scholarly journals Experimental set-up and the associated model for squeal analysis

2020 ◽  
Vol 21 (2) ◽  
pp. 204 ◽  
Author(s):  
Martin Duboc ◽  
Vincent Magnier ◽  
Jean-François Brunel ◽  
Philippe Dufrénoy
Keyword(s):  
Mechanical Vibration ◽  
High Amplitude ◽  
Friction Material ◽  
Contact Length ◽  
Material Behavior ◽  
Major Influence ◽  
Pin On Disc ◽  
Set Up ◽  
The One ◽  
Improved Model

Brake squeal is commonly defined at frequency upper than 1000 Hz and occurs if the system has a very high amplitude mechanical vibration with sound pressure level above 120 dB. Many studies are devoted to this problem and many of recent ones show that contact conditions and friction material behavior have a major influence on squeal occurrence. To investigate this aspect, an experimental set-up has been developed in this study. It is based on a simplified system in order to focus on the influence of the material in the one hand and surface conditions in the other hand. In this paper, the design of the pin-on-disc is described and an analytical model is also presented in order to understand the dynamic behavior of the system. Macroscopic aspects are investigated by varying the pin geometry. The results show clearly the influence of the variation of the contact length size on squeal occurrence. Comparison with the model shows good agreement and exhibit the necessity of considering an improved model of the friction material behavior. This study also gives information on the comprehension of squeal mechanisms.

Effect of size and shape of copper alloys particles on the mechanical and tribological behavior of friction materials

2020 ◽  
Vol 21 (6) ◽  
pp. 613
Author(s):  
Amira Sellami ◽  
Nesrine Hentati ◽  
Mohamed Kchaou ◽  
Mohammad Asaduzzaman Chowdhury ◽  
Riadh Elleuch
Keyword(s):  
Tribological Behavior ◽  
Copper Alloys ◽  
Physical And Mechanical Properties ◽  
Friction Material ◽  
Material Behavior ◽  
Brake Pad ◽  
Friction Materials ◽  
Physical Density ◽  
Pin On Disc ◽  
Young Module

Friction materials are composed of numerous ingredients which differ from nature and particles size. Each ingredient has its own impact on the mechanical and tribological behavior of the material. Brass ingredients have a great impact on the thermal gradient dissipation in the sliding contact between disc and brake pad material. In this research, the influence of different sizes and forms of brass ingredient was studied on the friction material behavior. The physical (density), mechanical (yield strength, young module) and thermal (thermal conductivity and specific heat) properties of the considered composites were characterized. Results proves that only physical and mechanical properties are sensitive to the changes in size and form of brass particles. The tribological behavior of the brake friction materials was also assessed using a pin-on-disc tribometer. The results show that bigger brass particles and their elongated shape allows it to be well embedded on the pad surface during braking application, and thus decreased wear rate . In contrast, the smaller particle decrease the friction stability and it rounded shape increase wear of the material since it tearing from the surface by abrasive wear.

scholarly journals Friction and Wear Characteristics of Rubber Resin-Bonded Metallic Brake Pad Materials

2019 ◽  
Vol 8 (6) ◽  
pp. 1312-1316
Keyword(s):  
Friction And Wear ◽  
Physical And Mechanical Properties ◽  
Friction Material ◽  
Brake Disc ◽  
Brake Pad ◽  
Sliding Velocity ◽  
Wear Characteristics ◽  
Pin On Disc ◽  
Set Up ◽  
Friction And Wear Characteristics

This paper aims to present comparative study of friction and wear characteristics of non-asbestos rubber resin bonded metallic based brake pad material. Friction material was compression moulded and machined to a sample size. Their physical and mechanical properties were studied. Experiments were conducted using Pin-on-disc test set-up against EN31 disc. Coefficient of friction and wear was measured for metallic based brake materials at varying conditions of temperature, sliding velocity, pressure and sliding distance. When brake pads are in contact with brake disc, heat is generated hence thermal behaviour of metallic based brake material and its impact on friction and wear were studied. Experiments, based on Taguchi’s analysis technique, using L9 orthogonal array were performed. On the basis of experimental results and S/N ratio analyses, ranking of the parameters have been done. It was found that temperature (95.37 %) and sliding velocity (2.99 %) are most affecting parameters in friction, However temperature (82.96 %) and pressure (6.80) in wear. The elemental composition of metallic based brake material was measured by EDS technique. SEM micrographs of brake pad samples were tested at different magnifications. Further detailed studies are suggested to evaluate wear rate, stopping distance under simulative test conditions alternate to asbestos based brake pad material.

