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Technical Paper

A Finite Element Method for Effective Reduction of Speaker-Borne Squeak and Rattle Noise in Automotive Doors

2011-05-17
2011-01-1583
Increasing sound quality with advanced audio technology has raised the bar for perceived quality targets for minimal interior noise and maximal speaker sound quality in a passenger vehicle. Speaker-borne structural vibrations and the associated squeak and rattle have been among the most frequent concerns in the perceived audio quality degradation in a vehicle. Digital detection of squeak and rattle issues due to the speaker-borne structural vibrations during the digital vehicle development phase has been a challenge due to the physical complexity involved. Recently, an effective finite element method has been developed to address structure-borne noise [1] and has been applied for detecting the issues of squeak and rattle in passenger vehicles due to vehicle-borne vibrations at vehicle, component and subcomponent levels [2, 3, 4, 5, 6, 7, 8].
Technical Paper

Finite Element Analysis of Light Vehicle Cab's Hydraulic Mount Based on Fluid-Structure Interaction Method

2011-05-17
2011-01-1604
Hyperelastic model constants of rubber material are predicted based on test date. The fluid-structure interaction model of light vehicle cab's hydraulic mount is established. Static characteristics of the hydraulic mount are analyzed by quasi-static method. In dynamic characteristics analysis, the flow model of fluid is set to turbulent K-Epsilon RNG. The dynamic stiffness and loss angle of the hydraulic mount are presented via the finite element model. The simulations of static and dynamic characteristics agree well with corresponding test results. The effects of main structure parameters to the dynamic characteristics of the hydraulic mount are analyzed based on the finite element model.
Journal Article

Simulating the Static and Dynamic Response of an Automotive Weatherstrip Component

2011-05-17
2011-01-1602
Understanding the resonant behavior of vehicle closures such as doors, hoods, trunks, and rear lift gates can be critical to achieve structure-borne noise, vibration, and harshness (NVH) performance requirements, particularly below 100Hz. Nearly all closure systems have elastomer weatherstrip components that create a viscoelastic boundary condition along a continuous line around its perimeter and is capable of influencing the resonant behavior of the closure system. This paper outlines an approach to simulate the static and dynamic characteristics of a closed-cell Ethylene Propylene Diene Monomer (EPDM) foam rubber weatherstrip component that is first subjected to a large-strain quasi-static preload with a small-strain sinusoidal dynamic load superimposed. An outline of a theoretical approach using “phi-functions” as developed by K.N. Morman Jr., and J.C.
Journal Article

Three-pass Perforated Tube Muffler with End-resonator

2011-05-17
2011-01-1529
The one-dimensional analytical approach, three-dimensional finite element method (FEM) and boundary element method (BEM) are developed to predict and analyze the acoustic attenuation performance of three-pass perforated tube muffler with end-resonator. For an elliptical muffler, the predictions of transmission loss from the FEM and BEM agree well each other throughout the frequency range of interest, while the one-dimensional analytical solution shows a reasonable agreement with the numerical predictions at lower frequencies and deviates at higher frequencies. The FEM is then used to investigate the effects of geometrical parameters and internal structure on the acoustic attenuation performance of three-pass perforated tube muffler with end-resonator.
Journal Article

Structural Optimization Method and Techniques to Reduce Radiation Noise

2011-05-17
2011-01-1505
A methodology to optimize sound pressure responses of a structure, producing a radiation noise due to structural vibration, is presented. The method involves a finite element analysis module to calculate structural vibration, an optimization module to perform sensitivity analysis and structural optimization, and an acoustic module to compute acoustic transfer vectors. The proposed design system is successfully implemented and is demonstrated in the paper using several example problems.
Journal Article

A FE Based Procedure for Optimal Design of Damping Package, with Presence of the Insulation Trim

