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Compression in the head-neck complex often causes fractures of the first cervical vertebra (C1). The type of fracture often determines whether the injury is stable or unstable, which significantly affects the ultimate injury severity. The often unstable bursting fracture of C1 is thought to be caused by a transformation of axial compressive forces into lateral bursting forces by the wedge-shaped lateral masses. The purpose of this study was to measure the orientation of the joint surfaces of C1 to determine whether this symmetry exists. An additional goal was to determine whether the orientation of the joint surfaces varied significantly with location on the surface. Direct measurements of surface coordinates were taken from 40 dried vertebrae. The angles of two areas on each of the four joint surfaces of the lateral masses of C1 were then calculated. The resulting angles agreed with previous investigations of upper cervical vertebral anatomy.

After a rear end impact, various clinical symptoms are often seen in car occupants (e.g. neck stiffness, strain, headache). Although many different injury mechanisms of the cervical spine have been identified thus far, the extent to which a single mechanism of injury is responsible remains uncertain. Apart from hyperextension or excessive shearing, a compression of the cervical spine can also be seen in the first phase of the impact due to ramping or other mechanical interactions between the seat back and the spine. It is hypothesized that this axial compression, together with the shear force, are responsible for the higher observed frequency of neck injuries in rear end impacts versus frontal impacts of comparable severity. The axial compression first causes loosening of cervical ligaments making it easier for shear type soft tissue injuries to occur.

In a review of 540 crashes in which the steering-wheel airbag deployed, 38% of the drivers sustained some level of upper extremity injury. The majority of these were AIS-1 injuries including abrasions, contusions and small lacerations. In 18 crashes the drivers sustained AIS-2 or-3 level upper extremity injuries, including fractures of the radius and/or ulna, or of the metacarpal bones, all related to airbag deployments. It was determined that six drivers sustained the fracture(s) directly from the deploying airbag or the airbag module cover. The remaining 12 drivers had fractures from the extremity being flung into interior vehicle structures, usually the instrument panel. Most drivers were taller than 170 cm and, of the 18 drivers, 10 were males.

Automobile insurance claims of two popular midsize cars with different air bag deployment frequencies -- the Dodge/Plymouth Neon and Honda Civic -- were examined to determine performance in higher severity crashes (the upper 30 percent of crashes ranked by adjusted repair cost). Previously, it was found that drivers sustained more, mainly minor, injuries in the Neon which had a higher deployment frequency in low speed crashes. This study examined, for these two cars, whether there was any trade-off associated with a higher deployment threshold. It was found that even at higher speeds, the Neon had a greater frequency of air bag deployments, which in turn resulted in a greater likelihood of driver injury. Once again upper extremity injuries were most prevalent for Neon drivers and were highest for female drivers. At the same time, there was little evidence that driver protection was compromised in the Civic in the more important high speed crashes.

This paper reviews the literature regarding injuries and fatalities in frontal accidents in vehicles equipped with air bag systems. An analysis is presented of the nature of fatal injuries attributable to airbag deployment, which accounts for the age, sex, and accident modality. Injury analysis is reviewed in the same fashion. Airbag-induced injuries appear to relate to the proximity of the motorist to the unit when it inflates. Suggestions have been made to modify seat belt systems, the ergonomics of the driver's position and the design of the airbag units to minimize deployment injury.

The body or chassis of the modern motor vehicle is still fundamentally and commonly designed on the horse and cart concept. This solid chassis, upon which the cart was built, offers little or no crushing zone effect in the event the motor vehicle and its occupants are subject to an impact due to a collision. Although we see an array of modern motor vehicle safety devices, injury and fatalities are still appearing at an alarming rate, some directly due to these safety devices. This paper attempts to present a synergistic approach to motor vehicle safety. One of the most important safety features that has been overlooked by most automobile manufacturers is a uniform crushing zone on bumper areas. It appears at present and possibly in the future that crushing zones on bumper areas have been and will be neglected. Thus a fundamental safety principle that could be used to prevent injury and fatalities in automobile accidents will be neglected.

