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Technical Paper

Structural-Acoustic Modeling & Optimization of a Submarine Pressure Hull

2019-06-05
2019-01-1498
The Energy Finite Element Analysis (EFEA) has been validated in the past through comparison with test data for computing the structural vibration and the radiated noise for Naval systems in the mid to high frequency range [Vlahopoulos, Wu, Medyanik]. A main benefit of the method is that it enables fast computations for full scale models. This capability is exploited by using the EFEA for a submarine pressure hull design optimization study. A generic but representative pressure hull from [Jackson] is considered. Design variables associated with the dimensions of the king frames, the thickness of the pressure hull in the vicinity of the excitation (the latter is considered to be applied on the king frames of the machinery room), the dimensions of the frames, and the damping applied on the hull are adjusted during the optimization process in order to minimize the radiated noise in the frequency range from 1,000Hz to 16,000Hz.
Technical Paper

Optimization of Multi-Layer Panel Constructions using Experimental Modeling via Transfer Matrix Method

2019-06-05
2019-01-1577
In a previous paper, a method was introduced to predict the sound transmission loss (STL) performance of multilayer panel constructions using a measurement-based transfer matrix method. The technique is unique because the characterization of the poro-elastic material is strictly measurement based and does not require modeling the material. In this paper, it is demonstrated how the technique is used to optimize the STL of lightweight, multi-layer panel constructions. Measured properties of several decoupler materials (shoddy and foam) are combined with sheet metal and barrier layers to find optimal combinations. The material properties are measured with the impedance tube per ASTM E2611.
Technical Paper

Engine Exhaust noise optimization using Sobol DoE sequence and NSGA-II Algorithms.

2019-06-05
2019-01-1483
Exhaust muffler is the most important component for overall vehicle noise signature. Optimized design of exhaust system plays a vital role in engine performance as well as auditory comfort. Exhaust orifice noise reduction is often contradicted by increased back pressure and packaging space. The process of arriving at exhaust design, which meets packaging space, back pressure and orifice noise requirements, is often manual and time consuming. Therefore, an automated numerical technique is needed for this multi-objective optimization. In current case study, a tractor exhaust system has been subjected to Design of Experiments (DoE) using SOBOL sequencing algorithm and optimized using NSGA-II algorithm. Target design space of the exhaust muffler is identified and modeled considering available packaging constrain. Various exhaust design parameters like; length of internal pipes, location of baffles and perforation etc. are defined as input variables.
Technical Paper

Multiphysics Multi-Objective Optimization for Electric Motor NVH

2019-06-05
2019-01-1461
Prediction of noise/vibration at the design stage is important for motor design. However, due to the multiphysics nature of the noise, vibration, harshness (NVH) simulation, an integrated workflow is required for wide adoption across industries [1-5]. ANSYS Workbench provides a platform where electromagnetic, structural and acoustic solvers can communicate with each other without user interventions. Based on the platform, multiple design points can be created with statistical sampling on given design spaces and solved by distributed high performance computers. Response surfaces can then be created with the solution from the design points and used for multi-objective optimization. To demonstrate the optimization workflow, multiple parameters for a motor design similar to the Prius motor are created.
Technical Paper

Improved measurement procedures for engine noise reduction with advanced microphones

2019-06-05
2019-01-1463
Introducing a new transducer concept has resulted in considerable reduction in setup time and at the same time improved accuracy and repeatability for engine bay noise transfer studies. The acoustic environment inside cars are one of the primary comfort parameters. This is made up of a number of contributions from drivetrain, auxiliary equipment, wind noise and tire noise, and all are influenced by the transfer from the source to the receiver. With the change from purely internal combustion engines to electrical or electrical assisted propulsion systems, a new set of noise sources are introduced in the engine compartment and this requires renewed focus on the transmission paths to the receivers inside the car cabin. Typically, one of the tools to study these mechanisms is by using a reverse transmission technique, placing a well-defined sound source in the receiver position inside the car and measure the resulting sound pressure levels in the engine compartment.
Technical Paper

