轻型货车制动系统设计（含CAD图纸、说明书）
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制动器设计含CAD
制动器设计cad图
轻型载货汽车设计制动系设计含CAD图纸
轻型载货汽车设计制动系设计含CAD图纸轻型载货汽车设计制动系设计
轻型货车制动系统
CAD图纸设计
制动器设计含说明书
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.Wear 232 1999 168175 rlocaterwear Tribological properties of automotive disc brakes with solid lubricants Luise Gudmand-Hyer a,), Allan Bachb, Georg T. Nielsenc, Per Morgena a Physics Department, Odense Uniersity, Campusej 55, 5230 Odense M, Denmark b Roulunds Fabriker, Hestehaen 51, 5260 Odense S, Denmark c Tristan, Kochsej 1, 2600 Glostrup, Denmark Abstract In automotive brake systems, high temperatures and pressures are generated at the contacting surfaces. This affects the pad and disc materials, creating a friction film between the surfaces, which consists of wear particles and volatile reactants from the pad and disc. To acquire suitable tribological properties, a pad matrix contains up to 20 different ingredients, mainly selected from experience. In the present report the effect of solid lubricants has been studied in three different pad matrices with relatively few components as compared to commercial brake pads. The components are Cu S, PbS and Sb S , which are known to modify and stabilise the friction coefficient. The 223 friction coefficient and wear rates of the pads are examined on a dynamometer, which simulates series of real-life car brake events. Two different energy levels and two ambient temperatures are included. After these tests, the brake disc surfaces are analysed with energy .dispersive X-ray EDX and Auger electron spectroscopy AES in combination with argon ion sputtering to study the microscopic lateral and in-depth distribution of elements on and below the surface, looking for traces of the friction film. These experiments are used to discuss the correlation between the tribological properties and the external variables braking temperature, solid lubricants and pad matrix. q1999 Elsevier Science S.A. All rights reserved. Keywords: Tribology; Automotive brakes; Solid lubricants; Friction film; Surface analysis 1. Introduction The development of new pad materials is a complicated matter as the components interact and synergetic effects that are hard to disentangle arise. Quite often, the selection of the different components is based on empirical experi- ence, which means that some components are added for reasons based more on tradition and less on knowledge about their influence on the brake performance. In the contact zone between the disc and pad, energy is trans- ferred and heat is dissipated. As a consequence, a friction film is created in the contact zone. The character of the film depends on the friction pad formulation. Metal sul- phides are known to modify and stabilise the friction coefficient, though the more specific effects are not well known. They are usually added though very expensive and .therefore primarily used for original equipment OE and ) Corresponding author. Tel.: q45-65573509; fax: q45-65158760; E-mail: lghfysik.ou.dk .original spare parts OES . Thus a better knowledge of the effects of adding those components can improve the opti- misation process and limit their use to minimise the price, which is an important issue in the car industry. Other groups have studied the formation of the friction film. They looked for the influence of the film properties on the friction coefficient. The chemistry of a solid transfer .film was studied with energy-dispersive X-ray EDX and w ximaging XPS by Wirth et al. 1 . A wear-in period has been described as the time during which the friction is fluctuating with decreasing amount of material transfer as stable conditions are reached. The specific role of additives with respect to the relative amount of iron and oxygen in w xthe discs was discussed recently by Holinski2 . The formation of an iron layer on asbestos brake pads sliding w xover steel surfaces has been investigated by Scieszka 3 with SEM together with tribo-oxidation. Experience from previous studies on friction film for- mation under tribological testing with samples of hard ball w x bearing steel indicated a very thin film of around 30 A 4 . The references above have inspired us to study the effects of metal sulphides on the formation of a friction 0043-1648r99r$ - see front matter q 1999 Elsevier Science S.A. All rights reserved. .PII: S0043-1648 99 00142-8 ()L. Gudmand-Hyer et al.rWear 232 1999 168175169 Table 1 The composition of the friction materials is given in vol.