Lars Olander

A Study of Airborne Wear Particles Generated From a Sliding Contact

Recently, much attention has been paid to the influence of airborne particles in the atmosphere on human health. Sliding contacts are a significant source of airborne particles in urban environment ...

Airborne wear particles from passenger car disc brakes: A comparison of measurements from field tests, a disc brake assembly test stand, and a pin-on-disc machine

Abstract Most modern passenger cars have disc brakes on the front wheels. Unlike drum brakes, disc brakes are not sealed off from the ambient air. During braking, both the rotor and the pads wear, and this wear process generates particles that may become airborne. In field tests it is difficult to distinguish these particles from others in the environment. It is thus preferable to conduct tests using laboratory test stands where the cleanness of the surrounding air can be controlled. However, the validity of results from these test stands should be verified by comparison with field tests. This article presents a comparison of the number and volume distributions of airborne wear particles as measured online in field tests, in a disc brake assembly test stand, and in a pin-on-disc machine. In all cases, grey cast iron rotors and low metallic pads were tested. A promising correlation between the three different test methods is shown. The number- and volume-weighted mean particle diameter for all test methods is about 0.4 and 2-3 μm, respectively.

Ultrafine particle formation from wear

Abstract Much attention is given to the consequences of airborne particles on human health and well-being. Wear is one source of airborne particles and contributions in the urban environments from wheel-to-rail contacts and disc brakes cannot be neglected. Traditionally, mechanical wear has been associated with the generation of particles of diameters of some microns. However, the research described has found ultrafine particle generation from wear processes. Particle generation from wear was measured under controlled laboratory conditions. The wear was created through sliding contact in a tribometer (type “pin-on-disc”) with different materials and with different sliding velocities and pressures, to represent rail traffic and automobile disc braking. Particle concentrations and size distributions in the air were determined for particle diameters from 10 nm up to more than 10 μm. For most materials and conditions three particle size modes were found: one at 50–100 nm, one at a few hundred nm and one at a few μm particle diameter.

10 – LOCAL VENTILATION

This chapter describes the aerodynamic principles, models, and equations that govern the flow and the contaminant presence and transport in a designated volume of a workroom. Local ventilation is often a very important part of the ventilation system, both in function and in construction. By using a local ventilation system of good design less air is needed to reach a specific contaminant level than is possible with general ventilation. Proper design and construction of a local ventilation system must account for hood flow rate, contaminant generation process and rate, and the generated flow rate of contaminated air. Thus, knowledge about airflow mechanics, process performance, and the contaminant source is essential. The purpose of local ventilation is to control the transport of contaminants at or near the source of emission, thus minimizing the contaminants in the workplace air. All local ventilation systems can, in principle, be manufactured for use in one or more of three different modes: fixed, flexible, and mobile.

The Tribological Efficiency and the Mechanism of Action of Nano‐Porous Composition Base Brake Lining Materials

Based on the comparative analysis of the experimental values determined for the tribological parameters for the three novel nano‐porous composition base and two conventional brake lining materials while friction with the grey cast iron disc, it was shown the considerable high tribological efficiency of the novel nano‐porous composition base lining materials in comparison with the conventional (from EU and USA market) brake lining materials. The explanation is given to the action mechanism of nano‐porous composition base brake lining material and its tribological efficiency basing on the “triple phase” tribo‐pair model.

Do Train Tunnels Need Ventilation Systems

Abstract A planned new train tunnel under the central parts of Stockholm was intended to be ventilated by natural ventilation and the movement of the trains. However, the amount of heat generated by the trains is so high that natural ventilation would give abnormal temperatures and velocities in the tunnel and at the stations. The heat adsorbed by the rock surrounding the tunnel can be neglected in comparison with the amount transported by air. Some of the problems with the ventilation system are described and also the problems with dust generation by the trains and the exposure to dust at the stations by the passengers. The final decision was to use glass walls at the stations to separate the ventilation for the tunnel from that for the stations.