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2016-09-27
Technical Paper
2016-01-8121
Riccardo Bianchi, Addison Alexander, Andrea Vacca
Vibrations at the cabin or at the implements of construction machinery represents important drawbacks from the points of view of machine productivity, safety and operator comfort. Oscillations of these machines are particularly relevant due to the absence of shock absorbers, typical of many machines such as wheel loaders, and their use in uneven ground conditions. Several hydraulic solutions have been proposed in the past to reduce oscillations at both the cabin or at the machine boom. Particularly, cabin oscillations can be attenuated by properly counteracting the exciting oscillatory forces from the tires with motion of the boom. Many state of the art machine utilize a passive methods to implement this strategy. The present work introduces a novel active solution, based on the control of the boom actuator without involving modifications of the standard hydraulic system.
2016-09-27
Technical Paper
2016-01-2096
Simon Schnieders, Dirk Eickhorst
Drilling of high-strength titan material and composites in combination creates complex challenges in order to achieve required productivity and quality. Long spiral chips are characteristically for the titan drilling process, which leads to e.g. chip accumulation, high thermomechanical load, surface damages and excessive tool wear. The basic approach is the substitution of today’s peck-drilling as current solution to this problem and the implementation of a vibration assisted drilling, so called micro-peck-drilling-process, to generate a kinematic chip breakage in a significant more efficient way. To meet perfectly the requirements regarding rates, quality and automation level, Broetje-Automation as system integrator has investigated and developed the implementation of different alternative high-performance systems and methods to approach the optimal oscillation movement of the tool.
2016-09-27
Technical Paper
2016-01-2097
Sylvain Laporte, Cosme De Castelbajac, Mathieu Ladonne
The Vibration Assisted Drilling (VAD) process has been implemented in Automated Drilling Units (ADU) on an industrial scale for almost a decade. Today more than 11000 ADUs are equiped with VAD systems and currently used on aircraft assembly lines. As well as drawing up a short report on the use of this new process, the authors make an assessment on new challenges that VAD has to face up. Indeed production rates are increasing and ADU manufacturers improve their technologies, one of the most recent and major development concerning the electrical motorization of the machines. These evolutions are as many opportunities for the VAD provided you have a clever understanding as well as an expert knowledge of the process. Thus the authors propose a new dynamic model of the whole VAD system which integrates the behavior of the part, cutting tool/material pair and the machine. The confrontation of model results and experimental validation tests demonstrates the relevance of the works.
2016-09-20
Technical Paper
2016-01-2009
Natasha Barbely, Narayanan Komerath, Nandeesh Hiremath
Coaxial rotors are finding use in advanced rotorcraft concepts. Combined with lift offset rotor technology, they offer a solution to the problems of dynamic stall and reverse flow that often limit single rotor edgewise forward flight speeds. Lower tip speed means reduced high speed impulsive noise. The need for an anti-torque tail rotor is eliminated, a major boon during operation in confined areas. However, the operation of two counter-rotating rotors in close proximity generates many possibilities for aerodynamic interactions between rotor blades, blades and vortices, and between vortices. The parameter design space is very large, and requires efficient computations as well as basic experiments to explore important physics determines performance, loads, and acoustics. Computations are done on the classic Harrington/Dingeldein rotor test case from the 1950s using the ROTUNS Navier Stokes code as well as the NASA OVERFLOW and/or HELIOS codes.
2016-09-18
Technical Paper
2016-01-1944
Seongjoo Lee, JeSung Jeon, ShinWook Kim, ShinWan Kim, Seong Rhee, Wan Gyu Lee, Young Sun Cho, Jeongkyu Kim
It is widely known that brake squeal repeatability and reproducibility are difficult to achieve whether a run on a vehicle on the road, a vehicle on a chassis dynamometer or a single brake on a noise dynamometer. At one time, the same brake may generate only low-frequency squeals (1.5 - 5 kHz) and at another time, only high-frequency squeals (5 - 20 kHz). More specifically, on a chassis dynamometer, the left side may produce only low-frequency squeals (or high-frequency squeals) while the right side produces only high-frequency squeals (or low-frequency squeals), or mixed squeals at different rates. The same phenomenon is observed when brakes are run on a noise dynamometer; more low-frequency squeals at one time or more high-frequency squeals at another time on an apparently same brake system. This study was undertaken to find out what causes these discrepancies.
