BWI Group North America

Kettering, OH, United States

BWI Group North America

Kettering, OH, United States

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Ballinger R.S.,BWI Group North America
SAE International Journal of Passenger Cars - Mechanical Systems | Year: 2016

The complex eigenvalue analysis has been used by the brake research community to study friction-induced squeal in automotive disk brake assemblies. The analysis process uses a nonlinear static pre-stressed normal modes analysis simulation sequence followed by a complex eigenvalue extraction algorithm to determine the dynamic instabilities. When brake hardware exists, good correlation between analysis results and experimental data can be obtained. Consequently, complex eigenvalue analysis can be a valuable method in an effort to understand brake components that might have a propensity to influence the noise behavior of a brake system. However, when hardware does not exist and the complex eigenvalue method is asked to be predictive, it becomes a difficult, if not impossible task. This paper will focus on some of the reasons the complex eigenvalue analysis method is not a reliable predictor of friction-induced squeal in automotive disk brake assemblies. Two general areas of modelling methodology are discussed. The first area of discussion focuses on generic FEA boundary conditions that are independent of the commercial code used. Examples of generic or non-code specific boundary conditions are rotor and wheel/wheel simulator or dynamometer attachment methodology and slide pin and piston penalty contact or radial coupling definitions. The second area of discussion focuses on specific boundary conditions that are commercial code dependent. An example of a specific boundary condition is the contact stiffness scale factor specification for all prestressed contact surfaces and the resulting pre-stressed normal modes analysis results. Inappropriate choices for these generic and specific boundary conditions will render the complex eigenvalue method incapable of functioning as a predictive tool for friction-induced squeal in automotive disk brake assemblies. © 2016 SAE International.


Farjoud A.,BWI Group North America | Taylor R.,BWI Group North America | Schumann E.,BWI Group North America | Schlangen T.,BWI Group North America
Vehicle System Dynamics | Year: 2014

This paper is focused on modelling, design, and testing of semi-active magneto-rheological (MR) engine and transmission mounts used in the automotive industry. The purpose is to develop a complete analysis, synthesis, design, and tuning tool that reduces the need for expensive and time-consuming laboratory and field tests. A detailed mathematical model of such devices is developed using multi-physics modelling techniques for physical systems with various energy domains. The model includes all major features of an MR mount including fluid dynamics, fluid track, elastic components, decoupler, rate-dip, gas-charged chamber, MR fluid rheology, magnetic circuit, electronic driver, and control algorithm. Conventional passive hydraulic mounts can also be studied using the same mathematical model. The model is validated using standard experimental procedures. It is used for design and parametric study of mounts; effects of various geometric and material parameters on dynamic response of mounts can be studied. Additionally, this model can be used to test various control strategies to obtain best vibration isolation performance by tuning control parameters. Another benefit of this work is that nonlinear interactions between sub-components of the mount can be observed and investigated. This is not possible by using simplified linear models currently available. © 2014 © 2014 Taylor & Francis.


Farjoud A.,BWI Group North America | Marcu F.,Caterpillar Inc. | Schumann E.,BWI Group North America
SAE Technical Papers | Year: 2012

This paper presents a novel 6-DOF multi-physics model of a cab suspension system. The model consists of a cab with six degrees of freedom supported by four fluid filled viscous mounts. In the literature, to the best of the authors' knowledge, all 6-DOF cab models have simplified fluid filled mounts as spring damper combinations. In its best case, a nonlinear stiffness relationship is allowed in the simplified models to capture the nonlinear behavior of the mounts and include geometric constraints and hard-stops. The novel model presented in this paper, however, includes a multi-physics model of the mounts. Each mount is represented by a molded assembly, two fluid chambers, a fluid track that connects the two chambers, and a gas chamber. Each mount can be pressurized or vented. A simple cavitation model is also used as an indicator of fluid cavitation in each mount. Additionally, all acceleration terms including cross-coupled and normal component accelerations are included in the 6-DOF model. Therefore, all nonlinear effects in various translational and rotational directions can be studied. This comprehensive cab model allows design engineers to choose fluid filled mount design parameters and mounting locations using a global design tool. The effects of a few design parameters on the overall response of the cab are studied and presented. Copyright © 2012 SAE International.


Farjoud A.,BWI Group North America | Bagherpour E.A.,University of Tehran
Journal of Intelligent Material Systems and Structures | Year: 2016

Electromagnet design is an important step in design of magneto-rheological devices. Magneto-rheological fluid flow is affected by a magnetic field created by an electromagnet. Electromagnet design affects both fluid flow and magnetic performance of any magneto-rheological device. This article presents a comprehensive process for electromagnet design. Currently, most design procedures only consider steady-state static operations. Magneto-rheological devices, however, rarely operate under steady-state conditions. Therefore, transient operation of electromagnets is as important as steady-state operations, if not more. In this article, both steady-state and transient design are presented in a systematic manner. The design process starts with the simplest one-dimensional linear static magnet analysis techniques and progresses toward nonlinear transient magnet design. Various examples are presented on magneto-rheological engine mount magnets. It is expected that the presented procedure facilitates design of magneto-rheological magnets and helps achieving an optimum design in a shorter time. © The Author(s) 2014.

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