Browse Topic: Body panels
This research analyzes the significance of air extractor on car door closing effort, especially within the context of highly sealed cabins. The goal is to measure their effectiveness in lowering pressure-induced resistance, study how the cut-out cross section and location affect performance, and its contribution to vehicle premium feel. Current vehicle design trends prioritize airtight cabin sealing for improving aerodynamic efficiency, NVH performance. This causes a problem in door closing operation. Air trapped while closing door creates transient pressure pulses. This pressure surge creates immediate discomfort to user i.e., Popping in Ears and requires high door closing force, and long-term durability problems in hinges and seals. In properly sealed cabins, air pressure resistance can contribute to 25% to 40% of total door closing force. Air extractors, usually installed in the rear quarter panels or behind rear bumpers, serve as pressure relief valves, allowing for a smoother airflow out of the cabin during such incidents. This passive system lowers door-closing effort, improves occupant experience, and safeguard structural components. A combination of CFD simulations, and real-world validations was employed to assess various air extractor configurations. Extractor size, location, flap design, and sealing levels of the vehicle were varied. Cabin pressure behavior and door closing force were evaluated under controlled and dynamic conditions. Comparative studies were also conducted across vehicle segments, including electric vehicles with high sealing requirements. Through these factors, this paper gives a holistic view to improve overall user experience as well as help to align with industry standards. The results have been backed with case studies as well as with simulation analysis to properly optimize the extractor design for new vehicles.
Customers are expecting higher level of refinement in electric vehicle. Since the background noise is less in electric vehicle in comparison with ICE, it is challenging for NVH engineers to address even minor noise concerns without cost and mass addition. Higher boom noise is perceived in the test vehicle when driven on the coarse road at a speed of 50 kmph. The test vehicle is rear wheel driven vehicle powered by electric motor. Multi reference Transfer Path Analysis (TPA) is conducted on the vehicle to identify the path through which maximum forces are entering the body. Based on the findings from TPA, solutions like reduction in the dynamic stiffness of the suspension bushes are optimized which resulted in reduction of noise. To reduce the noise further, Operational Deflection Shape (ODS) analysis is conducted on the entire vehicle to identify the deflection shapes of all the suspension components and all the body panels like floor, roof, tailgate, dash panel, quarter panel and doors at the problematic frequency. Based on ODS, the components having higher deflections at the problematic frequency is identified. Modifications are proposed to improve the dynamic stiffness of the structure at the problematic frequency and the contribution of each modification for cabin noise reduction is discussed. Solutions like tuned mass dampers (TMD) on suspension components are explored and the critical parameter which should be considered to get maximum reduction in noise with TMD is also discussed. With all the modifications, the noise levels are reduced by 5 dB (A) at problematic frequency. NVH criteria which should be considered related to suspension system to avoid boom noise concern in electric vehicle is also discussed.
In general, in-cabin booming noise is low frequency (20 Hz∼300 Hz) phenomenon which excites the cabin structure mainly due to excitations from the powertrain, exhaust system, road loads, etc. When a vehicle drives over road seams or a bumpy surface, low-frequency drumming noise 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. The regular practice in vehicle development is finite element method (FEM) to obtain acoustical transfer functions of the body, and multi body simulation to get suspension load characteristics. The full vehicle simulation needs more time for analysis and extracting data. So traditional computational aided engineering (CAE) will not support development timeline. Market has become very dynamic, benchmark changes very often, so getting complete data is difficult for very accurate analysis in ‘early to market’ project timeline. Most of the automotive companies are using computational tools for predicting road noise in simulation phase. But with the help of method, we developed can predict road noise at early design stage itself. It is a novel hybrid tool which can give strong directional results in comparatively lesser time. This user-friendly hybrid tool is developed for predicting and improving road noise at early stage with limited data, especially for new age battery electric vehicle. The inputs used during the initial stage of the program are vibration data of benchmark vehicle at body attachment points, targets, or simulation data (DPDS, NTF), etc. By the proposed methodology, overall trend of road noise can be predicted. In addition to that critical paths can be identified by using transfer path analysis. Once the project/program matures, we can use physically measured data (DPDS & NTF) of the trimmed body and perform the robust root cause analysis to identify the critical paths. Based upon the analysis, modifications to be made on actual body structure for effective drumming reduction. Hence new hybrid approach is proposed, which consists of mathematical model and design philosophy for better in cabin noise. It is worth to note that there are some limitations in the tool and results from the calculations such as granularity of benchmark test data availability, accurate trimmed body level test or simulation data.