2016-09-18
Technical Paper
2016-01-1933
Mingzhuo Li, Dejian Meng, Lijun Zhang
Brake judder severely affects the riding comfort and safety of vehicle. For the brake corner system, a rigid-flexible coupling model are established based on ADAMS. In the model, brake pads, caliper, anchor and knuckle are flexible body, and the contacts between pads and disc and the contact between pads and caliper are defined in detail. Meanwhile, the vibration acceleration of the brake corner components and the contact forces between disc and pads are used as evaluation index and the evaluation system of brake judder are improved. The analysis results show that the novel model and evaluation system can be used to predict brake judder effectively.
2016-09-18
Technical Paper
2016-01-1911
Philippe Dufrenoy
A multiscale model of a disc brake including material and surface heterogeneities Y. Waddad; V. Magnier; P. Dufrénoy* ; G de Saxcé University of Lille Cité scientifique Avenue Paul Langevin F-59655 Villeneuve d’Ascq Cedex * Corresponding author : philippe.dufrenoy@univ-lille1.fr During friction it is well known that the real contact area is much lower to the theoretical one and that it evolves constantly during braking. It influences drastically the system’s performance. Conversely the system behavior modifies the loading conditions and consequently the contact surface area. This interaction between scales is well-known for the problematic of vibrations induced by friction but also for the thermomechanical behavior. Indeed, it is necessary to develop models combining a fine description of the contact interface and a model of the whole brake system. This is the aim of the present work. The macroscopic model is obtained with Finite Element analysis.
2016-09-18
Technical Paper
2016-01-1931
Aaron Völpel, Georg Peter Ostermeyer
In today’s research and development of brake systems the model-based prediction of complex vibrations and NVH phenomena play an important role. Despite the efforts, the high dimensional computational simulation models only provide a limited part of the results gained through experimental measurements. Several reasons are discussed by the industry and academic research. One potential source of these inadequacies is the very simple formulation of the friction forces in the simulation models. Due to a significant shorter computation time (by orders of magnitude), the complex eigenvalue analysis has been established, in comparison to the transient analysis, as the standard method in the case of industrial research, where systems with more than one million degrees of freedom are simulated.
2016-09-18
Technical Paper
2016-01-1915
Meechai Sriwiboon, Seong Rhee, Kritsana kaewlob, Nipon Tiempan, Rungrod Samankitesakul
Two formulations have been selected and tested for this investigation; Low-Copper NAO and Copper – Free NAO. Each formulation was processed to achieve 3 levels of porosity; 12, 17 and 22%. Each sample was tested for hardness (HRR, HRS, and HRL), natural frequencies and compressibility plus performance testing for friction, wear and brake squeal. This paper describes correlations or lack of them between all the measurements.
2016-09-18
Technical Paper
2016-01-1919
Joo Sang Park, Min Gyu Han, Seon Yeol Oh
Basically caliper piston leading offset is to make a squeal noise bad based on sprag-slip theory. This paper introduce the experimental test results to investigate the relationship between the leading offset and the squeal noise. Also using a transient analysis and a complex eigenvalue analysis(CEA) simultaneously, the comparison between the experimental approach and the numerical approach is carried out to understand the squeal mechanism caused by the sprag-slip of pad behavior. During the squeal, the ODS is recorded by 3D laser vibrometer to correlate CAE results. Even if CEA is very popular CAE tool to study the squeal noise induced by a self-excited vibration, there are some limitations to duplicate the real phenomenon containing unstable behaviors due to pad weak contact stiffness and friction characteristics depending on the relative velocity because of considering self-excited vibration mechanism only.
