Browse Topic: Friction materials
This SAE standard specifies a method for testing and measuring a normalized elastic constant of brake pad assemblies using ultrasound. This document applies to disc brake pad assemblies and its coupons or segments used in road vehicles.
This document covers the mechanisms from the power cylinder, which contribute to the mechanical friction of an internal combustion engine. It will not discuss in detail the influence of other engine components or engine driven accessories on friction.
Wear phenomenon has extensively been published in the literature and this paper presents a methodology of how the wear models were used to assess the risk of failures in a field application, through endurance testing at a system level. Correlation of the wear prediction by the model with actual measurement was performed and used to predict the field operation reliability. Results are shown for sliding wear as well as impact wear phenomenon in this paper. In the case of sliding wear, wear modeling and prediction was done for a friction material using a system level metric, and the mean wear predicted was not different from the model predicted values at 95% confidence under a field application duty cycle.
This SAE Recommended Practice establishes a standard method to perform screening test sequences that identify a brake friction material’s effectiveness under various test conditions. The result is an evaluation of brake friction material effectiveness under a set of defined braking conditions considered most relevant to automobile braking system development.
This SAE Recommended Practice is intended as the definition of a standard test, which may be subject to frequent change to keep pace with experience and technical advances. This should be kept in mind when considering its use. The SAE No. 2 friction test is used to evaluate the friction characteristics of automatic transmission plate clutches with automotive transmission fluid combinations. The specific purpose of this document is to define a µPVT test for the evaluation of the variation of wet friction system low speed slip characteristics as a function of speed, temperature, and pressure. This procedure is intended as a suggested method for both suppliers and end users. The only variables selected by the supplier or user of the friction system are: Friction material Fluid Reaction plates Oil flow (optional) These four variables must be clearly identified when reporting the results of this test. If any of the test parameters or system hardware as described in this document are changed
The moisture adsorption kinetics of copper-free brake pads was studied to confirm an earlier finding that the adsorption weight gain follows a logarithmic relationship with respect to the square root of humidity exposure time and the relationship is linear in the beginning. When the pad cure temperature was raised from 120 to 180 and 240 °C, the adsorption rate increased. The 180 °C cure produced the highest pad modulus. With increasing moisture adsorption, the pad compression modulus increased just like the pad dynamic modulus, meaning decreasing compression/compressibility while the ISO ‘compressibility’ determined after 3 compressions under 160 bars increased in contradiction. It is concluded that the ISO ‘compressibility’ is a destructive hardness measurement like the Gogan or Rockwell hardness: the key difference is the indenter covers the entire surface of the pad. The true compressibility must be determined as an inverse function of bulk modulus. It is recommended that the pad
As the vehicle electrification progresses and the demand for acoustic comfort increases, the NVH performance of brakes becomes more important theme. In-plane squeal of disc brake is one of phenomena that is difficult to countermeasure. In this study, we used array microphones to search for sound sources of in-plane squeal in order to elucidate the mechanism. The Microphones were set in the out-of-plane direction and the lateral direction of a disc in brake components on a full-sized dynamometer. In the vibration mode in which in-plane stretch vibration was dominant, the sparse and dense parts showed high sound pressure. 3D laser vibrometer was used to check displacements of the disc, and the result indicated a possibility that the sparse and dense parts could vibrate in the out-of-plane direction and generate the sound. Then, complex eigenvalue analysis (CEA) and acoustic simulation were conducted to validate the experimental results. Firstly, frequency of instability mode occurred in
This SAE Standard specifies a method for testing and measuring elastic constants in friction materials by precise ultrasonic velocity measurements. Measurement methods are also described for measurement of the out-of-plane modulus as a function of pre-load as well as the measurement of engineering constants as a function of temperature. Finally, methods are formulated to produce all engineering constants as a function of pre-load and temperature.
This SAE Recommended Practice is intended for measuring the static brake torque performance of a pnuematically actuated brake assembly, friction material, and drum/disc combination on an inertia brake dynamometer.
Friction materials are consisted of mixed organic and inorganic raw materials to achieve aimed brake performance and physical properties. In order to manufacture friction materials with stable quality, it is desired that these raw materials are uniformly dispersed, and at the same time it is important to understand the state of distribution during material developments. However, it is difficult for visualizing the dispersion of organic materials, and there are few reports of effective methods. In this study, a use of TOF-SIMS is established as a novel analytical approach for imaging the distributed states of constituent components in friction materials.
