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A systematic study of the principles of a novel airbag inflator type, the‘Stored Liquefied Gas Inflator’,was performed by means of tank tests and high-speed cinematography. The new inflator is intended primarily for side-impact airbags and is based on the rapid flashing of liquefied CO2 . The new approach leads to a simple, inexpensive, environmentally attractive and safe device. Experiments were performed at different initial vessel and tank conditions and allowed the identification of the dominant physical phenomena in the components of the system, the definition of the design parameters, and the assessment of the performance. The optimal storage pressure was determined and the inflator’s behavior was observed to depend strongly on ambient temperature. The addition of small amounts of various organic liquids to the liquefied CO2 to a significant increase in performance. The potential of the novel inflator was assessed and suggestions to increase its performance were formulated.

A hybrid-inflator simulation program, H-ISP, has been developed to facilitate the evaluation of hybrid inflators for airbag systems. Based on fundamental principles of species mass and energy conservation and gas dynamics, this program can simulate the complex thermo-chemical processes of a hybrid inflator, including solid propellant combustion, single-phase or two-phase flow, multiple chemical species with temperature- and composition-dependent thermal properties, and heat transfer phenomena. In this paper, we present the theory, computer program structure and usage of H-ISP with an example.

At least 160 reports and documents have been written on rear impact crashes and occupant protection since 1964. Reviewing automotive crash safety research has identified the importance of reducing relative motion between the head, neck, and torso. Although rear impact accidents produce relatively few severe injuries, National Automotive Sampling System (NASS) Crashworthiness Data System (CDS) data base analysis has determined that rear impact accidents are second only to frontal impacts in terms of cost to society.

The absolute severity of a vehicular crash cannot be determined until the crash event is complete. However, airbag sensing systems are required to discriminate the severity of a crash event in the first milliseconds of an impact. Future airbag systems will require even more discrimination capability than current systems to provide separate deployment thresholds for advanced technologies such as multi-staged airbags and pre-tensioners and threshold shifting for belted and unbelted occupants. A prototype advanced sensing system has been tested to improve the severity measurement of an impact and offer multiple deployment thresholds without increasing the time required for event discrimination. Results of crash tests and the system's performance are discussed.

Adhesive joining is a common autobody subassembly technique especially for outer panels, where visible spot welding is objectionable. To accommodate mass production with the use of certain adhesives very high thermal gradient usually exists, which may result in panel dimensional distortion and variation. The temperature distribution over location and over time are monitored, and its impact to panel dimension is investigated. Experimental results on the effect of the distance between panel and induction coil on the panel temperature is obtained. The thermal induced shape distortion is simulated with a simplified FEA model. The approach to improvement of the induction curing process is discussed.

New environmental emissions standards for automotive assembly plants are currently under development, as mandated by the U.S. Clean Air Act Amendments of 1990. The implementation of these standards, anticipated to be finalized by the year 2000, will drive changes in both the technology and the operational procedures at the plants. While innovative paint technologies such as waterborne or powder paints can potentially improve plant environmental performance, introducing these materials into the production process can impact existing equipment and procedures. Understanding where and how to make these changes most effectively is a major challenge. Automotive assembly plants must balance reduction in emissions and production costs with maintaining the quality of the vehicle finish.

This study addresses the effects of sheet metal thickness on the frictional forces which develop when a strip of sheet metal is pulled through a draw bead configuration. This situation is represented by the draw bead simulator (DBS) test. Sheet steels of various thicknesses in the range 0.5-1.5 mm (0.02-0.06 inches) were used for the analysis. Generally, the coefficient of friction decreases with increasing sheet thickness when the conventional expression for coefficient of friction (μ) is used. A correction factor is proposed which normalizes the μ-value over a range of thicknesses. Also, suggested uses, limitations and improvements for the device are made.