2016-09-18
Technical Paper
2016-01-1920
Deaglan O'Meachair, Matthew Crumpton, Antonio Rubio Flores, Juan Garcia, Pablo Barles, Stamatis Angelinas
Bentley Motors Ltd. has developed a Carbon Silicon Carbide (CSiC) brake system for it’s Mulsanne product, introduced at 17MY. The CSiC brake system is conceived as a performance brake system, and as such offers notable improvements in brake performance In developing the brake system, particular focus was placed on meeting the refinement levels required for a premium product, and indeed as the flagship model for Bentley Motors, NVH refinement of the brake system was of particular concern. This paper intends to discuss the technical performance of the brake system and review the NVH performance of the brakes. This paper will also demonstrate the effect of vehicle isolation on the cabin NVH, and ultimately the passenger experience, by comparing the noise and vibration content in the wheel arch with that apparent to the driver.
2016-09-18
Technical Paper
2016-01-1922
Yongchang Du, Yujian Wang
Modelling of disc is crucial in analyzing brake squeal since the disc rotates past the non-rotating pads and the pads are coupled with different areas of the disc at different times. However, in most of the complex eigenvalue analysis of brake squeal, the effect of disc rotation was ignored. This paper proposes a closed-loop coupling model for brake squeal analysis. A modal parameter–based rotating disc model, whose dynamic behavior is represented by rotation speed-dependent equivalent modal parameters, is built through space and time-frequency transformation between reference and moving systems. The orthogonality of the equivalent modal parameters in state-space is derived. By performing modal synthesis in state-space, the rotating disc is incorporated into brake squeal closed-loop coupling model with other stationary components. Dynamic instability of the system is solved through complex eigenvalue analysis in state-space.
2016-09-18
Technical Paper
2016-01-1918
Yusuke Aoki, Yasuyuki kanehira, Yukio Nishizawa
Brake squeal is an uncomfortable noise that occurs while braking. So, it is an important issue for automobile quality to prevent brake products from squealing. Brake shims are widely used to reduce squeal occurrence rate. To quantify the anti-squeal effect of shims, loss factor has been measured with a bending mode tester, instead of repeating many dynamometer tests. However, there are cases where measurement results have less correlation to actual squeal suppression rate. Therefore, we have to evaluate the anti-squeal effect by dynamometer or on an actual car until the best shim can be selected. In this work, we focused on the differences between measurement conditions and actual braking conditions of shims to obtain a good correlation. The bending mode tester measures loss factor under pressure-free condition even though shims are compressed by pistons or cylinders towards the backplate of the pad.
2016-09-18
Technical Paper
2016-01-1921
Yusuke Sunagawa, Tsuyoshi Kondo
Brake squeal noise is generally classified into two vibration modes of disc. One is called “out-of plane mode” which vibrates in disc’s out-of-plane direction. The other is “In-plane mode” which vibrates in disc’s in-plane direction, it means the disc is contracted partially or is extended. There are few “In-plane noise” analysis reports from Disc pad standpoint, so it has been unclear how disc pad contributes to “In-plane mode” until now. This paper confirms that we successfully analyzed direct pad vibration mode by laser scanning under in-plane mode condition. Based on these results, we assume that pad stiffness affected in-plane mode and carried out validation tests.
2016-06-15
Technical Paper
2016-01-1823
Andrea Grosso, Martin Lohrmann
Abstract Operational Transfer Path Analysis (OTPA) assess the possible ways of energy to transfer from the various sources of excitation to a given target location. Applied to vehicle engineering, the OTPA provides indication about dominant sources and path contributions. However, it can only analyze the actual system under test and cannot predict if an improvement can be achieved by applying a counter measure. A careful interpretation of the measurement results is therefore necessary in order to define an effective engineering solution strategy. In this paper the RMA (Response Modification Analysis) technique is used to facilitate a sensitivity analysis, gaining insight whether energy is likely to be rerouted. This gives additional understanding of OTPA results, indicating which counter measure is most effective. The RMA is applied to a real measurement scenario, showing the advantage of the combination of OTPA with RMA for correctly identifying the relevant sources and paths.
