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Technical Paper

Development and Application of a Shape-Topology Optimization System Using a Homogenization Method

The shape and topology optimization method using a homogenization method is a powerful design tool because it can treat topological changes of a design domain. This method was originally developed in 1988 [1] and have been studied by many researchers. However, their scope of application in real vehicle design works has been limited where a design domain and boundary conditions are very complicated. The authors have developed a powerful optimization system by adopting a general purpose finite element analysis code. A method for treating vibration problems is also discussed. A new objective function corresponding to a multi-eigenvalue optimization problem is suggested. An improved optimization algorithm is then applied to solve the problem. Applications of the optimization system to design the body and the parts of a solar car are presented.
Technical Paper

Analysis of Thermal Fatigue Resistance of Engine Exhaust Parts

The thermal fatigue resistance of engine exhaust system parts has conventionally been evaluated in thermal fatigue tests conducted with a restrained specimen. However, the test results have not always been consistent with data obtained in engine endurance tests. Two new evaluation methods have been developed to overcome this problem. One is a method of predicting thermal fatigue life on the basis of nonlinear elastic and plastic thermal analyses performed with a finite element model and the ABAQUS program. The other is a method of evaluating exhaust system parts using an exhaust system simulator. This paper describes the concepts underlying the two methods and their relative advantages.
Technical Paper

Establishment of a Method for Predicting Cam Follower Wear in the Material Development Process

Many studies have been reported concerning fundamental tribological research aimed at reducing the severe valve train wear that occurs in internal combustion engines. In this paper, cam follower wear was theoretically and experimentally analyzed at the material development stage. Statistical methods have been applied to practical use in determining the material properties quantitatively. Based on the results, a method for predicting cam follower wear has been derived which has made it possible to develop new valve train systems more efficiently. Further, a guideline for developing new wear resistant materials was also clarified. Finally, the precision high chrominum cast iron rocker arm is described, along with its application to a new NISSAN high-performance 4-cylinder DOHC engine, as an example of the use of this method to develop new wear-resistant materials.
Technical Paper

Pre-Processor for Finite Element Analysis and Its Application to Body Structure

An easy-to-use pre-processor system through which finite element analysis can be applied to routine design works is needed. We have developed a general purpose pre-processor system to be used for body structures and a number of other automobile parts. It can apply to shell, beams and/or solid structures, and has functions to generate input data, to check structures by drawing and to calculate the section constants of beam elements. It has become possible to discuss the detail design of structures because we could obtain a fine mesh models easily from complicated structures such as a automobile body.
Technical Paper

Reduction of Transaxle Gear Noise by Gear Train Modification

As the quietness of vehicles has been continually improved in recent years, there have been stronger requirements to reduce transmission gear noise and thereby improve transmission quality. So far efforts to achieve quieter gears have generally focused on ways of reducing the excitation forces of individual gears. In addition to these traditional methods, there is a greater need today to adopt a new approach to gear noise reduction in which improvements are made to the gear train itself as the transmitter of vibration in the transmission. This paper describes the systematic approach taken to reduce the overall gear noise of the new RE4F04A four-speed automatic transaxle.The cross-sectional view is shown in Fig. 1. The vibration characteristics of this automatic transaxle were first identified by finite element analysis, and an investigation was made of a gear train structure that would be effective in reducing gear noise.
Technical Paper

An Investigation of Steering Column Collapse Behavior Using Finite Element Analysis

For the purpose of protecting the driver from injury in a crash, a safety standard has been established that specifies the allowable impact force when the driver hits the steering wheel as a result of an impact. In this work, an investigation was lade of steering column collapse behavior in which the steering column was constructed such that the crash energy was absorbed by the bending and tearing of a thin steel plate. As a result, a finite element analysis method has been developed for conducting an impact analysis using a ductile fracture model of the thin plate. This method makes it possible to predict the collapse behavior of the steering column and the deceleration that develops on the body block of the safety standard test model.
Technical Paper

A Study of a Method for Predicting the Risk of Crossing-Collisions at Intersection

The probability or risk of traffic accidents must be estimated quantitatively in order to implement effective traffic safety measures. In this study, various statistical data and probability theory were used to examine a method for predicting the risk of crossing-collisions, representing a typical type of accident at intersections in Japan. Crossing-collisions are caused by a variety of factors, including the road geometry and traffic environment at intersections and the awareness and intentions of the drivers of the striking and struck vehicles. Bayes' theorem was applied to find the accident probability of each factor separately. Specifically, the probability of various factors being present at the time of a crossing-collision was estimated on the basis of traffic accident data and observation survey data.
Technical Paper

