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Statistical Energy Analysis (SEA) is widely used for modeling the vibro-acoustic response of large and complex structures. SEA makes simulations practical thanks to its intrinsic statistical approach and the lower computational cost compared to FE-based techniques. However, SEA still requires underlying models for subsystems and junctions to compute the SEA coefficients which appear in the power balance equations of the coupled system. Classically, such models are based on simplified descriptions of the structures to allow analytical or semi-analytical developments. To overcome this limitation, the authors have proposed a general approach to SEA which only requires the knowledge of impedances of the structures to compute SEA coefficients. Such impedances can always be computed from an accurate FE model of each component of a coupled system.

The tooth surface error will affect the contact pattern and transmission error of the hypoid gear, which may result in an unfavorable dynamic response. The tooth surface error can be generated by machine tool errors, such as blade wear. The most common forms of blade wear are the positive cutter radius and the positive blade angle error. In addition, in the cutting process of face-hobbed hypoid gear, the continuous indexing motion will aggravate the blade wear due to the alternating cutting force. Most previous studies on the influence of hypoid gear tool errors only focus on the contact pattern and static transmission error. However, there are very few studies about the effect of tool errors on hypoid gear dynamic responses. In this paper, a hypoid gear tooth surface, mesh, and linear dynamic model with tool errors were established.

Pass-by noise measurement is mandatory for automotive manufacturers for conformity of production. With evolving of pass-by noise requirements (under 68 dB in 2024), all the stakeholders should be able to comply with this criterion. OEMs, suppliers of passive acoustic treatments, road manufacturers and tire manufacturers are concerned and should deploy efforts to provide solutions for control of exterior noise. In this regard, simulations are preferable over measurement campaigns as they can provide fast feedback on passive exterior treatments for exterior noise control. In the particular case of Lightyear vehicles, the main contributors to pass-by noise are tyres and in-wheel motors. Considering that, a contribution of each of these two sources of noise to pass-by noise will be described. Tyre sources and motor sources will be replaced by simple monopole sources. The results of this simulation will be compared to the pass-by noise measurements.

Layered materials are one of the most commonly used acoustical treatments in the automotive industry, and have gained increased attention, especially owing to the popularity of electric vehicles. Here, a method to model and couple layered systems with various layer types (i.e., poro-elastic layers, solid-elastic layers, stiff panels, and fluid layers) is derived that makes it possible to stably predict their acoustical properties. In contrast with most existing methods, in which an equation system is constructed for the whole structure, the present method involves only the topmost layer and corresponding boundary conditions at two interfaces at a time, which are further simplified into an equivalent interface with a new group of boundary conditions. As a result, for a multi-layered system, the proposed method splits a complicated system into several smaller systems and so becomes computationally less expensive.

It is well known today that Biot parameters are the intrinsic material properties of porous media such as foams and fibers. They are to porous media what Young’s modulus is to steel panels. Once these Biot parameters are accurately known, one can trust that a predictive simulation model will yield the corresponding level of accuracy. But how accurate must these Biot parameters be to warrant a safe level of accuracy of the resulting simulation models. This paper analyzes various round-robin tests publications related to measurements of Biot parameters (acoustic and elastic) and uses the reproducibility of measured data from the numerous laboratories involved to evaluate the effect of the observed measured variability on simulation models accuracy when predicting transmission loss, surface absorption and actual SPL response inside a vehicle.

Simulation and testing are often done by different engineers in different departments of a company. This can lead to disconnects and unrealistic predictions, especially if the person doing simulations does not have an experimental background. On the other hand, experimental results can also include errors that result in misleading answers. It is important for the engineer doing either testing or simulation to have a feel for what results are plausible and what results might be suspect. This paper will provide examples where error crept into testing or simulation that could have been caught and corrected early if a good feel for “reasonable” results had been in place. The paper will also make the case for simulation engineers to be provided with some experimental background, so that they have a better physical understanding of the structures or components being simulated. The ideal case is where the same person is responsible for both simulation and experimental validation.

The technology of active sound generation (ASG) for automobiles is one of the most effective methods to flexibly achieve the sound design that meets the expectations of different user groups, and the active sound synthesis algorithms are crucial for the implementation of ASG. In this paper, the Kaiser window function-based the harmonic synthesis algorithm of automobile sound is proposed to achieve the extraction of the order sounds of target automobile. And, the suitable fitting functions are utilized to construct the mathematical model between the engine speed information and the amplitude of the different order sound. Then, a random phase correction algorithm is proposed to ensure the coherence of the synthesized sounds. Finally, the analysis of simulation results verifies that the established method of the extraction and synthesis of order sound can meet the requirements of target sound quality.

