A study of the influence of humidity on the friction and squeal generation of automotive brake pads

2001 ◽  
Vol 215 (3) ◽  
pp. 329-342 ◽  
Author(s):  
M. Eriksson ◽  
A. Lundqvist ◽  
S. Jacobson
Keyword(s):  
Relative Humidity ◽  
Coefficient Of Friction ◽  
Metal Content ◽  
Air Humidity ◽  
Brake Squeal ◽  
Humid Atmosphere ◽  
High Metal Content ◽  
Cent Relative Humidity ◽  
The Coefficient Of Friction ◽  
Low Humidity

In order to clarify the influence of humidity on the coefficient of friction and brake squeal generation, a series of brake rig tests has been performed. The influence of both air humidity and pad humidity was evaluated. The results show that, between 20 and 80 per cent relative humidity, air humidity has a limited influence on the coefficient of friction. Nevertheless, in a humid atmosphere the friction coefficient was considerably lower than in a wet environment for two of the pads and higher for one pad. This is believed to be an effect of different mechanisms of tribofilm formation on the pad surfaces. The tribofilm observed on the pads mainly consists of iron oxide originating from the disc. The film is more easily formed in dry environments and preferentially by the pads with low metal content. The friction increase often seen during each individual stop is slightly lower at high air humidity. This effect is more pronounced for the pads with high metal content. Generally, the pads with smooth surfaces were less sensitive to changes in humidity. Only a limited correlation was found between relative humidity and brake squeal generation. One of the pads generated considerably more squeal in low humidity. None of the pads showed the opposite behaviour.

scholarly journals Fretting wear rate of sulphur deficient MoSx coatings based on dissipated energy

2001 ◽  
Vol 16 (12) ◽  
pp. 3567-3574 ◽  
Author(s):  
Xiaoling Zhang ◽  
W. Lauwerens ◽  
L. Stals ◽  
Jiawen He ◽  
J-P. Celis
Keyword(s):  
Relative Humidity ◽  
Wear Rate ◽  
Coefficient Of Friction ◽  
Contact Stress ◽  
Ambient Air ◽  
Fretting Wear ◽  
Dissipated Energy ◽  
Wear Volume ◽  
The Coefficient Of Friction ◽  
Crystallographic Orientations

The fretting wear of sulphur-deficient MoSx coatings with different crystallographic orientations has been investigated in ambient air of controlled relative humidity. The coefficient of friction and the wear rate of MoSx coatings sliding against corundum depend not only on fretting parameters like contact stress, fretting frequency, and relative humidity, but also strongly on the crystallographic orientation of the coatings. For randomly oriented MoSx coatings, the coefficient of friction and the wear rate increased significantly with increasing relative humidity. In contrast, basal-oriented MoSx coatings were less sensitive to relative humidity. The coefficient of friction of both types of MoSx coatings decreased on sliding against corundum with increasing contact stress and decreasing fretting frequency. A correlation between dissipated energy and wear volume is proposed. This approach allows detection in a simple way of differences in fretting wear resistance between random- and basal-oriented MoSx coatings tested in ambient air of different relative humidity.

scholarly journals Ammonia concentrations in a free-stall dairy barn

2014 ◽  
Vol 14 (1) ◽  
pp. 153-166 ◽  
Author(s):  
Piotr Herbut ◽  
Sabina Angrecka
Keyword(s):  
Relative Humidity ◽  
Weather Conditions ◽  
Ammonia Concentration ◽  
Air Humidity ◽  
Movement Velocity ◽  
Air Movement ◽  
Air Temperatures ◽  
Relative Air Humidity ◽  
Measurement Results ◽  
Low Humidity

AbstractThe paper presents the results of research on indoor ammonia (NH3) concentrations in the air in a free-stall barn. The differences in measurement results mainly depended on the season and weather conditions. The study also showed a significant correlation (P<0.01) between the NH3 concentration and temperature, relative humidity and air movement velocity inside the barn. The lowest NH3 concentration was recorded in the summer (0.0 ppm) in the presence of high air temperatures, low humidity and increased exchange of ventilated air. In winter during severe frosts, highest ammonia concentration (8.0 ppm) was noted, caused by limited ventilation. The highest daily ammonia concentration was usually recorded during the night. This was due to increased relative air humidity and low air velocities. It was concluded that the average level of ammonia of 2.73 ppm during the entire year was significantly below values defined as harmful for animals and people.

