Transfer path analysis (TPA) has become a widely used diagnostic technique in the automotive and other sectors. In classic TPA, a two-stage measurement is conducted including operational and frequency response function (FRF) phases from which the contribution of various excitations to a target quantity, typically cabin sound pressure, are determined. Blocked force TPA (also called in situ Source Path Contribution Analysis, in-situ TPA and component TPA) is a development of the classic TPA approach and has been attracting considerable recent attention. Blocked force TPA is based on very similar two stage measurements to classic TPA but has two major advantages: there is no need to dismantle the vehicle and the blocked forces obtained are an independent property of the source component and are therefore transferrable to different assemblies. However, despite the now widespread reliance on classic TPA, and the increasing use of blocked force TPA in the automotive sector, it is rare to see any evaluation of the associated uncertainties. This paper therefore aims to summarize recent work and provide a guide to the evaluation…

Due to the increasing number of battery electric vehicles (BEVs), the engineering fields regarding driving comfort and NVH issues are becoming more and more challenging: many new factors affect the development of BEVs NVH package. The noise sources related to the powertrain are different from the traditional ones of internal combustion engines, for instance due to the presence of tonal components, strong harmonics and potential whining noise.To satisfy NVH specifications and the need for lightweight solutions to increase driving range, it is important to mask as much as possible the noise coming from the engine bay with materials both lightweight and acoustically performing. Moreover, for electric vehicles new interesting solutions are possible with the introduction of new components that do not find room under the hood of ICE or hybrid vehicles. These components, if properly designed, could lead to significant NVH benefits. The present paper reports the NVH effects of one of these new components, the frunk, a small compartment inside the engine bay, functionally similar to the trunk.In this paper, the design-by-simulation of a…

Middle and high frequency vibro-acoustic simulation of complex shape insulators requires using 3D poroelastic finite elements. This can be applied to either the whole part (up to 2500 Hz maximum) or through singly curved pre-computed Insertion Losses (up to 5000 Hz maximum) to be introduced in large SEA or energy-based models. Indeed, a dependence of the Insertion Loss slopes of noise treatments following the curvature is observed both experimentally and numerically. Beyond frequency range limitations, poroelastic finite element simulations following all curvatures and thickness 3D maps typically take too much time of up to a few hours each. A cylindrical Transfer Matrix Method spectral approach significantly reduces the time for the calculation of singly curved Insertion Losses up to 10 kHz to only a few minutes. This simplifies enormously the SEA modeling effort enabling easier, more precise fully trimmed vehicle middle and high frequency vibro-acoustic simulations. A dash insulator Insertion Loss numerical validation case will be presented comparing the different methods.

In any machinery, avoiding noise and vibration completely is a difficult task due to the structural dynamic behaviors of components. To safeguard the operator, it is important to best isolate the operator station from NVH environment. Cabin isolation is an important aspect to minimize structure borne noise and tactile vibrations to be transferred into the cabin. Isolators are selected based on the isolation system inertial properties at mounting locations in the operating frequency range interested. The most important assumption to select isolators are that the active side and passive side of the isolators are nearly rigid so impedance mismatch is created for effective isolation.This paper describes the importance of dynamic stiffness of the structures on both the active and passive side for better NVH performance. NVH performance of passive side is evaluated analytically and computationally in terms of tactile vibrations and structure borne noise for various ratios of the dynamic stiffness over isolator stiffness. The isolator selection criterion is also discussed based on rigid body modes, operating frequency range, transmissibility ratio, and kinematic energy distributions.

