Browse Topic: Hoods
For analysing flow and acoustic induced structural vibration, a fully run time coupled framework combining a hybrid CFD-CAA approach with a modal response simulation was validated and presented at the ISVNH 2022 (SAE Technical Paper 2022-01-0938). In this paper i We apply this CFD–CAA–modal coupling method to a series-representative bonnet geometry and demonstrate its capability to capture flow and aeroacoustically driven vibration with two-way coupling. ii We analyse the modal properties of the bonnet and show that confined air volumes beneath the bonnet can introduce significant fluid loading effects, which are already embedded in experimentally validated FE modal models and must therefore be treated carefully in two-way coupled simulations. iii We validate the fully coupled aeroelastic simulation against wind-tunnel measurements with undisturbed inflow, show close agreement with the measured vibration response and analyse that the dominant excitation is in this case from below the bonnet due to acoustic pressure fluctuations.
Industries are following a tedious product development cycle for developing their product. In product development major steps includes design ideas, Drawings, CAD, CAE, Testing and design improvement cycle. This is a monotonous process and takes time which impacts on its time to deliver product and cost on development. Now a days industries are fast growing and targeting to reduce development cycle time and cost. AI&ML is impacting almost all areas in the industry and significantly reducing efforts time and cost. To make use of AI&ML in CAE, Altair Physics AI is an effective tool. To ensure the design of product traditional way is to develop a CAD of the product, develop, perform CAE and analyze performance. If we consider CAE procedure it is time consuming process which includes FEA model build, applying boundary conditions, running simulation and analyzing results which could take minutes to hours. By using ML with Physics AI we can make predictions on new design of the product in seconds and significantly save time and cost. To demonstrate the CAE acceleration process with physic AI we have solved two case studies. The first case study is head impact on hood where ML tool will predict deformation contour of the hood, acceleration and displacement curve of the impactor. The second case study is Tube crush analysis where prediction of tube deformation pattern, force and energy curve for different tube length and impact velocity is carried out. For both Case studies we have used TCS inhouse data to train test and prediction of the ML model. For Head impact case study, it gives lower training loss with more than 90 percent prediction accuracy. Similarly for tube crush study it gives good accuracy and predicts comparable behavior patten with CAE results. Physic AI ML tool accelerates the design and development cycle and can be utilized in different product development. Implementation of ML accelerates the CAE process in design and development of products. It saves a lot of time in multiple design iteration study. Similar method can be implemented for different CAE cases.
Audi has streamlined the A6 lineup. The automaker announced this past summer that the fancier-looking A7 (which was essentially an A6 glow up) was being pulled from the North American market. Now it's reduced the engine offerings from three to one. After a recent drive of the 2026 model, what's left under the hood was the best choice. But you might want to wait a few months if you're interested in the vehicle.
Volvo Trucks North America launches the all-new VNR with standard D13 VGT engine and announces an upcoming CARB- 24 Omnibus compliant engine variant. When Volvo Trucks revealed its all-new VNR regional haul truck in March 2025, it also marked the launch of something new under the hood: the Volvo D13 VGT (variable geometry turbo) engine. The new D13 VGT engine will be standard in the VNR and optional for the VNL day cab. The D13 VGT engine builds on improvements launched with the D13 Turbo Compound engine, which is standard on the new VNL (www.sae.org/news/2024/02/volvo-vnl-launch) that commenced commercial production at the New River Valley assembly plant in Dublin, Virginia, in October 2024.
Hood insulators are widely used in automotive industry to improve noise insulation, pedestrian impact protection and to provide aesthetic appeal. They are attached below the hood panel and are often complex in shape and size. Pedestrian head impacts are highly dynamic events with a compressive strain rate experienced by the insulator exceeding 300/s. The energy generated by the impact is partly absorbed by the hood insulators thus reducing the head injury to the pedestrian. During this process, the insulator experiences multi-axial stress states. The insulators are usually made of soft multi-layered materials, such as polyurethane or fiberglass, and have a thin scrim layer on either side. These materials are foamed to their nominal thickness and are compression molded to take the required shape of the hood. During this process they undergo thickness reduction, thereby increasing their density. Hence, the material properties vary greatly based on the thickness and strain rate experienced by the material. This paper presents a methodology for characterization of hood insulator materials at strain rates ranging from 0.01/s to 300/s for use in finite element (FE) simulations. A rate dependent material model is validated against the results of hemispherical punch tests. Unique tensile response of the hood insulator materials at high strain rates and the challenges it poses for material modeling is discussed in detail. In addition, challenges with specimen extraction and tensile testing of soft multilayer materials are presented, and the improved tensile testing procedure is proposed.