Rail Corrugations Caused by Low Coefficient of Friction in a Submarine Railway Tunnel

2005 ◽  
Author(s):  
Makoto Ishida ◽  
Fusayoshi Aoki ◽  
Yasutomo Sone ◽  
Takumi Ban ◽  
Kensuke Shirouzu
Keyword(s):  
Coefficient Of Friction ◽  
Interaction Model ◽  
Railway Track ◽  
Railway Vehicle ◽  
Vertical Force ◽  
Large Problem ◽  
Railway Tunnel ◽  
Humid Atmosphere ◽  
The Coefficient Of Friction ◽  
Railway Rail

One of some types of rail corrugations is caused on railway rail surface in a submarine tunnel. It poses a large problem from the aspects of railway vehicle and railway track deterioration. In this paper, the mechanism of the rail corrugations was studied with the focus placed on roll-slip of wheel and rail interface. Traction and vertical force interacting between wheel and rail were investigated by a vehicle/track interaction model, and the coefficient of friction (COF) on rail surface was measured. Also, the rail surface was analysed with infrared to understand the chemical composition of surface layer influenced by salty and very humid atmosphere in the submarine tunnel. β-FeOOH was found out as a cause of reducing COF on rail surface.

scholarly journals Influence of environmental conditions and oxidation on the coefficient of friction using microalloyed rail steels

2020 ◽  
pp. 095440972092568
Author(s):  
JL Viesca ◽  
S González-Cachón ◽  
A García ◽  
R González ◽  
A Bernardo-Sánchez ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Iron Oxides ◽  
Coefficient Of Friction ◽  
Environmental Conditions ◽  
Rail Steel ◽  
Water Film ◽  
Atmospheric Conditions ◽  
Railway Systems ◽  
Pin On Disc ◽  
The Coefficient Of Friction

In railway systems, certain atmospheric conditions – mainly related to temperature and relative humidity – lead to the creation of iron oxides which can affect the coefficient of friction between the wheel and the rail. This can result in increased wear of the rail, reducing its service life and thus increasing replacement costs. Pin-on-disc tests were conducted in a climate chamber to study the influence of environmental conditions and iron oxides on the coefficient of friction. The iron oxides generated on the surface of specimens extracted from microalloyed rail steel during wear tests were analysed using X-ray diffraction. The results show that hematite (α-Fe2O3) is the predominant iron oxide among all the oxides generated on the worn surfaces. It was further noted that the oxide layer resulting from the rise in both temperature and relative humidity does not significantly affect the average coefficient of friction for each steel samples tested. High relative humidity combined with high temperature leads to the formation of α-Fe2O3, which tends to increase the coefficient of friction. However, a boundary lubrication effect is observed at higher relative humidity due to a condensed water film, which reduces the coefficient of friction and counteracts the increase of the coefficient of friction expected due to the presence of hematite.

The importance of weight loss in reducing breakdown of Jonathan apples

1968 ◽  
Vol 8 (32) ◽  
pp. 377 ◽  
Author(s):  
KJ Scott ◽  
EA Roberts
Keyword(s):  
Weight Loss ◽  
Relative Humidity ◽  
Calcium Chloride ◽  
Practical Method ◽  
High Relative Humidity ◽  
Cent Relative Humidity ◽  
Low Humidity ◽  
Initial Storage

