-141 ◽  
Author(s):  
Andrzej N. WIECZOREK
Keyword(s):  
Experimental Studies ◽  
Structural Steels ◽  
Operating Conditions ◽  
Ring Test ◽  
Test Rig ◽  
Wear Properties ◽  
Aggressive Action ◽  
Low Wear ◽  
Loss Of Mass ◽  
Wear Tests

The paper presents the wear properties of hard-wearing steels and structural steels used in mining and transport machines exposed to the aggressive action of the environment, which have been determined experimentally in the presence of diverse abrasive materials. The wear tests were carried out on a ring-on-ring test rig simulating the operating conditions of elements exposed to abrasive wear. The samples were subjected to tests in conditions of sliding contact, and the main destructive process was micro-cutting of the surface with loose corundum or quartz grain. In the case of the coal abrasive, only slight grinding in of the mating surfaces was observed. The loss of mass in the samples was measured as the parameter characterizing the wear. It was then used to determine the volume loss. Based on the results obtained, it was found that the wear resistance of hard-wearing steels was approximately four times higher as compared to S355J2 structural steel for the corundum and quartz abrasives. In the case of the coal abrasive, there was a relatively low wear for all of the materials examined.

Assessment of tribological behavior and physicochemical properties alterations of polytetrafluoroethylene imposed by wear test

2017 ◽  
Vol 69 (4) ◽  
pp. 550-558 ◽  
Author(s):  
Joao Luiz do Vale ◽  
Carlos Henrique da Silva ◽  
Carlos M.G. da Silva Cruz
Keyword(s):  
Tribological Behavior ◽  
Wear Test ◽  
Test Sequence ◽  
Scanning Calorimetry ◽  
Crystallinity Degree ◽  
Content Type ◽  
Before And After ◽  
Wear Products ◽  
Property Changes ◽  
Wear Tests

Purpose The purpose of this article is to discuss the tribological behavior of polytetrafluoroethylene (PTFE) and property changes imposed by wear tests. Design/methodology/approach Long-duration dry wear tests were carried out in a sliding bearing on shaft tribometer. Differential Scanning Calorimetry (DSC) and Fourier Transformed Infrared Spectroscopy (FTIR) analyses were performed in the PTFE in its original condition and after the tests. Findings The wear products merged in multilayer films and were expelled out of the test sequence. Through DSC and FTIR analyses in the polymeric material, before and after tests, it was possible to verify an increase of the crystallinity degree of PTFE, as well as absence of crystalline fusion of the material. The wear products presented changes in the infrared spectra, which suggests the occurrence of some bonds of hydrogen and oxygen. Originality/value It was verified on correlation that fibril mechanism, which occurred during PTFE wear, and its crystallinity degree increase. Also, analysis of PTFE wear products showed CO and CH bonds, which were imposed by wear test.

scholarly journals Development of the design of the research module - model of a high-temperature surface with induction heating

2021 ◽  
Vol 2088 (1) ◽  
pp. 012053
Author(s):  
A N Varava ◽  
A S Demidov ◽  
A V Zakharenkov ◽  
V D Loktionov ◽  
A T Komov ◽  
...  
Keyword(s):  
High Temperature ◽  
Energy Density ◽  
Test Bench ◽  
High Energy ◽  
High Energy Density ◽  
Operating Parameters ◽  
Cooling Efficiency ◽  
Two Component ◽  
New Research ◽  
Temperature Surface

Abstract The paper describes a test bench for evaluating the cooling efficiency of a working area with a high energy density using a two-component dispersed coolant flow. The design of a pneumatic sprayer and the scheme of the working area cooled by a two-component dispersed flow are described. A description of the design of the new research module and a scheme for installing thermocouples on it is given. A method for measuring the temperature of the walls of the research module is proposed. Adjustment tests were performed at the operating parameters of the coolant p water = 2,5·105 Pa, p air = 2,0·105 Pa, G water = 0,048 kg/c; G air = 1,7·10−3 kg/c.

“Easier, Less Stressful, and Better Results”: Sociology and Criminal Justice Majors’ Experience of Library Research before and after Library Instruction

2020 ◽  
pp. 0092055X2097026
Author(s):  
Nicole Willms ◽  
Kelly O’Brien-Jenks
Keyword(s):  
Literature Review ◽  
Research Methods ◽  
Research Process ◽  
Literacy Skills ◽  
Library Instruction ◽  
Library Research ◽  
Before And After ◽  
Information Literacy Skills ◽  
Criminal Justice Majors ◽  
New Research

This article argues for the incorporation of library instruction into research methods courses to foster information literacy skills important to disciplinary specialization. The evidence in support emerges from a collaborative teaching and assessment project conducted by a research methods instructor and a faculty instructional librarian. The project evaluated the effectiveness of library instruction in two ways: One, essays in which students described their research process before and after library instruction were evaluated qualitatively for dominant themes. Two, students’ postinstruction literature review projects were assessed using a rubric to determine the degree to which students met learning outcomes. These assessments indicate that library instruction led to several positive outcomes. In the essays, many students described increases in skills and confidence as well as appreciation for the new research tools introduced. In sampled literature review assignments, students demonstrated skills that met or exceeded expectations.

