A robust sequential hypothesis testing method for brake squeal localisation

This contribution deals with the in situ detection and localisation of brake squeal in an automobile. As brake squeal is emitted from regions known a priori, i.e., near the wheels, the localisation is treated as a hypothesis testing problem. Distributed microphone arrays, situated under the automobile, are used to capture the directional properties of the sound field generated by a squealing brake. The spatial characteristics of the sampled sound field is then used to formulate the hypothesis tests. However, in contrast to standard hypothesis testing approaches of this kind, the propagation environment is complex and time-varying. Coupled with inaccuracies in the knowledge of the sensor and source positions as well as sensor gain mismatches, modelling the sound field is difficult and standard approaches fail in this case. A previously proposed approach implicitly tried to account for such incomplete system knowledge and was based on ad hoc likelihood formulations. The current paper builds upon this approach and proposes a second approach, based on more solid theoretical foundations, that can systematically account for the model uncertainties. Results from tests in a real setting show that the proposed approach is more consistent than the prior state-of-the-art. In both approaches, the tasks of detection and localisation are decoupled for complexity reasons. The localisation (hypothesis testing) is subject to a prior detection of brake squeal and identification of the squeal frequencies. The approaches used for the detection and identification of squeal frequencies are also presented. The paper, further, briefly addresses some practical issues related to array design and placement. (C) 2019 Author(s)

Study of Brake Pad Shim Modification to Improve Stability Against High Frequency Squeal Noise by Finite Element Analysis

This research studying on brake pad shim design with 4 configurations to improve the brake squeal noise phenomenon for high frequency noise in the range of 4-16 kHz. Various shims were designed with different configurations to increase structural damping and avoid instabilities in a brake system, which arise from friction drawing the vibration modes to coalesce between brake disc and brake pads. Then, the suspect brake module was tested in the laboratory using a dynamometer machine to confirm brake frequency noise parameters and conditions. The numerical models including brake disc, brake pad and brake pad shim were created using finite elements software and the unstable modes analysed for negative damping and positive real part values with the Complex Eigenvalue Analysis (CEA) technique. The simulation result showed that the instability of the brake system comes from mode coupling of the brake disc and brake pads in the out-of-plane modes (11ND) and (2 ND), respectively. The brake pads shim design1, design2 and design3 are component which goes in between the calipers and brake pads, were able to avoid high frequency brake squeal but make the noise move toward the direction of the lower frequency. The brake pad shim design4 is the good structure modification to avoid high frequency brake squeal and low frequency

Sustainable government policy as silver bullet to sustainable business incubation performance In Nigeria

Business incubation has variously been described as a support programme that assist the early-stage entrepreneurs to develop and stay on their own. Furthermore, business incubation programme has been acknowledged as an economic development tool most countries globally adopted. The aim of this study is to examine the contribution of government policy on the relationship between the critical success factors (CSFs) and incubator performance in Nigeria. The questionnaire method of data collection was used to gather 113 usable questionnaires from incubatees in Nigeria’s business incubators. Structural Equation Modeling (SEM) was performed to determine the result using the Partial Least Square (PLS) Software. Government policy as a moderator did not show a significant moderation relationship between the CSF and incubator performance

Proceeding Of Mechanical Engineering Research Day 2016 (MERD’16)

This Open Access e-Proceeding contains a compilation of 105 selected papers from the Mechanical Engineering Research Day 2016 (MERD’16) event, which is held in Kampus Teknologi, Universiti Teknikal Malaysia Melaka (UTeM) - Melaka, Malaysia, on 31 March 2016. The theme chosen for this event is ‘IDEA. INSPIRE. INNOVATE’. It was gratifying to all of us when the response for MERD’16 is overwhelming as the technical committees received more than 200 submissions from various areas of mechanical engineering. After a peer-review process, the editors have accepted 105 papers for the e-proceeding that cover 7 main themes. This open access e-Proceeding can be viewed or downloaded at www3.utem.edu.my/care/proceedings. We hope that these proceeding will serve as a valuable reference for researchers. With the large number of submissions from the researchers in other faculties, the event has achieved its main objective which is to bring together educators, researchers and practitioners to share their findings and perhaps sustaining the research culture in the university. The topics of MERD’16 are based on a combination of fundamental researches, advanced research methodologies and application technologies. As the editor-in-chief, we would like to express our gratitude to the editorial board and fellow review members for their tireless effort in compiling and reviewing the selected papers for this proceeding. We would also like to extend our great appreciation to the members of the Publication Committee and Secretariat for their excellent cooperation in preparing the proceeding of MERD’16

