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Metal additive manufacturing has high potential to produce automobile parts, due to its shape flexibility and unique material properties. On the other hand, residual stress which is generated by rapid solidification causes deformation, cracks and failure under building process. To avoid these problems, understanding of internal residual stress distribution is necessary. However, from the view point of measureable area, conventional residual stress measurement methods such as strain gages and X-ray diffractometers, is limited to only the surface layer of the parts. Therefore, neutron which has a high penetration capability was chosen as a probe to measure internal residual stress in this research. By using time of flight neutron diffraction facility VULCAN at Oak Ridge National Laboratory, residual stress for mono-cylinder head, which were made of aluminum alloy, was measured non-distractively. From the result of precise measurement, interior stress distribution was visualized.

A compact intelligent power unit capable of being installed under the rear seating was developed for the 2018 model year Accord Hybrid that is to be equipped with the SPORT HYBRID Intelligent Multi Mode Drive (i-MMD) system. The space under the rear seat features multiple constraints on dimensions. In the longitudinal direction, it is necessary to attempt to help ensure occupant leg room and to position the fuel tank; in the vertical direction, it is necessary to attempt to help ensure occupants comfort and a minimum ground clearance; and in the lateral direction, it is necessary to avoid the position of the body side frames and the penetrating section of the exhaust pipe. The technologies described below were applied in order to reduce the size of components, making it possible to position the IPU amid these constraint conditions.

This research investigated the mechanism of the effects of hydraulic dampers, which are attached to vehicle body structures and are known by experience to suppress vehicle body vibration and enhance ride comfort and steering stability. In investigating the mechanism, we employed quantitative data from riding tests, and analytical data from simplified vibration models. In our assessment of ride comfort in riding tests using vehicles equipped with hydraulic dampers, we confirmed effects reducing body floor vibration in the low-frequency range. We also confirmed vibration reduction in unsprung suspension parts to be a notable mechanical characteristic which merits close attention in all cases. To investigate the mechanism of the vibration reduction effect in unsprung parts, we considered a simplified vibration model, in which the engine and unsprung parts, which are rigid, are linked to the vehicle body, which is an elastic body equipped with hydraulic dampers.

Initiation and propagation of ductile fractures in crashed automotive components made from high strength steels are investigated in order to understand the mechanism of fracture propagation. Fracture of these components is often prone to occur at the sheet edge in a strain concentration zone under crash deformation. The fracture then extends intricately to the inside of the structure under the influence of the local stress and strain field. In this study, a simple tensile test and a 3-point bending test of high strength steels with tensile strengths of 590 MPa and 1180 MPa are carried out. In the tensile test, a coupon having a hole and a notch is deformed in a uniaxial condition. The effect of the notch type on the strain concentration and fracture behavior are investigated by using a digital imaging strain measurement system.

Combined Brake System for small motorcycles has been developed. In small motorcycles, some models have a hydraulic disc brake both in the front and rear wheels but many of them have a hydraulic disc front brake and a mechanical drum rear brake. Accordingly, it was necessary to develop a new system to link the hydraulic system with the mechanical system to allow an application of Combined Brake System to these models. In this paper, a CBS having a new configuration is described where a disc brake and a drum brake are linked in a simple lever structure of an input force distributor, and an inhibitor spring at the foot pedal. With this mechanism equipped, the distribution of brake forces is controlled. When a large input force is applied, a large proportion of brake force is applied to the front brake to obtain adequate deceleration. When a mild input force is applied, which is frequently operated, the brake force proportion is large in the rear compared to the front.

The strength characteristic of CFRP composite materials is often dependent on the internal micro-structural fracture mode. When performing a simulation on composite structures, it is necessary to take the fracture mode into account, especially in an automobile body structure with a complex three-dimensional shape, where inter-ply fractures tend to appear due to out-of-plane load inputs. In this paper, an energy-based inter-ply fracture model with fracture toughness criteria, and an intra-ply fracture model proposed by Ladeveze et al. were explained. FEM analyses were performed on three-dimensional test specimens applying both fracture models and the simulated results were compared with experimental ones. Reproducibility of the fracture mode was confirmed and the importance of combining both models was discussed.

The process for setting the marketability targets and achievement methods for automotive interior quietness (as related to air borne noise above 400Hz, considered the high frequency range) was established. With conventional methods it is difficult to disseminate the relationship between the performance of individual parts and the overall vehicle performance. Without new methods, it is difficult to propose detailed specifications for the optimal sound proof packages. In order to make it possible to resolve the individual components performance targets, the interior cavity was divided into a number of sections and the acoustic performance of each section is evaluated separately. This is accomplished by evaluating the acoustical energy level of each separate interior panel with the unit power of the exterior speaker excitation. The applicability of the method was verified by evaluating result against predicted value, using the new method, during actual vehicle operation.

In this study, we developed a simulation method for rough road running condition to reproduce the behaviors of a vehicle body and to precisely estimate the input loads to the frame. We designed the simulation method focusing on a front fork model and a rider model optimized for this type of analysis. In the suspension model development, we conducted detailed measurement of the suspension characteristics on a test bench. Based on the yielded results, the friction force, as well as the spring reaction force and the damping force, was reproduced in the suspension model. The friction of the suspension varies depending on the magnitude of the reaction force associated with bending and this effect was also implemented in the model. Regarding the rider model, the actual behavior of a rider was investigated through the recorded motion video data and used to define the necessary degrees of freedom.

