Role of thermal conductivity in controlling the tribo-performance of non-asbestos organic brake-pads

2020 ◽  
Vol 54 (27) ◽  
pp. 4145-4155
Author(s):  
Vishal Mahale ◽  
Jayashree Bijwe
Keyword(s):  
Thermal Conductivity ◽  
Structural Integrity ◽  
Critical Issue ◽  
Frictional Heat ◽  
Friction Materials ◽  
Excessive Heat ◽  
Brake Pads ◽  
Back Plate ◽  
Identical Composition

The range of thermal conductivity of friction materials is a critical issue since lower thermal conductivity leads to accumulation of frictional heat on the working surface, which results in excessive fade, while higher thermal conductivity leads to excessive heat flow towards back-plate resulting to “spongy brakes”. Therefore, thermal conductivity of the friction materials across the brake-pads should not be high while along the length of brake-pad; it should be high. To enhance the thermal conductivity, metals in the form of powder or fibres are used in the friction materials. Apart from improvement in thermal conductivity, strength and structural integrity, metals get actively involved in controlling the tribo-performance. Their role as improver of thermal conductivity and hence indirectly tribo-performance can never be known clearly. Keeping this in view, it was proposed to design a bulk of pad rather than the surface. Three types of pads with identical composition but differing in the bulk/body were designed by placing a thin fabric layer of Cu (2 mm away from surface) in one pad and two layers in other pad. The third pad did not contain any fabric. The developed pads were characterized for physical, chemical, thermal, and mechanical properties. Tribo-performance was evaluated on full-scale inertia dynamometer by following the JASO C 406 testing standard. It was concluded that Cu fabric inclusion led to improvement in thermal conductivity and heat exaction capacity, which in turn, improved the tribo-performance of pads significantly.

Thermal and Fade Aspects of a Non Asbestos Semi Metallic Disc Brake Pad Formulation with Two Different Resins

2012 ◽  
Vol 622-623 ◽  
pp. 1559-1563
Author(s):  
M.A. Sai Balaji ◽  
K. Kalaichelvan
Keyword(s):  
Thermal Stability ◽  
Friction And Wear ◽  
Phenolic Resin ◽  
Structural Integrity ◽  
Friction Material ◽  
Performance Criteria ◽  
Brake Pad ◽  
Friction Materials ◽  
Brake Pads ◽  
Thermal Stability Of

The formulation of a brake pad requires the optimization of multiple performance criteria. To achieve a stable and adequate friction (µ), the brake pad materials should have low fade and higher recovery characteristics coupled with less wear and noise. Among the properties mentioned, resistance to fade is very difficult to achieve. The type and amount of resin in the friction material is very critical for structural integrity of the composites. The binder should not deteriorate under any diverse conditions. The thermal stability of friction materials and its capacity to bind its ingredients collectively under diverse conditions depend upon the quality and proportion of resin. The current work evaluates the fade and recovery behaviour of developed friction composites from two different resins which are traditional straight phenolic resin and the alkyl benzene modified phenolic resin. Two brake pads with these different resins were fabricated as per Industrial Standard. TGA is carried between 150 – 4000 C as this zone of temperature is very critical which accounts for the weight loss (Thermal degradation). Friction and wear studies were carried out on a friction coefficient test rig as per SAE J661a standard. The results showed that the fade and wear of the friction materials were closely related to the thermal decomposition of the binder resin and durability of the contact plateaus, which were produced by the compaction of wear debris around hard ingredients on the rubbing surface. It was clearly observed that the friction materials with modified resin showed significant reduction in fade %. Friction materials made with higher thermal stability showed resistance to fade. However wear didn’t show much noticeable changes.

scholarly journals Role of Promaxon-D in Controlling Tribological Performance of Cu-Free Brake Pads

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 441
Author(s):  
Bhaskaranand Bhatt ◽  
Navnath Kalel ◽  
Ashish Darpe ◽  
Jayashree Bijwe
Keyword(s):  
Aquatic Life ◽  
Hydrated Calcium Silicate ◽  
Friction Materials ◽  
Brake Pads ◽  
Test Standards ◽  
Enhanced Sensitivity ◽  
Noise Vibration ◽  
Almost All ◽  
The Cost

