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2015-09-29
Technical Paper
2015-01-2871
Mounika Katragadda, Kalyan Deepak Kolla, Venkata Suresh Yaparala
Fatigue that is induced due to vibration is known as vibration induced fatigue. There are two approaches to evaluate this, viz., time & frequency domain. A straight forward and widely used method is rainflow counting technique in time domain. This counting algorithm is readily available and apart from the time history, it needs only one variable input (number of stress ranges). In case of longer time histories, time domain approach may consume lot of time and resource, which shifts our interest towards frequency domain methods. In frequency domain, Dirlik's method is proven to be robust and gives closer results to time domain. Since Dirlik's approach is probabilistic, there are different variables (such as stress ranges, scaling factor for RMS value to predict maximum stress etc.) to be considered for cumulative fatigue damage evaluation.
2015-09-27
Technical Paper
2015-01-2686
Enrique Wegmann, Achim Dohle
The NVH behaviour of brake systems remains a core problem of the brake industry. Many efforts have been made to achieve a better system understanding but the prediction of noise occurrence based on measurable parameters remains unsatisfying. By considering the brake pad as one key component within the brake system, different measurement methods nearly describing its material properties have been developed until today. This work analyses the correlation of all important, state of the art friction material/pad parameter measurement methods to the NVH behaviour of a specific brake system on a statistical basis. The answer to the question “does the NVH parameter for friction materials exist”? will be derived from the correlation results.
2015-09-27
Technical Paper
2015-01-2690
Joo Sang Park
This paper introduce several practical cases to cure the squeal noise by investigating pad unstable behaviour and self-excited vibration, and propose frequency guide lines for better noise performance. These guide lines are very useful for designers especially at the initial design stage. By using historical DOE, practical frequency guide lines will be proposed to achieve better noise performance at the initial design stage by using historical database analysis. This study has some limitations that the guide lines are available for disc. It will be further study for other brake components. In conclusion, the practical guide lines for robust disc design will be proposed after analyzing a pad unstable behaviour and disc self-excited vibration during squeal by theoretical , numerical and experimental approach. Finally the guide lines is validated by statistical approach by reviewing historical DOE for various brake systems.
2015-09-27
Technical Paper
2015-01-2689
Katsuhiro Uchiyama, Yuji Shishido
Last year we presented the FEA simulation of  “spring - mass (Pad’s shape) model” from stick-slip phenomenon for improvement of creep groan. Creep groan is one of representative groan noise on automobile brake system.    As a result of parameter study with various pad shape (chamfer, slot, etc.…), we showed that brake pad with radial slot angle has a range which increases creep groan performance.   This year we would like to present our study for advantageous direction for reduction of creep groan which will focus on friction material Mu vs. Velocity (M-V) property, friction material physical properties and relative velocity between brake pads and rotor by advanced brake assembly FEM model which considers torsional stiffness of suspension.
2015-09-27
Technical Paper
2015-01-2684
Seongjoo Lee, ShinWook Kim, ShinWan Kim, Seong Rhee
A correlation between brake squeal and disc wear was reported previously. This investigation was undertaken to confirm the correlation and to characterize the disc wear particles transferred to the sliding surface of the NAO pad. It is found that the iron distribution on the pad is very non-uniform; at some locations, the iron concentration reaches the level of Low Steel Lomets (15-20wt%); and squealing brakes exhibit increased amounts of transferred disc wear particles on the pad surface. These transferred particles are found as small and flattened thin metallic sheets, which are different from relatively large “metal pick-up” pieces.
2015-09-27
Technical Paper
2015-01-2687
Aditya Kant Choudhary, Yogesh Mense, Saurabh Singh, Arun Kumar S
Brake noise is one of the common complaints and an irritant not just for the vehicle occupants but equally for the passers-by. Brake noise is actually vibration that is occurring at a frequency that is audible to the human ear. This occurrence of brake noise like brake squeal (>1 kHz) and groan (<1 kHz) is often very intense and can lead to number of customer complaints. During a brake noise event, vehicle basic structure and suspension system components are excited due to brake system vibration and result in a resonance that is perceived in the form of a noise. Proposed work discusses an experimental study that is carried out on a commercial vehicle for addressing customer complaints regarding disc brake squeal and groan noise. Based on the preliminary inputs, vehicle level study was carried out in order to simulate the problem and objectively capture its severity.