A new front bumper, blow molded from an engineering thermoplastic, is being used to provide full 8 km/h federal pendulum and flat-barrier impact protection, as well as angled barrier protection on a small passenger car. The low intrusion bumper is compatible with the vehicle's single-sensor airbag system and offers a 5.8 kg mass savings compared with competitive steel/foam systems. This paper will describe the design and development of the bumper system and the results achieved during testing.

The stiffness of randomly oriented, thermoplastic bulk molding compound (TP-BMC) composites can be increased in a 3-point loading test through the use of commingled thermoplastic materials. Bumper beams for a typical midsize vehicle produced from combinations of these 2 materials were molded and tested using a static bumper test setup that measures the applied load and resulting deflection. A design of experiments investigation based on the Taguchi methods [1] were used to compare the effects of 4 material and processing variables on static load. The optimum levels for each variable were found to achieve maximum load at 25 mm deflection, which led to a manufacturing strategy for selectively increasing the stiffness of TP-BMC composites for bumper beams. This paper details the development work.

The stiffness of randomly oriented, glass-mat thermoplastic (GMT) composites with a polypropylene matrix can be increased in a 3-point loading test through the selective use of a co-mingled E-glass and polypropylene filament thermoplastic prepreg. Bumper beams for a typical midsize vehicle made from combinations of these 2 materials were molded and tested using a static bumper test setup, with load being measured as a function of deflection. A design of experiments investigation based on the Taguchi methods [1, 2] was used to compare the effects of 4 glass-mat orientation variables on the measured static load response of the molded bumper beams. This led to follow-up tests of materials and design strategies for selectively increasing the stiffness of the GMT composites at select locations in the bumper beam. The details of the investigation and results will be discussed in this paper.

A conceptual step-pad bumper system has been designed for a sport utility vehicle. This bumper incorporates an all-thermoplastic solitary beam/fascia with a Class A finish and a replaceable, grained thermoplastic olefin (TPO) or urethane step pad. The rear beam is injection molded and the cover plate features integrated through-towing capabilities and electrical connections. The bumper is designed to pass FMVSS Part 581, 8 km/h impacts. The system can potentially offer a 5.0-13.6 kg weight savings at comparable costs to conventional step-pad bumper systems. This paper will detail the design and development of the concept and finite-element analysis (FEA) validation.

The instrument panel (IP) is one of the largest, most complex, and visible components of the vehicle interior, and like most other major systems in passenger cars and light trucks, it has undergone considerable aesthetic and functional changes over the past decade. This is because a number of design, engineering, and manufacturing trends have been driving modifications in both the role of these systems and the materials used to construct them since the mid- '80s. This paper will trace the recent evolution of IP systems in terms of the trends affecting both design and materials usage. Specific commercial examples will be used to illustrate these changes.

One of the methods used to mechanically fasten a component such as a radio, cluster or finish panel to a plastic instrument panel substrate involves driving a screw through a metal push-nut which has been inserted into an opening in the plastic instrument panel substrate. A primary failure mode which has been observed for this type of joint is cracking of the plastic substrate surrounding the metal push-nut. Finite Element Analysis (FEA) has been employed to optimize the design of the push-nut opening in a polycarbonate substrate and minimize the potential for cracking of the plastic. For the FEA, the implicit version of the ABAQUS program was used. It was determined that the induced stress in the plastic instrument panel substrate from the fastening process can be minimized by controlling the dimensions of the push-nut opening such that push-nut recess is minimized and the thickness of the substrate in the region whether the push-nut engages is optimized.

The instrument panel is one of the most difficult components of the automobile to recycle. It is difficult to remove and contains a variety of different plastic materials. Through improved design and coordination, the instrument panel may be made more recyclable and environmentally friendly. The proper selection of materials to minimize material count and maximize separability is critical. Proper selection of assembly and disassembly techniques is also needed.