%. The numbers in parenthesis indicate the reference friction material without metal sulphide .Main elementCharacteristic namesNmet vol.%Low1 vol.%Low2 vol.% .FibreOrganic aramid5 5.411 125 5.4 .Metal9 9.8 .Other inorganic18 19.615 16.318 19.6 .FillersBarytes, friction dust, and vermiculite41 44.625.5 27.729 31.5 .MetalsBrass5 5.49 9.8 .AbrasivesZirconium silicate5 5.45 5.4 .Aluminium oxide0.5 0.5 .BindersResin, rubber23 25.026 28.326 28.3 . . .Metal sulphideCopper, lead or antimony sulphide8 08 08 0 Total vol.%100100100 film in a brake system and its effect on the surface of the disc as indication of specific wear and friction behaviour. 2. Materials and experimental procedures 2.1. Friction pad formulation Three different base matrices are designed especially for this project, and they are simplified and compared to a commercial brake pad. The matrices are: one with no .metal fibre Nmet and two with a low content of metal .fibreLow1 and Low2 . The Nmet is very simple with only six components while Low1 and Low2 consist of 1314 constituents. Three different metal sulphides are added to the base matrices to examine their effects. We labelled the different brake pads with the base matrix and the respective additive, e.g., Low1-Cu is the label of base matrix Low1 with 8 vol.% Cu S added, and Low1-Ref 2 designates the base matrix Low1 without metal sulphide. In this case the vol.% in Table 1 are adjusted to equal a total of 100% of the components in the brake pads. 2.2. Tribological tests The samples are tested on a dynamometer equipped with a car brake caliper. Two test procedures one at low and one at high duty are designed to examine the effects of the metal sulphides at two different energy .inputs. The test at low duty 1A consists of 600 braking cycles performed from 50 kmrh down to rest. When the temperature of the disc has decreased to 508C, the next braking cycle begins. Each braking is performed with a constant braking pressure. During braking the torque is measured, from which the friction coefficient is extracted as the ratio between measured momentum and braking pressure multiplied by a constant value accounting for the geometry. A similar procedure is performed at high duty .2A , and the parameters are summarised in Table 2. Before each test a new disc is mounted on the rig. The discs used are Volvo standard rear discs, which are unven- tilated. After testing, the discs are labelled according to type of friction material and test procedure, e.g., Low1-Sb- 1A corresponds to base matrix Low1 with antimony sul- phide tested at 1A. After the dynamometer testing, the discs are cut into pieces of 14=14 mm2with a saw while cooling with a commercial fluid to prevent heating. The samples are stored in atmospheric air before analysis. The wear of the .pads is measured as change of thickness mm and weight .loss g . Compared to the friction material, the wear of the discs is estimated to be much lower as it is immeasurable using a micrometer screw. 2.3. Surface analysis First, the samples of the disc are analysed in a Jeol 35 keV electron microscope with an EDAXe EDX system. The analysis is performed as a spot analysis, using a primary energy of 15 keV. The composition is calculated from the peaks with the EDAXe computer program that fits the background of the spectra with a smooth function and subtracts it from the spectrum. The peaks are com- pared to standard spectra from a database, and evaluated w xwith the ZAF-method 5 . The surfaces of the discs are examined with SEM in which an image is created with secondary electrons ejected from the surface. The combi- nation SEMrEDX is a strong tool to get a quick overview Table 2 Dynamometer tests 1A and 2A, indicating the initial velocity from which the braking is performed, the initial temperature of the disc when each braking cycle begin, and the applied brake pressure. The cycles are repeated N times DynamometerVelocityTemperaturePressureStop no. .testkmrh8CbarN 1A507030600 2A12020040350 ()L. Gudmand-Hyer et al.rWear 232 1999 168175170 of both the topography and the main composition of the surface of a large number of samples in a short time. Afterwards, a selection of the samples is examined with .Auger electron spectroscopy AES . This is done with 3 keV primary electron energy combined with depth profil- ing using 1 keV argon ion sputtering for 1 min between each recorded spectrum. This analysis method is very surface sensitive and gives the concentration