scholarly journals Measuring the Safety Effect of Raised Bicycle Crossings Using a New Research Methodology

1998 ◽  
Vol 1636 (1) ◽  
pp. 64-70 ◽  
Author(s):  
Per Gårder ◽  
Lars Leden ◽  
Urho Pulkkinen
Keyword(s):  
Bayesian Approach ◽  
Research Methodology ◽  
Accident Analysis ◽  
Traffic Calming ◽  
Expert Model ◽  
Before And After ◽  
Study Methodology ◽  
Safety Effect ◽  
New Research ◽  
Before And After Study

Before-and-after study methodology was developed and applied to evaluating the effect on bicyclists’ safety of raising urban bicycle crossings by 4 to 12 cm. In total, 44 junctions were reconstructed in this way in Gothenburg, Sweden. Four of these were studied in detail. Before the implementations, bicyclists were riding either in the roadway or on separate paths parallel to the roadway. The paths then ended with short ramps or curb cuts at each cross street, and bicyclists used nonelevated, marked bicycle crossings, similar to pedestrian crosswalks but delineated by white painted rectangles rather than zebra stripes. The results show that the paths with raised crossings attracted more than 50 percent more bicyclists and that the safety per bicyclist was improved by approximately 20 percent due to the increase in bicycle flow, and with an additional 10 to 50 percent due to the improved layout. However, the increased bicyclist volume means that the total number of bicycle accidents is expected to increase. Besides accident analysis, the change in risk was estimated using four different methods: surveys of bicyclists and experts, respectively; conflict data; and a quantitative expert model. Using a Bayesian approach for combining the results shows that the most likely effect of raising the bicycle crossing is a risk reduction of around 30 percent, compared with the before situation with a conventional bicycle crossing. Motorists and pedestrians also saw safety benefits from this traffic-calming measure.

THE ASSESSMENT OF TRIBOLOGICAL PROPERTIES IN ROLLING-SLIDING CONTACT IN RECIPROCATING MOTION ON A DEVICE FOR SURFACE WEAR TESTING

Tribologia ◽  
2017 ◽  
Vol 273 (3) ◽  
pp. 13-19
Author(s):  
Henryk BĄKOWSKI ◽  
Zbigniew STANIK
Keyword(s):  
Financial Burden ◽  
Sliding Contact ◽  
Wear Testing ◽  
High Mass ◽  
Rolling Stock ◽  
Main Task ◽  
Surface Wear ◽  
Reciprocating Motion ◽  
Experimental Apparatus ◽  
Wear Tests

The paper presents wear tests of a sample made of rail steel in a reciprocating motion on an experimental apparatus for surface wear testing. Professional machines for wear tests of rolling-sliding contact, whose main task is to simulate the multiple passage of rolling stock, are large in size and have a significant financial burden on the implementation of scientific projects. The mobile device used for surface wear testing in reciprocating motion has a number of advantages over existing research units with high mass and high financial costs. The proposed device makes it possible to significantly reflect the actual conditions of co-ordination of a rollingsliding contact, for example, the wheel-rail assembly, while maintaining a reasonable financial outlay for the entire project. The results obtained are highly consistent with those obtained under real conditions, which allows us to put forward far-reaching assumptions about the durability of the contact in question and its wear resistance.

scholarly journals TRIBOLOGICAL PROPERTIES OF Ti-6Al-7Nb ALLOY AFTER ISOTHERMAL OXIDATION

Tribologia ◽  
2019 ◽  
Vol 285 (3) ◽  
pp. 5-12
Author(s):  
Krzysztof ANIOŁEK ◽  
Adrian BARYLSKI ◽  
Denis OSIOR
Keyword(s):  
Friction Coefficient ◽  
Tribological Properties ◽  
Isothermal Oxidation ◽  
Bearing Steel ◽  
Oxide Layers ◽  
Resistance To Sliding ◽  
Before And After ◽  
Wear Products ◽  
Wear Tests

The paper presents the characterization of tribological properties of the Ti-6Al-7Nb alloy before and after isothermal oxidation in different friction couples. Microscopic observations have shown that uniform oxide layers were obtained, which evenly covered the entire surface of the investigated samples. It was found that oxide layers deposited on the Ti-6Al-7Nb alloy substrate contribute to a considerable improvement of the tribological properties. The best resistance to sliding wear was shown by the layer obtained at a temperature of 600°C. It was also shown that presence of oxide layers on the surface of the Ti-6Al-7Nb alloy leads to an increase in the friction coefficient. The highest increase in the value of the friction coefficient was observed for a surface oxidized at 650°C during interaction with an Al2O3 ball. SEM observations of traces of the tribological interaction showed the presence of numerous scratches and fine wear products on the friction surface. For the non-oxidized condition, after interaction with a ball made of bearing steel 100Cr6, the presence was found of alternating, morphologically varied areas which had formed as a result of corrugation wear. Tests have shown that isothermal oxidation eliminates this disadvantageous phenomenon.

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