Browse Topic: Hoods
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
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
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
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
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
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
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
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
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
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
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
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
The pursuit of improved fuel economy through weight reduction, reduced manufacturing costs, and improved crash safety can result in increased compliance in automobile structures. However, with compliance comes an increased susceptibility to aerodynamic and vibratory loads. The hood in particular withstands considerable aerodynamic force at highway speeds, creating the potential for significant aeroelastic response that may adversely impact customer satisfaction and perception of vehicle quality. This work seeks an improved understanding in computational and experimental study of fluid-structure interactions between automobile hoods and the surrounding internal and external flow. Computational analysis was carried out using coupled CFD-FEM solvers with detailed models of the automobile topology and structural components. The experimental work consisted of wind tunnel tests using a full-scale production vehicle. Comparisons between numerical and experimental results yielded important
Carbon fiber reinforced plastic (CFRP) composites have gained particular interests due to their high specific modulus, high strength, lightweight and resistance to environment. In the automotive industry, numerous studies have been ongoing to replace the metal components with CFRP for the purpose of weight saving. One of the significant benefits of CFRP laminates is the ability of tailoring fiber orientation and ply thickness to meet the acceptable level of structural performance with little waste of material capability. This study focused on the concurrent optimization of ply orientation and thickness for CFRP laminated engine hood, which was based on the gradient-based discrete material and thickness optimization (DMTO) method. Two manufactural constraints, namely contiguity and intermediate void constraints, were taken into account in the optimization problem to reduce the potential risk of cracking matrix of CFRP. The design objective was the minimization of the mass of the CFRP
U.S. Army Operational Test Command Fort Hood, TX 254-287-9993
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