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08.01 Vehicle Noise & Vibration, Part 1

Turbulent model validations with CFD/wind tunnel test and application to statistical energy analysis for wind noise prediction
Time: 7:40 pm


Abstract ID: 1330

Wind noise is becoming to have a higher priority in automotive industry. Several past studies investigated whether SEA can be utilized to predict wind noise by applying a turbulent spectrum model as the input. However, there are many kinds of turbulent models developed and the appropriate model for input to SEA is still unclear. Due to this, this paper focuses on clarifying an appropriate turbulent model for SEA simulation. First, the input turbulent pressure spectrum from five models are validated with wind tunnel tests and CFD. Next, a conventional numerical approach is used to validate models from the aspect of response accuracy. Finally, turbulent models are applied to an SEA model developed for a wind tunnel, and the SEA response is validated with test data. From those input/response validations, an appropriate turbulent model is investigated.

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Method for Localisation of Sound Sources and Aggregation to an Acoustic Center
Time: 7:20 am

Author: Yannik Weber

Abstract ID: 1689

Preliminary work by the IPEK - Institute of Product Engineering at KIT has shown that the simulated pass-by measurement for exterior noise homologation of vehicles has relevant optimization potential: the measurement can be carried out in smaller halls and with a smaller measurement setup than required by the norm and thus with less construction cost and effort. A prerequisite for this however is the scaling of the entire setup. For the scaling in turn, the sound sources of the vehicle must be combined to a single point sound source - the acoustic centre. Previous approaches for conventional drives assume a static centre in the front part of the vehicle. For complex drive topologies, e.g. hybrid drives, and unsteady driving conditions, however, this assumption is not valid anymore. Therefore, with the help of an acoustic camera, a method for localizing the dominant sound sources of the vehicle and a software-based application for summarizing them to an acoustic centre were developed. The method is able to take into account stationary, unsteady and sudden events in the calculation of the acoustic centre, which is moved as a result. Using substitute sound sources and two vehicles, the method and the used measurement technology were examined and verified for their applicability.

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NEMO project: acoustic detection of vehicle engine speed
Time: 6:00 am

Author: Truls Berge

Abstract ID: 1718

As part of the EU Horizon2020 project NEMO, SINTEF has developed an algorithm to detect the engine speed of passing vehicles. Some road vehicles can emit abnormal high noise levels or high levels of exhaust gases in urban conditions. The high noise level can be related to aggressive driving (high acceleration and high engine speed), to a modified or malfunctioning exhaust system, or to other vehicle defects. It is well-known that many motorcycles or mopeds often are equipped with non-original exhaust mufflers, giving high noise levels that can be a nuisance to the community. In the NEMO project, the detecting of so-called high emitters (HE) is essential to reduce the impact of such vehicles on the environment and public health. To enable to categorize HE vehicle based on the driving behaviour, it is necessary to detect both acceleration and corresponding engine speed. The paper describes the principle of the algorithm developed and results from testing on vehicles, including a motorcycle. This test shows that it is feasible to estimate the engine speed, also when the vehicle is accelerating, if the number of cylinders is available for the estimation. Further testing of the algorithm is planned within the NEMO project.

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Impact of a tunnel on the TL of a vehicle floor in bare and trimmed conditions and investigation on the most suitable simplified geometry able to better represent such impact
Time: 7:00 am

Author: Federico Di Marco

Abstract ID: 2109

NVH engineers are faced with the challenge of designing trim parts for vehicle interior and exterior, like inner dash insulators, carpets, underbody shields or engine encapsulations, which can be made with very different Bills of Materials (BOMs) including among others foams, felts or heavier layers. The measurables commonly used to rank various solutions are Transmission Loss (TL) and absorption. Depending on the numerical analysis method, different approaches may be considered for the evaluation of the TL of an automotive component. In particular, in Statistical Energy Analysis (SEA), automotive components are modeled as an assembly of panels having a simple shape, e.g. flat panels and/or panels with single or double curvature. Furthermore, in SEA the trim is normally modeled by means of the Transfer Matrix Method (TMM), which is essentially a 2-dimensional methodology. This paper intends to analyze in some depth the level of approximation that these practices bring with themselves, specifically in relation to the modelling of an automotive floor. More in detail, the aim of the paper is first to investigate what impact has the presence of the tunnel on the TL of a vehicle floor in bare and trimmed conditions and then to evaluate if the presence of the tunnel can be better modeled by using a semi-cylinder or three flat plates welded together in a trapezoidal shape, both shapes considered as a reasonable simplification of the actual geometry of a typical tunnel. The analysis is carried out at simulation level using FE.  To investigate both air bone noise and structure borne noise transmission, two types of excitations are used: a diffuse acoustic pressure field applied to the entire floor surface and an imposed displacement applied to the edge of the floor surface. Furthermore, 3 different kind of trims are taken into consideration in order to analyze if and how the tunnel modeling strategy may influence the evaluation of the trim effectiveness.

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Experimental study on cushioning behaviors of foam with different skin-liked covers
Time: 6:40 am

Author: heye xiao

Abstract ID: 2477

Periodic structures were used in foams to improve their cushioning ability in previous studies?which are usually constructed by additive manufacturing methods with high cost. To improve cushioning property of the foam materials at a low cost, foams with skin covers are proposed in this paper to provide a new idea for a structural design that is inspired by the composition of animal skins. The foam without covers and covered with three different skin types, including square shape, circle shape, and Pearlfish skin, are investigated in this study. The stiffness and acceleration responses of these structures are measured by static loading and dropping test respectively, which are used to evaluate their static and dynamic cushion properties. Based on the tested results, it demonstrated that the cover skins could improve the stiffness of the foam materials and decrease acceleration response of mass fixing on them in dropping test at 0.4 m and 0.5 m. The enhancement for cushion ability of the proposed structure in this paper is proved experimentally.

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Modeling and analysis for dynamic behavior of elevator traction system under the braking of safety gear
Time: 6:20 am

Author: Xiaolong Ma

Abstract ID: 2505

In the emergency case when the elevator car is over speeding in the downward direction, the traction car will be stopped rapidly by the braking of safety gear. However, the counterweight and the traction sheave are still moving, which maybe induces the collision between the counterweight and the traction sheave, the slip and off-track between the traction sheave and the rope. Therefore, a two sides mass-spring-damping rope model was proposed in this paper to investigate the dynamic behavior of elevator traction system under the braking of safety gear. In this model, the interaction between the car and the counterweight on both sides of the traction sheave was introduced. Meanwhile, the slip behavior and various constraints between the rope and traction sheave were respected in this model. Especially, the rope slack and the rope length change were considered to approach the mechanical properties of real rope. Furthermore, a numerical scheme based on Newmark- method was applied to solve the proposed dynamic model. Then the impacts of the braking force on the dynamic behavior of elevator traction system under different working conditions were deeply studied. Results showed the braking force of the safety gear, the speed and the acceleration of the traction sheave had great influences on the bounce of the counterweight. In fact, the braking performance, the vibrations of the car, rope and counterweight could be well analyzed based on this model, which is key for the realization of the steady and safe braking of traction elevator.

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