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This study concerns a dissimilar materials joining technique for aluminum (Al) alloys and steel for the purpose of reducing the vehicle body weight. The tough oxide layer on the Al alloy surface and the ability to control the Fe-Al intermetallic compound (IMC) thickness are issues that have so far complicated the joining of Al alloys and steel. Removing the oxide layer has required a high heat input, resulting in the formation of a thick Fe-Al IMC layer at the joint interface, making it impossible to obtain satisfactory joint strength. To avoid that problem, we propose a unique joining concept that removes the oxide layer at low temperature by using the eutectic reaction between Al in the Al alloy and zinc (Zn) in the coating on galvanized steel (GI) and galvannealed steel (GA). This makes it possible to form a thin, uniform Fe-Al IMC layer at the joint interface. Welded joints of dissimilar materials require anticorrosion performance against electrochemical corrosion.

This study examined methods of machining a microsurface texture on the surface of the rolling elements of a toroidal continuously variable transmission (CVT) for improving the traction coefficient. The microsurface texture of the toroidal surfaces consists of tiny circumferential grooves (referred to here as micro grooves) and a mirror-like surface finish similar to the rolling surface of bearings. Hard turning with a cubic boron nitride (cBN) cutting tool, grinding with a cBN wheel and micro forming were applied to machine the micro grooves. The results made clear the practical potential of each method. A micro forming device was also developed for use in actual production. A mirror-like surface finish and micro crowning of the convex portions of the microsurface texture were simultaneously executed by superfinishing them with a fine-grained elastic superfinishing stone.

In 2006, Nissan began limited leasing of the X-TRAIL FCV equipped with their in-house developed Fuel Cell (FC) stack. Since then, the FC stack has been improved in cost, size, durability and cold start-up capability with the aim of promoting full-scale commercialization of FCVs. However, reduction of cost and size has remained a significant challenge because limited mass transport through the membrane electrode assembly (MEA) has made it difficult to increase the rated current density of the FC. Furthermore, it has been difficult to reduce the variety of FC stack components due to the complex stack configuration. In this study, improvements have been achieved mainly by adopting an advanced MEA to overcome these difficulties. First, the adoption of a new MEA and separators has improved mass transport through the MEA for increased rated current density. Second, an integrated molded frame (IMF) has been adopted as the MEA support.

This paper proposes a new hierarchical optimization technique for the vehicle body structure, by combining topology optimization and shape optimization based on the traction method. With the proposed approach, topology optimization is first performed on the overall allowable design domain in 3D. The surface is extracted from the optimization result and converted to a thin shell structure. Shape optimization based on the traction method is then applied to obtain an overall optimal body shape. In the shape optimization process, iterative calculations are performed in the course of consolidating parts by deleting those whose contribution is small. The result obtained by applying this method to the front frame structure of a vehicle is explained. The resultant optimal shape has stiffness greater than or equal to the original structure and is 35% lighter. This confirms the validity of the proposed technique. It was found, however, that some issues remain to be addressed.

A light weight,multifunctional plastic reinforcement has been developed for the outer body panels of vehicles. This new plastic reinforcement,composed mainly of polyvinylchloride resin, epoxy resin and an organic foaming agent, provides a 63% weight reduction over conventional plastic reinforcements, while adding the damping function to outer body panels. This paper introduces the process followed in developing the new plastic reinforcement and describes its characteristics. This new plastic reinforcement is already employed in the Nissan S-Cargo model, and it will be adopted in other passenger car models to be released in the near future.

The life of an automotive engine is often limited by the ability of its components to resist wear. Zinc dialkyldithiophosphate (ZDDP) is an engine oil additive that reduces wear in an engine by forming solid antiwear films at points of moving contact. The effects of this additive are fairly well understood, but there is little theory behind the kinetics of antiwear film formation and removal. This lack of dynamic modeling makes it difficult to predict the effects of wear at the design stage for an engine component or a lubricant formulation. The purpose of this discussion is to develop a framework for modeling the formation and evolution of ZDDP antiwear films based on the relevant chemical pathways and physical mechanisms at work.

