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Finite element modeling based on both 3-D shape measurement and experimental stress-strain relationship was applied to the FEM simulation for estimating the crashworthiness of automobile parts. Compared with the result dynamic crash test using hat-square-column type specimen made of 300 - 590MPa grade steels, the accuracy of the FEM simulation was evaluated for various modeling methods. It was revealed that the modeling of corner radius, bulging of specimen wall and strain rate sensitivity of materials played important roles in predicting the actual dynamic deformation process and the force-stroke relationship.

This paper presents a simulation method and its application which enables the establishment and satisfaction of side impact design requirements. Three key phases are described: 1. Determination of desirable side intrusion velocity characteristics which minimize occupant injury in light of both ECER95 and FMVSS 214 regulations. 2. Development of a condensed vehicle model which enables the velocity characteristics determined in 1) to be translated into meaningful design parameters. 3. Practical application of the method showing how it can be used to: define side structure design requirements achieve desired velocity profiles enhance understanding of design cause and effect

Compressible plastic foams are used throughout the interior and bumper systems of modern automobiles for safety enhancement and damage prevention. Consequently, modeling of foams has become very important for automobile engineers. To date, most work has focused on predicting foam performance up to approximately 80% compression. However, in certain cases, it is important to predict the foam under maximum compression, or ‘bottoming-out.’ This paper uses one such case-a thin low-density bumper foam impacted by a pedestrian leg-form at 11.1 m/s-to investigate the ‘bottoming-out’ phenomenon. Multiple material models in three different explicit Finite Element Method (FEM) packages (RADIOSS, FCRASH, and LS-DYNA) were used to predict the performance. The finite element models consisted of a foam covered leg-form impacting a fixed bumper beam with a foam energy absorber.

Laminated side glazing is a rapidly growing new application, driven by consumer demand for improved intrusion resistance and increased comfort. Performance requirements for movable door glass applications are different from laminated windshield (LWS) needs. Criteria for satisfactory performance are discussed and the performance of commercially available interlayers compared. Performance differences are significant, indicating that interlayer selection is critical for acceptable side glazing performance. The most important performance attribute is the ability to maintain adhesive bond strength to glass at the high interlayer moisture content present at exposed edges.

This paper presents the results of a comprehensive research program addressing the safety issues pertaining to using Polycarbonate glazing for non-windshield vehicle glazing. A series of crash test procedures were used to evaluate the Polycarbonate glazing alternative. The test procedures utilized included High Speed Lateral Impact (HSLI), Narrow Object Intrusion or Pole Impact, Dynamic Rollover, and Inverted Vehicle Drop tests. It should be noted that component-level dynamic impact testing of a variety of Polycarbonate designs was previously conducted as part of this ongoing research program [1]. This testing included 40 lb guided headform and Free Motion Headform (FMH) testing. In regard to vehicle glazing, there are a number of important occupant safety issues. These include occupant containment, injury due to occupant impact with glazing, and laceration. Throughout the project, emphasis was placed on the careful monitoring of the test results with regard to these three issues.

This paper describes an analytical method to find optimal side structure of convertible vehicle for occupant protection using full vehicle finite element model compared with typical notch-back style vehicle. The strategy of occupant protection for convertible vehicle is quite different from that of notch-back sedan in the view point of vehicle structure due to the limitations in building concept of side structures. In this study, the strategy leading to reliable results in the convertible type vehicle will be discussed. This analysis work shows a good preliminary result for predicting vehicle side structure behavior and occupant injury in early stage of car developing program.

The impact behavior of a vehicle frame is studied in this research. We focus on frontal impact in which the vehicle with an initial velocity is set in full contact with a rigid barrier at zero inclination angle. It is generally agreed and widely noted that in both physical crash tests and crash simulation analyses, there tend to exist significant variations in the final deformation shape for crash tests under what appear to be the same conditions. The purpose of this paper is to demonstrate that structural bifurcation could be the potential cause of the apparent randomness in frontal impact deformation. Advanced finite element analysis is used to study the impact behavior. A simple thin-walled beam element with box cross section is used to model the side rails of the vehicle frontal frame. Comparisons are made between impact of the perfect structure and the structure with a slight initial geometric imperfection.