Traditionally vehicles are designed for wind noise under ideal steady wind conditions. But, passenger comfort is affected by high modulation of cabin noise while cruising in traffic, due to variations of instantaneous wind speed and direction from driving through large-scale turbulence. In consequence, designing a vehicle for best performance in a low-turbulence wind tunnel may lead to issues during on-road conditions. To better predict the interior noise corresponding to on-road turbulence, a simulation approach is proposed combining an upstream turbulence flow simulation with an SEA vehicle model. This work is an extension of existing well validated procedures for steady wind conditions. Time-segmented transient loads on panels and steady-state structural acoustics transfer functions are combined, producing interior noise results for a series of overlapping time segments.

With a view to promote mobility electrification, improved comfort and handling with lower cost are crucial factors in next generation of EV and HEV design. In contrast to ICE platform, electrified counterparts displays distinct NVH characteristics that present challenges in terms of weight transfer, steering, motor vibrations, etc. From a holistic perspective, this paper proposes a semi active suspension system serving dual purpose of dynamic damping and power rejuvenation utilizing electric motor as part of the tuned mass damper inertia system. A variable inertance mechanism is developed in form of geartrain while motor vibration itself receives calculated harness through tuned mass damping. Furthermore, suspension deformation undergoes desirable mitigation as a result of effective simulated annealing optimization focused on shifting objective value according to input tradeoff prediction.

In our modern world, data is the most valuable resource, and companies are seeking to gather and analyze data as much as possible. This has spread to the NVH industry, and as we create new tools and hardware to collect dynamic systems data, we need a robust and viable method to analyze never previously seen data that may behave in ways that are not outlined with current equations or models. Data such as vibration at a certain area of a vehicle or stresses on a novel suspension system are examples of situations where proper data collection can be had but approaching the mathematical analysis with traditional mathematical knowledge may not fully reveal the physics behind the dynamics of the system. Thus, it’s very desirable to have a tool to extract mathematical equations that represent the dynamics of the system from data and use it to gain a better understanding of the system.

Pulse Width Modulation or PWM has been widely used in traction motor control for electric propulsion systems. The associated switching noise has become one of the major NVH concerns of electric vehicles (EV). This paper presents a multi-disciplinary study to analyze and validate current ripple induced switching noise for EV applications. First, the root cause of switching noise is identified as high frequency ripple components superimposed on the sinusoidal three-phase current waveforms, due to PWM switching. Measured phase currents correlate well with predicted current data using a semi-analytical hardware-in-the-loop (HIL) method. Next, the realistic ripple currents are utilized to predict the electro-magnetic dynamic forces at both the motor pole pass orders and the switching frequency plus its harmonics. Special care is taken to ensure sufficient time step resolution to capture the ripple forces at varying motor speed.

Current and future EV’s contain significant amounts of complex electrical hardware, including rechargeable energy modules, control units, cooling systems and wiring situated inside the cabin usually below the carpet , seats or trunk trim and below the cabin floor. These items, whilst likely to have a direct impact on transmission loss, are increasingly difficult to evaluate via typical methods of computer based simulation. The packaging space allocated for control units which may require an air gap between the Body in white and the carpet for aspects of heat stabilization can be problematic. These gaps introduce complex noise transmission within the carpet which tend to exclude simulation using transfer matrix method (TMM) NVH lay-up models. Also in the case of battery installations their high bulk mass doesn’t necessarily transpire to a large expected increase in the floor systems transmission loss. The accurate prediction of these systems requires advanced modeling techniques.

Abstract: This paper describes the characteristics and advantages of a coaxial eBeam axle, and in particular, its NVH performance under various noise excitations including eMotor and the gearing system. The NVH CAE model of the eBeam axle is established, and structural vibration and noise radiation of the motor and gearbox are simulated and analysed. The results are used in the design optimization for NVH performance refinement. NVH validation test data is presented and compared with NVH simulation results, showing excellent correlation. Test data shows that the eBeam axle vibration and noise levels are well below the stringent targets.

