Input Parameters for Airborne Brake Wear Emission Simulations: A Comprehensive Review

Brake wear-derived particles: Single-particle mass spectral signatures and real-world emissions

Brake wear is an important but unregulated vehicle-related source of atmospheric particulate matter (PM). The single-particle spectral fingerprints of brake wear particles (BWPs) provide essential information for understanding their formation mechanism and atmospheric contributions. Herein, we obtained the single-particle mass spectra of BWPs by combining a brake dynamometer with an online single particle aerosol mass spectrometer and quantified real-world BWP emissions through a tunnel observation in Tianjin, China. The pure BWPs mainly include three distinct types of particles, namely, Ba-containing particles, mineral particles, and carbon-containing particles, accounting for 44.2%, 43.4%, and 10.3% of the total BWP number concentration, respectively. The diversified mass spectra indicate complex BWP formation pathways, such as mechanical, phase transition, and chemical processes. Notably, the mass spectra of Ba-containing particles are unique, which allows them to serve as an excellent indicator for estimating ambient BWP concentrations. By evaluating this indicator, we find that approximately 4.0% of the PM in the tunnel could be attributable to brake wear; the real-world fleet-average emission factor of 0.28 mg km^-1 veh^-1 is consistent with the estimation obtained using the receptor model. The results presented herein can be used to inform assessments of the environmental and health impacts of BWPs to formulate effective emissions control policies.

A supervised machine learning approach to classify traffic-derived PM sources based on their magnetic properties

Environmental magnetism techniques are increasingly used to map the deposition of particulate pollutants on any type of accumulative surfaces. The present study is part of a collective effort that begun in recent years to evaluate the efficiency of these techniques involving a large range of measurements to trace the source signals. Here we explore the possibilities provided by the very simple but robust k-near-neighbors algorithm (kNN) for classification in a source-to-sink approach. For this purpose, in a first phase, the magnetic properties of the traffic-related sources of particulate matter (tire, brake pads, exhaust pipes, etc.) are used to parameterize and train the model. Then, the magnetic parameters measured on accumulating surfaces exposed to a polluted air as urban plant leaves and passive filters are confronted to the model. The results are very encouraging. The algorithm predicts the dominant traffic-related sources for different kinds of accumulative surfaces. The model predictions are generally consistent according to the sampling locations. Its resolution seems adequate since different dominant sources could be identified within one street. We demonstrate the possibility to trace traffic-derived pollutants from sources to sinks based only on magnetic properties, and to eventually quantify their contributions in the total magnetic signal measured. Because magnetic mapping has a high-resolution efficiency, these results open the opportunity to complement conventional methods used to measure air quality and to improve the numerical models of pollutant dispersion.

The influence of the brake pad construction on noise formation, people's health and reduction measures

The brake system is one of the most important systems on the vehicle, especially from the aspect of traffic safety. The use of the braking system comes with many undesirable effects, such as brake wear and noise emission. The noise that originates from brakes is related to the wear of brake elements, the applied materials for manufacture, to the elements which are connected to each other, and all of this represents a very challengeable problem in the automotive industry. In this paper are presented the dominant parameters that influence noise formation, where the main focus was placed on brake pads, as well as how the noise influences people's health. After that, further, in the paper, it was analyzed the influence of the brake pads' construction on the noise formation, and at the end are given the measures for noise reduction. The conclusions of the paper show that the construction of brake pads significantly influences noise emission, noise negatively influences on the people health, and because of the negative influence on the people health, some solutions show that it is necessary to include insulators in the construction of brake pads, and if the space in which people reside is observed, it is necessary during construction to use materials which will prevent noise conduction, into the space in which people reside.

Process Optimization of Automotive Brake Material in Dry Sliding Using Taguchi and ANOVA Techniques for Wear Control

In this paper, an investigation of the load-dependent wear behavior of copper-free semi-metallic brake material is presented. The experiments were conducted in ambient thermal settings with varying sliding velocities (3.141 m/s, 2.09 m/s, and 1.047 m/s), normal load (60 N, 50 N, and 40 N), and sliding distance (4500 m, 3000 m, and 1500 m). Taguchi’s method was used in designing experiments to examine the output through an L9 orthogonal array. ANOVA was used to identify the consequence of interactions among different constraints. It also established the significant contribution of each process factor. The objective was set as the ‘smaller is better’ criterion to find minimum wear conditions. The impact of the normal load on the wear process was found to be maximum (71.02%), followed by sliding velocity (27.84%) and sliding distance (1.14%). The optimum condition for the minimum wear rate was found at 40 N normal load, 1500 m sliding distance, and 3.14 m/s sliding velocity. The results were confirmed with validatory friction experiment runs. The resulting error was within 10% error, which verified the experiment methods. The SEM investigation of worn surfaces of pin and disc confirmed abrasive wear and adhesive wear at 60 N and 40 N, respectively.