Prediction and Analysis Technology Development for Impact Noise

In order to enhance product attraction, it is important to reduce the impact noise when a vehicle go over bumps such as bridge joints. Vehicle performance to transitional noise phenomena is not yet analyzed well. In this paper, a prediction method is established by vector composition and inverse Fourier transform with the combination of Multibody Dynamics (MBD) and FEM. Also, a root cause analysis method is established with the following three mechanism analysis methods; transfer path analysis, mode contribution analysis, and panel contribution analysis.
Technical Paper

Variable Characteristic Permanent Magnet Motor for Automobile Application

This paper describes a variable magnetomotive force interior permanent magnet (IPM) machine for use as a traction motor on automobiles in order to reduce total energy consumption during duty cycles and cut costs by using Dy-free magnets. First, the principle of a variable magnetomotive force flux-intensifying IPM (VFI-IPM) machine is explained. A theoretical operating point analysis of the magnets using a simplified model with nonlinear B-H characteristics is presented and the results are confirmed by nonlinear finite element analysis. Four types of magnet layouts were investigated for the magnetic circuit design. It was found that a radial magnetization direction with a single magnet is suitable for the VFI-IPM machine. Magnetization controllability was investigated with respect to the magnet thickness, width and coercive force for the prototype design. The estimated variable motor speed and torque characteristics are presented.
Technical Paper

A Model Based Design Methodology for Variable Flux PMSMs to Obtain Desired Speed-Torque Characteristics

Variable flux permanent magnet synchronous machines (VFPMSMs) have been designed by using finite element analysis (FEA) to evaluate speed-torque capability considering requirement for magnetization state (MS) manipulation. However, due to its unique characteristic to change the MS, numerous combinations of design parameters need to be evaluated to achieve a final design. To accelerate the design process, this paper presents a method that consists of an equivalent magnetic circuit model and a process to obtain magnet width and thickness that satisfy target maximum torque and power factor (P.F.) capability. This model includes magnet operating point analysis under given magnet width and thickness condition to achieve target MS and avoid demagnetization at full load. This analysis provides desired stator magnetomotive force, magnet and stator induced flux linkage. Therefore, expected torque and P.F. capability is calculated.
Technical Paper

Finite Element Analysis of Hard and Soft Tissue Contributions to Thoracic Response: Sensitivity Analysis of Fluctuations in Boundary Conditions

Thoracic trauma is the principle causative factor in 30% of road traffic deaths. Researchers have developed force-deflection corridors of the thorax for various loading conditions in order to elucidate injury mechanisms and to validate the mechanical response of ATDs and numerical human models. A corridor, rather than a single response characteristic, results from the variability inherent in biological experimentation. This response variability is caused by both intrinsic and extrinsic factors. The intrinsic factors are associated with individual differences among human subjects, e.g., the differences in material properties and in body geometry. The extrinsic sources of variability include fluctuations in the loading and supporting conditions in experimental tests.
Technical Paper

Study of a Method for Reducing Drum Brake Squeal

Since the modal density of a drum brake system is higher than that of a disc brake system, it is very difficult to identify the cause of brake squeal. The causes of squeal were examined by both complex eigenvalue analysis and experimental analysis. It was confirmed that a complex eigenvalue analysis of a finite element model, a technique so far generally applied to disc brake squeal studies, was effective in analyzing squeal problems of drum brakes.
Technical Paper

Effective Numerical Simulation Tool for Real-World Rollover Accidents by Combining PC-Crash and FEA

With SUVs and minivans accounting for a larger share of the US market in the past decade, rollover accidents have drawn greater attention, leading to more active research from different perspectives. This ranges from investigations for elucidating the basic causes and mechanisms of rollover accidents to studies of more advanced occupant protection measures. As the phenomenon of a rollover accident is longer in duration than frontal, side or rear impacts, it is relatively difficult [1] to simulate such accidents for experimental verification and also for proper evaluation of occupant restraint system performance. In this work, we focused on the trip-over type, which occurs most frequently, and performed simulations to reproduce real-world rollover accidents by combining PC-Crash and FEA.
Technical Paper