Body-in-White Joint Stiffness Sensitivity Analysis

2019-06-05
2019-01-1494
The three major objectives of a car design are reduced costs, maximized performance and improved fuel economy. The total mass of a car has a direct effect on all these three objectives. Around 25% of the total mass of a typical car is accumulated in its Body-In-White (BIW). Thus, reducing the total mass of the BIW while satisfying the target stiffness is of utmost importance in the early stages of design. Reducing the total mass of the BIW involves the identification of potential sites for mass reduction and stiffness improvement. The joints of the BIW are often the most critical locations that decide the overall stiffness of the BIW. Understanding the contribution of each joint towards the overall stiffness is thus of paramount importance towards improving the stiffness of the BIW. This paper describes a new approach of identifying the contribution of each joint in a BIW towards the overall stiffness of the BIW.
Technical Paper

Simulation Analysis of a Dual-purpose Intelligent Mobile Platform for Highway and Railway

2019-06-05
2019-01-1499
Railways play a huge role in China's transportation industry. In order to ensure intelligence, advanced technology, and high efficiency in functions such as railway inspection, rescue, and transportation, a dual-purpose intelligent mobile platform for both roads and railways was developed. Due to the height limitation of this platform, resilient wheels and rubber dampers with short stroke are used as the suspension system for the rail chassis. Based on this special suspension form, the dynamic model of the whole platform is derived, and the simulation model of the whole platform is established in SIMPACK software. The effects of resilient wheels’ axial stiffness, radial stiffness and vertical stiffness, lateral stiffness of rubber dampers on the vertical and lateral smoothness of the platform were studied. It is found that the increase of the radial stiffness of the resilient wheels will deteriorate the vertical smoothness and lateral smoothness of the platform.
Technical Paper

Interior Noise Contribution Analysis and BEV Sound Package Development

2019-06-05
2019-01-1505
Due to the energy crisis and environmental pollution, many countries have released policies to promote the development and sales of new energy vehicles. New energy vehicles have become the focus of attention of various OEMs and component manufacturers. Sound package components have a great influence on the acoustic performance in the vehicle. Compared with traditional fuel vehicles, new energy vehicles have differences in body structure, parts layout, and noise sources. Furthermore, the sources of the noise inside the vehicle and the control measures will also change, so the sound packages should also be adjusted accordingly. In this paper, different types of vehicle SEA models were established based on real vehicles to analyze the interior acoustic performance. The contribution analysis method was used to compare the contribution differences of the sound package subsystems between the traditional fuel vehicle and the new energy vehicle.
Technical Paper

Application of Model Order Reduction to nonlinear Finite Element tire models for NVH design

2019-06-05
2019-01-1507
In order to meet customer NVH performance requirements, tire manufacturers continuously strive to improve their tire designs. Building and testing new designs has been the standard procedure for many years now. However, as the need to simultaneously optimize multiple performance criteria increases and development cycles become shorter, predictive numerical simulation techniques could be used rather than time consuming physical experiments. Especially since many tire performance areas are coupled, the experimental approach often lacks detailed insights which numerical simulations can provide. Currently, no industrially applicable fully predictive high fidelity numerical approach that incorporates the use of nonlinear Finite Element (FE) tire models for NVH design is available in literature. Therefore, a fully predictive numerical simulation approach that predicts the rolling of a tire over a coarse road surface is described in this work.
Technical Paper

Vibro-acoustic transfer function measurement in vehicles using dodecahedral sound source and its application for material assessment

2019-06-05
2019-01-1532
NVH is an important aspect of vehicle design since it is one of the highest priorities and biggest influencing factors for customer while making decision to buy a vehicle. Hence, automotive engineers strive to design the superior cabin compartment to maintain pleasant levels of noise, vibration and the overall experience within the vehicle. To quantify the amount of energy transmitted between source and receiver region, transfer function analysis is primarily used. The focus of this paper is to measure vibro-acoustic transfer function using reciprocity approach instead of direct impact test measurement. It is found that the vibro-acoustic reciprocity holds true even for non-linear system like vehicle. The reciprocal measurement involves usage of dodecahedral sound source to acoustically excite the cabin from desired seating location and accelerometers are placed at all the locations of interest on vehicle body.
Technical Paper