of the compo- nents with depth as spectra are recorded between each cycle of argon iron sputtering. With AES it is possible to see other elements than with EDX, e.g., oxygen and carbon which are believed to play an important role in the formation of a friction film. 3. Results 3.1. Friction and wear The average friction levels measured for each braking cycle for dynamometer tests 1A and 2A are shown in Fig. 1. The two graphs show how the friction level develops .from the beginning, during conditioning bedding-in until the end. At that stage the friction level is stable and the surfaces are analysed to study the existence of a friction Fig. 1. The friction levels of different brake couples measured on a dynamometer. The shown friction material is base matrix Low1 with .Cu S, PbS or Sb S , and the reference without a metal sulphide.a 223 .Dynamometer test 1A. b Dynamometer test 2A. Fig. 2. Dynamometer results. The average friction of the different friction . .materials tested against cast iron brake discs B . The pad wear = . a .Dynamometer test 1A. b Dynamometer test 2A. film. These results are typical for all friction materials, though with some variations in the friction level between the three base matrices. The results of wear and friction are visualised in Fig. 2. The friction value is the average value of the measured friction after the bedding-in period when the friction has stabilised, which is respectively after 200 and 100 stops for dynamometer test 1A and 2A. A comparison of the differ- ent friction materials for dynamometer test 1A shows little variation of the wear, around 0.10.3 mm. The friction varies from 0.360.53. For all three base matrices the friction is highest for Sb S , around 0.470.49, and a little 23 lower for PbS, around 0.400.47. The largest variations are seen with Cu S, from 0.370.53. For dynamometer 2 test 2A, the wear varies much more with the friction material, from 1.56.5 mm. The wear is by far highest for base matrix Nmet and much lower for Low1 and Low2. The addition of one of the metal sulphides to Low1 improves the wear, and the situation is opposite for Low2. Addition of Cu S leads to relatively higher wear and 2 .sometimes lower friction. The repeated measurements show some variations for both friction and wear. The variation is 510% on the friction, and 2030% on the pad wear. Several factors cause the large variations of wear. Before the weight ()L. Gudmand-Hyer et al.rWear 232 1999 168175171 measurement, wear particles are not removed. The thick- ness is affected by the permanent swell of the pads after heating. The roughness of the discs varies, which can cause different wear during bedding-in. The result is there- fore to be used merely as indication of the trend. 3.2. SEM The surfaces of the discs are examined with SEM in which the image is created with secondary electrons ejected from the surface. The image reflects a dependency both on topography and composition. Fig. 3 shows an image of a new disc before and after testing scanned with 15 keV and magnified 400=. The underlying longitudinal lines are from the machining of the disc. Apart from that, two .different areas are circled. One area looks smooth S and .the other area is roughR . Both types of areas are found on all the discs including the new disc. The next paragraph presents the results of EDX examinations of the rough and smooth areas to demonstrate the character of the friction film. 3.3. EDX analysis After testing, all the discs have been analysed with EDX at a smooth and rough area. The overall results are discussed by comparing two discs, one tested against the reference material without a metal sulphide and the other tested against a friction material with antimony sulphide. The variation from sample to sample is comparable to the differences between the individual friction materials. The scatter from spot to spot on one sample reflected the surface topography; thus, the smooth areas were similar in composition. A typical example of the EDX analysis of the discs is shown in Figs. 4 and 5 of Low1-Sb-1A and Low1-Sb-2A, .respectively, giving the composition of both a roughR .and a smooth S part of the discs. The spectra in Fig. 4a .and Fig. 5a are both recorded at a smoothSarea. The former shows no other components than those from the disc: silicon, iron and manganese. The latter shows some similarities with Fig. 4b and Fig. 5b, which are recorded at .roughR areas on the discs. These spectra contain peaks from