The passenger car segment has been extremely competitive and automotive OEMs are thriving to provide superior customer experience. Door closing is an event that requires slamming of the door with a certain velocity to get the door latched. A good latching provides that thud sound and assurance of the door getting closed for an SUV. While the door is closed, it pushes the volume of air inside the cabin. As the amount of air moved in is proportionate to the size of the door it becomes more critical for the SUV segment of vehicles to ensure the air extraction path is efficient. Else, steep pressure rise inside the cabin causes severe discomfort to the passengers sitting inside the vehicle. Current work focused on the process of simulation of cabin pressure while door closing, implementing changes based on results and validating with test results. Test results are in close correlation with simulation predictions. Also, it emphasizes that body panel changes made to improve the airflow path are extremely necessary. The outcome has been excellent, rated by jury members, and the proposed changes have been realized for production.
Automotive door seal has an important function which is used extensively where interior of the vehicle is sealed from the environment. Problem with door seal system design will cause water leakage, wind noise, hard opening or closing of doors, gap and flushness issue which impair customer’s satisfaction of the vehicle. Moreover, improper design of seal can lead to difficulty in installation of door seal on body panel. The design prudence and manufacturing process are important aspect for the functionality and performance of sealing system. However, the door sealing system involves many design and manufacturing variables. At the early design stage, it is difficult to quantify the effect of each of the multiple design variables. As there are no physical prototypes during rubber profile beading-out stages, engineers need to carry out non-linear numerical simulations that involve complex phenomena as well as static and dynamic loads for door seal. This paper presents a digital simulation design tool based on FEM, basic governing laws and incompressibility constraints. Door seal was analyzed for compression load deflection (CLD) behavior using nonlinear finite element analysis in MSC Marc Mentat™. The analysis results provided some major parameters, such as seal deformation, contact pressure and contact length of seal, which would influence the functionality and performance of the door sealing system. The analysis results have been compared with available test data, and very good correlation was obtained. This analysis also evaluated the influence of manufacturing deviations. This analysis method developed into a tool that is capable of predicting water leakage, wind noise and hard to open/close problems caused by either product design or manufacturing process.
Laminated steel body panels are used in different applications in vehicles, such as dash panels and wheel wells. A part made out of laminated steel has the potential to provide structure-borne noise reduction and also improve the airborne noise reduction of the part compared to a monolithic part. The use of laminated steel has been more critical when there are deep draws on the part as the deep draws cause localized resonances which degrade the acoustic performance significantly. However, due to lightweighting demands, hybrid laminated panels, commonly known as acoustic patch laminates have become very attractive. This paper discusses the damping and sound transmission loss performances of a dash panel part with monolithic, laminated, and acoustic patch panels. The paper discusses the damping performance below 1000 Hz, including the data analysis process and the effectiveness of the acoustic patch laminates for both structure borne and airborne noise studies including coincidence dip issues. Finally, the paper discusses the potential of the acoustic patch laminates to address lightweighting demands and acoustic values that are driving the vehicle industry today.