2015-09-27
Technical Paper
2015-01-2685
Diego Masotti, Patric Neis, Ney Ferreira, Kássio Gomes, Jean Poletto, Luciano Matozo
The present work presents evaluation of the sliding surface morphology of brake pads during stick-slip process. For doing that, a brake friction material was subjected to slide against a brake disc under conditions favorable to produce stick-slip phenomenon. The experiments were conducted in a laboratory-scale tribometer, which was especially designed to test brake pads used in vehicle. Optical microscope images of the material’s surface were obtained at different stages of the braking test. These images were post-processed in appropriate computational software and by means of the segmentation technique the real contact area, size and amount of contact plateaus related to the brake pad surface were estimated. Coefficient of friction resulting from the tests was measured and it is also discussed throughout this paper.
2015-09-27
Technical Paper
2015-01-2688
Hayuru Inoue, Kumi Hashimoto, Yoichi Kumemura
It is well known that improving NV performance and weight saving are reciprocity. Brake squeal free is one of the top priority issues during development of brake system. On the other hand, the needs for light weight brake system are getting higher due to recent trends of economizing fuel consumption and high driving performance. In order to obtain coexistence of brake squeal free and the weight saving, shape optimization technique has been proposed adaptation to calculating of complex eigenvalue analysis which analyzes self-excited vibration. Solving the structural instability problems by complex eigenvalue analysis in consideration of frictional force is widely handled using finite element method (FEM). The positive real part of complex eigenvalue is identified brake squeal which has unstable vibration by stability evaluation by complex eigenvalue analysis.
2015-09-27
Technical Paper
2015-01-2691
Ju Young Kim, Jeongkyu Kim, Young Min Kim, Wontae Jeong, Hojoon Cho
In the brake system, unevenly distributed disc-pad contact pressure distribution during braking is not only a loss of braking power but also a main cause of system instability which lead to squeal noise. In this reason there has been various attempts to measure contact pressure distribution. In the brake industry, static pressure distribution is measured and utilized to guess actual pressure distribution. In this study new test method is designed to quantitatively measure dynamic contact pressure distribution between disc and pad in vehicle testing. Upon various driving conditions and shape of pad, characteristics of dynamic contact pressure distribution were analyzed. Based on those results, analytical model updated and found to better detect propensity of brake squeal.
2015-09-27
Technical Paper
2015-01-2682
Masaaki Nishiwaki, Ryutaro Misumi
High brake performance is required for vehicle safety. At the same time, mass reduction of brake system is also required for vehicle economic long run. Under these backgrounds, high friction coefficient pad materials come to be adopted for brake system. But it is well known that brake squeal is often caused by high friction coefficient pad materials. Therefore, brake squeal research is one of very important technical issues for vehicles design. Disc brake squeal is caused by small disturbance in dynamic unstable systems. Today, disc brake squeal can be simulated by FE Analysis in actual disc brake, but it is remained a technical issue of small disturbance, brake squeal trigger of friction force variation. Low-frequency disc brake squeal around 2 kHz can be caused by forced vibration during brake application, which is shown by N.Ishihara and me in references (1). This research suggests the trigger of disc brake squeal generation.
2015-09-27
Technical Paper
2015-01-2683
Sarah Chen, Steve Hoxie
Developing a quiet brake system has been a constant task for OEM as well as their brake suppliers. Squeal problems may taint the image of a car manufacturer and cause substantial revenue loss from warranty claims despite the fact that the brake remains fully functional and safe. As a major component in the brake system, the rotor plays significant role in brake noise performance. Because of the cost and damping property advantages, gray iron is still the most widely used material for brake rotor application. When pads/rotor coupling is looked at to minimize noise issues, however, most efforts have been on pads and insulators. Rotor specifications are rather general and the component is typically accepted based on grades defined by mechanical property minimum (mostly in G3000 SAE J431).
2015-09-27
Technical Paper
2015-01-2673
Toshikazu Okamura
Brake judder is one of the most serious problems in automotive-brake systems and brake discs play a significant role in judder. There are two types of brake judder: cold and hot. Hot judder is caused by the thermo-mechanical deformation of a disc rotor due to high-speed brakings. There are several causes and shapes of disc’s thermo-mechanical deformation, e.g. coning and wave-like shapes. The circumferential wave-like shapes of brake discs are typically found as a butterfly shape in the second order of the rotational speed and corrugation (or heat spots) around tenth order of that. They are caused by thermo-mechanical buckling and are the significant cause of hot judder. The author focuses on the effects of material and dimensional homogeneity on the transient and permanent deformation of ventilated discs in the low orders of the rotational speed during repetitive high-speed brakings.