components with origin in the pad matrix. The existence of several components with origin in the pad indicates a transfer of friction material. The ratios between antimony and sulphur, and barium and sulphur, which are original compounds in the pads, are especially interesting. If chemical changes have taken place, their ratios in the discs should have changed from the values of the original material. The element concentrations for Low1-Sb-1A and 2A and Low1-Ref-1A and 2A are calculated from the spectra, as shown in Table 3. For all eight measurements shown, except for Low1-Ref-1A, the ratio MnrFe is almost the same. At the rough areas, the ratio BarS and SbrS are the . .same for Low1-Sb-1AR and Low1-Sb-2AR , but the concentrations are different. This indicates that the surface layers are similar and that the same reactions have taken place, but the thickness of the layers is different. At the smooth areas no antimony and barium is found .for Low1-Sb-1A S , only sulphur, copper, and zinc. This .is in contrast with the spectrum of Low1-Sb-2A S , which .contains the same elements as Low1-Sb-2ARbut the ratios between the elements are different. Compared to . .Low1-Sb-2A S , Low1-Ref-2A S contains 10 times less sulphur and no barium, indicating that no friction material . .Fig. 3. Typical SEM images of a cast iron disc before and after testing on a dynamometer. The rough R and smooth S areas are indicated with a circle. . .a New disc. b Low1-Sb-2A. ()L. Gudmand-Hyer et al.rWear 232 1999 168175172 . .Fig. 4. Typical EDX-spectra measured on the cast iron disc surface tested against friction material Low1-Sb-1A. The spectra are recorded on a a smooth area and b a rough area. ()L. Gudmand-Hyer et al.rWear 232 1999 168175173 . .Fig. 5. Typical EDX-spectra measured on the cast iron disc surface tested against friction material Low1-Sb-2A. The spectra are recorded on a a smooth area and b a rough area. ()L. Gudmand-Hyer et al.rWear 232 1999 168175174 has been transferred at the smooth areas for the reference material. The ratio ZnrCu is the same for Low1-Ref-1A . .S and Low1-Ref-2A S . 3.4. AES depth profile The existence of antimony on the surface can be ob- served in Fig. 6 showing a decreasing concentration with depth; thus, antimony has been transferred and dissolved at the very upper surface of the disc. The amounts of iron, oxygen and carbon also change with depth. The oxygen concentration follows the iron concentration closely, in- creasing with depth whereas the carbon concentration de- creases. The ratio between iron and oxygen indicates that a homogeneous phase of FeO has formed at the surface. This iron oxide phase is stable compared to higher oxidation w xlevels and is discussed by Jansson et al. 6 . A further discussion of the AES analysis of all samples is to be published later in relation to a discussion of the general concepts of formation of the friction film. 4. Discussion It takes many small bits of information to create a full picture of the effects, e.g., to see which constituents have been transferred and which are gone or not active. Also, the atomic stoicheiometric percentages indicate if there has been any chemical change. When one component is pre- sent with a different relative amount than the original constituent, as in the case of barium sulphate and antimony sulphide, it indicates a chemical reaction. The present measurements and procedures allow for at least a partial understanding of the friction film formation process. This is definitely demonstrated here with Low1- Sb-2A where a friction film forms at 120 kmrh, 2008C, and a brake pressure of 40 bar at the presence of antimony sulphide in the pad. In this case, even smooth-looking areas of the disc have undergone compositional modifica- tion, as shown with EDX. The presence of sulphur moni- Table 3 Surface concentration measured with EDX of the cast iron discs tested with the friction materials Low1-Sb and Low1-Ref analysed at smooth . .S and roughR areas on the discs ElementLow1-Sb-1ALow1-Sb-2ALow1-Ref-1A Low1-Ref-2A . . . . . . . .SRSRSRSR At.%At.%At.%At.% SiK3.310.3 SK10.00.13.00.112.1 SbL BaL2.914.9 MnK1.40.8 FeK95.475.289.558.795.178.093.953.9 CuK0.96.7 ZnK0.40.5 Fig. 6. A typical AES depth profile measured on the cast iron disc surface tested against friction material Low1-Sb-1A. Intensity of the signals from oxygen, carbon, iron, antimony and sulphur is mounted against sputter time in minutes.
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