Tailored welded blanks are increasingly being used in the motor vehicle sector, the purpose of these blanks being to reduce weight and production costs by means of a reduction in the number of parts to be assembled. The stamping of welded blanks gives new freedom in the optimization of the final geometry while raising a series of difficulties. The goal of this paper is to show a new way to stamp tailored blank with a new tool: the regulated blank-holder with localised force control. This blank holder offers thus a response to all specific tailored blanks problems.

The weight reduction potential of Hylite sandwich sheet in applications where bending stiffness is the design criterion is approx. 65% over steel sheet and 30% over aluminum sheet. The sandwich sheet (0,2/0,8/0,2mm aluminum/polypropylene/aluminum) has proven its functionality in numerous prototype car body parts which have been tested thoroughly by car manufacturers. In order to demonstrate its suitability in today's car manufacturing environment Hoogovens Hylite in close collaboration with Volkswagen AG and Grau Werkzeug- und Formenbau GmbH has set up a prevalidation line for the production of car hoods. The emphasis in the project has been on deep drawing and an innovative hemflanging technology involving a preparatory ‘ribbing’ operation. The aim was to prove that the deep drawing and subsequent hem flanging operation can be carried out in an acceptable cycle time at high quality standards and at a low rejection rate.

Tube hydroforming is a technology that is new to many and proving it's merits as a viable and often superior alternative to welding tubular assemblies from stampings. This paper discusses how pressure sequence and high pressure hydroforming techniques work, how two functionally similar parts made by its respective technology compare and the dimensional stability of parts made with pressure sequence hydroforming. Data comparing the 2 processes show a substantial benefit when using pressure sequence hydroforming considering processing steps, hydroforming equipment, energy consumption, cycle time and floor space requirements. PSH dimensional stability compares very well with welded assemblies. High pressure dimensional data is unavailable which prevents comparison. Comparisons using specific information that has only recently become available should be interesting and valuable to anyone wanting to learn more about this emerging industry and technology.

The ULSAB project, conducted by a consortium of 35 international steel producers, clearly demonstrates that the application of tubular hydroformed components offers a large contribution to the structural and crash performance of the Body in White whilst offering both a weight and cost saving [1, 2]. Although the number of hydroformed parts is only two (the left and right side roof rail) the potential in other hollow components is high. What needs to be proven is the viability in mass production. This incorporates not only the hydroforming technology itself, but also the availability of large diameter thin walled tubes. This paper will only deal with the first item for which Hoogovens Steel Strip mill Products and Dr. Meleghy Hydroforming GmbH have formed a partnership in October 1996. The objectives of the partnership are the development of forming simulation models and determine the relation between material characteristics and the hydroforming process.

A series of inflator tank tests was carried out to determine the amount of transient heat losses to the tank wall during these tests. The time history data of tank wall temperature, and tank interior gas temperature and pressure, were measured. The tank wall temperature data were analyzed using an inverse heat conduction method to generate the transient heat loss fluxes from the tank gas to the tank wall. The validity of the results are discussed along with the physical reasoning and experimental observations. This is the first part of an effort in a research project to develop a comprehensive heat transfer model to predict the transient heat losses to the tank wall during the inflator tank test.

Fifty-three static out-of-position tests were conducted with a “small female” dummy placed in three different positions, and with distances of 0 mm and 50 mm from the airbag. The driver-side module with a single-stage inflator was additionally tested with inflator versions tailored to 80%, 60%, 40% and 20% of peak tank pressure, in order to simulate the first of two stages of a dual-stage inflator. In general, biomechanical loadings decreased with less inflator propellant. Critical chest loadings were measured down to the 60%-stage. The neck extension bending moment exceeded the limit only with the lOO%-charge. With distances of 50 mm, none of the threshold values were exceeded. Energy reductions of 20% between two stages did not necessarily reduce occupant loadings.