2011-05-17
2011-01-1693
Typically, in the automotive industry, the design of the body damping treatment package with respect to NVH targets is carried out in such a way to achieve panel mobility targets, within given weight and cost constraints. Vibration mobility reduction can be efficiently achieved thanks to dedicated CAE FE tools, which can take into account the properties of damping composites, and also, which can provide their optimal location on the body structure, for a minimal added mass and a maximized efficiency. This need has led to the development of different numerical design and optimization strategies, all based on the modeling of the damping composites by mean of equivalent shell representations, which is a versatile solution for the full vehicle simulation with various damping layouts.
Technical Paper

Modeling of Stiffened Panels Using the Energy Finite Element Analysis

2011-05-17
2011-01-1696
Stiffened panels are encountered in many engineering systems since the stiffeners comprise the mechanism which provides support and rigidity to the panel's skin. Either a mechanical excitation or an acoustic load can be applied on a stiffened panel creating vibration that is transmitted in all panel components. Mechanical excitation tends to be localized in nature, originating from operating machinery mounted on the panel, while the acoustic excitation tends to be distributed over the entire panel, since it typically originates from an external acoustic source which creates an acoustic field impinging on the entire panel. In the Energy Finite Element Analysis (EFEA) various degrees of fidelity are possible when modeling the response of a stiffened panel. In this paper, the theoretical background and the corresponding implications associated with each alternative modeling approach are presented first.
Journal Article

Finite Element Model for Spot Welds Using Multi-Point Constraints and its Dynamic Characteristics

2011-05-17
2011-01-1697
In this paper, we focus on the ACM2 (Area Contact Model 2) model as a simplified spot weld model suitable for vibration analysis and reveal its dynamic characteristics. First, the theoretical background of the multi-point constraint (MPC) used in the ACM2 model is explained. Next, we examine in detail the effect of the mesh pattern surrounding a spot weld on the modal properties (natural frequency and mode shape) of a spot welded structure. Finally, an appropriate mesh size in the area of the spot weld for the ACM2 model is presented. As an example, we used two steel plates joined by three spot welds. The results show that the configuration and size of the patch (group of shell elements in the ACM2 model) significantly affect the modal properties of the model. When the centers of the patch and the solid element that represent the spot weld are coincident, the natural frequencies monotonically increase with the patch size.
Technical Paper

FEM Evaluation of Elastic Wedge Method for Damping of Structural Vibrations at Low Frequencies

2011-05-17
2011-01-1689
This paper presents new results regarding damping of structural vibrations using the elastic wedge method. An elastic wedge is a plate, or a rod, whose thickness decreases smoothly towards zero. Flexural vibration energy accumulates at the thinner edge and thus, effective damping can be easily achieved. The method has been proposed to reduce flexural vibrations of structures in the high frequency range, like vibration of turbine blades. In this research, the application of the elastic wedge method to reduce structural vibration in low frequency ranges is investigated using FEM. The structure under analysis is a heavy machinery bed structure. Two rod elastic wedges are attached to that bed. The target frequency range to be damped is between 150 and 250Hz. The results show that the elastic wedge method can effectively reduce the structural vibration of the bed in the target frequency range.
Technical Paper

Prediction of Structural Acoustic Radiation for Compressor Considering Airflow Pulsed Load

2011-05-17
2011-01-1722
A coupled vibro-acoustic of a compressor modeling process was demonstrated for predicting the acoustic radiation from a vibrating compressor structure based on dynamic response data. FEM based modal analysis of the compressor was performed and the result was compared with experimental data, for the purpose of validating the FE model. Modal based force response analysis was conducted to calculate the compressor's surface vibration velocity on radiating structure, using the load which caused by mechanical excitation as input data. In addition, due to the coolant had oscillating gas pressure, the gas pulsed load was also considered during the dynamic response analysis. The surface vibration velocity solution of the compressor provided the necessary boundary condition input into a finite element/boundary element acoustic code for predicting acoustic radiation.
Technical Paper