Copper appears to be an indispensable ingredient of non-asbestos organic (NAO) brake friction materials owing to its multifunctionality. However, recent findings proved it as a threat to aquatic life and efforts were initiated worldwide over the last few years to find a substitute for it. Recently, the authors’ group had reported on the potential of particulate Promaxon-D (hydrated calcium silicate), a porous material for enhancement of noise–vibration (NV) performance of Cu-free brake pads. It was felt necessary to investigate how Promaxon-D (PD) contributes to controlling tribo-performance of brake pads since this aspect is most important for the brake friction materials. A series of five types of brake pads was developed by keeping parent composition fixed and varying the theme ingredient PD content from 0–20 wt.%. The tribo-performance was evaluated on a full-scale brake inertia dynamometer as per the JASO C406 test standards. The increase in PD contents led to a reduction in density, hardness, and thermal conductivity while an increase in porosity and compressibility. With the increase in PD contents, almost all tribo properties such as average μ, fade ratio, and recovery ratio got enhanced, sensitivity of µ for pressure, speed, and temperature lowered but at the cost of wear resistance. Finally, the worn surfaces of pads and discs were observed under a scanning electron microscope equipped with energy dispersive X-ray (SEM-EDX) to find out the presence of various elements at the contact zone and to monitor specific topographical events responsible for wear mechanism.

Lattice Thermal Conductivity Modelling of a Diatomic Nanoscale Material

2020 ◽  
Vol 10 (5) ◽  
pp. 602-609
Author(s):  
Adil H. Awad
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Correction Term ◽  
Nanoscale Material ◽  
New Approach ◽  
Two Samples ◽  
Conductivity Modelling ◽  
Callaway Model

Introduction: A new approach for expressing the lattice thermal conductivity of diatomic nanoscale materials is developed. Methods: The lattice thermal conductivity of two samples of GaAs nanobeam at 4-100K is calculated on the basis of monatomic dispersion relation. Phonons are scattered by nanobeam boundaries, point defects and other phonons via normal and Umklapp processes. Methods: A comparative study of the results of the present analysis and those obtained using Callaway formula is performed. We clearly demonstrate the importance of the utilised scattering mechanisms in lattice thermal conductivity by addressing the separate role of the phonon scattering relaxation rate. The formulas derived from the correction term are also presented, and their difference from Callaway model is evident. Furthermore their percentage contribution is sufficiently small to be neglected in calculating lattice thermal conductivity. Conclusion: Our model is successfully used to correlate the predicted lattice thermal conductivity with that of the experimental observation.

scholarly journals Lipid Transporters Beam Signals from Cell Membranes

Membranes ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 562
Author(s):  
Miliça Ristovski ◽  
Danny Farhat ◽  
Shelly Ellaine M. Bancud ◽  
Jyh-Yeuan Lee
Keyword(s):  
Membrane Proteins ◽  
Lipid Bilayers ◽  
Lipid Composition ◽  
Structural Integrity ◽  
Current Knowledge ◽  
Integral Membrane Proteins ◽  
Cellular Membranes ◽  
Cytoplasmic Proteins ◽  
Lipid Transporters

Lipid composition in cellular membranes plays an important role in maintaining the structural integrity of cells and in regulating cellular signaling that controls functions of both membrane-anchored and cytoplasmic proteins. ATP-dependent ABC and P4-ATPase lipid transporters, two integral membrane proteins, are known to contribute to lipid translocation across the lipid bilayers on the cellular membranes. In this review, we will highlight current knowledge about the role of cholesterol and phospholipids of cellular membranes in regulating cell signaling and how lipid transporters participate this process.

The effect of oestrogen withdrawal on cardiac Ca2+ regulation and the influence of GPER1

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
A.J Francis ◽  
J.M Firth ◽  
N Islam ◽  
J Gorelik ◽  
K.T MacLeod
Keyword(s):  
Heart Failure ◽  
Structural Integrity ◽  
Left Ventricular ◽  
Funding Source ◽  
Hormonal Changes ◽  
Ion Conductance ◽  
Developing Heart ◽  
Rapid Stimulation ◽  
Post Menopausal

Abstract Background Post-menopausal women have an enhanced risk of developing heart failure, attributed to declining oestrogen levels during menopause. However, the signalling mechanisms remain undetermined. Purpose We aim to determine the role of G-protein coupled oestrogenic receptor 1 (GPER1) in intracellular Ca2+ regulation and the consequences of hormonal changes that may exacerbate the pathophysiology of heart failure. Methods Ovariectomy (OVx) (mimics menopausal hormone changes) or sham surgeries were conducted on female guinea pigs. Left ventricular cardiomyocytes were isolated 150-days post-operatively for experimental use. Cellular t-tubule network and structural integrity was measured using fluorescent di-8-ANEPPs staining and scanning ion conductance microscopy. GPER1 expression and localisation was measured by Western blot and immunostaining. The role of GPER1 activation was measured using selective agonist G-1 in electrophysiological and Ca2+-sensitive dye fluorescence experiments. Results Following oestrogen withdrawal, the t-tubule network density decreased by 13% and z-groove index reduced by 15%. GPER1 predominantly localised to the peri-nuclear endoplasmic reticulum and its expression increased by 32% in OVx. Action potential duration (APD) prolonged in OVx and following GPER1 activation, APD90 shortened by 11% and 25% in sham and OVx respectively. OVx cells had larger peak inward Ca2+ current (ICaL) (by 22%) and sarcoplasmic reticulum (SR) Ca2+ content (by 13%), compared with sham. While GPER1 activation had little effect on peak ICaL or SR content, it reduced Ca2+ transient amplitude (by 20%), SR fractional release (by 11%) in OVx cells. The frequency of occurrence of spontaneous Ca2+ waves evoked by periods of rapid stimulation reduced by 40% and wave-free survival time prolonged in OVx cells following GPER1 activation. Conclusions In the hearts of an animal species whose electrophysiology and intracellular Ca2+ regulation is akin to humans, we show that following oestrogen deficiency, the t-tubule network is down-regulated and becomes disorganised, GPER1 expression is increased and its activation induces negative inotropic responses in cardiomyocytes. This may limit the adverse changes to Ca2+ signalling reported in OVx that could be pro-arrhythmic and exacerbate the progression to heart failure. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): British Heart Foundation