scholarly journals The Impact of Heat Treatment on the Behavior of a Hot-Dip Zinc Coating Applied to Steel During Dry Friction

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 660
Author(s):  
Dariusz Jędrzejczyk ◽  
Elżbieta Szatkowska
Keyword(s):  
Heat Treatment ◽  
Wear Resistance ◽  
Friction Coefficient ◽  
Dry Friction ◽  
Zinc Coating ◽  
Pin On Disc ◽  
The One ◽  
The Impact ◽  
Coating Hardness ◽  
Anticorrosion Properties

The analyzed topic refers to the wear resistance and friction coefficient changes resulting from heat treatment (HT) of a hot-dip zinc coating deposited on steel. The aim of research was to evaluate the coating behavior during dry friction after HT as a result of microstructure changes and increase the coating hardness. The HT parameters should be determined by taking into consideration, on the one hand, coating wear resistance and, on the other hand, its anticorrosion properties. A hot-dip zinc coating was deposited in industrial conditions (according EN ISO 10684) on disc-shaped samples and the chosen bolts. The achieved results were assessed on the basis of tribological tests (T11 pin-on-disc tester, Schatz®Analyse device, Sindelfingen, Germany), microscopic observations (with the use of optical and scanning microscopy), EDS (point and linear) analysis, and microhardness measurements. It is proved that properly applied HT of a hot-dip zinc coating results in changes in the coating’s microstructure, hardness, friction coefficient, and wear resistance.

scholarly journals The Swiss National Park

Oryx ◽  
1955 ◽  
Vol 3 (2) ◽  
pp. 64-70
Author(s):  
G. N. Zimmerli
Keyword(s):  
National Park ◽  
Swiss Society ◽  
Large Area ◽  
Nature Protection ◽  
Swiss National Park ◽  
Plant Life ◽  
Eastern Border ◽  
Set Up ◽  
The One ◽  
Protection Commission

The idea of a Swiss national park originated with the Swiss Society for Nature Research and this Society played the leading part in its realization. In 1906 the Society set up as part of its own organization a Swiss Nature Protection Commission and charged it to search for an area in Switzerland suitable for establishment as a reserve, in which all the animal and plant life could be protected against interference by man and so could be left entirely to the play of natural forces. It was not easy to find in Switzerland a suitably large area which still retained its original characteristics, was virtually free from human settlement, and contained some wealth of fauna and flora. After a careful survey of the whole country it became clear that the most suitable region was the Lower Engadine, with its isolated valleys on the eastern border of the country. The district in which, at the beginning of the century, bears had still lived was the one in which primitive nature could be found in its truest state.

Evaluation of changes in mechanical properties of O-ring in one-piece and two-piece ball retained implant-supported overdentures: A three-year retrospective study.

2021 ◽  
Author(s):  
Fathima Banu Raza ◽  
Anand Kumar
Keyword(s):  
Mechanical Properties ◽  
Wear Resistance ◽  
Retrospective Study ◽  
Statistical Analysis ◽  
Wear Rate ◽  
Digital Camera ◽  
Maximum Displacement ◽  
Pin On Disc ◽  
The One ◽  
Insight Into

The o-rings in ball retained overdentures deteriorate with time and need replacement to restore the retentive quality. We evaluated retrospectively the mechanical properties of o-rings after 3 years in function in one and two-piece implant-supported overdentures. The o-rings were retrieved from one-piece (Myriad snap, Equinox-Straumann, 3.3 x 13mm) and two-piece (Neo Biotech, 3.3 x 13mm) implant-supported overdenture patients. A total of 16 pairs of matrices were tested for wear, type of damage and elasticity using Pin on Disc method, USB Digital Camera in 30x zoom and Universal Tensile Machine respectively. The statistical analysis for independent groups were done with the Mann-Whitney U test. Assessment of used O-rings showed 84% more wear in the two-piece system with an abrasive type of damage while 46% wear in the one-piece system with a compressive type of damage. The o-rings in one-piece system showed increase in elongation and maximum displacement to 2% and 7% respectively, while two-piece system showed decrease in elongation and maximum displacement by 13% and 6% respectively. In one-piece system, the loss of retention was more with slow wear rate and in two-piece system, the wear resistance of O-rings decreased due to increased stiffness. Further studies to evaluate the changes in O-ring with increased sample size and at interval 1 year will pave way for insight into the progressive changes in the mechanical properties of an O-ring.