Borderline Design of Crankshafts Based on Hybrid Simulation Technology

2009-06-15
2009-01-1918
This paper introduces different modeling approaches of crankshafts, compares the refinement levels and discusses the difference between the results of the crankshaft durability calculation methodologies. A V6 crankshaft is considered for the comparison of the refinement levels depending on the deviation between the signals such as main bearing forces and deflection angle. Although a good correlation is observed between the results in low speed range, the deviation is evident through the mid to high speed ranges. The deviation amplitude differs depending on the signal being observed and model being used. An inline 4 crankshaft is considered for the comparison of the durability results. The analysis results show that the durability potential is underestimated with a classical crankshaft calculation approach which leads to a limitation of maximum speed of 5500 rpm.
Technical Paper

Vibro-Acoustic Simulation of Diesel Injection Ducts

2009-05-19
2009-01-2057
High pressure pipes of the diesel injection system seem to represent a weak point in terms of vibration and acoustic radiation of the whole injection system. Investigations have highlighted this phenomenon. The injectors induce acoustic waves which propagate in the viscous diesel contained in the injection pipes. A strong coupling can occur sometimes between these acoustic waves and the duct structural modes leading to intensive mechanical vibration and acoustic radiation; and sometimes to a possible failure of the pipe. Numerical simulations offer a good platform to predict such vibration and can be used in order to prevent any structural component failure and to decrease the resulting acoustic radiation. This paper presents a vibro-acoustic study performed with the finite element code ACTRAN to estimate which parameters play a role in this process and to provide some guidelines for avoiding problems.
Technical Paper

Modeling, Design and Validation of an Exhaust Muffler for a Commercial Telehandler

2009-05-19
2009-01-2047
This paper describes the design, development and validation of a muffler for reducing exhaust noise from a commercial tele-handler. It also describes the procedure for modeling and optimizing the exhaust muffler along with experimental measurement for correlating the sound transmission loss (STL). The design and tuning of the tele-handler muffler was based on several factors including overall performance, cost, weight, available space, and ease of manufacturing. The analysis for predicting the STL was conducted using the commercial software LMS Virtual Lab (LMS-VL), while the experimental validation was carried out in the laboratory using the two load setup. First, in order to gain confidence in the applicability of LMS-VL, the STL of some simple expansion mufflers with and without extended inlet/outlet and perforations was considered. The STL of these mufflers were predicted using the traditional plane wave transfer matrix approach.
Journal Article

Prediction of Muffler Insertion Loss by a Hybrid FE Acoustic-SEA Model

2009-05-19
2009-01-2042
A reactive aftermarket automotive style muffler was considered for development and validation of a procedure to numerically predict and experimentally validate acoustic performance. A CAD model of the silencer was created and meshed. The silencer interior included two sections of perforated pipe, which were included in the cavity mesh. A hybrid FE-SEA (Statistical Energy Analysis) numerical model consisting of a finite element acoustic cavity excited by a diffuse acoustic field at the inlet and coupled via hybrid junctions to SEA semi-infinite fluids on both the inlet and outlet. The hybrid FE-SEA model solves very rapidly on a desktop PC making iterative numerical design a realistic option. To validate the predictions, an experimental setup was created to directly measure the muffler insertion loss. This was done by using a broadband acoustic source piped into a hemi-anechoic chamber.
Technical Paper

Predicting Shell Vibration and Implosion Issues in Automotive Muffler Design

2009-05-19
2009-01-2038
The muffler shell of an automotive exhaust system can cause significant NVH (noise/vibration/harshness) issues like shell vibration and radiated noise, buzzing, rattling, and implosion problems. Due to the complex relationship between the dynamic behavior of the muffler shell and many parameters like engine operating temperature, curvature of the shell, material density, shell thickness and baffle spacing, the NVH engineers have experienced difficulties identifying the root cause of problems and solutions to them. By considering all design parameters, a theoretical study on shell vibration has been conducted to investigate applicability of an analytical technique to predict and solve the NVH issues of an automotive muffler. We have identified the most promising shell vibration theories by comparing the solutions with the results from modal test and finite element analysis.
Journal Article