This paper outlines the relationship between airbag door choices and instrument panel coverstock materials which are being used in the global automotive market for passenger vehicles as well as those materials that are being considered for use in future vehicles. The introduction of an invisible airbag door into the instrument panel is changing the material and testing requirements as safety and reliability are now key considerations. Increasing material options are available to meet these requirements. In this paper, we review the material options, processing methods available, advantages/disadvantages of each, and the current market status of the different materials.

This work compares the relative importance of material anisotropy in sheet forming as compared to other material and process variables. The comparison is made quantitative by the use of normalized dependencies of depth to failure (forming limit is reached) on various measures of anisotropy, as well as strain and rate sensitivity, friction, and tooling. Comparisons are made for a variety of forming processes examined previously in the literature as well as two examples of complex stampings in this work. The examples cover a range from nearly pure draw to nearly pure stretch situations, and show that for materials following a quadratic yield criterion, anisotropy is among the most sensitive parameters influencing formability. For materials following higher-exponent yield criteria, the dependency is milder but is still of the order of most other process parameters.

In many instances, automotive companies wish to create both a left-hand drive and a right-hand drive version of the same vehicle. When the vehicle has relatively low sales volumes, it is imperative to reduce investment costs wherever possible. One successful - if challenging - way is by producing the instrument panel system for both versions off the same tooling. This feat was accomplished in the case of the '97 Jeep® Wrangler, saving the company approximately $7 million.

Springback is one of the main problems in sheet metal bending operations. Theoretically, an accurate description of strain distribution and stress distribution is required in order to predict the springback behavior of a bending component. Prediction of strain distribution needs a good geometrical model while prediction of stress distribution needs both an accurate strain description and an accurate stress-strain relationship. In this paper, a new model is developed for strain calculation in plane strain bending. The displacement of the neutral surface, the thickness change, the stress and strain distributions over the sheet thickness, the bending moment and the springback curvature are examined using this new model and useful conclusions are obtained. The new model is also compared with Hill's pure bending model, the membrane theory (plus post-processing) and the shell theory. The application ranges and the limitations of the membrane theory and the shell theory are discussed.

The functional performance of the instrument panel has been changing dramatically since the late 80s, with FMVSS 208 legislation and its related impact on the addition of air bags and knee bolsters. In addition to addressing occupant safety legislation through more safety components, as well as navigation, security, comfort, informational and other systems are being added to the instrument panel as the consumers' desire for enhanced features continues. At the same time, consumers still want a product that is uncomplicated, affordable, aesthetically pleasing and - at the same time - doesn't limit valuable interior compartment space. The early efficient integration of these components (electrical, architecture, HVAC, steering) in the design, engineering and assembly process will be the areas of requirement that will have a primary effect on IP system cost in the future.

This article describes a fast design oriented tool to provide predictions of springback in automotive stampings. The new program, FAST_SPRINGBACK, utilizes the results of another membrane finite element code, FAST_3D, which performs a one step simulation of the forming process. The significant feature of the new springback tool is its ability to quickly predict the different modes of springback deformations as well as residual stresses that will affect the final shape and performance of the formed part. An important aspect of the program is its capability to integrate with existing CAD tools, thus enabling the designer to perform checks on the candidate part geometry in the early design stages.

In order to reduce fuel consumption light weight vehicles are in development. For this HSLA- steel, bakehardening- steels, stainless-steels and aluminum will be used for the body in white of personal cars. To form inner automotive parts of high dimensional accuracy out of steel with high strength or out of aluminum and to form automotive parts of high surface quality as well as of high dimensional accuracy a reproducible forming process is needed. For low volume cars tools and dies have to be as cheep as possible. The press has to be able to take over die functions and over the stroke steerable blankholder forces. Tools and dies for high volume parts can use expensive tools and dies like dies with nitrogen cylinders. In the future these cylinders will have the possibility to steer the pressure and so in turn the blankholder force over the stroke. See paper „Force- Stroke- Curve of Gas Springs” (State-of-the-Art Stamping) held on the same conference.