Low-cost solid FeS lubricant as a possible alternative to MoS2 for producing Fe-based friction materials

Three reaction systems of MoS_2-Fe, FeS -Fe, and Fe S-Fe-Mo were designed to investigate the use of FeS as an alternative to MoS_2 for producing Fe-based friction materials. Samples were prepared by powder metallurgy, and their phase compositions, microstructures, mechanical properties, and friction performance were characterized. The results showed that MoS_2 reacts with the matrix to produce iron-sulfides and Mo when sintered at 1050°C. Iron-sulfides produced in the MoS_2-Fe system were distributed uniformly and continuously in the matrix, leading to optimal mechanical properties and the lowest coefficient of friction among the systems studied. The lubricity observed was hypothesized to originate from the iron-sulfides produced. The Fe S-Fe-Mo system showed a phase composition, porosity, and density similar to those of the MoS_2-Fe system, but an uneven distribution of iron-sulfides and Mo in this system resulted in less-optimal mechanical properties. Finally, the Fe S-Fe system showed the poorest mechanical properties among the systems studied because of the lack of Mo reinforcement. In friction tests, the formation of a sulfide layer contributed to a decrease in coefficient of friction（COF） in all of the samples.

Effect of ZrSiO_4 on the Friction Performance of Automotive Brake Friction Materials

Friction-wear properties of the ZrSiO4 reinforced samples were measured and compared with those of plain bronze based ones. For this purpose, density, hardness, friction coefficient wear behaviour of the samples were tested. Microstructures of samples before and after sintering and worn surfaces were also investigated by scanning electron microscopy （SEM）, and the wear types were determined. The optimum friction-wear behaviour was obtained in the sample compacted at 500 MPa and sintered at 820℃. Density of the final samples decreased with increasing the amount of reinforcing elements （ZrSiO4） before pre-sintering. However after sintering, there is no change in density of the samples including reinforcing elements （ZrSiO4）. With increasing friction surface temperature, a reduction in the friction coefficient of the samples was observed. However, the highest reductions in the friction coefficients were observed in the as-received samples containing 0. 5% reinforced ZrSiO4. The SEM images of the sample indicated that while bronze-based break lining material without ZrSiO4 showed abrasive wear behaviour, increasing the amount of ZrSiO4 resulted a change in abrasive to adhesive wear mechanism. All samples exhibited friction-wear values, which were within the values shown in SAE-J661 standard. With increasing the amount of reinforcing ZrSiO4, wear resistance of the samples was increased. However samples reinforced with 5% and 6% ZrSiO4 showed the best results.

Effects of Rare Earths on Properties and Microstructure of Automotive Friction Materials

Rare earth compounds as modifiers used widely in modern friction materials can enhance the interfacial binding of constituents of materials and improve the comprehensive properties of materials evidently. However, there are still few reports on application of rare earth in automotive friction materials. In order to study the effect mechanism of rare earths in friction materials, a rare earth compound was selected as additive and the effects of materials doped with or without rare earth on friction and wear properties of materials were studied. The microstructure and worn surface morphology were observed by scanning electron microscopy and the macro performance was discussed. Worn surface element constitution of materials was analyzed by energy dispersive spectroscopy. Effect mechanism of rare earths on friction and wear behaviors of friction materials were discussed. The results show that doping rare earths in friction materials can stabilize friction coefficient, lower the wear rate of materials and increase the impact strength of materials. The flexibility and fracture resistance of materials is greatly improved. Worn surface of materials doped with rare earth is compact and the surface adhesion is greatly enhanced.

Preparation and Characterization of Semi-Metal Friction Materials Doping Rare Earths

In order to study the effects of preparation process on the performance and microstructure of the materials, semi-metal friction materials doping rare earths were produced. Different influencing factors in preparation processes (forming pressure, hot-pressing temperature, etc.) were investigated and the optimum technological parameters were selected. The results showed that preparation processes has correlation with the properties of the materials. The morphology of worn surface was observed by scanning electronic microscope, and the conclusion was drawn that wear mechanisms of the materials were mainly abrasive wear, adhesive wear and fatigue wear. Doping RE in the materials can improve the interfacial bonding among the components of semi-metal friction materials and make the structure of the materials more impact.