Studies were made of the effect of different treatments on weight loss and breakdown of Jonathan apples. The apples were stored at 30�F under high relative humidity except while the following treatments were applied : initial storage at 30�F for 2, 4, 6, 8, and 10 weeks at 65 per cent relative humidity ; storage at 30�F over calcium chloride for 8 weeks ; hydrocooling ; step-wise cooling from 36�F to 30�F ; and warming the fruit at 68�F for 24 hours. The level of breakdown in all treatments depended on the loss in weight of the fruit. Initial storage at low humidity appears to be a practical method of reducing breakdown.

scholarly journals Characterization of the Effect of Moisture on Tribology of Titanium Rubbed Against Different Pin Materials

2020 ◽  
pp. 1-10
Author(s):  
Bodhi R. Manu ◽  
Adam M. Schroeder ◽  
Ahalapitiya H. Jayatissa
Keyword(s):  
Friction Coefficient ◽  
Relative Humidity ◽  
Coefficient Of Friction ◽  
Water Film ◽  
Interfacial Surface ◽  
The Coefficient Of Friction ◽  
The Mean ◽  
Machine Parts ◽  
Pin On Disk

Tribology investigations were conducted to understand the effect of humidity and water adsorption at the interfacial surface on the friction coefficient of titanium. Pin-on-disk tribometer tests were conducted at different levels of humidity ranging from 0% to 71% RH using aluminum and steel pins on a titanium plate. The variation of the mean coefficient of friction was plotted as a function of relative humidity. The friction coefficient slightly decreased when the relative humidity was increased from 0% to 10% RH. However, it increased with a further increase in humidity. The maximum friction coefficients were observed at 55% and 65% RH for steel and aluminum, respectively. The thickness of the wear tracks also showed the same trend as the friction coefficient. Under high humidity conditions, water vapor can condense on the surface of the moving machine parts. To understand the influence of this water film, a pin-on-disk test was carried out on a sample where a thin film of water masks metal surfaces from contact. Although the coefficient of friction was similar for both the aluminum and steel pins’ interaction with titanium (~0.36), the wear tracks were not formed for steel pin/titanium interaction even though this experiment was conducted for more cycles.

Experimental Investigation of aluminum doping crumb rubber/epoxy composite in reciprocating motion

2015 ◽  
Vol 3 ◽  
pp. 1
Author(s):  
Goutam Chandra Karar ◽  
Nipu Modak
Keyword(s):  
Experimental Investigation ◽  
Coefficient Of Friction ◽  
Epoxy Composite ◽  
Normal Load ◽  
Crumb Rubber ◽  
The Other ◽  
Reciprocating Motion ◽  
Molding Process ◽  
Friction Tester ◽  
The Coefficient Of Friction

The experimental investigation of reciprocating motion between the aluminum doped crumb rubber /epoxy composite and the steel ball has been carried out under Reciprocating Friction Tester, TR-282 to study the wear and coefficient of frictions using different normal loads (0.4Kg, 0.7Kgand1Kg), differentfrequencies (10Hz, 25Hz and 40Hz).The wear is a function of normal load, reciprocating frequency, reciprocating duration and the composition of the material. The percentage of aluminum presents in the composite changesbut the other components remain the same.The four types of composites are fabricated by compression molding process having 0%, 10%, 20% and 30% Al. The effect of different parameters such as normal load, reciprocating frequency and percentage of aluminum has been studied. It is observed that the wear and coefficient of friction is influenced by the parameters. The tendency of wear goes on decreasing with the increase of normal load and it is minimum for a composite having 10%aluminum at a normal load of 0.7Kg and then goes on increasing at higher loads for all types of composite due to the adhesive nature of the composite. The coefficient of friction goes on decreasing with increasing normal loads due to the formation of thin film as an effect of heat generation with normal load.

scholarly journals The contribution of PIP2-type aquaporins to photosynthetic response to increased vapour pressure deficit