Acoustic Analysis of Exhaust Muffler of a 4-Stroke Engine

2009-06-15
2009-01-1980
A one-dimensional analysis was performed to analyze a three-pass muffler with perforated tubes for Transmission Loss, using numerical decoupling approach. Effect of mean flow on transmission loss inside the muffler was studied. To account for the three-dimensional nature of acoustic waves at higher frequencies, a three dimensional finite element analysis was done using SYSNOISE. The Transmission loss results of the three-dimensional analysis were compared with those of one-dimensional analysis for no flow case and shown to agree reasonably for lower frequency range.
Technical Paper

Improving Vehicle Vibration Behavior via Structural Modification with Random Road Input

2009-05-19
2009-01-2093
The aim of this research is the modification of frequency response of transmitted vibration to vehicle body via alternating the geometry of vehicle structural components. For this purpose after transmitting the FE model of vehicle body into ADAMS software and building full vehicle model, mode shapes, natural frequencies and transmitted vibration to the vehicle cabin in sensitive points were obtained. It has been shown that changing the engine ram geometry and adding strengthening components, not only affect the natural frequencies of vehicle body but also could modify the natural frequencies of full vehicle model. The result of using random road input demonstrates that the amplitude of the vibration transmitted to the vehicle cabin in modified model is decreased.
Technical Paper

Complex Mode Analysis on Disc Brake Squeal and Design Improvement

2009-05-19
2009-01-2101
Squeal noise in vehicle disc brakes is perceived by comsumers as both annoying and warranty cost. The mechanism is considered a mode coupling phenomenon also referred to as coalescence. In this paper, the system eigenvalues have been computed using a technique based on the • nite element method in order to obtain the dynamical properties of the disc brake assembly. The simulated squeal results were compared with the brake noise test that was in accordance with SAE J2521 standard and showed good correlation for some squeal frequencies which indicated that the research on disc brake squeal using complex mode could predict squeal propensity of the disc brake. Among the methods that have been used to control squeal noise, increasing the system damping has been shown to be very effective. The most commonly used method to increase system damping consists of attaching multi-layer laminates on the back of the brake pads.
Technical Paper

High Frequency Brake Squeal Prediction Index for Disc In-plane Mode

2009-05-19
2009-01-2102
As well as performance and safety, sensibility factor such as brake squeal noise has become an important factor to consider in today’s automotive industry. However, regardless of its importance, reduction of brake squeal noise has remained as one of the biggest challenges that have not yet been solved. Recently, many studies are being conducted to reduce squeal noise with the development of numerical analysis using FEM(Finite Element Method). This paper deals with complex eigenvalue analysis with commercial software program ABAQUS to resolve the squeal noise related to disc in-plane mode which is reported to occur frequently in the squeal noise frequency band 1~20kHz. As the reliability of the FE model is the most critical factor in numerical analysis, the FE model is first correlated with FRF modal test of each brake part and measurement of material property of pad with the anisotropic character through ultrasonic methods.
Journal Article

A Study of Effects of Brake Contact Interfaces on Brake Squeal

2009-05-19
2009-01-2100
Brake squeal is caused by the friction-induced vibration at the rotor/pad interfaces (primary contact interfaces) in a disc brake system. While there have been numerous research work evaluating the influence of primary contact interfaces on brake squeal, few studies can be found on the effect of the secondary contact interfaces, i.e., outer pad/caliper fingers, inner pad/pistons and pad/abutment, which can also significantly affect brake squeal based on our various dynamometer and vehicle tests. It is therefore the objective of this paper to investigate both the primary and the secondary contact interfaces and their influence on brake squeal. Simplified analytical models are created to gain insight into the stability of the brake system under low and high brake pressure; non-linear FEA analysis is employed for parametric study and countermeasure development; dynamometer and vehicle tests are used for verification.
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