This document details one of the connections of the SAE J3105 document. The connections are referenced in the scope of the main document SAE J3105. SAE J3105/2 details the vehicle-mounted pantograph, or the bus-up connection. All the common requirements are defined in the main document; the current document provides the details of the connection. This document covers the connection interface relevant requirements for an electric vehicle power transfer system using a conductive automated charging device based on a conventional rail vehicle pantograph design. To allow interoperability for on-road vehicles (in particular, buses and coaches), one configuration is described in this document. Other configurations may be used for non-standard applications (for example, mining trucks or port vehicles).
In the past decades, automotive structure design has sought to minimize its mass while maintaining or improving structural performance. As such, topology optimization (TO) has become an increasingly popular tool during the conceptual design stage. While the designs produced by TO methods provide significant performance-to-mass ratio improvements, they require considerable computational resources when solving large-scale problems. An alternative for large-scale problems is to decompose the design domain into multiple scales that are coupled with homogenization. The problem can then be solved with hierarchical multiscale topology optimization (MSTO). The resulting optimal, homogenized macroscales are de-homogenized to obtain a high-fidelity, physically-realizable design. Even so MSTO methods are still computationally expensive due to the combined costs of solving nested optimization problems and performing de-homogenization. To address these issues, this paper presents an efficient de-homogenization method that can be applied to any macroscale topology in order to obtain a high-fidelity multiscale structure. In contrast to prior de-homogenization methods, an alternative representation of the rectangular hole microstructure is proposed so that it is only dependent on the local density and stress distributions. Consequently, MSTO methods are not needed for the de-homogenization method to be applied. This makes the method applicable to any conceptual design, including those from simple single-scale TO codes. Additionally, the proposed de-homogenization method avoids the expensive mapping optimization problem associated with most projection de-homogenization methods by clustering sub-domains of the structure into discrete orientation angles. Pre-computed microstructures for each of the discrete angles are then assembled into each sub-domain. The proposed method is showcased for the design of a simple bumper and hood structure. The material distribution of each component is optimized in a two-dimensional TO problem for maximum stiffness.
Pedestrian passive safety and active safety both develop rapidly, such as new structural hoods/airbags for pedestrian protection and emergency automatic braking/forward collision warning are used in advanced driver assistance system (ADAS). In this study, improved pedestrian passive safety is to obtain optimal hood structural parameters and add an active pop-up hood. Headform impactor, hood model, simplified vehicle and head impaction models were established, and nine key test points were selected for crash simulation tests. After the simulation, the pedestrian protection performance of the initial hood is evaluated and analyzed based on the head injury criterion (HIC) values. Combined with the orthogonal experimental design method, this study acquired the best structural parameters scheme and applied to the active pop-up hood. The validation results show that after applying the optimal structural parameters to the active pop-up hood, the pedestrian protection performance of the hood is improved and the pedestrian passive safety performance of the smart vehicle is enhanced.
Prevailing global industry has set an environment that fosters the search for new procedures, technology and/or knowledge that allows time reduction in vehicle development and, at the same time, to offer the best strength and reliability characteristics to the customers. Constant improvement mindset is applied to those systems that yield the highest interaction with the final user, among those, it is paramount to take notice of systems like the vehicle closures (such as liftgates, hood, doors, etc.). In automotive industry, the efforts to comply with high standards are often focused to incorporate new materials, which are resistant and lightweight, on the other hand, this project explores the liftgate behavior from a more fundamental standpoint, which is the geometry and how it is related to the requirements that the liftgate should comply with. In this article, a research was conducted to establish which components have a high influence in the structural integrity of the liftgate, using as a starting point the structural testing’s that are performed to sign off the closures design during the product development stage. Furthermore, a comparison analysis between different liftgate structures, stand out the geometric design patterns of the interior panel of the liftgate that is present in the hatchback and sport utility vehicles. Finally, this project includes optimization proposals that determined the inner panel geometric form that enables the liftgate to comply with the structural requirements and comparison of the liftgate assessments results between the commonly used profiles across the industry.
Vehicle hood design is a typical multi-disciplinary task. The hood has to meet the demands of different attributes like safety, dynamics, statics, and NVH (Noise, Vibration, Harshness). Multi-disciplinary optimization (MDO) of vehicle hood at early design phase is an efficient way to support right design decision and avoid late-phase design changes. However, due to lacking in CAD models, it is difficult to realize MDO at early design phase. In this research, a new method of design and optimization is proposed to improve the design efficiency. Firstly, an implicit parametric hood model is built to flexibly change shape and size of hood structure, and generate FE models automatically. Secondly, four types of stiffness analysis, one type of modal analysis, together with pedestrian head impact analysis were established to describe multi-disciplinary concern of vehicle hood design. Finally, a platform is developed to integrate parametric modeling and CAE software to automatically conduct design of experiment (DOE) sampling, undertaking sensitivity analysis and find the optimal result. The results show that application of this method results in weight reduction from 16.8 kg to 14.83 kg and improves pedestrian protection performance score from 6.57 to 7.74 at the same time according to the China New Car Assessment Program (CNCAP).
