The environment is an increasingly important concern today and no economy is unaffected. This also applies to the friction braking system industry, because of the particles emitted during each braking process. As braking is a complex process, depending on speed, vehicle weight, level of deceleration, as well as environmental conditions such as temperature and humidity which influence the type and nature of the particles emitted, ranging from very fine to coarse. Depending on their nature, these emissions can end up in the environment in the draining water or in the air we breathe. In the literature there are more and more studies about airborne particles; they all show that mainly emitted particles during braking have a distribution which varies with the braking conditions from nano to micro particles. For these reasons, Mercedes Benz AG is looking for suitable methods to understand and analyse the braking emissions and countermeasures to recover the emitted particles. Simulations could support here to provide meaningful information regarding brake dust flow also it can enlarge the view including surrounding components and the full vehicle airflow in the wheel housing. Companies specialized in numerical solutions are also challenged to identify which method would be the most suitable to study the trajectory evolution of these particles after their emission. In this context Altair Engineering proposes the use of the Discrete Element Method (DEM) used in the EDEM software. The DEM method is suitable for studying the behaviour of a very large number of particles interacting with each other and with their environment. The method can be easily coupled with other numerical solutions such as CFD. The numerical characteristics of the problem require a good strategy to solve the equations in an acceptable time. In the presentation, a numerical model representing a vehicle wheel-housing and the braking system will be presented to visualize the evolution of the emission trajectories for certain braking scenario. The aim of these studies is to evaluate if the numerical models are solvable and if their results bring a better understanding of the problems encountered. Eventually a simulation containing a countermeasure will be carried out to estimate the prediction of effectiveness of this measure.

Although brake squeal noise has been studied for many years, it is still challenging to remove or reduce squeal noise. Structural changes of brake system to reduce squeal noise are usually made through dynamometer testing in an iterative way based on engineering knowledge, past experience and etc. While these methods work well for simple problems, they are time consuming when there are squeal of multiple frequencies.

Complex eigenvalue analysis is a widely accepted tool for reducing brake squeal noise in the brake industry. Many papers proved that complex eigenvalue analysis is useful for reducing instabilities of brake system. This paper presents a new procedure for reducing instabilities. That is to separate contributing modes of the most contributing component using shape optimization. Desirable directions for separation of contributing modes are determined by modal participation factor to system (MPFS), modal participation factor to component (MPFC) and generalized coordinate (GC). Shape optimization is carried out using Altair Optistruct software to increase frequency difference between the contributing modes in the component level. The objective function of the optimization is mass minimization and design variables are defined in several domains of component. The frequency difference of contributing modes is set to constant value as constrain conditions.

The results show that this procedure can be successfully applied to complex eigenvalue analysis for reducing brake squeal noise and increase efficiency by eliminating the trial and error process.