Anders Söderberg

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.

Using finite element analysis to predict the brake pressure needed for effective rotor cleaning in disc brakes

The general trend toward increased use of computer models and simulations during product development calls for accurate and reliable product models. The function of many products relies on contact interfaces between interacting components. Simulating the behavior of such products requires accurate models of both components and interfaces. Depending on the purpose of the simulation, interface models of different degrees of detail are needed. In simulating very large systems with many interfaces, it might be computationally expensive to integrate detailed models of each individual interface. Condensed models, or abstractions, that describe the interface properties with the fewest degrees of freedom are therefore required. This thesis deals with the modeling and simulation of mechanical interfaces in a systems context. The five appended papers discuss the issue from both the simulation and tribological points of view. The aim is to study how friction and wear can be modeled in the behavioral simulation of technical systems and to discuss the convenience and applicability of using different types of models as building blocks of a system model in simulations. Paper A reviews existing friction models of sliding contacts under different running conditions. Paper B uses a simplified contact model, the elastic foundation model, to model friction in a boundary-lubricated rolling and sliding contact. The model is integrated into a dynamic rigid body model of a mechanical system, and the system behavior is simulated. Paper C discusses the application of the elastic foundation model to rough surface contact problems and investigates how the error in its results depends on surface roughness. Papers D and E address how the wear of the contact surfaces at the pad-to-rotor interface in a passenger car disc brake can be simulated using finite element analysis (FEA).

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.

Simulation of Airborne Wear Particles from Disc Brakes

During braking, both the rotor and the pads are worn in disc brakes. This wear process generates particles which may become airborne. In passenger car field tests it is difficult to distinguish the ...

Model-based reliability analysis

Abstract The main function of a heavy truck is to transport goods, with ton-kilometers/year as an example of a major quantitative performance measure. Furthermore, the truck is directly operated by a driver, who has several additional functional requirements, of both ergonomic and communicative characters. Failure of these functions may be a subjective experience, differing between drivers, but the failures are still important. Todays just-in-time delivery systems rely on getting the goods on time, and this requires high availability. Availability is reduced not only by technical failures but also by subjectively experienced failures, because these also require repairs, or downtime. Product reliability is a systems property that cannot be attributed to a single component. It is in many cases related to interaction between components, or to interaction between humans and the technical system, in the case of subjectively experienced failures. Reliability assessments of systems with interactive functions require a system model that includes the interfaces between the technical system and human features that are carriers of interactive functions. This paper proposes a model of system architecture, for the purpose of reliability assessments, that integrates different and complementary representations, such as function–means diagrams and a design structure matrix. The novelty of the presented approach is that it treats and integrates the technical and the human subsystems through the human–technical system interfaces. The proposed systems reliability approach is described and verified with a component analysis case study of an extended truck cab and driver system.

DSM-based Reliability Analysis of Modular Architectures

The main function of a heavy truck is to transport goods. Furthermore,the truck is directly operated by a driver, who has several additional functionalrequirements, of both ergonomic and communicat ...

Modeling transient behavior of a mechanical system including a rolling and sliding contact

Thefriction and wear of rolling and sliding contacts are criticalfactors for the operation of machine elements such as bearings,gears, and cam mechanisms. In precision machines, for example, themai ...

Scaling effects of measuring disc brake airborne particulate matter emissions – A comparison of a pin-on-disc tribometer and an inertia dynamometer bench under dragging conditions

An important contributor to non-exhaust emissions in urban areas is airborne particulate matter originating from brake systems. A well-established way to test such systems in industry is to use inertia dynamometer benches; although they are quite expensive to run. Pin-on-disc tribometers, on the other hand, are relatively cheap to run, but simplify the real system. The literature indicates promising correlations between these two test stands with regard to measured airborne number distribution. Recent studies also show a strong dependency between the airborne number concentration and the disc temperature. However, a direct comparison that also takes into account temperature effects is missing. The aim of this paper is, therefore, to investigate how the transition temperature is affected by the different test scales, under dragging conditions, and the effects on total concentration and size distribution. New and used low-steel pins/pads were tested against cast iron discs/rotors on both the aforementioned test stands, appositely designed for particulate emission studies. A constant normal load and constant rotational velocity were imposed in both test stands. Results show that a transition temperature can always be identified. However, it is influenced by the test scale and the frictional pair status. Nevertheless, emissions are assessed similarly when an equivalent frictional pair status is analysed (e.g. run-in). Further investigations for fully run-in samples on the pin-on-disc should be performed in order to finally assess the possibility of using the tribometers for the initial assessment of different friction materials.

PRODUCT ARCHITECTURE TRANSITION IN AN EVOLVING MULTI-BRAND ORGANISATION

A modular architecture is a strategic means to deliver external variety and internal commonality. A methodology for product modularization that integrates complexity and strategies is proposed and logically verified with an industrial case from the heavy truck business area. The case study indicates that the new methodology is capable of identifying and proposing reasonable module candidates that address product complexity as well as company specific strategies.