2015-09-15
Technical Paper
2015-01-2477
Alessandro Gardi, Roberto Sabatini
A number of initiatives are aiming at assessing and reducing the impact of air transport on the environment. This extensive endeavour is soliciting a substantial evolution in the measurement of the environmental impacts and on the assessment of the effective gains attained by the R&D outcomes. Legislation is already being progressively extended in several countries to limit or penalise noise emissions, and analogous regulatory actions can be foreseen with respect to atmospheric pollutants. This research activity is developing laser-based Light Detection and Ranging (LIDAR) systems for characterisation of gaseous pollutants and particulate concentrations in high space and time resolutions. The employed measurement principle is based on Differential Absorption LIDAR technique, in a bistatic layout. After the initial feasibility study, two candidate bistatic system layouts have been proposed.
2015-09-15
Technical Paper
2015-01-2620
Philip Van Baren
Random vibration control systems produce a PSD plot through a method of averaging the FFT of individual frames of data. Modern controllers can set the DOF, or number of frames in the averaged PSD signal. The PSD is a way to present a random signal with high excursions from the mean in a format that makes it easy to determine the validity of the test. This process takes time as many frames of data are collected to generate the PSD and the test can appear to be out of tolerance until the controller has enough data. A random signal that achieves an in-tolerance condition immediately after starting or during level changes can create dangerous over or under test conditions within specific frequency bands and should be avoided. Take-Away 1: What is Random? Take-Away 2: Why is it represented as a PSD? Take-Away 3: How can you minimize out of tolerance events?
2015-09-15
Technical Paper
2015-01-2605
Jamnie Yazmín Achem Calahorra, Hilda E. Esparza Ponce, Patricia Zambrano Robledo, Facundo Almeraya Calderón, Citlalli Gaona Tiburcio
Thin films deposited by magnetron sputtering are review in terms of their potential and present uses in the aircraft industry. The aircraft alloys substrates were Ti-6Al-4V and Incoloy 800H/HT, using a target of YSZ with nominal composition of 8% Y2O3 (wt%) and the remainder of ZrO2. The chemical composition of the films was determined by EDX. The electrochemical noise behavior show that the coatings decreased propagation of pitting, leading to a state of passivation or uniform corrosion, and also possess superior corrosion resistance over the individually substrates.
2015-09-15
Technical Paper
2015-01-2435
Ramakrishnan Murthy
One major problem that any product (say Motor, engines etc) which converts electrical energy into a mechanical energy would have is resonance. It has tendency to damage any material when the products operating frequency matches the resonant frequency. The major consequences of this resonant frequency in Flight at run-time could be catostrophic. Generally it is a practice to avoid running at the resonant frequency. This is done as a fixed method where the systems are designed not to run on resonant frequency, i.e. a subsystem in a system is now being designed for that system alone which will not match the resonant frequency. But the same subsystem may not be suitable for some other system. Hence this requires multiple designs. However this idea is to make a design generic where any subsystem can be used in any system irrespective of its resonant frequency. The technique uses the PID algorithm. This method will be helpful is having a single design for different systems.
2015-09-15
Technical Paper
2015-01-2501
Cosme de Castelbajac, Sylvain Laporte, Julian Lonfier, Emmanuel Puviland
Over the last few years, a number of aircraft production lines have seen their production rate increase. In some cases, to avoid bottlenecks in the assembly lines, the productivity of processes needs to be improved while keeping existing machine-tools. In this context, the case of drilling machine-tools tends to require particular attention, especially when multi-material parts are drilled. In such instances, the Vibration Assisted Drilling (V.A.D.) process can be a way to improve productivity and reliability while controlling quality standards. This article presents a case of a drilling/countersinking process for stainless steel and titanium stack parts. Firstly, the article assesses the feasibility and benefits of using Vibration Assisted Drilling and Countersinking with the current cutting-tools.