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 the simulation software. The effects of resilient wheels’ axial stiffness, radial stiffness and vertical stiffness, lateral stiffness of rubber dampers on the vertical and lateral stability of the platform were studied. It is found that the increase of the radial stiffness of the resilient wheels will deteriorate the vertical stability and lateral stability of the platform. The increase in the axial stiffness of the resilient wheels will deteriorate the vertical stability of the platform and the lateral stability will be improved. The increase…

An automatic tensioner used in an engine front end accessory drive system (EFEADS) is taken as a study example in this paper. The working torque of the tensioner, which consists of the spring torque caused by a torsional spring and the frictional torques caused by the contact pairs, is analyzed by a mathematic analysis method and a finite element method. And the calculation and simulation are validated by a torque measurement versus angular displacement of a tensioner arm. The working torques of the tensioner under a loading and an unloading process are described by a bilinear hysteretic model, and are written as a function with a damping ratio. The rule of the action for the damping devices is investigated based on the simulation and a durability test of the tensioner. A finite element method for the tensioner without damping device is established. Then the radial deformation for the torsional spring under an unconstrained state is obtained. The analysis results have a good correlation with the measurements. The method presented in this paper is beneficial for…

Today’s trend of combustion engine development for cars is characterized with; high torque, low engine speed, low weight, high degree of cyclic irregularity, low excitation frequency due to fewer cylinders active e.g. 4-cylinder or less.This implies in respect of vibrations that it is crucial to control powertrain rigid body modes and place these were they cannot be reached and induced by the low exciting harmonic frequencies for low engine speeds or idling. It is also important to control the overall flexible vibration modes.A mathematical CAE model is created in simulation software AVL-EXCITE in order to handle the vibration phenomenon as a first step. But it is absolutely necessary to “verify” these models with real measurements in respect of NVH and if needed upgrade the CAE model if there are detected deviations. The NVH-test is done with testing tool DEWESoft.The purpose of below paper is to do model verification on a concrete example in respect of powertrain vibrations. Volvo Cars in-line 4-cylinder VEA diesel engine in rig installation is the object for the paper of model…

This paper aims to study the NVH and acoustic performance of a 3-phase AC induction motor in order to develop an approach to reduce the magnetic component of noise from an electric motor in an electric vehicle (EV). The final goal of this project is to reduce the magnetic component of sound from the motor by making modifications to the end bracket of the motor housing.EVs are being considered the future of mobility mainly due to the fact that they are environment-friendly. As many companies are already investing in this technology, electric drives are set to become extremely popular in the years to come. The heart of an EV is its motor. Modern electric vehicles are quiet, furthermore with the lack of an IC engine to mask most sounds from other components, the sound from the electric motor and other auxiliary parts become more prominent. The primary source of electromagnetic noise in a motor arises from magnetic flux variations in the air gap which interfere with the resonant frequencies of the stator core. These flux…

Sound intensity measurement techniques that used a two-microphone configuration, were first developed in the late 1970s. Originally, the focus was on improving precision during testing or post-processing. However, with the advent of modern, sophisticated equipment, the focus has shifted to the apparatus. Availability of phase-matched microphones has made post-test correction obsolete as the microphones eliminate a majority of the errors before the data is even collected. This accuracy, however, comes at a cost, as phase-matched microphones are highly priced. This paper discusses employing the method of improving post-processing precision, using inexpensive, current equipment. The phase error of the system is corrected using a simple calibration technique and a handheld phase calibrator that is similar to the one used for amplitude calibration of microphones. The intensity probe and calibrator is manufactured using rapid prototyping and the executable software that goes with the probe is designed in NI LabVIEW. The entire setup uses inexpensive parts to lower the cost and modern software to compensate for the errors due to these parts. The design of the probe and…

This paper provides an overview of a custom software developed to obtain measurement data in a self-contained acoustic test facility system used for conducting random incidence sound absorption tests and sound transmission loss tests on small samples in accordance with SAE J2883 and J1400 standards, respectively. Special features have been incorporated in the software for the user to identify anomalies due to extraneous noise intrusion and thereby to obtain good data. The paper discusses the thoughts behind developing user-friendly algorithms and graphical user interfaces (GUI) for the sound generation, control, data acquisition, signal processing, and identifying anomalies.