2016-06-15
Technical Paper
2016-01-1805
Florian Zenger, Clemens Junger, Manfred Kaltenbacher, Stefan Becker
Abstract A low pressure axial fan for benchmarking numerical methods in the field of aerodynamics and aeroacoustics is presented. The generic fan for this benchmark is a typical fan to be used in commercial applications. The design procedure was according to the blade element theory for low solidity fans. A wide range of experimental data is available, including aerodynamic performance of the fan (fan characteristic curve), fluid mechanical quantities on the pressure and suction side from laser Doppler anemometer (LDA) measurements, wall pressure fluctuations in the gap region and sound characteristics on the suction side from sound power and microphone array measurements. The experimental setups are described in detail, as to ease reproducibility of measurement positions. This offers the opportunity of validating aerodynamic and aeroacoustic quantities, obtained from different numerical tools and procedures.
2016-06-15
Technical Paper
2016-01-1806
Sumon Sinha, Farokh Kavarana, Dan Williams, Kazuya Asao
Abstract A high performance rigid airfoil profile sunroof wind deflector has been developed for high speed freeway driving with the sunroof open. This deflector is clearly superior to the conventional bar type deflector and less expensive compared to tall flexible fabric mesh deflectors applied on high end vehicles today. It provides superior speech intelligibility under high speed driving with sunroof open. The criterion for designing this deflector was to get the highest airspeed possible to span the sunroof opening under all conditions. The customized shape also utilizes flow unsteadiness, including those at the onset of buffeting, in order to condition the shear layer. The airfoil profiled deflector yielded superior mid and high frequency acoustic performance with acceptable low frequency performance. A shorter airfoil deflector was sufficient to keep the external airflow from entering the forward tilted sunroof opening on a mid-size SUV under test.
2016-06-15
Technical Paper
2016-01-1803
Hannes Frank, Claus-Dieter Munz
Avoiding narrowband components in the acoustic spectrum is one of the most critical objectives in the automotive aeroacoustic optimization process. The underlying physical mechanisms are not completely understood. In a preceding numerical and experimental investigation, we performed large eddy simulations of an early-development stage realistic side-view mirror, where tonal noise was captured and the principle mechanisms were identified. In this contribution, we present simulations on a simplified two-dimensional geometry that is based on these findings. It is shown that the basic flow topology relevant for tonal noise generation on the original side-view mirror as well as the tonal noise source is reproduced in the 2D case. Furthermore, we present comparisons with measurements and the necessity and influence of a splitter plate downstream of the 2D body to avoid large scale vortex shedding.
2016-06-15
Technical Paper
2016-01-1802
Mehdi Mehrgou, Franz Zieher, Christoph Priestner
Abstract Recently, hybrid and fully electric drives have been developing widely in variety, power and range. The new reliable simulation approaches are needed, in order to meet the defined NVH targets of these systems and implementing CAE methods for front loading, Design Validation Process (DVP). This paper introduces the application of a novel NVH analysis workflow on an electric vehicle driveline including both electromagnetic and mechanical excitations for an absolute evaluation of the NVH performance. At first, the electromagnetic field is simulated using FEM method to extract the excitations on the stator, rotor bearings as well as the drive torque. Then, the multibody dynamic model of the driveline is built-up, driven by this torque. The effect of eccentricity and skew angle of rotor in electromagnetic excitations are shown.
2016-06-15
Technical Paper
2016-01-1796
Aurélien Cloix, Jean-Luc Wojtowicki
Abstract The current paper is based on the French research program TESSA (“Transfert des Efforts des Sources Solidiennes Actives”). A specific task within TESSA project consists in the characterization of the measurements variability between several laboratories, of the blocked forces on a water pump of a heat engine. This paper focuses only on the measurements carried out at Vibratec laboratory. Two kinds of measurements have been carried out: direct measurements, using force sensors, which is the target of the inter-laboratory measurements, and an inverse method without force sensor requirements. Reproducibility and repeatability tests have been done in order to quantify the measurement variability within the same laboratory, in preparation for the inter-laboratory disparity analysis.
2016-06-15
Technical Paper
2016-01-1798
Quentin Buisson, Jean-Louis Guyader, Serge Puvilland, Xavier Carniel, Maximilien Soenen
Abstract The goal of the present study is to provide a simple method to compare structure borne noise sources in order to choose the most efficient one, considering the transmission of dynamic forces. It is well known that mechanical sources are not only dependent of the source itself but also of the receiving structure, in addition real sources cannot be reduced to a transverse force acting on the structure but more complicated effect like moment excitation must be taken into account. The advantage of the reception plate method is to characterize the source globally by the level of vibration of the reception plate whatever the type of excitation, the idea is basically to characterize mechanical sources as it is done for acoustical sources in reverberant rooms. A reception plate test bench has been developed to determine the power injected by mechanical sources. Two prototype plates have been designed in order to have different receiving mobilities.
