Search Results

A practical modeling methodology for adhesively bonded structures using discrete springs has been developed for crash simulation. As a first step, a series of coupon tests with adhesively bonded substrates have been conducted under tension, peel and shearing. Both deformable and rigid substrates have been used in these tests. The resulting data has been used to determine the properties of the adhesive springs. A set of numerical simulations of the coupon tests have been conducted to verify that the adhesive spring properties derived earlier do indeed represent the mechanical properties of the physical adhesives in the coupon tests.

Finite element simulations are widely used for simulating disc brake squeal and the aim of this paper is to further increase the understanding of the effect of insulators. An earlier paper has presented an experimental technique for measuring the properties of the viscoelastic materials [1] and it has been shown how these data can be used in simulating brake response [2]. This paper deals with the sensitivity of a FE brake model to frequency dependent shim material properties and it is documented that with the current options for modeling shims in complex eigenvalue analysis it is only possible to accurately simulate response in a narrow frequency range. A procedure to find optimized parameters for a current damping model is discussed. The best α and β values for a Rayleigh damping model is found by obtaining a least square best fit in a frequency range of interest.

One of the key selling criteria of brake linings is their related cost per life time. Individual wear rates must match a required service interval which in most cases is part of the warranty a vehicle is sold with. OEMs, brake manufacturers as well as friction material suppliers are therefore conducting in-depth investigations on the wear behaviour of brake systems and their friction pair. These consider various parameters influencing pad and rotor life expectancy as part of the pre selection process before running final fleet trials for confirmation. Thus, selecting the right test procedures and parameters for the determination of wear rates is key in enabling a confident life time prediction. As of today, a multitude of wear test procedures are used in the automotive industry, each of them related to the specific experience of the respective OEM or BM.

Disc brake squeal is a very complicated phenomenon, and the influence of insulators in suppressing squeal is not fully understood. The aim of this paper is increase the understanding of the effect of insulators. A previous paper [1] presented an experimental technique for measuring the frequency- and temperature- dependent properties of viscoelastic materials currently used in insulators. The present work continues by considering the coupled vibrations of the brake pad and insulator. A comparison of natural frequencies found from experimental modal analysis and finite element modeling indicates agreement to with 5%. Experimentally determined modal loss factors of the brake pad vary dramatically with frequency, changing by a factor of 2 over the frequency range 2-11 kHz. A method for including this frequency dependence, as well as the frequency dependence of the insulator material, in state-of-the-art finite element software is proposed.

Metal pickup is a phenomenon that can be observed during dynamic braking with automotive disc brakes. Hard metallic particle agglomerations embedded in the friction materials rubbing surface can lead to severe disc scoring, accelerated wear and deterioration of the friction surface of either brake disc or brake pad. Such kind of surface conditions are also suspected for generating brake squeal, even if a direct root cause effect had not been proven so far. Disc scoring effects have been reported for all kinds of applications, reaching from small passenger cars up to commercial vehicles as well as railroad brakes. Although such phenomena are known since long, they still appear causing problems in brake systems of today. Some recent papers have described the effect and mentioned preferable conditions for the appearance of metal pickup. Specific procedures have been proposed for provocation of the effect to allow a better and more systematic investigation of the influencing parameters.

North American drivers particularly dislike wheel dust (brake dust on their wheels). For some vehicle lines, customer surveys indicate that wheel dust is a significant concern. For this reason, Ford and its suppliers are investigating the root causes of brake dust and developing test procedures to detect wheel dust issues up-front. Intuitively, it would appear that more brake wear would lead to more wheel dust. To test this hypothesis, a gage was needed to quantitatively measure the wheel dust. Gages such as colorimeters were evaluated to measure the brightness (L*) of the wheel, which ranged from roughly 70-80% (clean) to 10-20% (very dirty). Gage R&R's and subjective ratings by a panel of 30 people were used to validate the wheel dust gages. A city traffic vehicle test and an urban dynamometer procedure were run to compare the level of wheel dust for 10 different lining types on the same vehicle.