Brake Squeal reduction through improved rotor damping

Brake Squeal Noise is a significant concern in the automotive industry and incurs enormous costs during brake system development and in brake system warranty. Several methods are utilized to minimize brake squeal, including frequency manipulation of individual brake system components through design and material modifications, active damping elements like pad shims and insulators, which typically add mass and cost to the brake system, as well as retesting costs. Brake rotors are made of grey cast iron due to their low cost, good machinability, wear and damping properties. Strength requirements limit the material damping obtainable on a consistent basis. Other methods to improve rotor damping include the use of steel inserts in the rotor plates and EDM machining of the brake rotors. Parts made with either process have been observed to reach very high levels of damping (Q factor of ~ 200) and entirely eliminate noise occurrences in the brake system.This research involves the characterization of the material and the additional processes required to achieve highly damped rotors, with a Q factor in the range of 100 to 300, which can provide significant brake noise reduction. It was discovered that electrical or magnetic processing of the rotors can create damping improvements in the range of 10 to 50 %, which are beneficial to reducing noise occurrences. EDM processing was primarily used for the study and Q factor improvements in the range of 30 to 50 % observed. Rotors with High C.E., Large Type A graphite with flake size 2 to 4, showed the largest benefits from the processing. Process DOE showed no effects of current on the damping improvements. A low processing time of 5 seconds on Non FNC rotors generated over 30 % damping improvements consistently. Noise occurrence reductions of 80 to 100 % were seen with the processed rotors. No detrimental effects were noted on other rotor performance characteristics including thermal cracking, brake torque variation, wear, and corrosion. Effects of time, temperature and wear on the damping improvements have been researched, and no significant losses were seen in typical operating conditions

Modelling and simulation of disc brake contact analysis and squeal

This thesis proposes a new methodology of predicting squeal using the finite element method in which three validation stages are established. A detailed 3-dimensional finite element model of a real disc brake is not only validated through modal analysis at the components and assembly levels but also through contact analysis where static contact pressure distribution and its contact area match with the experimental results. The main key issue in this research is the refinement of contact interface model of the friction material. Having assumed a smooth and flat surface (or perfect contact interface) in the past, current research considers a real surface topography of which measurementsa re carried out in order to obtain a realistic contact interface model. It is found that with the refined disc brake model, a good correlation is achieved between the predicted results and experimental ones on the contact pressure distribution and contact area at the piston and finger pads. Complex eigenvalue analysis that is available in ABAQUS software package is used as the main tool to predict squeal generation. Prediction of squeal occurrence is limited to a frequency range of I kHz to 8 kHz. Simulations of disc brake squeal are performed at different friction characteristics with the inclusion of friction damping for the perfect contact interface and real contact interface models. It is shown that the real contact interface model predicts squeal occurrences much better than the perfect contact interface model by considering the effect of negative u-v slope and friction damping. Comparison between complex eigenvalue analysis and dynamic transient analysis using a reduced FE model is also made for different contact schemes. It is found that using small sliding with Lagrange multiplier contact scheme predicted results in both analyses in a good agreement. Wear effects on instability of the disc brake assembly are also simulated. The results show that with the inclusion of wear, unstable frequencies are predicted to appear and disappear as wear progresses even though similar boundary conditions and operating conditions are imposed to apparently the same disc brake model. This phenomenon may explain the fugitive nature of squeal behaviour

Optimization of Damping in Self-Excited Mechanical Systems

Self-excited vibrations, such as squealing of disc brakes or galloping of overhead transmission lines, are often accompanied by undesired phenomena. The appearance of self-excitation is ascribed to an instability originating either from negative damping or from non-conservative coupling of motion coordinates. In a linearized description, the stability behavior of such circulatory systems strongly depends on the structure of the damping matrix as well as the relation of all matrices involved. Considering the distinct physical origins of energy dissipation, some of the resulting damping matrices have a stabilizing effect, while others may contribute to destabilization. In this context, the present thesis addresses two major scientific objectives. First, a deeper understanding is promoted regarding the influence of velocity proportional forces on the stability of linear mechanical systems featuring circulatory and gyroscopic terms. Analytical investigations deliver detailed insights into the required structure of the damping matrix either for stabilization or the avoidance of destabilization. Second, stability is assessed by means of quantitative measures. On this basis, a technique for stability optimization is established. The method relies on decomposing the damping matrix into component matrices which are associated with different physical origins. Suitable variation of these submatrices yields a reduced tendency of self-excitation. Beneficial damping configurations are determined with respect to predefined constraints, as they naturally appear in engineering. The meaningfulness of the obtained results is judged in terms of dependence on parameter fluctuations and technical feasibility. Serving as representative examples, various models of disc brakes and overhead transmission lines are studied numerically at different levels of complexity