In use cars often drive through the wakes of other vehicles. It has long been appreciated that this imposes a fluctuating onset flow which can excite a structural response in vehicle panels, particularly the bonnet. This structure must be designed to be robust to such excitation to guarantee structural integrity and maintain customer expectations of quality. As we move towards autonomous vehicles and exploit platoons for drag reduction, this onset flow condition merits further attention. The work reported here comprises both measurements and simulation capturing the unsteady pressure distribution over the bonnet of an SUV following a similar vehicle at high speed and in relatively close proximity. Measurements were taken during track testing and include 48 static measurement locations distributed over the bonnet where the unsteady static pressures were recorded. This is complemented by computational fluid dynamics simulations using a commercially available Lattice-Boltzmann based Very Large Eddy Simulation approach. Comparisons between experiment and simulation are based on time-averaged static pressure coefficients, pressure time-histories and spectra. This provides a dataset that includes both time-averaged and unsteady correlation, demonstrating that such simulations can provide a good representation of on-track effects.
The importance of fluid-structure interaction (FSI) is of increasing concern in automotive design criteria as automobile hoods become lighter and thinner. This work focuses on computational simulation and analysis of automobile hoods under unsteady aerodynamic loads encountered at typical highway conditions while trailing another vehicle. These driving conditions can cause significant hood vibrations due to the unsteady loads caused by the vortex shedding from the leading vehicle. The study is carried out using coupled computational fluid dynamics (CFD) and computational structural dynamics (CSD) codes. The main goal of this work is to characterize the importance of fluid modeling fidelity to hood buffeting response by comparing fluid and structural responses using both Reynolds-Averaged Navier-Stokes (RANS) and detached eddy simulation (DES) approaches. Results are presented for a sedan trailing another sedan. Comparisons between RANS and DES emphasize the importance of turbulence modeling fidelity in order to capture the unsteadiness of the flow and the vibration response of the hood. These comparisons include analysis of the lift forces, pressure loads on the hood, power spectral density (PSD) analysis of the flow in the region between the two vehicles, and displacement at discrete points on the hood. As expected, DES predicts higher frequency content and significantly higher turbulence levels than RANS. The hood response is found to be sensitive to these characteristics. The increased levels of turbulence result in up to 40-60% higher maximum peak-to-peak deformation and the excitation of a torsional mode of the trailing vehicle hood.
This document details one of the connections of the SAE J3105 document. The connections are referenced in the scope of the main document SAE J3105. SAE J3105/2 details the vehicle-mounted pantograph, or the bus-up connection. All the common requirements are defined in the main document; the current document provides the details of the connection. This document covers the connection interface relevant requirements for an electric vehicle power transfer system using a conductive automated charging device based on a conventional rail vehicle pantograph design. To allow interoperability for on-road vehicles (in particular, buses and coaches), one configuration is described in this document. Other configurations may be used for non-standard applications (for example, mining trucks or port vehicles).
The stamping process is commonly used, it is easily found in vehicles manufacturing. The stamping tool is composed by elements such as: die, punch, drawbeads and blankholder. The objective of this paper is to improve the structural stiffness and to reduce the weight of die through numerical optimization. Usually are used standardized stamping tool's parts that follows standard guidelines. The only part of stamping tool considered in the methodology was the die, other parts like punch and blankholder can also be optimized. A vehicle hood was designed in CAD and after that it was exported to CAE to start the simulations, the first step was the die generation. After that, a stamping process was simulated and the contact forces in the die were extracted and then applied in the control volume designed in CAD. Finally, the constraints, objectives and parameters were changed, so the topological optimization was generated. The results were interpreted and a layout were design in CAD following the pattern given by the optimization. Two different load cases are applied to the die tool, one transportation case and one operation case. The last geometry designed was meshed and submitted at the same load obtained in the stamping simulation process. Displacement and stress simulations caused by loads and own die weight were done. The same process was used in the standard die. The final results show a weight reduction of 13.64% and a decrease in max stress of 18.11%. The obtained results prove the importance of a topological optimization in this kind of project.