Standards organizations develop standards depending on the need in the market place. With the change in vehicle design, lightweighting structures, and body panels made out of aluminum and composites, SAE’s Acoustical Materials Committee is developing a new damping standard. This standard is also very suitable in determining the damping performance of materials used in the off-highway applications, where the thickness of the steel body panel is much greater than in the automotive application. The general methodology of this standard is based on the mechanical impedance measurement method and has been developed with the general consensus of automotive engineers, suppliers, and independent test laboratories. This method is essentially based on the fact that a bar is excited at the center by a shaker. The force exerted by the shaker and the corresponding vibration is measured at that point to determine the frequency response function of the mechanical impedance signal. This paper discusses the need and challenges in developing this standard including differences between the proposed and other current damping standards. The paper also discusses the round robin data analysis that have been done so far to understand the consistency of the data for complete analysis.
Automotive Event Data Recorders (EDRs) are often utilized to determine or validate the severity of vehicle collisions. Several studies have been conducted to determine the accuracy of the longitudinal change in velocity (ΔV) reported by vehicle EDRs. However, little has been published regarding the measurement of EDRs that are capable of reporting lateral ΔVs in low-speed collisions. In this study, two 2007 Toyota Camrys with 04EDR ECU Generation modules (GEN2) were each subjected to several vehicle-to-vehicle lateral impacts. The impact angles ranged from approximately 45 to 135 degrees and the stationary target vehicles were impacted at the frontal, central, and rear aspects of both the driver and passenger sides. The impact locations on the bullet vehicles were the front and rear bumpers and the impact speeds ranged from approximately 7.9 to 16.1 km/h. Instrumentation was mounted at the approximate center of gravity (CG) of the target vehicles, as well as on the front reinforcement bar, rear body panel, airbag ECU, B-pillars, and C-pillars to evaluate the varying lateral ΔV (ΔVy) readings from the 3 sensor locations (ECU, B-pillar, C-pillar) represented in the Toyota EDR and to account for rotational (yaw) effects on the data. The lateral ΔVs reported by the Toyota EDRs were then compared to the recorded ΔVys from the reference instrumentation mounted within the test vehicles. A comparison of the data revealed a general under-reporting of impact severity from the Toyota EDRs at the ECU sensor when compared to reference instrumentation at the vehicle CG for impacts near the center of the target vehicle where the vehicle typically rotated about its frontal aspect. There was a general over-reporting of impact severity from the Toyota EDRs at the ECU sensor when compared to reference instrumentation at the vehicle CG for impacts near the front (heavy) axle of the target vehicle where the vehicle rotated about its rear aspect. Rotational data from the reference instrumentation and the distance between the ECU and reference instrumentation at the CG was also utilized to calculate the corresponding ΔVy at the ECU location for a direct comparison to the Toyota EDR measurement at the ECU (maximum of 12.0% difference). A comparison of the data recorded at the Toyota ECU sensors and the reference instrumentation mounted to the ECUs revealed accurate measurements by the Toyota ECU sensor (maximum of 7.6% difference). Differences in reported values between the 3 aforementioned Toyota sensor locations, as well as non-recordings and longitudinal ΔV recordings from the Toyota EDRs were also evaluated.
Vehicle cabin comfort emphasizes a specific image of a brand and its product quality. Low frequency powertrain induced noise and vibration levels are a major contributor affecting comfort inside passenger cabin. Thus, using hydraulic mount is a natural choice. Introduction of lighter body panels coupled with cost effective hydraulic mounts has resulted in some additional noises on rough road surfaces which are challenging to identify during design phase. This paper presents a novel approach to identify two such noises i.e. Cavitation noise and Mount membrane hitting noise based on component level testing which are validated at vehicle experimentally. These noises are encountered at 20~30kmph on undulated road surfaces. Sound quality aspect of such noises is also studied to evaluate the solution effectiveness.
