Passenger car disc brakes are a source of ultrafine, fine, and coarse particles. It is estimated that 21% of total traffic-related PM₁₀ emissions in urban environments originate from airborne brake wear particles. Particle number emission factors are in the magnitude of 10¹⁰ km⁻¹ wheel brake during real-world driving conditions. Due to the complexity of the tribological processes and the limited observability of the friction zone between brake disc and pad, the phenomena causing particle emission of disc brakes are only partially understood. To generate a basis for understanding the emission process and, based on this, to clarify which influencing variables have how much potential for reduction measures, one approach consists in the identification and quantification of influencing variables in the form of emission maps. The subject of this publication is the influence of disc brake temperature on ultrafine, fine, and coarse particle emissions, which was investigated with a systematic variation of temperature during single brake events on an enclosed brake dynamometer. The systematic variation of temperature was achieved by increasing or decreasing the disc temperature stepwise which leads to a triangular temperature variation. Two types of brake pads were used with the main distinction in its chemical composition being organic and inorganic binder materials. The critical disc brake temperature for the generation of ultrafine particles based on nucleation is at approximately 180 °C for pads with an organic binder and at approximately 240 °C for pads with inorganic binder materials. Number concentration during those nucleation events decreased for successive events, probably due to aging effects. PM₁₀ emissions increased by factor 2 due to an increase in temperature from 80 °C to 160 °C. The influence of temperature could be only repeatable measured for disc brake temperatures below 180 °C. Above this temperature, the emission behavior was dependent on the temperature history, which indicates also a critical temperature for PM₁₀ relevant emissions but not in an increasing rather than a decreasing manner.

Besides particulate emissions from engine exhausts, which are already regulated by emission standards, passenger car disc brakes are a source of particulate matter. With the current car fleet it is estimated that up to 21% of the total traffic related PM₁₀ emissions in urban environments originate from brake wear and reduction of brake dust emissions is subject of current research. For the purpose of reducing brake dust emissions by choosing low-emission operating points of the disc brake, the knowledge of the emission behavior depending on brake pressure, wheel speed, temperature and friction history is of interest. According to the current state of research, theoretical white box modeling of the emission behavior is complicated due to the complexity of tribological contact between pad and disc. Thus experimental black box modeling is supposed to describe emission behavior. In order to minimize the influence of disturbances and therefore to improve prediction accuracy of such empirical models, system identification methods based on periodical test signals, such as brake pressure sine, are used for this application. To adopt these test signals, which are established in transfer function measurements, to the application of brake particle measurements and to develop an experimental design, system theoretical quantities, such as cutoff frequency, signal to noise ratio and hysteresis, are determined in dynamometer tests. Therefore measurements of the system’s response to step and sine test signals are analyzed. System identification is executed and the applicability of periodical test signals to brake particle measurements is proven.

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