2016-06-15
Technical Paper
2016-01-1794
Jonathan Caprile, Claire Chaufour, Pierre Emile Chartrain
Abstract In automotive NVH, the noise generated by a powertrain is still one of the major noise sources especially at low and mid vehicle velocity. For this reason automotive OEMs are continuously focusing on methods to efficiently analyze this noise source. For this purpose, a well-established simulation methodology can provide results thoroughly, within a limited amount of time and with a reduced cost contrary to experiments which are involved in late design phases and are more expensive. This paper aims at presenting an approach to simulate efficiently the acoustic radiation from automotive components. With this aim in mind, the acoustic response of a realistic powertrain unit subjected to working conditions ranging from 1000 RPM to 4500 RPM is studied until 3000 Hz. Several radiating boundary conditions will be assessed in order to detect the most efficient set-up for this kind of problem and to extract the optimized modeling guidelines.
2016-06-15
Technical Paper
2016-01-1792
Aurélien Lonni, Olivier Tanneau
Abstract Nowadays, downsizing and turbochargers are more frequently used, mostly for petrol engines. It can lead to an increase of NVH issues related to the turbos, such as the hiss noise propagation in the air ducts. Hutchinson, among all its activities, supplies rubber and plastic parts for the car industry, especially in fluid management systems. The turbocharger’s airborne noise issue has now been tackled for ten years by implementing acoustic devices in the line and providing solutions to car manufacturers with our hot-side rubber ducts. In this paper, will be first presented the main HP air loop NVH issues, and then explained an approach to design technical solutions. Generally speaking, the noise propagates inside the hot side air hoses, crosses the weakest parts of the system by acoustic emissivity to reach finally the driver and passengers’ ears.
2016-06-15
Technical Paper
2016-01-1793
Sandra Forget, Nicolas Totaro, Jean-Louis Guyader, Michel Schaeffer
Abstract The constant evolution in the automotive sector to achieve more eco-friendly vehicles has induced the development of more efficient systems with new components and innovative materials. To evaluate the impact of these technologies or to improve them in terms of NVH performances, acoustic engineers rely on experimental tests and numerical computations. In this context, the use of experimental noise sources identification and characterization methods can provide interesting approaches. However, classical methods usually used in industry like the Nearfield Acoustical Holography (NAH) or the Beamforming techniques are quickly limited, in particular in terms of precision in localization, for such analysis support. The presented method, named M-iPTF for Mixed inverse Patch Transfer Functions, is more suitable as it is able to localize and quantify all acoustic source fields directly on the real geometry of a complex structure.
2016-06-15
Technical Paper
2016-01-1821
Lin Du, Mats Abom, Mikael Karlsson, Magnus Knutsson
Abstract To tune the acoustics of intake systems resonators are often used. A problem with this solution is that the performance of these resonators can be affected a lot by flow. First, for low frequencies (Strouhal-numbers) the acoustic induced vorticity across a resonator inlet opening will create damping, which can reduce the efficiency. Secondly, the vorticity across the opening can also change the end-correction (added mass) for the resonator, which can modify the resonance frequency. However, the largest problem that can occur is whistling. This happens since the vortex-sound interaction across a resonator opening for certain Strouhal-numbers will amplify incoming sound waves. A whistling can then be created if this amplified sound forms a feedback loop, e.g., via reflections from system boundaries or the resonator. To analyse this kind of problem it is necessary to have a model that allows for both sound and vorticity and their interaction.