Catic Friction Materials Company

The Catic Friction Materials Co. Ltd in Shandong Province is a joint venture between the China Aero Technology I/E Corp, Beijing Company and the Yimeng Braking Materials Factory in Shandong Province. It deals mainly in semi metallic nonasbestos brake flakes for car use and related products. It has RMB20 million of total investment, 1, 200 staff and workers,

Effect of zinc powder content on tribological behaviors of brake friction materials

Brake friction materials with different zinc powder contents(0,2,4,6,8 wt.%)were fabricated via powder metallurgy method.The results indicate that with the increasing zinc powder content,the density and thermal conductivity of the materials gradually increase,while the hardness decreases monotonously.With increasing zinc powder content,the curve of the nominal friction coefficient shows fluctuating trend but the lowest friction coefficient also shows an increase.However,the wear rate and braking noise of the friction material monotonously decrease with increasing zinc content.This effect may be attributed to the transformation of the tribological mechanism from adhesive wear and abrasive wear to adhesive wear.The brake friction material with 4 wt.%zinc powder exhibits both the best tribological and noise performance.

Tribological and mechanical behaviours of resin-based friction materials based on microcrack filling

To enhance the friction performance of resin-based friction materials,five types of specimens with different polymer ether ketone(PEEK)contents were fabricated and their physiomechanical behaviours were tested and,their tribological properties were investigated using a JF150F-II constant-speed tester.It was found that the addition of PEEK had a positive influence on the properties of the friction materials,and sample FM-3(the shorthand of‘Friction Materials-3’,containing 2 wt%PEEK)exhibited improved friction performance with a fade ratio and recovery ratio of 8.6%and 101.1%respectively.Among all samples,FM-4(the shorthand of‘Friction Materials-4’,con-taining 3 wt%PEEK)had the lowest specific wear rate with a value of 0.622×10^(−7)cm^(3)(N⋅m)^(−1)at 350℃.The PEEK can fill the microcracks in the composite at a high tem-perature and can also cover the hard abrasive particles to prevent them from directly damaging the composite.The findings from this study afford a foundation for studies to further improve the properties of resin-based friction materials.

Optimization of pore structure and wet tribological properties of paper-based friction materials using chemical foaming technology

Paper-based friction materials are porous materials that exhibit anisotropy;they exhibit random pore sizes and quantities during their preparation,thereby rendering the control of their pore structure difficult.Composites with different pore structures are obtained by introducing chemical foaming technology during their preparation to regulate their pore structure and investigate the effect of pore structure on the properties of paper-based friction materials.The results indicate that the skeleton density,total pore area,average pore diameter,and porosity of the materials increase after chemical foaming treatment,showing a more open pore structure.The addition of an organic chemical foaming agent improves the curing degree of the matrix significantly.Consequently,the thermal stability of the materials improves significantly,and the hardness and elastic modulus of the matrix increase by 73.7%and 49.4%,respectively.The dynamic friction coefficient increases and the wear rate is reduced considerably after optimizing the pore structure.The wear rate,in particular,decreases by 47.7%from 2.83×10^(−8) to 1.48×10^(−8)cm^(3)/J as the foaming agent content increases.Most importantly,this study provides an effective method to regulate the pore structure of wet friction materials,which is conducive to achieving the desired tribological properties.