2021 ◽  
Author(s):  
D Israel ◽  
S Khan ◽  
C R Warren ◽  
J J Zwiazek ◽  
T M Robson
Keyword(s):  
Vapour Pressure Deficit ◽  
Air Humidity ◽  
Wild Type ◽  
Knockout Mutant ◽  
Evaporative Demand ◽  
Co2 Transport ◽  
Whole Plant ◽  
Knockout Mutants ◽  
Leaf Level ◽  
Low Humidity

Abstract The roles of different plasma membrane aquaporins (PIPs) in leaf-level gas exchange of Arabidopsis thaliana were examined using knockout mutants. Since multiple Arabidopsis PIPs are implicated in CO2 transport across cell membranes, we focused on identifying the effects of the knockout mutations on photosynthesis, and whether they are mediated through the control of stomatal conductance of water vapour (gs), mesophyll conductance of CO2 (gm) or both. We grew Arabidopsis plants in low and high humidity environments and found that the contribution of PIPs to gs was larger under low air humidity when the evaporative demand was high, whereas any effect of lacking PIP function was minimal under higher humidity. The pip2;4 knockout mutant had 44% higher gs than the wild type plants under low humidity, which in turn resulted in an increased net photosynthetic rate (Anet). We also observed a 23% increase in whole-plant transpiration (E) for this knockout mutant. The lack of functional AtPIP2;5 did not affect gs or E, but resulted in homeostasis of gm despite changes of humidity, indicating a possible role in regulating CO2 membrane permeability. CO2 transport measurements in yeast expressing AtPIP2;5 confirmed that this aquaporin is indeed permeable to CO2.

scholarly journals Tribological Aspects, Optimization and Analysis of Cu-B-CrC Composites Fabricated by Powder Metallurgy

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4217
Author(s):  
Üsame Ali Usca ◽  
Mahir Uzun ◽  
Mustafa Kuntoğlu ◽  
Serhat Şap ◽  
Khaled Giasin ◽  
...  
Keyword(s):  
Weight Loss ◽  
Wear Rate ◽  
Coefficient Of Friction ◽  
Applied Load ◽  
Practical Significance ◽  
Tribological Characteristics ◽  
M 10 ◽  
Wide Range ◽  
The Coefficient Of Friction ◽  
Four Levels

Tribological properties of engineering components are a key issue due to their effect on the operational performance factors such as wear, surface characteristics, service life and in situ behavior. Thus, for better component quality, process parameters have major importance, especially for metal matrix composites (MMCs), which are a special class of materials used in a wide range of engineering applications including but not limited to structural, automotive and aeronautics. This paper deals with the tribological behavior of Cu-B-CrC composites (Cu-main matrix, B-CrC-reinforcement by 0, 2.5, 5 and 7.5 wt.%). The tribological characteristics investigated in this study are the coefficient of friction, wear rate and weight loss. For this purpose, four levels of sliding distance (1000, 1500, 2000 and 2500 m) and four levels of applied load (10, 15, 20 and 25 N) were used. In addition, two levels of sliding velocity (1 and 1.5 m/s), two levels of sintering time (1 and 2 h) and two sintering temperatures (1000 and 1050 °C) were used. Taguchi’s L16 orthogonal array was used to statistically analyze the aforementioned input parameters and to determine their best levels which give the desired values for the analyzed tribological characteristics. The results were analyzed by statistical analysis, optimization and 3D surface plots. Accordingly, it was determined that the most effective factor for wear rate, weight loss and friction coefficients is the contribution rate. According to signal-to-noise ratios, optimum solutions can be sorted as: the highest levels of parameters except for applied load and reinforcement ratio (2500 m, 10 N, 1.5 m/s, 2 h, 1050 °C and 0 wt.%) for wear rate, certain levels of all parameters (1000 m, 10 N, 1.5 m/s, 2 h, 1050 °C and 2.5 wt.%) for weight loss and 1000 m, 15 N, 1 m/s, 1 h, 1000 °C and 0 wt.% for the coefficient of friction. The comprehensive analysis of findings has practical significance and provides valuable information for a composite material from the production phase to the actual working conditions.

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