Role of electron–phonon coupling in thermal conductivity of metallic nanofluids

2019 ◽  
Vol 52 (48) ◽  
pp. 485302 ◽  
Author(s):  
Dong-Xing Song ◽  
Yu-Feng Zhang ◽  
Wei-Gang Ma ◽  
Xing Zhang
Keyword(s):  
Thermal Conductivity ◽  
Phonon Coupling ◽  
Electron Phonon Coupling

scholarly journals Role of the Ndc1 interaction network in yeast nuclear pore complex assembly and maintenance

2009 ◽  
Vol 185 (3) ◽  
pp. 475-491 ◽  
Author(s):  
Evgeny Onischenko ◽  
Leslie H. Stanton ◽  
Alexis S. Madrid ◽  
Thomas Kieselbach ◽  
Karsten Weis
Keyword(s):  
Nuclear Pore Complex ◽  
Structural Integrity ◽  
Fluorescent Protein ◽  
Interaction Network ◽  
Nucleocytoplasmic Transport ◽  
Nuclear Pore ◽  
Binding Partners ◽  
Interaction Partners ◽  
Redundant Functions

The nuclear pore complex (NPC) mediates all nucleocytoplasmic transport, yet its structure and biogenesis remain poorly understood. In this study, we have functionally characterized interaction partners of the yeast transmembrane nucleoporin Ndc1. Ndc1 forms a distinct complex with the transmembrane proteins Pom152 and Pom34 and two alternative complexes with the soluble nucleoporins Nup53 and Nup59, which in turn bind to Nup170 and Nup157. The transmembrane and soluble Ndc1-binding partners have redundant functions at the NPC, and disruption of both groups of interactions causes defects in Ndc1 targeting and in NPC structure accompanied by significant pore dilation. Using photoconvertible fluorescent protein fusions, we further show that the depletion of Pom34 in cells that lack NUP53 and NUP59 blocks new NPC assembly and leads to the reversible accumulation of newly made nucleoporins in cytoplasmic foci. Therefore, Ndc1 together with its interaction partners are collectively essential for the biosynthesis and structural integrity of yeast NPCs.

Role of graphene waviness on the thermal conductivity of graphene composites

2012 ◽  
Vol 111 (1) ◽  
pp. 221-225 ◽  
Author(s):  
Ke Chu ◽  
Wen-sheng Li ◽  
Hongfeng Dong
Keyword(s):  
Thermal Conductivity

Balancing of Values and the Value of Balancing (Part One)

2021 ◽  
pp. 13-24
Author(s):  
Gadis A. Gadzhiev ◽  
◽  
Elena A. Voinikanis ◽  
Keyword(s):  
Human Rights ◽  
Critical Issue ◽  
Specific Mode ◽  
Constitutional Order ◽  
Basic Law ◽  
The Relationship

The article discusses the specific mode of existence of values – balancing or op­timization when it comes to deontological values. The authors using examples of values such as the principles of law and human rights, the rules of balancing are analyzed, which, according to G. Hart's classification, are secondary norms. The critical issue for the legal balancing procedure is the relationship between legal reality and values as such. Are the constitutional and legal values set by the Basic Law (Constitution), or do they objectively exist in society as a general (pre-constitutional) order of values? Should the Basic Law be confined to its own text and remain value-neutral in this sense? Are legal values purely deonto­logical, or can they be related to utilitarian goals and interests? The second part of the article explores the value of balancing as one of the methods for resolving the most complex legal conflicts. The well-known dispute between J. Habermas and R. Alexy about the admissibility of balancing of human rights demonstrates how complex and philosophically rich the legal balancing procedure is. Based on Luhmann’s concept of the cognitive openness of law, at the end of the article, the authors substantiate their own position on the role of values in modern justice.

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