2016-06-15
Technical Paper
2016-01-1822
Drasko Masovic, Franz Zotter, Eugene Nijman, Jan Rejlek, Robert Höldrich
Abstract Radiation of sound from an open pipe with a hot mean flow presents one of the classic problems of acoustics in inhomogeneous media. The problem has been especially brought into focus in the last several decades, in the context of noise control of vehicle exhaust systems and jet engines. However, the reports on the measurements of the radiated sound field are still rare and scattered over different values of subsonic and supersonic flow speeds, cold and hot jets, as well as different sound frequency ranges. This paper focuses on low Mach number values of the mean flow speed and low frequencies of the incident (plane) sound waves inside an unflanged cylindrical pipe with a straight cut. It presents the results of the far-field radiation pattern measurements and compares them with an existing analytical model from the literature. The mean flow inside the pipe reached Mach number values up to 0.25 and temperature up to 300°C.
2016-06-15
Technical Paper
2016-01-1820
Mikael Karlsson, Magnus Knutsson, Mats Abom
Abstract This work explores how fluid driven whistles in complex automotive intake and exhaust systems can be predicted using computationally affordable tools. Whistles associated with unsteady shear layers (created over for example side branches or perforates in resonators) are studied using vortex sound theory; vorticity in the shear layer interacts with the acoustic field while being convected across the orifice. If the travel time of a hydrodynamic disturbance over the orifice reasonably matches a multiple of the acoustic period of an acoustic feedback system, energy is transferred from the flow field to the acoustic field resulting in a whistle. The actual amplitude of the whistle is set by non-linear saturation phenomena and cannot be predicted here, but the frequency and relative strength can be found. For this not only the mean flow and acoustic fields needs to be characterized separately, but also the interaction of the two.
2016-06-15
Technical Paper
2016-01-1818
Raimo Kabral, Lin Du, Mats Abom, Magnus Knutsson
Abstract The concept of IC engine downsizing is a well-adapted industry standard, enabling better fuel conversion efficiency and the reduction of tailpipe emissions. This is achieved by utilizing different type of superchargers. As a consequence, the additional charger noise emission, at the IC engine inlet, can become a problem. In order to address such problem, the authors of this work have recently proposed a novel dissipative silencer for effective and robust noise control of the compressor. Essentially, it realizes an optimal flow channel impedance, referred to as the Cremer impedance. This is achieved by means of a straight flow channel with a locally reacting wall consisting of air cavities covered by an acoustic resistance, e.g., a micro-perforated panel (MPP). In this paper, an improved optimization method of this silencer is presented. The classical Cremer impedance model is modified to account for mean flow dependence of the optimal wave number.
2016-06-15
Technical Paper
2016-01-1816
Heiki Tiikoja, Fabio Auriemma, Jüri Lavrentjev
Abstract In this paper the propagation of acoustic plane waves in turbulent, fully developed flow is studied by means of an experimental investigation carried out in a straight, smooth-walled duct. The presence of a coherent perturbation, such as an acoustic wave in a turbulent confined flow, generates the oscillation of the wall shear stress. In this circumstance a shear wave is excited and superimposed on the sound wave. The turbulent shear stress is modulated by the shear wave and the wall shear stress is strongly affected by the turbulence. From the experimental point of view, it results in a measured damping strictly connected to the ratio between the thickness of the acoustic sublayer, which is frequency dependent, and the thickness of the viscous sublayer of the turbulent mean flow, the last one being dependent on the Mach number. By reducing the turbulence, the viscous sublayer thickness increases and the wave propagation is mainly dominated by convective effects.
2016-06-15
Technical Paper
2016-01-1814
Maxime Legros, Jean Michel Ville, Solène Moreau, Xavier Carniel, Christophe Lambourg, Guillaume Stempfel
Abstract The new requirements during the first stages of the conception of a HVAC prompt the designer to integrate the acoustic problematic increasingly upstream. The designer needs to select a coherent components’ choice in order to comply with the specifications in terms of aeraulic and acoustic performances. A tool has been created to guide the designer’s choices based on an acoustic synthesis which is a design and/or diagnosis approach used to analyze and predict the acoustic behavior of a complex system. The synthesis is developed in order to propose an approach which considers the integration effects and some interaction effects. The acoustic synthesis results are the starting point of a psycho-acoustic study providing audio samples of the prediction and indications of the HVAC acceptance by the prospective user. Also, one may compare the results of different acoustic synthesis projects to study the influence of the parameters on the acoustic prediction.
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