One-sixth scale model airbag modules have been used to investigate flow aspiration effects in passenger-side airbag modules. A similarity analysis between flows in the model and the prototype unit assures reasonable approximation of the actual flows. In the controlled flow environment of the model, flow visualization suggests that the underexpanded jet structure follows the universal relationship based on experimental data and shows that aspiration occurs through the aspiration holes. Detailed velocity measurements provide the ratio of the mass added to the discharged gas for a single firing. The same approaches can be applied in the design of full-scale airbag systems.

In automotive industry, aggressiveness of airbags is associated with the output of inflators, which is often presented by tank pressure. The purpose of this paper is to give an in-depth discussion of the thermodynamics behind the airbag inflator so that we can understand correctly and utilize properly the relationship between inflator power and tank pressure. In this paper, through a more rigorous derivation and a detailed analysis of the tank tests, we not only qualitatively analyze the relationship of inflator power to tank pressure, the heat transfer effect and the gas composition effect, but also we quantify the contribution of these parameters. The numerical algorithm and calculations also have been shown here for the most common types of the inflators, such as azide and non-azide pyrotechnic inflators, stored gas inflators and hybrid inflators to verify the analytic predictions and conclusions.

According to general knowledge, thermoplastics composites have relatively bad performances in comparison with thermoset composites. Nevertheless, the use of some new materials based of continuous glass fiber reinforced composites allows other perspectives for the application of thermoplastics composites. The continuous fiber reinforced TP composite, with E modulus up to 30000 MPa and tensile strength up to 400 MPa, will help us to reach more critical specifications. These kind of product are unfortunately unable to flow in ribs or every not drapable shape. To achieve this goal it is possible to combine with the high performances composites an other material wich is able to flow.

A demand for high-quality body panels has been needed in the automotive industry in recent years. However, the quality aspect has not been achieved by a number of companies because it has not been classified until now. It is the intention of this paper to outline the total surface-quality classification, particularly for automotive body panels. The surface classification will be compiled from a number of important sources in the automotive industry. The methodology will then be implemented in an Automotive Advisory System by which the design for manufacture philosophy will be controlled.

The Finite Element Analysis (FEA) is widely used in automotive industry for many applications, such as structural analysis, computational fluid dynamics (CFD), vibration behavior and acoustic properties, crashworthiness and, more recently, manufacturing process simulation. For all these FEA applications, accuracy is always a key issue. The analysis accuracy depends mainly on two factors: on one hand the FEA codes and on the other hand the definition of boundary conditions and material properties. Over the years, most FEA codes are well tested for accuracy through numerous benchmarks: therefore breakthroughs in further accuracy improvement from the aspect of FEA codes are difficult to achieve. On the other aspect, there is some room for FEA improvement by means of more accurate definition of material properties. In this paper, a new methodology for improving analysis accuracy by considering thickness variations of the component is proposed and validated using a structural body part.

The paper provides an overview of recent advances and applications of One Step FEM solvers in the automotive industry. The advances include, among other things, 1. Enhanced pre-processing (e.g. i. Integration with CAD Systems, ii. Automeshing), 2. Die processing geared functions (e.g. i. Automatic tipping, ii. Autoboundary conditions; to reduce effort in selecting the boundary conditions for achievement of a specific target strain in the panel), 3. More robust mechanics and realistic modeling of process (e.g. i. Autobending to accommodate membrane as well as bending and unbending effects, ii. Passive force formulation for a more realistic modeling of the external forces required to form the part, as well as iii. Curved binder capability; for more accurate prediction of binder effects), and 4. Enhanced post-processing and interpretation of results (e.g. i. Residual stresses, ii. Advanced FLD manipulation, iii.

This study compared laser and fine plasma technology for cutting typical electro-galvanized steel and aluminum automotive stampings. Comparisons were made of various aspects of cut quality, accuracy, disturbance of parent material, cycle time, and capital and operating costs. A sensitivity analysis was included to determine how different scenarios would impact the operating costs. It was found that both processes were capable of high quality cuts at 3800mm/min. Capital savings were achievable through the fine plasma system, but careful consideration of the specific application was essential. This work will allow for an advised comparison of options for sheet metal flexible cutting.