Pin-on-disc study of dry sliding behavior of Co-free HVOFcoated disc tested against different friction materials

The dry sliding behavior of three commercial friction materials(codenamed FM1,FM2,and FM3)tested against a Co‐free cermet coating produced by high‐velocity oxy‐fuel(HVOF)on gray cast‐iron discs is investigated.FM1 is a conventional low‐metallic friction material,FM2 is developed for using against HVOF‐coated discs,and FM3 is a Cu‐free friction material with a low content of abrasives and a relatively high concentration of steel fibers.For the tribological evaluation,they are tested on a pin‐on‐disc(PoD)test rig against Co‐free HVOF‐coated discs,with particular attention to the running‐in stage,which is fundamental for the establishment of a friction layer between the two mating surfaces,i.e.,the pin and disc.The PoD tests are performed at room temperature(RT)and a high temperature(HT)of 300℃.At RT,all materials exhibit a long running‐in stage.At HT,no running‐in is observed in FM1 and FM2,whereas a shorter running‐in period,with respect to the RT case,is observed in FM3 followed by the attainment of a comparatively high coefficient of friction.At RT,the pin wear is mild in all cases but severe at HT.FM3 shows the lowest wear rate at both temperatures.Moreover,the coated disc shows no wear when sliding against the FM3 friction material.All the results are interpreted considering the microstructural characteristics of the friction layers formed on the sliding surfaces.The findings of the present study provide insights into reducing wear in braking system components and hence reducing environmental particulate matter emissions from their wear,through the use of disc coatings.

Non-asbestos Friction Materials Manufacturing in China--Present Situation and Future Prosperity

In the "Industrial Policy of the Motor Industry" which was published on Feb. 19, 1994, the Chinese Government focuses more attention on the development of auto parts industry aiming to adjust the industrial set-ups of auto parts industry, and foster and develop a number of backbone enterprises and striving for a greater progress in production scale, product development and production engineering in the end of the 9th Five-Year-Plan.CATARC has been authorized by the MMI to compose the contemplation and framework of the development of some key auto parts for the 9th Five-Year-Plan. The key auto parts are classified into 25 categories which are listed below:EFI system, spark plug, valve, tappet, piston & piston ring, bearing bush, turbo charger, diesel engine high-pressure pump, aluminium radiator, filters, diaphragm spring clutch, constant velocity universal joint, vacuum servo booster & master cylinder, non-asbestos friction materials, brake tube, brake hose, steering gear, steering ball joint, shock

Effect of Friction Reclaimed Materials of Waste Brake-shoe on Basic Performance of Mortar

Discarded train brake shoes mainly consist of steel-backed friction material. To be better reutilized, its essential features and its interaction in cement-based material need to be studied. Consequently, particle size analysis, SEM, IR and TGA were used to investigate two types of waste brake shoes, i e, mechanical grinding friction reclaimed material of waste brake-shoe（G-FRMWBS） and pyrolysis-friction reclaimed materials of waste brake-shoe（P-FRMWBS）. The latter exhibited less organic content, larger range of particle size distribution and smaller medium particle diameter. Both types contained inorganic particles of spherical and irregular shapes, striped with steel fiber. Upon isometric substituting fine aggregates, G-FRMWBS lifted the strength of mortar effectively that was increased by 16.6% and 17.5% when the replacing rate was 5%; the value went up to 19.2% and 19.2% when the replacing rate was 10%. Moreover, inclusion of FRMWBS enhanced the chloride penetration resistance, and optimized the pore characteristic and ITZ（interfacial transition zone） as well.

Asbestos Exposure during Gasket Removal from Aircraft Engine

We have previously evaluated asbestos exposure associated with various maintenance procedures on light aircraft. The purpose of this study was to evaluate asbestos exposure during engine maintenance on light aircraft. This test was designed to evaluate the potential for asbestos exposure to mechanics and others who remove asbestos-containing engine gaskets from reciprocating style aircraft engines. Utilized in this test was an air cooled, horizontally opposed, aviation gasoline burning engine, assembled during 1986 and operated intermittently up into 2015, having accumulated 1680 hours run time. Nearly 75% of the asbestos-containing gaskets installed during 1986 were still in place at the time of testing. Chrysotile asbestos contents of such gaskets ranged from 55% to 60% by area, for those of sheet style and 5% by area, for the spiral wound metal/asbestos style. Despite the levels of effort required to effect gasket removals, the professional aircraft mechanic was not exposed to airborne asbestos fibers at the lower limits of sampling and analytical detection achieved;all of which were substantially less than the current Occupational Safety and Health Administration Permissible Exposure Limits for asbestos. The results of this testing indicate an absence of gasket related asbestos exposure risk to mechanics who work with light aircraft engines, including those having asbestos-containing gaskets. These results are consistent with the findings of Mlyarek and Van Orden who studied the asbestos exposure risk occasioned during overhaul of larger radial style reciprocating aircraft engines [1].