The kinetics of moisture adsorption is studied for copper-free brake pads. The pad weight gain is found to increase linearly with the square root of exposure time to humidity at a given temperature in the initial stage of adsorption - the higher the humidity, the higher the weight gain. Pads cured at 150°C adsorb less moisture than pads cured at 220°C. As the moisture content in the pad increases, the tangent modulus increases while the secant modulus decreases, resulting in decreasing compressibility associated with the tangent modulus of compression and increasing compressibility associated with the secant modulus of compression - compressibility defined as a reciprocal of compression modulus. Static modulus of compression, dynamic modulus of compression and hardness measurements are compared, and they all show the same trend. A rate constant of adsorption is proposed to define and compare moisture sensitivity of friction material
This SAE Recommend Practice specifies a method for measuring the deflection of friction materials and disc brake pad assemblies in a manner more consistent with classical material compressive strain testing. This SAE test method differs from SAE J2468 in the preload and maximum load applied to the test sample when deflection is measured. It adopts the material applied stress levels found in ISO 6310 (0.5 to 8.0 MPa) using a 25 mm diameter flat plunger.
Advanced features in automotive systems often necessitate the management of complex interactions between subsystems. Existing control strategies are designed for certain levels of robustness, however their performance can unexpectedly deteriorate in the presence of significant uncertainties, resulting in undesirable system behaviors. This limitation is further amplified in systems with complex nonlinear dynamics. Hydro-mechanical clutch actuators are among those systems whose behaviors are highly sensitive to variations in subsystem characteristics and operating environments. In a P2 hybrid propulsion system, a wet clutch is utilized for cranking the engine during an EV-HEV mode switching event. It is critical that the hydro-mechanical clutch actuator is stroked as quickly and as consistently as possible despite the existence of uncertainties. Thus, the quantification of uncertainties on clutch actuator behaviors is important for enabling smooth EV-HEV transitions. In this paper, a
The static coefficient of friction between lining and shoe plays a fundamental role in the lining fixing project, which is the most important parameter for the riveted joint calculation. For the lining riveting, the rivet needs to ensure that friction material and shoe remain in contact through the normal force applied on the surfaces, but the rivet should not be exposed to shear forces. Thus, the brake torque transmission must occur through the static coefficient of friction between lining and shoe, not allowing relative slips or movements between the pair in contact. Therefore, the present study aims to understand the influence of the static friction coefficient between lining and shoe as a function of the lining internal superficial roughness, from the evaluation of different roughness conditions - contact area with shoe -. The static coefficient of friction between lining and shoe is a complex measurement to be performed, due to the cylindrical geometry of the drum brake system, so
Thermoelastic instabilities in the contact of brake friction material cause hotbands and hotspots on the surface of brake disc. These phenomena generate thermal stresses that result in generation of cracks, which limit the lifetime of the discs. In the present work, the influence of the chemical composition of brake discs on the thermoelastic behavior of the system and on the lifetime of the discs was investigated. The experimental evaluation was carried out in an inertial dynamometer using the SAE J3080 standard procedure applied on a brake system. Two discs (namely A and B) with different chemical compositions were subjected to the tests. The brake pad composition was kept fixed. The thermoelastic effects on the inner surface of the disc were observed by contact (thermocouple) and noncontact measurement techniques (thermography), as well as through photographic images of the disc’s surfaces. Disc A showed negligible amount of Nb while disc B exhibited 0.360%. Besides, disc B
The braking capacity of reducing the speed or even keeping the vehicle stoped is extremely important in the design of any brake system, as more than meeting legislation requirements; it directly affects the safe operation of the vehicle and its users. A fundamental component, which requires notable attention, is the friction material, which is designed to establish a compromise between mechanical properties, friction coefficient, noise propensity, deformation, wear, among others. However, braking capacity is a combined response for several of these friction material properties, along with the performance of other brake system components, such as the brake chamber, disc and caliper. This work aims to analyze firstly the influence of the friction material deformation and secondly the brake system deformation on the total stroke of the brake chamber. To the first one, three different formulations of friction material, applied to commercial vehicles, were selected. For these materials
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