A Comparison of Near-Field Acoustical Holography Methods Applied to Noise Source Identification

2019-06-05
2019-01-1533
Near-field Acoustical Holography (NAH) is an inverse process, in which sound pressure measurements made in the near-field of an unknow sound source can be used to reconstruct the sound field so that source locations to be clearly identified. NAH was originally based on performing spatial transforms of arrays of measured pressures and then processing the data in the wavenumber domain, a procedure that entailed the use of very large microphone arrays to avoid spatial truncation effects. Over the last twenty years, a number of different NAH methods have been proposed that can reduce or avoid spatial truncation issues: for example, Statistically Optimized Near-field Acoustical Holography (SONAH), various Equivalent Source Methods (ESM), etc.
Technical Paper

Optimal Pressure Relief Groove Geometry for Improved NVH Performance of Variable Displacement Oil Pumps

2019-06-05
2019-01-1548
Variable Displacement Oil Pump (VDOP) is becoming the design of choice for engine friction reduction and fuel economy improvement. Unfortunately, this pump creates excessive pressure ripples, at the outlet port during oil pump shaft rotation, causing oscillating forces within the lubrication system and leading to the generation of objectionable tonal noises and vibrations. In order to minimize the level of noise, different vanes spacing and porting geometries are used. This paper presents an optimization method to identify the best geometry of the oil pressure relief groove. The method integrates adaptive meshing, 3D CFD simulation, Matlab routine and Genetic Algorithm based optimization. The genetic algorithm is used to create the required design space in order to perform a multi-objective optimization using a large number of parameterized groove geometries. Results of this optimization method are discussed and a design guideline for the oil pressure relief groove is disclosed.
Technical Paper

Driveline NVH integration of A NA truck program

2019-06-05
2019-01-1559
In current automotive industry, it is well known that the driveline subsystem and components are normally from different automotive suppliers for OEMs. In order to ensure proper system integration and successful development of driveline system NVH performances, collaboration efforts between OEMs and suppliers are very demanding and important. In this paper, a process is presented to achieve successfulness in developing and optimizing vehicle integration through effective teamwork between a driveline supplier and a major OEM. The development process includes multiple critical steps. They include target development and roll down, targets being specific and measurable, comprehension of interactions of driveline and vehicle dynamics, accurate definition of sensitivity, proper deployment of modal mapping strategy, which requires open data sharing; and system dynamics and optimization.
Technical Paper

Equivalent material properties of Multi-layer, light weight, high performance damping material and its performance in applications

2019-06-05
2019-01-1573
In this study, we investigated two aspects of a multi-layer, lightweight damping treatment. The first aspect studied was an equivalent material property estimate for a simplified finite element (FE) model. The simplified model is needed for computational efficiency, i.e. so that Tier 1 and OEM users can represent this complex, multi-layer treatment as a single, isotropic solid layer plus an aluminum constraining layer. Therefore, the use of this simplified FE model allows the multilayer treatment to be included in large body-in-white structural models. The equivalent material property was identified by first representing three unique layers (two adhesive layers plus a connecting standoff layer) by a single row of isotropic solid elements, then using an optimization tool to determine the “best fit” for these properties, Young’s modulus and material loss factor.
Technical Paper

Material Characterization of Multi-Layered Noise Control Treatments from Random-Incidence Sound Transmission

2019-06-05
2019-01-1575
Sound propagation through noise control treatment is governed by fluid, mechanical and geometric properties of the materials. The knowledge of material properties is important to improve the acoustical performance of the resulting noise control products. A method based on optimization together with genetic algorithm is used to estimate material properties of multi-layered treatments. Unlike previous inverse characterization approaches based on normal incidence performance metrics measured using standing wave impedance tubes, the current approach is based on random incidence performance metrics. Specially, the insertion loss ‘measured’ from two room transmission loss suite is utilized. To validate the applicability of the proposed method, numerically synthesized insertion loss computed from known material properties are used. In order to properly represent the ‘measured’ values, noise is added to the numerically synthesized insertion loss values.
Technical Paper