2015-09-15
Technical Paper
2015-01-2485
Mark Benjamin Geiger, John Michael Ster
Powered hand tools have become essential to a range of industrial operations since their introduction in the late 1800s. However, progress often comes with risk. A range of potential hazards associated with power tool use include noise, a range of ergonomic stresses and physical safety hazards. One of the less publicized risks is hand-arm vibration, previously called Raynaud’s Syndrome of occupational origin, a neurovascular disease associated with intense and prolonged exposures to vibration – most commonly from powered hand tools. Despite initial US reports in the early 1900s, the disease has remained under-recognized in the US. European Union regulations have created an increased awareness of hand-arm vibration disease and demand for low-vibration powered hand tools, while the US has lagged in this regard. (See additional resources)* The wide range of vibration (and noise) created by alternative products performing the same function makes initial product selection critical.
2015-09-15
Technical Paper
2015-01-2586
Bradley Michael, Rani Warsi Sullivan, Dulip Samaratunga, Ratneshwar Jha
The vibration response from undamaged and damaged polymer matrix composite beams at four elevated temperatures is analyzed using the Hilbert-Huang Transform (HHT) technique. The HHT shows potential in identifying the nonlinear damaged response of the beams. Using empirical mode decomposition to separate superposed modes of signals, several intrinsic mode functions can be determined which can reveal more information about complex nonlinear signals than traditional data analysis techniques such as the Fourier Transform. The composite beams of angle-ply construction are fabricated from an out-of-autoclave uniaxial carbon/epoxy prepreg (CYCOMTM-5320-1/T650). Delaminations in the composite layups are introduced by insertion of mold release wax films. A shaker-table fixture was used for the vibration testing of all beams in a vertical cantilever configuration. High temperature piezoelectric accelerometers were used to obtain the vibration data for a frequency range of 2-100 Hz.
2015-09-06
Technical Paper
2015-24-2526
Borislav Klarin, Thomas Resch, Chiara Sessarego, Giorgio Spanu, Gianni Lamonaca
Modern engines with low number of cylinders (I4, I3, I2) are typically equipped with a mass balancing unit to reduce free mass forces and moments and to keep powerunit vibrations, transferred via the mounts into the chassis, on an acceptable level and by that meet the required comfort quality. Typical disadvantages of mass balancing systems are increased friction, which reduces the engine efficiency, but also space, costs, increased complexity and negative effect on the engine acoustics. Especially the latter is defined by the design of the drive for the balancer unit. In many cases, this is realized by a gear drive, directly driven from the crankshaft. Therefore, special care has to be taken for the layout of this gear(s) to avoid potential rattle, gear tooth failure and negative noise transfer from gear contact to the housing structure (e.g. increased axial excitation due to selection of helix angle).
2015-09-06
Technical Paper
2015-24-2531
Marco Leonetti, Michael Bargende, Martin Kreschel, Christoph Meier, Horst Schulze
Due to the demands for today’s passenger cars regarding fuel consumption and emissions, exhaust turbo charging has become a fundamental step in achieving these goals. Especially in upper and middle class vehicles it is also necessary to consider the noise comfort. Today, floating bushings are mainly used as radial bearings in turbochargers. In the conventional operating range of the turbocharger dynamic instability occurs in the lubrication films of the bearings. This instability is transferred by structure-borne noise into audible airborne sound and known as constant tone phenomenon. This phenomenon is not the major contributor of the engine noise but its tonal character is very unpleasant. In order to gain a more detailed understanding about the origin of this phenomenon, displacement sensors have been applied to the compressor- and the turbine-side of the rotor, to be able to determine the displacement path.
2015-09-06
Technical Paper
2015-24-2387
Emiliano Vitaliani, Daniele Di Rocco, Martin Sopouch
The aim of this paper is the study of the Centrifugal Pendulum Vibration Absorber (CPVA) dynamic behaviour, with the background of improved vibration isolation and damping quality through a wide range of operating speeds. The CPVAs are passive devices, which are used in rotating machinery to reduce the torsional vibration without decreasing performance. After a first use of these damping systems in the field of aeronautics, nowadays CPVAs are employed also in railway and automotive applications. In principle, the CPVA is a mass, mounted on a rotor, which moves along a defined path relative to the rotor itself, driven by centrifugal effects and by the rotor torsional vibrations. The advantage that such absorbers provide is the capability to counteract torsional vibrations arising with frequencies proportional to the mean operating speed. This is in particular the case with Internal Combustion Engines (ICE) where the induced vibrations are caused by the combustions process.