The structure of weakly compressible grid-generated turbulence

2001 ◽  
Vol 432 ◽  
pp. 219-283 ◽  
Author(s):  
G. BRIASSULIS ◽  
J. H. AGUI ◽  
Y. ANDREOPOULOS
Keyword(s):  
Mach Number ◽  
Large Scale ◽  
Isotropic Turbulence ◽  
Three Dimensional ◽  
High Amplitude ◽  
Time Dependent ◽  
Wide Range ◽  
Dynamical Flow ◽  
Set Up ◽  
Decay Exponent

A decaying compressible nearly homogeneous and nearly isotropic grid-generated turbulent flow has been set up in a large scale shock tube research facility. Experiments have been performed using instrumentation with spatial resolution of the order of 7 to 26 Kolmogorov viscous length scales. A variety of turbulence-generating grids provided a wide range of turbulence scales with bulk flow Mach numbers ranging from 0.3 to 0.6 and turbulent Reynolds numbers up to 700. The decay of Mach number fluctuations was found to follow a power law similar to that describing the decay of incompressible isotropic turbulence. It was also found that the decay coefficient and the decay exponent decrease with increasing Mach number while the virtual origin increases with increasing Mach number. A possible mechanism responsible for these effects appears to be the inherently low growth rate of compressible shear layers emanating from the cylindrical rods of the grid. Measurements of the time-dependent, three dimensional vorticity vectors were attempted for the first time with a 12-wire miniature probe. This also allowed estimates of dilatation, compressible dissipation and dilatational stretching to be obtained. It was found that the fluctuations of these quantities increase with increasing mean Mach number of the flow. The time-dependent signals of enstrophy, vortex stretching/tilting vector and dilatational stretching vector were found to exhibit a rather strong intermittent behaviour which is characterized by high-amplitude bursts with values up to 8 times their r.m.s. within periods of less violent and longer lived events. Several of these bursts are evident in all the signals, suggesting the existence of a dynamical flow phenomenon as a common cause.

scholarly journals Mineral fertilizers as a governing factor of the regulation of the number of fungi in soil

2009 ◽  
pp. 201-207 ◽  
Author(s):  
Marijana Pesakovic ◽  
Dragutin Djukic ◽  
Leka Mandic ◽  
Milan Rakicevic ◽  
Rade Miletic
Keyword(s):  
Soil Fungi ◽  
Mineral Fertilizer ◽  
Mineral Fertilizers ◽  
Nitrogen Rate ◽  
Nutritive Medium ◽  
Governing Factor ◽  
Npk Fertilizer ◽  
Set Up ◽  
The One ◽  
Fertilizer Rates

Over 2003-2005 period, a study was performed on the effect of different rates of NPK fertilizer of formulation 8:16:24 + 3% MgO (N1 - 400 kg ha-1; N2 - 600 kg ha-1; N3 - 800 kg ha-1; N4 - 1000 kg ha-1) on development of the soil fungi. The trial was set up in the experimental plum orchard established by Fruit Research Institute Cacak, and the laboratory of Department of Microbiology, Faculty of Agronomy Cacak. Unfertilized soil was used as the control soil. Each of the stated variants was carried out in three replications. The size of the basic plot was 68 m2. The effect of the studied mineral fertilizer rates was determined three times over the growing season, the number of fungi being checked by the indirect rarefaction method on Chapek nutritive medium. The results of the study inferred that the application of mineral fertilizers brought about the decrease in the number of fungi. Of all studied variants, the one with the highest nitrogen rate (variant N4) exhibited the strongest effect. The influence of the fertilizer was highest at the third sampling. Furthermore, the effect was highest in season 2003.

scholarly journals PLATFORM COOPS NOW!: A team entrepreneurship capacity building program to create platform coops