CAE Methods for Predicting Radiated Noise From Large Diameter Single-Piece Aluminum Propeller Shafts With Liner Treatments

2019-06-05
2019-01-1560
In recent truck applications, single-piece large-diameter propshafts, in lieu of two-piece propshafts, have become more prevalent to reduce cost and mass. These large-diameter props, however, amplify driveline radiated noise. The challenge presented is to optimize prop shaft modal tuning to achieve acceptable radiated noise levels. This paper will cover the development of a two-step CAE method to predict modal characteristics and airborne noise sensitivities of large-diameter single piece aluminum propshafts fitted with different liner treatments. The first step is the use of a traditional CAE software to calculate prop surface response. The second step is a boundary element simulation to calculate prop surface radiating noise under the excitation obtained from the first step. Finally, test data, acceleration and acoustic, in both subsystem and vehicle levels are presented to assess the accuracy of the CAE method.
Technical Paper

Gear system parameters and its influence on gearbox noise

2019-06-05
2019-01-1562
Gear tonal noise is one of the fundamental problem in a gearbox. Gear tooth deflection generates dynamic forces that lead to unwanted load fluctuations, thus noise. Various factors that are considered to control this noise include proper gear macro design, stiffening the structure, microgeometry corrections etc. however understanding various parameters influencing the gear whine, some to mention like different harmonic components of TE, temperature effects, components of forces also will lead to more accurate remedial solutions. The study in this paper discusses about the influence of such parameters that are associated with gear whine and will give a guideline for the designer for the optimized design. The analysis will be performed on a simple external helical gear mesh model in LDP tool for generating loads and TE. The radiated noise also will be monitored to study the influence of aforementioned parameters.
Technical Paper

Dynamic optimization of driving axle hypoid gears based on tooth contact characteristics control

2019-06-05
2019-01-1563
Hypoid gear is widely applied on automotive axle to transmit movement and power between crossed axle, and its meshing transmission has a significant influence on driving system noise of complete vehicle. Therefore, the drive noise of main hypoid gear pair at drive axle should be strictly controlled to reduce the complete vehicle noise. Meshing internal excitation of hypoid gear is a main source of vibration noise, closely connected with geometrical shape and meshing status. There is no comprehensive analysis on the impact of various contact patterns on vibration noise in previous studies. Therefore, the accurate control method of contact characteristics of hypoid gears is studied in this paper.
Technical Paper

An acoustic target setting and cascading method for vehicle trim part design

2019-06-05
2019-01-1581
The first concern in the vehicle trim part design may be its acoustic targets, which are generally defined by absorption area or coefficients, transmission loss (STL) or insertion loss (SIL). The acoustic target break down or cascading in vehicle design is referred to as the process to decide the trim part acoustic targets so as to guaranty the whole vehicle acoustic performance. In many cases, these targets are decided by experience or even subjective evaluation. Simulation based transfer path analysis (TPA), which trace the energy flow from source, through a set of paths, to a given receiver, provides another solution of this problem. Inspired by TPA, this paper proposes a component level target setting method based on the statistical energy analysis (SEA), which is recognized as an efficient method for vehicle NVH analysis in mid and high frequencies.
Technical Paper

Acoustic Effects of Lightweighting in a Sport Utility Vehicle

2019-06-05
2019-01-1506
Recently a vehicle study was performed to determine if the current production sound package in a sport utility vehicle could be improved while reducing or maintaining the weight. The study focused on sound package parts which typically utilize a heavy barrier layer to provide sound transmission loss: carpet, rear wheelhouse inner and trunk insulation, and dash inner. In addition, the heavy-weight underbody shields were replaced with lightweight compressed fiber to allow for increased coverage and to evaluate the effect on additional possible engine noise paths. Testing was performed both at the component level in the laboratory and at the vehicle level on the road. This paper presents the results of that study. It was found that the sound levels were improved slightly with the lower-weight parts, while articulation index was greatly improved. This was due to a combination of two factors.
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