Study Of Friction Behavior Test Method For Automotive Brake

Automobile symbolizes the development of science and technology. One ofthe main character of automobile is brake performance, which is a decisive factorto the behavior of auto dynamical performance. Brake performance is the mostimportant factor of braking system. It attracts more and more concern in frictionmaterial industry to adopt various test method to study the brake assemblies andevaluate the brake linings friction behavior. Brake test also has a comprehensiveapplication in the development and selection of friction materials. Domestic evaluation of automobile brake friction behavior is actualized inChase machine and constant speed friction test machine at present, adoptingGB5764 and SAE-J661 test method. These machines have an advantage of shorttest cycle, small expenditure and are simple in comparison. However, it can hardlysimulate the real driven condition and dynamic characteristic of brake system, thusgiving low nicety in friction behavior evaluation. Some domestic brake and frictionmaterial manufacturers have already introduced brake inertia dynamometer inevaluating the friction performance of brake assemblies. Inertia test is time andmoney dissipative especially when the corresponding test method is not asadvanced. It is right being lack of advanced test method that causes the test levelgap between China and other countries.In this paper, automobile brake system design theory and friction materialapplication theory are systematically studied based on the analysis of currentdomestic auto brake friction behavior evaluation. Two type of brake frictionbehavior test machine and test method are analyzed: 1, Chase machine applicationtheory, structure and test method;2, Inertia dynamometer application theory,structure and prevailing brake assemblies test method. Reliability of inertiadynamometer brake performance test is argued by comparison of the componentand function of the two machines. The trueness of the simulation of the dynamicbrake process is testified by the study of test procedure. Inertia dynamometer hasbetter simulation of the real braking process and reproduces this application in amore thorough way, which is also discussed in this paper by analyzing twodifferent methods of the above two machines.A new recommended inertia dynamometer test method SAE-J2681 (InertiaDynamometer Friction Behavior Assessment for Automotive Brake System) bybrake inertia dynamometer test standard committee and member bodies isintroduced by analyzing the brake simulating condition (driven speed, braketemperature, brake force, deceleration level, etc) of SAE-J2681 test procedure andnarrating the range of brake friction behavior parameters. The correctness ofSAE-J2681 main setting parameters (deceleration and friction coefficient) are alsoverified by analyzing the definition of these parameters. When we take the testcondition and step of brake assemblies friction behavior evaluation inertiadynamometer test method QC/T564-1999 (brake efficiency, fade-recovery, etc) asreference, SAE-J2681 has more test condition and simulation step thanQC/T564-1999 while it covers every test item of the later, which proves theequivalence and prominence of SAE-J2681 over QC/T564.Test data of the same type of brake linings (disc brake linings of WL) bySAE-J2681 and QC/T-564-1999 on the same inertia dynamometer (NT11) areanalyzed in this paper. SAE-J2681 test method is proved to be reliable and feasiblein the evaluation of brake friction behavior by drawing up the test data of bothQC/T564-1999 and SAEJ-2681. It can be concluded from the whole timeconsumption comparison that SAEJ-2681 test method is more economical, havinga time consumption of 40% to 50% of that of QC/T564-1999. Test data on Chasemachine and test data of the same type of brake linings by SAE-J2681 andQC/T564-1999 are analyzed briefly to show the limit and error of friction behaviorevaluation by SAE-J661 on Chase machine. SAE-J2681 is proved to be effectiveand applicable in brake friction behavior assessment. It can be concluded thatSAE-J2681 is more applicable in the evaluation of brake friction behavior oninertia dynamometer.SAE-J2681 test method pays less attention on the wearability of brake linings,thus has no special abrasion item. This item must be considered to fit the domesticpractice when SAE-J2681 test method is adopted in China.The outcome of this paper provides a rather perfect reference for domesticbrake friction behavior evaluation. It is also feasible to be adopted as industrystandard. The practical tryout of new product development and quality control insome brake factories proves it to be an effective method.