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 conduc...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.展开更多
Existing hydraulic braking systems in the vehicle is composed of the brake pedal, the hydraulic booster and the hydraulic caliper. The driver transmits one＇s breaking intent through the brake pedal stroke and force. ...Existing hydraulic braking systems in the vehicle is composed of the brake pedal, the hydraulic booster and the hydraulic caliper. The driver transmits one＇s breaking intent through the brake pedal stroke and force. The hydraulic booster can amplify the pedal force, only when the engine operates. The hydraulic caliper is composed of cylinders, pistons. There are also hydraulic pipes from the booster to the caliper. Currently, X-By-Wire technology is researched actively due to the exhaustion of fuel and the regulation of CO2. As a chain of this trend, the e-pedal and an electric mechanical brake （EMB） also are highlighted. At the beginning of EMB development, high-torque and high-power motors are required in order to implement the existing hydraulic calipers＇ clamping force. This has some limits as the need of big spaces and high costs. Then the electro wedge brake （EWB） is launching with self-reinforcement features of the wedge structure. EWB can generate big clamping forces with small size and low-torque motors with good braking-efficiency. In recent, the disc＇s circumferential face clamping one has been researched, for better heat-emission ability and better braking-efficiency compared to the existing disc＇s lateral face clamping method. But, this circumferential face clamping method can have worse unbalance-wear features compared to lateral face clamping one. In this study, the authors describe their circumferential EWB concepts, the method for reducing unbalance-wear feature of circumferential EWB, and the cost-effective implementation of circumferential EWB, in particular focused on nonlinear counter-wedge profile which is appropriate to reduce unbalance-wear.展开更多
Compared to the current eddy braking patterns using a single magnetic source,hybrid excitation rail eddy brakes have many advantages,such as controllability,energy saving,and various operating models.Considering the l...Compared to the current eddy braking patterns using a single magnetic source,hybrid excitation rail eddy brakes have many advantages,such as controllability,energy saving,and various operating models.Considering the large braking power consumption of the high-speed train,a hybrid excitation rail eddy brake system,which is based on the principle of electromagnetic field,is proposed to fulfill the needs of safety and reliability.Then the working processes of the mechanical lifting system and electromagnetic system are demonstrated.With the electromagnetic system analyzed using the finite element method,the factors such as speed,air gap,and exciting current have influences on the braking force and attractive force.At last,the structure optimization of the brake system is discussed.展开更多
基金Project(2016YFB1100103)supported by the National Key Research and Development Program of ChinaProject(KC1703004)supported by the Science and Technology Planning Project of Changsha City,ChinaProject(2018ZZTS127)supported by the Fundamental Research Funds for the Central Universities of Central South University,China。
文摘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.
文摘Existing hydraulic braking systems in the vehicle is composed of the brake pedal, the hydraulic booster and the hydraulic caliper. The driver transmits one＇s breaking intent through the brake pedal stroke and force. The hydraulic booster can amplify the pedal force, only when the engine operates. The hydraulic caliper is composed of cylinders, pistons. There are also hydraulic pipes from the booster to the caliper. Currently, X-By-Wire technology is researched actively due to the exhaustion of fuel and the regulation of CO2. As a chain of this trend, the e-pedal and an electric mechanical brake （EMB） also are highlighted. At the beginning of EMB development, high-torque and high-power motors are required in order to implement the existing hydraulic calipers＇ clamping force. This has some limits as the need of big spaces and high costs. Then the electro wedge brake （EWB） is launching with self-reinforcement features of the wedge structure. EWB can generate big clamping forces with small size and low-torque motors with good braking-efficiency. In recent, the disc＇s circumferential face clamping one has been researched, for better heat-emission ability and better braking-efficiency compared to the existing disc＇s lateral face clamping method. But, this circumferential face clamping method can have worse unbalance-wear features compared to lateral face clamping one. In this study, the authors describe their circumferential EWB concepts, the method for reducing unbalance-wear feature of circumferential EWB, and the cost-effective implementation of circumferential EWB, in particular focused on nonlinear counter-wedge profile which is appropriate to reduce unbalance-wear.
基金Project supported by the National Natural Science Foundation of China(Nos.50877070 and 51105331)the Special Financial Grant from the China Postdoctoral Science Foundation(Nos.201104720 and 201104721)
文摘Compared to the current eddy braking patterns using a single magnetic source,hybrid excitation rail eddy brakes have many advantages,such as controllability,energy saving,and various operating models.Considering the large braking power consumption of the high-speed train,a hybrid excitation rail eddy brake system,which is based on the principle of electromagnetic field,is proposed to fulfill the needs of safety and reliability.Then the working processes of the mechanical lifting system and electromagnetic system are demonstrated.With the electromagnetic system analyzed using the finite element method,the factors such as speed,air gap,and exciting current have influences on the braking force and attractive force.At last,the structure optimization of the brake system is discussed.