In general, the improvement of vehicle body stiffness involves a trade-off with the body weight. The objective of this research is to derive the lightest-weight solution from the original vehicle model by finding the optimized spot-weld layout and body panel thickness, while keeping the body stiffness and number of spot welds constant. As the first step, a method of deriving the optimal layout of spot welds for maximizing body stiffness was developed by applying the topology optimization method. While this method is generally used in shape optimization of continuous solid structures, it was applied to discontinuous spot-weld positions in this work. As a result, the effect of the spot-weld layout on body stiffness was clarified. In the case of the body used for this research, body stiffness was improved by about 10% with respect to torsion and vertical and lateral bending.

This paper presents a new method for calculating optical flow using data from a high frame-rate camera. We focused on a feature of image data captured with a high frame-rate camera in which objects do not move more than one pixel between successive frames. This approach eliminates repetitive processing for object identification among frames taken at different sampling times. High-speed processing hardware architecture was designed with sequential processing only, and the algorithm was implemented in a field programmable gate array. The resultant unit can calculate optical flow for a 640×120 pixel size image with a 480-Hz processing cycle and 0.5-μsec processing latency.

In the initial design stage, it is important to discuss what kind of body concept is effective from a viewpoint of environment burden reduction. This paper describes the importance of both weight reduction and recycling through conducting LCA (Life Cycle Assessment) for four kinds of body structures. In addition, using each software, DFMA (Design for Manufacture and Assembly), DFE (Design for Environment) and LCA to parts unit, each effectiveness was discussed through the assessment of the material-hybrid body.

Vehicle weight reduction, reduced costs and improved safety performance are the main driving forces behind material selection for automotive applications. These goals are conflicting in nature and solutions will be realized by innovative design, advanced material processing and advanced materials. Advanced high strength steels are engineered materials that provide a remarkable combination of formability, strength, ductility, durability, strain-rate sensitivity and strain hardening characteristics essential to meeting the goals of automotive design. These characteristics act as enablers to cost- and mass-effective solutions. The ULSAB-AVC program demonstrates a solution to these conflicting goals and the advantages that are possible with the utilization of the advance high strength steels and provides a prediction of the material content of future body structures.

A plastic intake manifold has been developed for the new QR engine. This manifold has an intricate shape owing to its performance and layout requirements. The die slide injection (DSI) method was selected to manufacture this complicated shape using the world's first application of a common mold forming technique for a three-piece structure. This paper describes the manufacturing technology and the measures adopted to ensure the strength of welded parts, which is a key point of this method. The benefits obtained by applying this plastic intake manifold to the new engine are also described.

Hydrofrorming is an efficient forming process to produce automotive parts for reducing weight of cars. In order to reduce the period of development of hydrofoming parts, numerical simulation using FEM is applied to evaluate formability. A pipe needs to be bent before hydroforming for forming complicated shape parts. A pipe bending process is also necessary to FEM simulation. In this paper, a highly effective method to create a bent pipe FEM model based on geometrical changing between a pipe before and after bending is proposed. The widely used draw bending process is supposed to be applied. The method can construct the model in a short time. Therefore total computation time can be reduced drastically. The effects of number of integration points and elements to the computed results and springback prediction after bending are also investigated. The proposed method are applied to a actual part, the computed results are in good agreement with the experimental results.

Car makers are working hard today to shorten development and production lead times through the use of flexibile manufacturing systems(FMSs)to meet diversified and individualized customer requirements. To achieve this goal, Nissan has been developing many kinds of new technologies and systems such as: (1) the intelligent body assembly system for body assembly processes; (2) a press die stamping simulation method and unified database for press die manufacturing; (3) a robot and facility teaching system using CAD data; (4) an automated assembly line for trim and chassis assembly operations. These new FMS methods have been implemented in many manufacturing areas, including the stamping shop, body assembly shop, painting shop and trim and chassis shop. This paper focuses mainly on the intelligent body assembly system as a typical example of the new production systems and technologies being developed at Nissan.

Recent years have seen remarkable advances in the development and diffusion of numerical analysis techniques using the finite element method for examining vehicle crashworthiness. The importance of numerical analysis in vehicle development work has also increased. One reason for this is that the use of numerical analysis makes it possible to study crash phenomena in detail based on calculated data which can not be obtained experimentally. In this study, the non-linear dynamic finite element program PAM-CRASH was applied to a vehicle frontal crash simulation to calculate the body deformation modes, the force transmitted at different sections of the body structure and the internal energy accumulation of each component. The results obtained provide a quantitative explanation of the deformation mechanism of the body structure.