2021 ◽  
pp. 135-156
Author(s):  
Liher Pillado Arbide ◽  
Ander Etxeberria Aranburu ◽  
Giovanni Tokarski
Keyword(s):  
Capacity Building ◽  
Sharing Economy ◽  
Digital Platforms ◽  
New School ◽  
Digital Era ◽  
The World ◽  
Set Up ◽  
The One ◽  
Building Program ◽  
Capacity Building Program

Traditional labour relationships have been disrupted due to the digital platforms based businesses. This article aims on the one hand to share the consequences the sharing economy has generated for workers, and how MONDRAGON’s principles as one of the best examples of worker owned business group in the world, can be applied within the new digital era. On the other hand, this paper provides a literature review on how digital platforms can operate with fairer principles based on the framework that platform coops consist of. Last but not least, Mondragon University and The New School have set up a capacity building program on team entrepreneurship and an online incubation program that aims to support the creation of platform coops, whose results after two editions and future opportunities for research are shared.

scholarly journals Improving Interior Environmental Quality Using Sustainable Design in Jordanian Hospital Bedrooms

2020 ◽  
Vol 9 (3) ◽  
pp. 443
Author(s):  
Saeed Hussein Alhmoud ◽  
Çiğdem Çağnan ◽  
Enis Faik Arcan
Keyword(s):  
Interior Design ◽  
Environmental Quality ◽  
Sustainable Design ◽  
Health Sector ◽  
Green Building ◽  
Climatic Conditions ◽  
Building Assessment ◽  
The World ◽  
Set Up ◽  
The One

As the wave of sustainability is sweeping across the major countries and cities of the world, the effect of the inevitable change is finding its way through to the health sector as well. Since the main functions of the hospital include healing the patient, it aims to provide adequate health services to people. Hospitals managers should strive to realize facilities that meet a certain level of demand. This study aims to present the interior environmental quality (IEQ) of bedrooms in Jordanian hospitals and propose a solution to improve indoor environment quality using sustainable design principles. A qualitative research methodology is used in this study. A comparative analysis is made between the original set up of the hospital buildings and the present conditions in which they are in. During the research, it was found that the design to be applied for a hospital should be following the healing environmental characteristics. Besides, the design of hospitals should be made with the climatic conditions of the area in mind. In the advanced countries of the world, hospitals are generally built with extensive research and important factors such as temperature, wind direction and humidity are taken into consideration. The design for a hospital building should be assessed according to the German Green Building Assessment (DGNB) criteria. It has been found that the one-bedroom is ideal for patients because it provides the necessary privacy and also greatly reduces the spread of the disease. In hygienic practices, there should be a first-class healing environment with evidence-based medical research. It was concluded that the practices involving the use of sustainable designs can be followed with the hints received from hospitals in the advanced countries of the world. Keywords: Jordan hospital; IEQ; bedroom; interior design; healthcare; green building assessment; DGNB

scholarly journals 4 The Court and Domestic and International Legal Systems

2020 ◽  
Author(s):  
Nussberger Angelika
Keyword(s):  
Human Rights ◽  
European Convention ◽  
Vienna Convention ◽  
Legal Systems ◽  
Member States ◽  
Supreme Courts ◽  
European Court ◽  
Set Up ◽  
The One ◽  
The Relationship

This chapter assesses the relationship between the European Court of Human Rights (ECtHR) and domestic and international legal systems. With the ratification of the European Convention on Human Rights (ECHR), the Member States accept to be bound by final judgments of the Court and to implement them in their domestic legal systems. The Convention system does not make any difference as to the set-up of the national legal system or to the hierarchical position accorded to the Convention in national law. This is in line with a purist international law perspective, summarized in Article 27 of the Vienna Convention of the Law on Treaties: ‘A party may not invoke the provisions of its internal law as justification for its failure to perform a treaty.’ However, from the constitutional law perspective of the Member States, the situation is much more multi-faceted and complex. While it is generally accepted that the Court's judgments are binding and have to be implemented, the relationship between the Convention and the national constitutions as well as between their respective guardians, the Court on the one hand and national constitutional or supreme courts on the other hand, is not seen as one-way and hierarchical, but nuanced and differentiated. Implementation of judgments is accepted to be a duty, but not necessarily without exceptions. The chapter then considers the relationship between the ECtHR and the European Court of Justice (ECJ).

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