Noise, vibration, and harshness (NVH) attribute is needed to be included in the vehicle structure design since improving the NVH characteristics enhances the ride quality experienced by the occupants. In this regard, an efficient method was proposed to investigate the structural dynamic response of an automotive body considering low-frequency NVH performances. Moreover, the improvement of an automotive structure under the constraint of NVH behavior was investigated by using the design of experiments (DOEs) method. The DOEs methodology was for screening of the design space and generating approximation models. Here, the thicknesses of panels consisting of a body-in-white (BIW) of an automotive were employed as design variables for optimization, whose objective was to increase the first torsional and bending natural frequencies. Central composite design (CCD) for DOEs sampling and response surface methodology (RSM) were employed to optimize the dynamic stiffness. Moreover, the effects of the selected variables as well as their binary interactions were modeled and the optimum conditions for rigidity improvement were obtained via the RSM. Furthermore, the validity of the proposed optimization scheme was verified through CAE analysis. The results indicated that the first torsion and bending natural frequency were improved compared to the baseline design. Additionally, precise surrogate models in polynomial terms for the first bending and torsion natural frequencies were obtained.
Understanding process induced fiber orientation distribution of composite body panels using nondestructive techniques is of prime interest. A compression molded sheet molding compound (SMC) panel is a good example of composite panels which are heavily affected by the molding process. Determination of the directionally dependent local coefficient of linear thermal expansion by digital image correlation yields information that is utilized to determine the local fiber misorientation and calculate the local SMC tensile modulus. In our current study, this methodology is utilized to determine the directional CLTE, permitting evaluation of the SMC properties in a multitude of directions not possible in destructive testing techniques. After obtaining the directionally dependent CLTE, a micromechanical approach is utilized to calculate the local SMC tensile modulus and glass fiber misorientation angle.
Two full-scale burn tests involving identical side-by-side all-terrain vehicles were conducted to evaluate fire spread, changes in temperature distributions over time, and how burn patterns correlated to the known point of origin of the fires. The fires were initiated by igniting body panels at opposite corners of the vehicles such that in one test the fire propagated downwind and, in the other, it propagated upwind. In both tests, drop-down from the body panels onto the tires resulted in ignition of the tires. This was an important feature of the mechanism of fire spread. Once the tires began to burn, a transition occurred and the rate of fire spread to the remaining portion of the vehicle increased. Although the time between fire initiation and this transition was significantly different in the two tests, the time to spread and to consume the remaining combustibles within each vehicle was relatively consistent, independent of wind direction. The variation of damage to painted surfaces, oxidation patterns on steel surfaces, and melt damage to aluminum components after the fire were similar in both vehicles but were not useful in determining the area of origin of the fire.
Upper frame deflection of automobile doors is a key design attribute that influences structural integrity and door seal performance as related to NVH. This is a critical customer quality perception attribute and is a key enabler to ensure wind noise performance is acceptable. This paper provides an overview of two simulation methodologies to predict door upper frame deflection. A simplified simulation approach using point loads is presented along with its limitations and is compared to a new method that uses CFD tools to estimate aerodynamic loads on body panels at various vehicle speeds and wind directions. The approach consisted of performing external aerodynamic CFD simulation and using the aerodynamic loads as inputs to a CAE simulation. The details of the methodology are presented along with results and correlation to experimental data from the wind tunnel.
The tendency for car engines to reduce the cylinder number and increase the specific torque at low rpm has led to significantly higher levels of low frequency pulsation from the exhaust tailpipe. This is a challenge for exhaust system design, and equally for body design and vehicle integration. The low frequency panel noise contributions were identified using pressure transmissibility and operational sound pressure on the exterior. For this the body was divided into patches. For all patches the pressure transmissibility across the body panels into the interior was measured as well as the sound field over the entire surface of the vehicle body. The panel contributions, the pressure distribution and transmissibility distribution information were combined with acoustic modal analysis in the cabin, providing a better understanding of the airborne transfer. Instead of operational outdoor tests, a tailpipe simulator and indoor measurements were used which allowed a clear verification of the accuracy of the contribution analysis. The study discusses reciprocity and the limitations of the panel discretization, and it showed that a reliable identification of the airborne panel contributions is possible.