Flow separation is one of the primary causes of increase in form drag in vehicles. This phenomenon is also visible in the case of lightweight vehicles moving at high speed, which greatly affects their aerodynamics. Spherical depressions maybe used to delay the flow separation and decrease drag in such vehicles. This study aims for optimization of aspect ratio (AR) of spherical depressions on hatchback cars. Spherical depressions were created on the bonnet of a generalized light vehicle Computer-Aided Design (CAD) model. The diameter of each spherical depression was set constant at 60 mm, and the center-to-center distance between consecutive spherical depressions is fixed at 90 mm. The AR of spherical depressions was taken as the parameter that was varied in each model. ARs 2, 4, 6, and 8 were considered for the current investigation. Three-dimensional (3D) CFD analyses were then performed on each of these models using a validated computational model. Vehicle travel velocities of 22, 24, 26, 28, and 30 m/s, which were nondimensionalized for scaling the results, were considered for analyses, in order to simulate the maximum travel velocity of light vehicles. Various parameters like the coefficient of drag, lift coefficient, and boundary layer separation were studied to investigate the impact of AR of spherical depressions on vehicle aerodynamics. A significant decrease in coefficient of drag was observed as a result of the addition of spherical depressions on the bonnet.
Head injuries are the main source of road fatalities when a pedestrian or other vulnerable road user (VRU) such as cyclist or motorcyclist is involved in an accident with the approaching high speed vehicle. The frontal part of a car such as engine hood (bonnet), lower-windshield area and A-pillars are the possible location of head impact in these accidents. The head impact with hard points located in these areas may result in the fatal head injuries. The effect of impact can be reduced by using the deployable pedestrian protection systems (DPPS) such as pop-up hoods and windshield airbag in the vehicle. The study indicates how these systems are effective in reducing the fatalities in pedestrian accidents and how to evaluate the performance of these deployable systems. The pedestrian & VRU road fatalities contribute to more than 33percent of total road fatalities in India. Worldwide regulations for pedestrian protection include the evaluation of head injuries at a relative speed of 35kmph. However, the actual impact can occur at higher speeds many times which results in high severity accidents which may lead to death of the victim. The study shows how the Active Hood (also called pop-up hood) reduces the risk on sever injuries in these accidents.
Road accidents are increasing now-a-days, Safety of pedestrian is the great concern. In average, 10% of urban pedestrian accidents are fatal. Statistics show that the impact on front side of cars is the major cause of pedestrian deaths (83.5%). The function of a vehicle’s engine hood is to keep its engine covered and allow access to the engine compartment as required for maintenance and repair. The hood structure not only protects the engine cavity, but also keeps pedestrians away from the parts of that cavity. The absorption capability and stiffness of hood structures are the key points considered when designing a vehicle’s hood. The impact of the pedestrian head on automotive hood results in major injuries and sometimes in death. Conventional engine hood results in greater Head Injury Criterion (HIC) values. GFRP pyramidal lattice core structures are used in automobiles which is used for good energy absorption. GFRP pyramidal lattice core sandwich engine hood absorbs impact energy rather than transmitting it to the head. This will minimize the severity rate of injury of pedestrian during accident. This report deals with the analysis of GFRP pyramidal lattice core sandwich engine hood in ANSYS workbench under impact loading. This work mainly focuses on reducing pedestrian accidents. The results of finite element modelling of pyramidal lattice core sandwich engine hood yields lesser HIC values. This shows GFRP pyramidal lattice core absorbs more impact energy from the pedestrian head.
The U.S. Navy is interested in strategies that divers could employ to protect them from loud underwater sounds. Sonar transmissions and other forms of underwater sound, such as that produced by noisy underwater tools, are an occupational hazard for U.S. Navy divers.
Road accident between pedestrian and motor vehicle causes severe injuries and even death of pedestrian. The accident statistics show that the possibility of injury to pedestrian is higher in case of collision with car on busy roads. In car and pedestrian collisions, the pedestrian’s head hits with car bonnet and suffer from multiple injuries such as skull fractures and brain injury. The role of car bonnet structural strength plays an important role in pedestrian head injury level. To provide enough structural strength the high bonnet thickness is provided with under bonnet stiffeners, however thick bonnet and stiffeners reduces deformation of the bonnet during collision and increases injury level to pedestrian. Hence optimum bonnet thickness, least number and geometry of stiffeners and enough structural strength is important for bonnet to reduce injury level. The aim of this study is to analyse the effect of car bonnet thickness, number and arrangement of under bonnet stiffeners on head injury levels with the help of head injury criteria (HIC). Head Injury Criteria (HIC) is a measure of the likelihood of head injury arising from an impact during a car crash. It indicatesthe level of injury caused during a particular crash. A typical modern car bonnet is selected for investigation with variety of bonnet material thickness and different configurations of under bonnet stiffeners and head injury criteria (HIC) is computed with the help of computer modelling. Further, head linear velocity, acceleration and head injury risk are predicted for probability of skull fracture. The geometry of bonnet is optimized with the help of optimization technique and optimized bonnet geometry is validated experimentally by designing a bonnet test facility and head form imparter.
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