2015-09-06
Journal Article
2015-24-2462
Fabio Auriemma, Heiki Tiikoja
The acoustic impedance exerted by a new type of element for noise control, the Micro-Grooved Elements (MGEs), has been broadly studied in this paper. The MGEs are typically composed of at least two overlying layers presenting macroscopic slots and a number of micro-grooves at least on one of the contact surfaces. Similarly to the Micro-Perforated Elements (MPEs), the MGEs have been proved to provide effective dissipation of acoustic energy by the means of viscous losses taking place in the micro-channels. However, in contrast to the typical MPEs, the MGEs use the grooves, instead of the holes, which the air is forced to pass through. It results in more cost effective elements, which have been found to represent an adequate alternative for fibrous materials, typically present in silencer units. This study represents a refined investigation on the acoustic impedance of the MGEs, aiming to provide a general formulation, valid for different internal configurations.
2015-09-06
Journal Article
2015-24-2527
Daniela Siano, Giovanni Ferrara, Giulio Lenzi, Danilo D'Agostino, Andrea Fioravanti
In an Internal Combustion Engine, the design of the intake system is a very critical aspect since it affects both the engine power output and noise emissions at the intake side. In particular, downsized VVA engines typically produce higher gas-dynamic noise levels since, due to the intake line de-throttling at part-load, a less effective attenuation of the pressure waves is realized. In this work, the acoustic performance of the intake air filter of a commercial VVA engine is numerically and experimentally analyzed. In particular, a FEM model of the system is realized in order to compute the Transmission Loss (TL) parameter of the base device. The numerical analysis is performed considering the absence or the presence of a mean flow inside the device, and accounts of fluid-structure interaction, which gives the possibility to determine the effect of structure participation on the TL profile.
2015-07-23
Article
Physics-based robot simulation leveraging stochastic optimization and game theory will support new NASA missions.
2015-06-30
Article
Off-highway machine mounting systems, especially the cab mounting system, significantly affect the operator comfort in the cab by providing enough damping for a good ride and isolating the structure-borne forces from traveling into the cab.
2015-06-29
WIP Standard
J1400
This SAE Recommended Practice presents a test procedure for determining the airborne sound barrier performance of materials and composite assemblies commonly installed in surface vehicles and marine products. This document is intended to provide a means of rank ordering barrier materials according to their sound transmission loss. At each test frequency the transmission loss (TL) is projected from the measured noise reduction of the test specimen using a correlation factor (CF). The respective CF for the test condition is determined as the differences between the measured noise reduction (MNR) of a homogeneous limp panel, such as lead, and its calculated field-incidence transmission loss. Latitude is permitted in certain test conditions that do not necessarily conform to all of the acoustical requirements of ASTM E 90.
2015-06-23
WIP Standard
J2889/1
This SAE Standard is derived from SAE J2805 and specifies an engineering method for measuring the sound emitted by M and N category road vehicles at standstill and low speed operating conditions.. The specifications reproduce the level of sound which is generated by the principal vehicle sound sources consistent with stationary and low speed vehicle operating conditions relevant for pedestrian safety. The method is designed to meet the requirements of simplicity as far as they are consistent with reproducibility of results under the operating conditions of the vehicle. The test method requires an acoustic environment which is only obtained in an extensive open space or in special designed indoor facilities replicating the conditions of an extensive open space. Such conditions usually exist during: Measurements of vehicles for regulatory certification. Measurements at the manufacturing stage. Measurements at official testing stations.
2015-06-18
Article
Passenger Experience automates cabin completion processes with essential intelligent “building blocks” capturing rules, regulations, and manufacturing knowledge to automate cabin interior design, development, and delivery.
2015-06-15
Technical Paper
2015-01-2319
Uije Kim, Matthew Maunder, Phil Grant, Duncan Mawdsley
Abstract A new pass-by noise test method has been introduced, in which engine speeds and loads are reduced (compared to the old test method) to better reflect real world driving behavior. New noise limits apply from 1 July 2016, and tighten by up to 4dB by 2026. The new test method is recognized internationally, and it is anticipated that the limits will also be adopted in most territories around the world. To achieve these tough new pass-by noise requirements, vehicle manufacturers need to address several important aspects of their products. Vehicle performance is critical to the test method, and is controlled by the full load engine torque curve, speed of response to accelerator pedal input, transmission type, overall gear ratios, tire rolling radius, and resistance due to friction and aerodynamic drag. Noise sources (exhaust, intake, powertrain, driveline, tires) and vehicle noise insulation are critical to the noise level radiated to the far-field.
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