Calorimetric measurements of the net heat input to the workpiece have been made to determine the effect of very high travel speeds on laser weld melting efficiency. Very high welding speeds are required in welding applications such as automotive where lasers are now applied extensively. Travel speeds as fast as 530 mm/s for continuous wave CO2 laser welding on 304 stainless steel have been examined in this study. Melting efficiency indicates what fraction of the laser power absorbed is used to produce melting rather than undesirable base metal heating. It was found that melting efficiency initially increased then slowly decreased as fusion zone dimensions changed. Dimensionless parameter correlations for melting efficiency based on heat flow theory have been presented for both 2D and 3D heat flow geometries. The levels of melting efficiency observed are close to the maximum values that are predicted with these correlations.

Process simulation for product and process design is currently being practiced in industry. However, a number of input variables have a significant effect on the accuracy and reliability of computer predictions. A study was conducted to evaluate the capability of finite element method (FEM) simulations for predicting part characteristics and process conditions in forming complex-shaped, industrial parts. In industrial applications, there are two objectives for conducting FEM simulations of the stamping process: (1) to optimize the product design by analyzing formability at the product design stage and (2) to reduce the tryout time and cost in process design by predicting the deformation process in advance during the die design stage. For each of these objectives, two kinds of FEM simulations are applied.

With the increased application of high strength steels in automotive body-in-white parts for weight reduction purposes, more emphasis is focused on springback as a major problem in stamping operations, in addition to panel breakage and wrinkling. Computer simulations using the finite element analysis (FEA) have been used to predict springback during early stages of die development processes to minimize potential springback related problems in production. However, the reliability of the springback simulation results relies directly on the accuracy of stress distributions from the forming simulation. Its complexity has brought many challenges not only to engineers and researchers in areas of FEA development and material modeling but also to FEA code end users. It is shown from this study that the springback simulation results vary with the yield criterion used in the forming simulation.

The analysis of localized necking is strongly dependent on the yield function. Numerous yield criteria have been advanced to characterize the plastic deformation of sheet materials. Among them Hill's 1948 and the fourth form of 1979 yield criteria are the most commonly used yield criterion. A new and user-friendly yield criterion was proposed by Hill in 1993, which uses five independent and easily-obtainable material parameters. The present investigation compares these three yield criteria in forming limit predictions based on the M-K approach. The M-K analysis based on Hill's 1993 yield criterion yields forming limit predictions for aluminum in good agreement with experimental data. All three yield criteria are found to provide acceptable predictions for aluminum killed steel.

A study on the FEA simulation of the springback prediction is summarized. The discussion is focused on the accuracy of the simulation and the factors that might contribute to the inaccurate results of the simulation. First, springback simulation results based on both 3 parameter Barlat plasticity model and transversely anisotropic plasticity model are studied. The numisheet'93 2D draw bending problem and a rail type automobile panel are selected for the material model study using LS-DYNA and LS-NIKE. The simulations based on different friction coefficients along the rolling direction and the transverse direction are studied using the DaimlerChrysler in-house FEA code Cform. A study is also performed to investigate the different springback behavior due to friction coefficient changes between the flat tooling area and the curved tooling area. Some other issues such as the dynamic effect and the penalty factor effect are also briefly discussed.

Adhesive bond-line read-through is a visible distortion of the substrate over a cured adhesive bond-line. Bond-line read-through deformations are primarily the result of a difference in the thermal expansion coefficients between the substrate and the adhesive. Substrate and adhesive thermo-mechanical properties play a large role in determining the severity of the distortions. This work describes the approaches taken to understand, predict, and minimize bond-line read-through. It presents a simple model which relates physical deflections in SMC (Sheet Molding Compound) sheets to the thermal stresses that arise as part of the adhesive cure cycle. Model predictions of both the shape and magnitude of the deflection over the bond-line will then be experimentally verified for two extreme types of bond designs. General approaches for reducing bond-line read-through by way of process, part design, and adhesive formulation modifications will be discussed.

Second-generation laser-marking technology (SGL) has proven to be a viable alternative to printed and adhesive labels for automotive products made from thermoplastic resins. Whether used for interior or underhood applications, virtually any thermoplastic automotive component that has a marking on it can be improved with this technology. Permanent, complex markings can be created that contain greater amounts of information on surfaces with complex curves. Furthermore, products now can be marked at any time in the manufacturing process, including at or near shipping, in a variety of languages and/or with indexed information to assist inventory control for automotive OEMs or suppliers. This technology helps reduce scrap rates due to poor printing or misplaced labels, and does not detract from the recycling of thermoplastic products. The greatest benefits of SGL are derived when the technology is used by design engineers early in the concept and planning stages of new product development.