New tools and technologies are helping engineers reduce vehicle Noise, Vibration and Harshness. The vehicle chief engineer did not like what he was hearing on this recent evaluation ride. He was reviewing a new transmission scheduled for production in his company's iconic sporty car. But the marriage of transmission and platform was generating unacceptably high cabin-noise levels. The CE wasn't pleased. His design and manufacturing engineers explained that the new gearbox featured a thin-wall aluminum case for reduced mass. However, the lightweight case was the noise transmitter.
Aluminum alloys are increasingly utilized in automotive body panels and crash components to reduce weight. Accurately assessing formability of the sheet metal can reduce design iteration and tooling tryouts to obtain the desired geometry in aluminum stampings. The current ISO forming limit curve (FLC) procedure is a position dependent technique which produces the FLC based on extrapolation at the crack location. As aluminum sheet metal use increases in manufacturing, accurate determination of the forming limits of this material will be necessary prior to production. New time dependent methods using digital imaging correlation (DIC) account for variations in material behavior by continuously collecting strain data through the material necking point. This allows more accurate FLC determination that is necessary for efficient design in the automotive stamping industry. Two different time dependent FLC analysis techniques using DIC were evaluated and compared with the position dependent ISO technique. All of the techniques were tested at room and elevated temperatures with aluminum 6xxx and 7xxx alloys to show the versatility of the techniques. The resulting FLC diagrams were compared after analysis of the data. Regardless of the testing temperature both tested time dependent techniques resulted in minor variation between trials. The DIC time dependent techniques proved to be more efficient without sacrificing accuracy and consistency. Additionally, time dependent methods displayed less conservative values than the ISO method and the FLC obtained using time dependent method was generally more practical than the ISO method.
Four full scale burn tests on aluminum body Ford F-150’s were conducted with four unique origins. The purpose of these burn tests was to determine if the origin of the fire could be accurately identified after the vehicle fires progressed to near complete burn (with near absence of the aluminum body panels). The points of origin for the four burn tests were: 1) Engine Compartment - driver’s side front of engine compartment, 2) Passenger Compartment - Instrument panel, driver’s side near the headlamp switch, 3) Passenger Compartment - passenger side rear seat, 4) Outside of Vehicle - passenger side front tire. Photographic, video, and temperature data was recorded to document the burn process from initiation to extinguishment. Post-fire analysis was conducted in an attempt to determine the origin of the fire based solely on the burn damage. The analysis showed that due to the lack of body structure remaining, since the aluminum body panels burned/melted, no origin could be determined for any of the four burned vehicles. As a result, with a near complete burn of an aluminum body vehicle, accurately determining the origin of a fire is not possible.
The paper presents the development of a proposed rear powertrain cooling system of a minivan. The packaging of cooling system is finalized such that the radiator faces towards the rear of the vehicle bumper which is opposite to the conventional rear cooling system (i.e. radiator faces towards the front of the vehicle). In the small minivan, the space ahead of the engine is used as a floor for passenger foot. Due to these space constraints, the cooling system has no choice, but to move rear of the vehicle and above the departure plane to meet packaging requirements. Furthermore, in the conventional rear cooling system, in front of the radiator, there is engine and exhaust system, which heats up the air going to the radiator and reduces radiator cooling performance. Thus the cooling system is placed such that the radiator faces the rear bumper to draw in cooler air. In this condition we don’t depend on the ram air but on the fan to meet required airflow. 1D simulation using LMS-Amesim and CFD tools FLUENT are used for conceptual study. Comparison study on air flow, cooling performance and under-hood temperature is done by testing on a mule vehicle. Grill opening, departure angle, critical components heights and surrounding body panels for underbody are considered in packaging of the vehicle. The air flow, ROA of Coolant and ROA of Oil are measured for two conditions, i.e. radiator facing towards rear bumper and radiator facing towards powertrain. It is observed that the effect of rear vortex has negligible impact on the airflow provided by the fan, for vehicle speed less than 65kmph.
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