Evaluations of dummy injury readings obtained in regulatory crash tests and new car assessment program tests provide indices for the development of crash safety performance in the process of developing new vehicles. Based on these indices, vehicle body structures and occupant restraint systems are designed to meet the required occupant injury criteria. There are many types of regulatory tests and new car assessment program tests that are conducted to evaluate vehicle safety performance in side impacts. Factoring all of the multiple test configurations into the development of new vehicles requires advanced design capabilities based on a good understanding of the mechanisms producing dummy injury readings. In recent years, advances in computer-aided engineering (CAE) tools and computer processing power have made it possible to run simulations of occupant restraint systems such as side airbags and seatbelts.

There are strong demands for vehicle weight reductions so as to improve fuel economy. At the same time, it is also necessary to ensure crash safety. One effective measure for accomplishing such both requirements conflicting each other is to apply advanced high strength steel (AHSS) of 780 MPa grade or higher to the vehicle body. On the other hand, higher strength steels generally tend to display lower elongation causing formability deterioration. Nissan Motor Corporation have jointly developed with steel manufacturers a new 980 MPa grade AHSS with high formability with the aim of substituting it for the currently used 590 MPa grade high-tensile steel. Several application technologies have been developed through the verifications such as formability, resistance spot weldability, crashworthiness, and delayed fracture.

A novel system for the forming of three dimensional sheet metal parts is described that can form a variety of part shapes without the need for fixed tooling, and given only geometry (CAD) information about the desired part. The central elements of this system are a tooling concept based on a programmable discrete die surface and closed-loop shape control. The former give the process the degrees of freedom to change shape rapidly, and the latter is used to insure that the correct shape is formed with a minimum of forming trials. A 540 kN (60 ton) lab press has been constructed with a 0.3 m (12 in) square pair of discrete tools that can be rapidly re-shaped between forming trials. The shape control system uses measured part shapes to determine a shape error and to correct the tooling shape. This correction is based on a unique “Deformation Transfer Function” approach using a spatial frequency decomposition of the surface.

In this paper we investigate the optimal forming of conical cups of AL 2008-T4 through the use of real-time process control. We consider a flat, frictional binder the force of which can be determined precisely through closed-loop control. Initially the force is held constant throughout the forming of the cup, and various levels of force are tested experimentally and with numerical simulation. Excellent agreement between experiment and simulation is observed. The effects of binder force on cup shape, thickness distribution, failure mode and cup failure height are investigated, and an “optimal” constant binder force is determined. For this optimal case, the corresponding punch force is recorded as a function of punch displacement and is used in subsequent closed-loop control experiments. In addition to the constant force test, a trial variable binder force test was performed to extend the failure height beyond that obtained using the “optimal” constant force level.

Draw beads are widely utilized as a mechanism for providing proper restraining force to a sheet in a forming operation. In this paper, numerical simulations using the nonlinear finite element method are conducted to model the process of drawing a sheet through various draw bead configurations to study the mechanics of draw bead restraint. By examing the sensitivity of the draw bead restraining force due to the change of the draw bead penetration, the work shows that the penetration has the potential to be a very good element for varying and controlling restraining force during the process. A closed-loop feedback control of draw bead penetration using a proportional-integral controller is achieved by the combination of the original finite element simulation and a special element which links penetration to a pre-defined restraining force trajectory.

Surface roughness of steel sheet for automotive use is one of the most important control items, because the surface roughness influences image clarity of painted surface, press formability and easiness in handling during manufacturing and processing of steel sheets. Laser texturing technology is introduced into a roll finishing process of cold rolling, and new type of regular surface roughness profile can be processed on the surface of steel sheets. Effective application method of this technology is investigated at the present day. In Japan, Laser-textured dull steel sheets are used for outer-panels of automotive body as the first application. And image clarity after painting of outer panels has been successful in improving. Nowadays, Laser texturing technology is actually used for manufacturing the high image clarity steel sheets, and they are manufactured in large quantities. Another application of Laser texturing technology is for the inner parts which require pressformability.