The industrial current design approach use more and more calculation tools to design technical parts. The more the properties of material are well known, the more the calculation is efficient and reliable. One of the way to recover real properties of a material is to measure them with an ultrasonic technique. This method is based on the fact that ultrasonic wave velocity depends on the material in which it goes through. Ultrasonic technique appears then like a reliable device to study the properties of a material directly on an injected part without destroying it, and can be used in laboratory to characterize plastic or metallic materials.

Tomorrow's winning powertrain solutions reside in those technology combinations providing optimized propulsion systems with zero emissions and no cost or performance penalty compared with today's vehicles. The recent Kyoto Protocol for CO2 reduction and the California Air Resources Board (CARB) thrust for zero emission vehicles along with the European Regulatory community, motivate car manufacturers to adopt new light body structures with low aerodynamic drag coefficients, low-rolling resistance and the highest efficiency powertrains. The environmental equation expresses car manufacturers aptitude and desire to create zero emission vehicles at acceptable levels of performance unlike limited range electrical powered vehicle products. The cheapest solution to the environmental equation remains the conventional internal combustion engine ($30 to $50 per kW).

Generally, ‘direct glazing’ is the bonding method used to install the automobile front and rear window glass. This bonding method is used for not only the safety of holding the glass in place but also for the marketability of appearance and precision, i.e. its fitting quality. In order to rationalize this bonding work process, sealant materials were developed with the function of temporarily supporting the glass, molding design specifications were developed with the function of spacer, and high-precision glass adhesion robots were developed (by Honda Engineering Co., Ltd.) in order to further raise the fitting quality. All this development made it possible to eliminate auxiiary fitting parts and to completely automate the glass bonding work process. As a result, the marketability of the vehicle is improved and the work process simplified to reduce costs.

The cost–effectiveness of using alternative fuels (AF) versus a conventional fuel (gasoline) in light duty vehicles is traditionally presented with a simple analysis on what can best be described as “one sheet of paper.” Unfortunately, oversimplification of the cost analysis can lead to extensive errors in the results and misleading cost and/or benefit conclusions. An extensive model for analyzing the costs and benefits of using alternative fuels has been developed which allows in–depth modeling of major characteristics of a single vehicle (or an entire fleet) which uses alternative fuel. Net present value (NPV) theorem financial modeling has been used to compute a true lifetime cost of ownership. An important output of the model is the required fuel spread needed in order to obtain a NPV of zero dollars, indicating that the savings resulting from using the alternative fuel offset the cost of the additional AF components.

The goal of this paper is to define and quantify the contribution of used parts to vehicle recycling. In 1997, this research was stimulated when the Federal Trade Commission opened hearings on the definition of recycling. At this time, general facts about the automotive recycling industry and reuse of automotive parts were hard to find. This study's goal was to produce actual data on the contribution of reuse to vehicle recycling and to answer questions about the industry. Can accurate reuse measurements be calculated with data collected from recyclers? What should be the expected average performance of a company in the recycling industry? What effect can reuse have on landfill avoidance? The results of this study established that the sale and reuse of used parts played a significant role in vehicle recycling. The Automotive Recyclers Association, representing the existing industry, testified at the FTC hearings using preliminary results from this study.

The slush molding process is still used by various automotive suppliers to produce dashboard skins. This skin production process allows freestyle for the conception of dashboards. In this process, PVC is still mainly used. Plastic Omnium Auto Interior has developed a TPO formulation for the slush molding process to replace the PVC material. This TPO formulation is based on an alloy of different polyolefins. This alloy is produced by a compounding operation and then the pellets obtained are cryogenically grinded to get a powder, or micropelletized under water but still under development. The TPO slush molding skin has to be lacquered to reach the automotive industry requirements: good heat resistance or color rubbing resistance, for example. To be environmentally friendly, Plastic Omnium Auto Interior developed a water based coating system in partnership with coating suppliers.