Method of Fatigue Life Estimation for Arc–Welded Structures

Two working groups in the JSAE Committee of Fatigue–Reliability Section1 are currently researching the issue of fatigue life by both experimental and the CAE approach. Information regarding frequent critical problems on arc–welded structures were sought from auto–manufacturers, vehicle component suppliers, and material suppliers. The method for anti–fatigue design on arc–welded structures was established not only by a database created by physical test results in accordance with the collected information but also with design procedure taking Fracture–Mechanics into consideration. This method will be applied to vehicle development as one of the virtual laboratories in the digital prototype phase. In this paper, both the database from bench–test results on arc welded structures and FEA algorithm unique to JSAE are proposed some of the analysis results associated with the latter proposal are also reported.
Technical Paper

FEM analysis on gap control mechanism in batting process of tailored blank sheets production

Recently tailored blank sheets are widely and very often applied to car body's panels in order to reduce weight and number of automobile parts. The tailored blank sheets are produced by welding more than two metal sheets. The gap between edges of blank sheets before laser welding should be controlled for obtaining good quality tailored blank sheets. Therefore control of gap within 0.1mm between batting two blank sheets for production is one of main subjects for producing tailored blank sheets. This report presents not only a new mechanism on gap control but also a development of Finite Element Method (FEM) analysis for prediction of gap. The new mechanism has been applied successfully to produce good quality tailored blank sheets. The gap prediction simulation can reduce the time for gap control apparatus design.
Technical Paper

A Study on the Cyclic Plastic Zone Size Method, ω*, for Digital Fatigue Life Prediction of Arc-Welded Joints

Various prediction methods have been proposed for evaluating the fatigue life of welded joints by combining finite element analysis (FEA) with an experimental database. However, to obtain more universal and accurate fatigue life predictions, it is necessary to have criteria for making integrated evaluations of the fatigue strength of welded joints. This paper presents a study that focuses on the local cyclic plastic zone size (ω*) as the criterion of fatigue strength and investigates its validity. The definition of ω* was given by the relationship between the stress state at the notch tip and the elastic strain which was defined along the strain-life fatigue curve (ε - N diagram) of a base metal. As a result of using ω*, it was found that an integrated fatigue life prediction was possible to a certain extent for notch and arc-welded joint specimens.
Technical Paper

Work Hardening and Strength Analysis of Steel Structure with Special Cross Section

This paper presents the results of a strength analysis of a newly developed steel structure featuring a special cross section achieved with the hydroforming process that minimizes the influence of springback. This structure has been developed in pursuit of further weight reductions for the steel body in white. A steel tube with tensile strength of 590 MPa was fabricated in a low-pressure hydroforming operation, resulting in thicker side walls. The results of a three-point bending test showed that the bending strength of the new steel structure with thicker side walls was substantially increased. A finite element crush analysis based on the results of a forming analysis was shown to be effective in predicting the strength of the structure, including the effect of work hardening.
Technical Paper

Vehicle Cornering and Braking Behavior Simulation Using a Finite Element Method

This paper presents a vehicle dynamic simulation using a finite element method for performing more accurate simulations under extreme operating conditions with large tire deformation. A new hourglass control scheme implemented in an explicit finite element analysis code LS-DYNA(1) is used to stabilize tire deformation. The tires and suspension systems are fully modeled using finite elements and are connected to a rigid body that represents the whole vehicle body as well as the engine, drive train system and all other interior parts. This model is used to perform cornering and braking behavior simulations and the results are compared with experimental data. In the cornering behavior simulation, the calculated lateral acceleration and yaw rate at the vehicle's center of gravity agree well with the experimental results. Their nonlinear behavior is also well expressed.
Technical Paper

Application of Hydroforming Simulation on Development of Automobile Parts

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.
Technical Paper

Automatic Transmission Shift Schedule Control Using Fuzzy Logic

The use of automatic transmissions is continually increasing because of their ease of operation. Transmission performance requirements that have become more important in recent years include smooth shift quality and a shift schedule that matches the driver's intentions. An electronically controlled automatic gearbox, which sets the shift schedule according to the vehicle speed and throttle valve opening, provides a dramatic improvement in shift quality over its hydraulically controlled counterpart. However, even with an electronically controlled automatic transmission, shift hunting occurs when driving uphill or towing an object Based on the use of fuzzy logic, a technique has been developed for estimating running resistance, represented by the road gradient. This technique has been incorporated in a new shift schedule control method that eliminates shin hunting Research is now under way on a fuzzy logic technique for inferring the driver's intention to accelerate