As automotive industry experiences a significant change in terms of the dynamic behavior of vehicles and an increasing demand for rapid design of products, accurate prediction of product performances in the early stages has become even more vital in the competitive environment. Shim-stack-type hydraulic dampers are widely used in automotive parts for both internal combustion engine (ICE) vehicles and electric vehicles (EV), and EVs are even more sensitive to the damper performance as ICE, a major NVH source is removed. However, the industry still struggles to obtain accurate models of the dampers due to their highly nonlinear hydro-mechanical behaviors. Bleed slits for a shim-stack-type hydraulic damper play a key role in determining the blow-off characteristics of a damper, and, consequently, accurate prediction of the blow-off characteristics is crucial in evaluating the damping performance of a vehicle.

Abstract: As an important vibration damping element in automobile industries, the rubber mount can effectively reduce the vibration transmitted from the engine to the frame. The influence of preload on the static characteristics of rubber mounts and the identification of hyper-elastic material model coefficients were studied. Firstly, a test rig for stiffness test of a mount with preload was designed, and the influence of preload on the static force versus displacement of mounts was studied. Then, the model for estimating force versus displacement of rubber mounts was established, the response surface model for identifying coefficients was established, and the identification method for estimating constitute parameter of rubber materials was proposed the crow search algorithm.

Abstract: As an important vibration damping element in automobile industries, the rubber mount can effectively reduce the vibration transmitted from the engine to the frame. In this study, a method of parameters identification of Mooney-Rivlin model by using surrogate model was proposed to more accurately describe the mechanical behavior of suspension. Firstly, taking the rubber mount as the research object, the stiffness measurement was carried out. And then the calculation model of the rubber mount was established with Mooney-Rivlin model. Latin hypercube sampling was used to obtain the force and displacement calculation data in different directions. Then, the parameters of the Mooney-Rivlin model were taken as the design variables. And the error of the measured force-displacement curve and the calculated force-displacement curve was taken as the system response. Two surrogate models, the response surface model and the back-propagation neural network, were established.

Tortuosity, viscous characteristic length and thermal characteristic length are three important parameters for estimating sound insulation and absorption parameters of porous materials, and it is usually measured by ultrasonic measurement technology, which is cost. In this paper, a method for identifying the tortuosity, viscous characteristic length and thermal characteristic length for the mixed porous fiber materials of kapok fiber with low melting fiber and polyester staple fiber is proposed. The tortuosity is calculated by using the porosity and high-frequency sound absorption coefficient of porous materials. Using JCAL (Johnson-Champoux-Allard-Lafarge) model and genetic algorithm, viscous characteristic length and thermal characteristic length are identified by using the measured parameters, the calculated tortuosity and the measured sound absorption coefficient of porous materials under normal incidence.

Most of the Automotive companies are using Simulation tools for predicting road noise in digital phase as a regular practice. But we can predict Road noise at early design stage itself by this hybrid tool in very quick time. In-cab booming noise is low frequency (20 Hz∼300 Hz) phenomenon excites the cabin structure, which occurs mainly due to excitations from the powertrain, exhaust system, road input, etc. When a vehicle drives over road seams or a bumpy surface, low-frequency noise called drumming is generated, causing driver discomfort. The generation of drumming noise is due to road irregularities, transferred and amplified through the vibration characteristics of the suspension, body frame, and body panels, as well as the acoustic characteristics of the vehicle interior. It is therefore difficult to take measures to get rid of drumming after the basic vehicle construction has been finalized.

Disc brake squeal is always a challenging multidisciplinary problem of vehicle noise, vibration, and harshness (NVH), which has been historically studied by many researchers. Theoretical analysis was carried on to study the disc brake squeal mechanism due to a small disturbance. Most methodologies were focused on linear modal approaches for harmonic vibration phenomena of large-scale models. But the time-domain approaches are very minimum due to being restricted to certain friction models or achievable vibration patterns and suffer from high computational costs which limits an extensive application as well. Herein, the time-domain approach is the effort of this research to explore the feasible modeling procedure how to correlate the squeal testing better.

For liquid fueled engine, the fuel atomization affects fuel’s evaporation, combustion, noise and vibration characteristics eventually. In this study, the effects of fuel species on the internal flow and near field primary breakup characteristics of a nozzle "Spray C" are investigated. Based on the framework of OpenFOAM, the newly developed solver which coupled cavitation model and the multifluid-quasi-VOF (Volume-of-Fluid) model, and combines the LES (large eddy simulation) are applied to simulate the nozzle inner flow and near field jet breakup when using diesel and biodiesel respectively. The transient characteristics of nozzle inner flow and near field spray of two different fuels were analyzed, and the variation of axial pressure and velocity of nozzle was obtained. The simulation results show that the cavitation of biodiesel with high viscosity and low saturated vapor pressure develops slower and weaker.