Squeak and rattle concerns account for approximately 10% of overall vehicle Things Gone Wrong (TGW) and are a major quality concern for automotive OEM’s. Door abnormal noises is one of the top 10 IQS concerns under any OEM nameplate. Door trim is one of the parts in closure assembly that significantly contributes to overall BSR quality perception. Door trim is mounted on door in white using small plastic clips and variability in clip properties can cause the overall variability in BSR performance. Here an attempt in made to evaluate the squeak and rattle performance of various door clips through objective parameters like interface dynamic stiffness and system damping. The methodology talks about using a simple dynamic system and evaluate stand-alone performance of clip. Transmissibility is calculated from the dynamic response of a mass supported by clip, later interface stiffness and damping are evaluated for different clips.
Authors : Guillaume BAUDET, Cécile DUTRION, Rémi LORENZI, Félix GENDRE, Shanshan GENG Renault Automotive wind noise is a complex phenomenon. Noise in the cabin depends of: - The exterior loading due to the flow around the vehicle - The transfer loss of seals and panels - The acoustic transfer function of the cabin Each part of this cascading must optimized to have a good final performance. So the exterior design is a key parameter because it influence the loading (pressure field) on the vehicle panels and seals. For some years, we know that the exterior loading is split in two parts: - Hydrodynamic (or turbulent) loading with high wave number pressure field - Acoustic loading with low wave number pressure field In this paper, we present a calculation process which enables to predict the acoustic source created by the lateral window at high speed which has a major contribution to the interior noise.
The magnitude of the turbulent pressure spectrum in fluid flow over an obstruction is usually much larger than in attached flow over a smooth surface. External features on a vehicle, such as windshield wipers, side mirrors and pillars which cause flow separation, are a major source of wind noise. The modeling of the pressure spectrum in separated flow is important for designing quiet vehicles. In this study wind tunnel tests have been performed with different shaped obstructions to measure and correlate the surface pressure spectra with flow parameters such as the pressure coefficient and separation size. The model by Chase for attached turbulent boundary layer pressures is generalized to apply to separated flow conditions.
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.
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.
Door latch closure sound has contribution on sound quality of vehicle door slam sound. This paper focuses on the modelling of subjective sound quality for door latch closure sound. 24 various latch closure sound samples were recorded by binaural artificial head in semi-anechoic room. To acquire subjective preference of the sounds, these samples were then evaluated subjectively by a novel dynamic paired comparison method which can reduce the evaluation work load and add new samples easily comparing to the traditional paired comparison method. During the subjective evaluation, the shudder effect induced by multi-impact of latch components during closing movement was found strongly affecting the subjective perception of door latch closure sound. By using wavelet analysis the mechanism of shudder effect was identified.
In recent work, it has been shown that conventional sound absorbing materials (e.g., lightweight fibrous media) can also provide structural damping when placed adjacent to vibrating structures, including infinite panels, partially-constrained panels and periodically-supported panels typical of aircraft structures. Thus, a fibrous layer may serve two functions at once: absorption of airborne sound and the reduction of structure-borne vibration. It has previously been found that the damping is primarily effective below the critical frequency of the structure, and that it results from viscous interaction between the fibrous layer and the panel’s evanescent near-field which causes there to be oscillatory, incompressible fluid motion parallel with the panel’s surface.
An important factor contributing to a customer’s subjective perception of a vehicle, particularly at the point-of-purchase, is the sound created by the passenger doors during closure events. Although these sounds are very short in duration the key systems that control the sounds produced can be highly coupled. Similarly, the necessary efforts required to understand key design criteria affecting the sound can also be highly complex. Within this paper sub-systems affecting the door closure sound are evaluated to understand key structural properties and behaviors toward the contribution to the overall sound produced. This begins with the subjective preferences of typical sounds and the difficulties with both measuring and reproducing these sounds appropriately and leads directly to the target setting and target cascading process.
Road induced noise is getting more and more significant in context of the electrification of the powertrain. The automotive industry is seeking for technologies to predict the contribution of vehicle components upfront, early in the development process. Classical Transfer Path Analysis (TPA) is a well-established technique that successfully identifies the transmission paths of noise and vibration from different excitation sources to the target responses, but has some drawbacks, such as that it requires the physical availability of the vehicle. To achieve shorter development cycles, avoid costly and time-consuming design iterations, and due to the limited availability of prototypes, engineers derived a method that addresses these requirements.
An automatic tensioner used in an engine front end accessory drive system (EFEADS) is taken as a study example in this paper. The output torque of the tensioner, which consists of the spring torque caused by a torsional spring, the damping torque caused by damping parts, and the frictional torques caused by a bushing and a rotational arm of tensioner, 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 output 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 parts is investigated based on the simulation and a durability test of the tensioner. A finite element method for the tensioner without damping part is established.
Method development for half shaft joint characterization to predict and evaluate its influence on low idle vibration in vehicle. Author: Prasad Vesikar, Saeed Siavoshani, Siemens PLM Yuan Wei, FCA LLC In conventional IC engine powered vehicles, engine low idle vibrations of vehicle between 20 to 50Hz range is very common NVH issue. Engine excitations pass through mounts and half shafts to body structure. Half shaft designs are observed to be major influencing factor in managing these low idle vehicle vibrations. Half shaft’s dynamic characteristics are mainly dependent upon the universal joints design in the shaft. To evaluate the half shaft designs for its influence on the low idle vibration in early phase of vehicle program, predictive model of shaft is required to be generated. The shafts at low idle engine running condition are at specific pre load and shafts needs to be characterized under that preload to use in the full vehicle predictive modeling.
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.