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Technical Paper

Automotive Roof Crush, Structural Foam Enhancement Solution

Vehicle rollover is a rare event on roads, compared to other types of crashes. According to National Highway Traffic Safety Agency, USA (NHTSA), rollovers account for only 3% of crashes in a year [1]. However, one third of the fatalities occur during a rollover and the numbers of such fatalities exceed over 10,000 per annum. The fatality and the injury rate makes rollover crash an important issue in vehicle safety. As part of reducing risk of death and serious injury from rollover crashes, a proposal has been made to upgrade FMVSS No. 216, Roof Crush Resistance [2]. This upgraded regulation mandates the increase in peak load carrying capacity of the vehicle structure from 1.5 times vehicle weight to 2.5 times vehicle weight. As such, the manufacturers are required to comply to this norm even with their existing vehicles. This necessitates a change in structural design of the vehicle to be able to withstand the additional load bearing capacity.
Technical Paper

Identification of Key Vehicle Parameters for Pedestrian Impact Safety

Pedestrians forming the most important casualty of road accidents, European countries have brought in new laws for vehicles to be made safer for pedestrian impacts. The needs of pedestrian safety are different from current requirements such as low speed or insurance impacts. To fulfill both traditional vehicle to vehicle and pedestrian safety requirements, design changes are needed to find a good balance. However, design limitations are imposed in order to conserve the styling and aesthetics of the front end, which define the image and often handling/aerodynamics of the car. Thus, numerous boundary conditions, both mechanical and non-mechanical, should be taken into account during the implementation of pedestrian safety solutions. This study breaks out part of vehicle front profile, which can be explicitly given values. These values have been based on 2-D simulations conducted across four vehicle categories available in the Indian scenario.
Technical Paper

Transverse Anisotropic Modeling of Honeycomb Extruded Polypropylene Foam in LS-Dyna to Optimize Energy Absorption Countermeasures

To meet automotive legal, consumer and insurance test requirements, the process for designing energy absorption countermeasures usually comprises Finite Element simulations of the specified test. Finite element simulations are used first to see if there is a need for an Energy Absorption countermeasure at all and if so, what type, material and shape. A widely used class of energy absorption countermeasures in automotive interior applications is honeycomb extruded polypropylene foams (HXPP). Under compression, these foams exhibit a constant plateau stress until late densification. This enables these foams to minimize packaging space for a given amount of energy to be absorbed or maximize energy absorption for a given packaging space. Robust and easy to use isotropic CAE material models have been developed for HXPP, however the true material properties are anisotropic and such a material model could be necessary in some cases.
Technical Paper

Polyurethane Foam Inserts for NVH and Structural Applications

The application of two-component polyurethane (PU) foam materials for acoustical and structural performance enhancements in vehicle structures have increased significantly in the past ten years. The benefits include NVH management (through effective cavity sealing), body stiffness improvements and energy management in crash applications. These PU foams can either be pumped into body cavities in the OEM assembly plants (bulk applied) or can be pre-molded into Structural Foam Inserts (SFI) and installed in the body-shop prior to full frame assembly. The choice of application type depends on vehicle-specific requirements and assembly plant criteria. The chemistry, plant application and benefits associated with bulk PU foam has already been cited in previous work.1, 2, 3 This paper showcases BETAFOAM™ SFI technology developed by Dow Automotive that complements traditional bulk foam technology.
Technical Paper

The Virtual Stiffness Profile - A Design Methodology for Pedestrian Safety

European car manufacturers and suppliers are currently stepping up the effort to develop solutions to meet pedestrian safety requirements, which will come into effect, starting in 2005. Numerous concepts, both active and passive, are being investigated to fulfil the pedestrian safety specifications, in addition to the many other limitations imposed on the front end of the car. All of them deal with the topic of energy absorption. Here, an approach to achieving a passive solution will be presented, describing the development of the ‘Virtual Stiffness Profile’ (VSP) to help identify the optimum balance of engineering and styling to meet the requirements. In this paper, specific emphasis is placed on the lower leg impact.
Technical Paper

Evolution of Structural Instrument Panels

In structural Instrument Panels the conventionally used cross car beam is eliminated by using the plastic structure as a load carrying construction. Due to the continuous search for lowering costs and weight in the development of new cars, the concept has been applied a number of times. Many articles have been published since on this subject, describing the design concepts, engineering development and types of plastic material applied. In general, the structural instrument panel assemblies show to have substantially lower cost and weight compared with conventional cross car beam based instrument panel structures while all of performance requirements are met. Also, improved packaging space, reduction in assembly time and improved recyclability are seen as major advantages. The use of state of the art Computer-Aided Engineering (CAE) has proved to reduce development time and costs.
Technical Paper

2002 Pontiac Montana Frequency Improvements Employing Structural Foam

This paper documents a joint development process between General Motors and Dow Automotive to improve primary body structure frequencies on the GM family of midsize vans by utilizing cavity-filling structural foam. Optimum foam locations, foam quantity, and foam density within the body structure were determined by employing both math-based modeling and vehicle hardware testing techniques. Finite element analysis (FEA) simulations of the Body-In-White (BIW) and “trimmed body” were used to predict the global body structure modes and associated resonant frequencies with and without structural foam. The objective of the FEA activity was to quantify frequency improvements to the primary body structure modes of matchboxing, bending, and torsion when using structural foam. Comprehensive hardware testing on the vehicle was also executed to validate the frequency improvements observed in the FEA results.
Technical Paper

Polyurethane Foam Systems For NVH and Improved Crashworthiness

Recently, automotive engineers have been looking at rigid polyurethane foam systems for the advantages their application brings to vehicle design and performance. The benefits range from NVH management achieved through effective body cavity sealing and improved structural dynamics, to enhanced vehicle crashworthiness. These benefits can be realized through application of polyurethane foam systems designed for energy management. These systems offer multifunctional, low cost solutions to traditional approaches and can be modeled early in the vehicle design stage. In many cases, the overall vehicle mass is reduced as reinforcements are eliminated and/or sheet metal thickness is decreased. Dow Automotive has developed a family of water blown polyurethane foams specifically for these applications. Development has focused on foam systems designed for impact optimization, allowing OEM's to optimize the body structure content.
Technical Paper

Acoustic and Structural Treatment of Body-in-White

Automotive body structures are developed to meet vehicle performance requirements primarily based on ride and handling, crashworthiness, and noise level targets. The body is made of a multitude of sheet metal stampings welded together. Other closures such as fenders, hood, doors and trunk lid are developed to match body interfaces, to contribute and participate in the overall vehicle response, and to meet the sub-system and system structural requirements. In order to improve performance and achieve weight reduction of the overall vehicle steel structure, new polymeric materials and treatment strategies are available to body structural engineers to optimize the response of the vehicle and to tune vehicle performance to meet specified functional requirements. If early integrated to the design cycle, these materials help not only improve the structural body response, but also decrease the weight of the integrated body structure.