Investigation on Interaction Mechanism of Components in Fiction Materials Doping Rare Earths

Semi-metal friction material was applied widely in brake process of traffic and dynamical system. The friction materials with rare earth additive were manufactured by heating press molding process. The effects of different reinforcing fibers and adhesives on the properties of the materials were studied by changing the formula. The results showed that the friction materials with YSM resin adhesive and hybrid fibers (Kevlar pulp and steel fiber) had higher and more stable friction coefficient and lower wear rate. Semi-metal friction materials with rare earths formed iron-rich surface layer in the worn surface, and the mechanisms of wear had obvious differences at typical temperature ranges.

A new visco-elastic contact model of traveling wave ultrasonic motor with stator frictional layer

A new contact model of traveling wave ultrasonic motor （TWUSM） with a visco-elastic stator frictional layer was presented. In this model, the initial boundaries were revised, and the rotor revolution speed could he calculated iteratively. This model was compared with compliant slider and rigid stator model. The results of motor characteristics simulations showed that the motors based on this model would gain bigger stall torque. Then the friction and wear characteristics of two models were analyzed. The motors based on this model had lower coefficient of friction and better wear resistance.

Tribological Properties of the Semi-metallic Friction Material with Nano-SiC

The tribological properties of the semi-metallic friction materials with nano-SiC were studied by the contrast experiments. The experimental result indicates that when the nano-SiC powder substitutes the general SiC powder, the friction coefficient is not obviously improved.On the contrary, the wear rate increases a little. The friction surfaces and the mixed powder were examined by a scanning electron microscope and the experimental data were analysed. The main reason, which leads to the high wear, is found.

Effect of thickness of friction material on contact state of ultrasonic motor

Performances of ultrasonic motor (USM) considerably depend on contact state between stator and rotor.Based on an electric contact method,the effects of thickness of single homogeneous friction material and gradient friction material on contact state between stator and rotor were studied.The relative contact length was employed to describe the contact characteristics of stator and rotor.With the decrease of thickness of friction material,the contact characteristic of stator and rotor were analyzed and compared when single homogeneous friction material and gradient friction material were used.The experimental results showed that the effect of gradient friction material on contact characteristic is smaller than that of single homogeneous friction material when the thickness of friction material decreases.The result can provide experimental guidance for design and choosing of friction material for USM.

BIFURCATION OF A SHAFT WITH HYSTERETIC-TYPE INTERNAL FRICTION FORCE OF MATERIAL

The bifurcation of a shaft with hysteretic internal friction of material was analysed. Firstly, the differential motion equation in complex form was deduced using Hamilton principle. Then averaged equations in primary resonances were obtained using the averaging method. The stability of steady_state responses was also determined.Lastly, the bifurcations of both normal motion (synchronous whirl) and self_excited motion (non_synchronous whirl) were investigated using the method of singularity. The study shows that by a rather large disturbance, the stability of the shaft can be lost through Hopf bifurcation in case the stability condition is not satisfied. The averaged self_excited response appears as a type of unsymmetrical bifurcation with high orders of co_dimension. The second Hopf bifurcation, which corresponds to double amplitude_modulated response, can occur as the speed of the shaft increases. Balancing the shaft carefully to decrease its unbalance level and increasing the external damping are two effective methods to avoid the appearance of the self_sustained whirl induced by the hysteretic internal friction of material.