Simulation methods for vehicle disc brake noise, vibration & harshness

After decades of investigating brake noise using advanced tools and methods, brake squeal remains a major problem of the automotive industry. The Finite Element Analysis (FEA) method has long been used as a means of reliable simulation of brake noise, mainly using the Complex Eigenvalue Analysis (CEA) to predict the occurrence of instabilities resulting in brake noise. However it has been shown that CEA often over-predicts instabilities. A major improvement for CEA proposed in this study is tuning the model with an accurate level of damping. Different sources of damping are investigated and the system components are tuned using Rayleigh damping method. Also, an effective representative model for the brake insulator is proposed. The FEA model of the brake system tuned with the damping characteristics highlights the actual unstable frequencies by eliminating the over-predictions. This study also investigates effectiveness of a hybrid Implicit-Explicit FEA method which combines frequency domain and time domain solution schemes. The time/frequency domain co-simulation analysis presents time-domain analysis results more efficiently. Frictional forces are known as a major contributing factor in brake noise generation. A new brake pad design is proposed, addressing the frictional forces at the disc-pad contact interface. This concept is based on the hypothesis that variation of frictional coefficient over the radius of the brake pad is effective in reducing the susceptibility of brake squeal

Amortir les vibrations et les instabilités sans se mettre dans tous ses états

Ce mémoire est une synthèse de l’essentiel de mes travaux de recherche depuis ma soutenance de thèseen 2005. Ces travaux ont été menés avec le support du Laboratoire de Supméca : le LISMMA, Laboratoired’Ingénierie des Systèmes Mécaniques et des MAtériaux. Tous ces travaux n’auraient évidemment pas vu lejour sans la contribution de mes collègues, Jean-Luc, Julie, Hamiddou, Christophe, Ayech et des étudiantsque nous avons encadré, Franck, Salma, Nicolas, Hugo, Fred, Fatma, Sylvain et bien d’autres. Certains de cesétudiants sont aujourd’hui des collègues, d’autres ont poursuivi leur trajectoire dans l’industrie ; tous m’ontbeaucoup apporté scientifiquement et humainement dans mon métier d’enseignant-chercheur.J’ai fait le choix de construire ce mémoire comme une collection d’articles précédée d’une synthèse de mestravaux de recherche. Ce choix a été motivé par les préconisations de l’école doctorale de l’Université Pierreet Marie Curie et par l’intérêt que je portais à l’exercice de synthèse qui me permet d’essayer de prendre unpeu de hauteur sur l’ensemble de ces travaux. Dans cette synthèse, certains détails sont évidemment omis,le lecteur trouvera les explications manquantes dans les articles. De même, volontairement, l’essentiel desréférences bibliographiques se trouve dans les articles et seules quelques références sont rappelées en pied depage. Dans un soucis de cohérence, certains travaux, dans lesquels ma contribution a été plus marginale nesont pas présentés dans ce mémoire. Le premier chapitre est une introduction détaillée qui effectue des rappelssur les comportements amortissants d’un point de vue rhéologique et leur portage dans les simulations. Leschapitres suivants sont les synthèses de mes travaux sur les couplages piézoélectriques, la viscoélasticité, lecrissement, l’amortissement par frottement.Ces travaux s’inscrivent dans le domaine des vibrations et plus largement dans celui des Sciences del’Ingénieur. Nous nous sommes tous posés la question de l’intérêt de faire encore de la recherche dans undomaine appliqué pour lequel les lois fondamentales sont déjà écrites. Notre apport se situe dans l’adaptationde théories ou d’outils mathématiques parfois abstraits, dans l’adaptation de méthodes venant d’autres domainesde la physique ou des sciences de l’ingénieur. L’avènement de l’informatique et l’augmentation de lapuissance de calcul permet aujourd’hui d’utiliser la simulation numérique pour prédire certains phénomènesou pour post-traiter des résultats d’expérience. Enfin l’existence d’un laboratoire dans une école d’ingénieurfavorise une forme d’enseignement par projets mettant en oeuvre des expériences et des simulations sur dessujets émergents