Analysis on Tribological Properties of Potentially New Friction Material with Response Surface Method

The tribological properties of newly developed friction material were evaluated by statistical analysis of the major affecting factors.The material for investigation was non-metallic friction material synergistically reinforced with aramid fibre and CaSO 4 whisker,which was developed for hoisting applications in coal mine.The response surface method（RSM）was employed to analyze the material performances affected by the independent and interactive effect of the factors under the normal working condition and severe working condition,respectively.Results showed that under the normal working condition,the newly developed material exhibited stable tribological properties which were insensitive to the test conditions.While under the severe working condition,the sliding velocity was the most dominant factor affecting the friction coefficient.Additionally,compared to the commercially available material,the modified material showed superior wear resistance and thermal stability.

Assessment of Asbestos Exposure Associated with a Brake Grinder

The wear patterns for drum-style automotive brakes tend to enlarge internal drum diameters. Such enlargement is most profound when used brake drums are machined to restore the metal friction surfaces. Specialized arc grinding machinery has been used to match replacement shoe-style brake friction materials to enlarged drums. The process of arc grinding removes friction material, thereby producing dust. When organic-style friction materials contained asbestos, use of arc grinding machinery posed an asbestos fiber exposure risk to operators and proximate personnel. The manufacturers of arc grinding machinery have incorporated local exhaust ventilation systems designed to capture and remove this dust at the point of grinding contact and propel this dust into collection bags or other systems. This research was designed to evaluate the dust capture and retention characteristics of a specific arc grinder product, when used to custom grind asbestos-containing brake friction materials. A Bear Model 1420 automotive brake shoe arc grinder was the subject of this study. During two separate but consecutive test sessions, newly relined sets of shoe-style automobile brake friction materials were precision ground. Both area and personal air samples were collected throughout each testing session. This work took place within a closed and unventilated metal building, with total interior volume of 2500 m3. Collected air samples were analyzed using phase contrast microscopy (PCM) and transmission electron microscopy (TEM). The results of analysis using PCM for personal samples (n = 6) ranged from <0.044 to 0.055 fibers per cc (f/cc) (mean 0.05). Follow-up analysis of these personal samples using TEM indicated asbestos-adjusted PCM exposures ranging from <0.0074 to 0.055 f/cc (mean ≤ 0.041). Area air samples, taken at distances ranging from 1.5 to 9 meters from the arc grinder (n = 12), showed asbestos-adjusted PCM concentrations ranging from <0.0075 to 0.041 f/cc (mean ≤ 0.017). The process of custom arc grinding shoe-style, asbestos-containing brake friction materials can cause exposure to airborne asbestos fibers. However, when done using properly equipped arc grinding machines, such exposures are not expected to exceed the current occupational exposure limits for asbestos of 0.1 f/cc 8-hour time-weighted average (TWA) or 1.0 f/cc 30-minute average.

Effect of Added Poly (vinyl pyrrolidone) during Condensation on Properties of Poly(p-phenylene terephthalamide)Pulp

Poly(p-phenylene terephthalamide)(PPTA)pulp was prepared by polycondensation of the p-phenylene diamine(PPDA)with terephthaloyl chloride(TPC)in the completely anhydrous solvent system of N-methyl pyrrolidone(NMP)having calcium chloride,in the presence of poly(vinyl pyrrolidone)(PVP)having a viscosity average molecular weight lower than 40 000.It was confirmed that the polycondensation could be accelerated,the inherent viscosity of the polymer could be increased,and the polymers could be fibrillated more easily by the addition of the PVP.FTIR and X-ray spectra proved that PVP had not combined into molecular chains of the resultant PPTA pulps.The morphology of the resultant pulps,the effect of viscosity average molecular weight,amount and adding mode of PVP on inherent viscosity,specific surface area,and mean length of the resultant pulps were discussed in detail.And the friction and wear properties of the compound reinforced by the resultant pulps were simply investigated.