In brake squeal analyses using FE models, minimizing the discrepancies in vibration characteristics between the measurement and the simulation is a key issue for improving its reproducibility. The discrepancies are generally adjusted by the shape parameters and/or material properties applied to the model. However, the discrepancy cannot be easily adjusted, especially, for the vibration characteristic of the disc model of a motorcycle. One of the factors that give a large impact on this discrepancy is a thermal history of the disc. That thermal history includes the one experienced in manufacturing process. In this paper, we examine the effects of residual stress on the natural frequency of motorcycle discs. The residual stress on the disc surface was measured by X-ray stress measurement method. It was followed by an eigenvalue analysis. In this analysis, we developed a unique method in which the residual stress was substituted by thermal stress.

Japanese accident statistics show that despite the decreasing trend of the overall traffic fatalities, more than 1,000 pedestrians are still killed annually in Japan. One way to develop further understanding of real-world pedestrian accidents is to reconstruct a variety of accident scenarios dynamically using computational models. Some of the past studies done by the authors' group have used a simplified vehicle model to investigate pedestrian lower limb injuries. However, loadings to the upper body also need to be reproduced to predict damage to the full body of a pedestrian. As a step toward this goal, this study aimed to develop a simplified vehicle model capable of reproducing pedestrian full-body kinematics and pelvis and lower limb injury measures. The simplified vehicle model was comprised of four parts: windshield, hood, bumper and lower part of the bumper. Several different models were developed using different combinations of geometric and stiffness representation.

The validity of evaluating FlexPLI peak injury measures has been shown by the correlation of the peak measures between a human FE model and a FlexPLI FE model. However, comparisons of tibia bending moment time histories (BMTHs) between these models show that the FlexPLI model exhibits a higher degree of oscillatory behavior than the human model. The goal of this study was to identify potential improvements to the FlexPLI such that the legform provides more biofidelic tibia BMTHs at the normal standing height. Impact simulations using a human FE model and a FlexPLI FE model were conducted against simplified vehicle models to compare tibia BMTHs. The same series of impact simulations were conducted using the FlexPLI models that incorporated potential measures to identify measures effective for further enhancement of the biofidelity. An additional analysis was also conducted to investigate the key factor for minimizing the oscillation of the tibia BMTH.

This paper describes the development of non-contacting detection type torque sensor that realizes a small lost motion with light weight and low cost. Pedal-equipped electric vehicles are becoming popular in recent years. In those vehicles, torque sensors are usually necessary for measuring the pedaling force to determine the motor torque. We applied an integrated sensing structure and a non-contacting scheme utilizing inverse-magnetostrictive material to minimize the lost motions. As for the sensing material, nickel-iron alloy plating was used to obtain a wide dynamic range. In the tests using the actual structure, the output linearity deterioration occurred because of the strain distribution dispersion produced by the ratchet drive structure. Therefore, the effect of this strain distribution was examined. The inverse-magnetostrictive sensing material of nickel-iron alloy plating has an extremum on its output curve.

Nd₂Fe₁₄B sintered magnets are used in the drive motors of hybrid, electric and other vehicles. A magnet in which rare earth content is reduced by means of a localized diffusion method has been developed in order to reduce the volume of dysprosium. The distribution of the demagnetization fields in a motor is not uniform, so the necessary coercivity distribution for the magnets was quantified using Computer-Aided Engineering (CAE). Then material specifications of the localized dysprosium diffusion satisfied with this coercivity distribution was determined, and optimal manufacturing conditions including the position of dysprosium diffusion were set. The coercivity distribution in every position of the magnet using localized diffusion method was inspected. As a result, the magnet was satisfied with coercivity distribution demanded by CAE.

The use of low-density materials in body panels is increasing as a measure to reduce the weight of the vehicle body. Honda has developed an aluminum/steel sheet hybrid door that is more effective in reducing weight than an all-aluminum door. Because aluminum was used in the door skin, bimetallic corrosion at the connection between the aluminum and the steel sheets represented an issue. It was possible that the difference in the electrical potential of the two metals might promote corrosion at the connection between the aluminum door skin and the steel sheet door panel, in particular at the lower edge of the door, where rainwater and other moisture tend to accumulate, with the result that the appeal of the exterior of the door might decline.

An attempt was made to apply the index U* in detail analysis of load paths in structural joints under static load, using as examples coupling structures of two joined frames with hat-shaped sections, and T-beam joint structures each including spot welds, both of which are widely used in automotive body structures. U* is a load path analysis index that expresses the strength of connection between load points and arbitrary points on a structure. It was possible to identify areas making up load paths by means of the magnitude of U* values, and to clarify the areas that should be coupled in order to achieve effective load transfer to contiguous members. In addition, because it is possible to determine whether or not each section of a structure possesses the potential for load transfer using U* analysis, the research also demonstrated that U* could be used as an indicator of joint structures providing efficient load transfer.

A new index U* for evaluating load path dispersion is proposed, using a structural load path analysis method based on the concept of U*, which expresses the connection strength between a load point and an arbitrary point within the structure. U* enables the evaluation of the load path dispersion within the structure by statistical means such as histograms and standard deviations. Different loading conditions are applied to a body structure, and the similarity of the U* distributions is evaluated using the direction cosine and U* 2-dimensional correlation diagrams. It is shown as a result that body structures can be macroscopically grasped by using the U* distribution rather than using the stress distribution. In addition, as an example, the U* distribution of torsion loading condition is shown to comprehensively include characteristics of the U* distribution of other loading conditions.

This paper discusses a method of predicting the torque distribution on planet gears originating in manufacturing errors, which is necessary for appropriate strength design of the gears in planetary gear sets. First, an expression of relation between manufacturing errors and the torque on the planet gears in a normal n-planet planetary gear set was derived. As a result, an equation expressing the distribution of torque to the planet gears was obtained. Tests were conducted to verify the validity of the equation in the case of a 4-planet planetary gear set. In order to predict the distribution of torque, it was necessary to estimate the stiffness of the planetary gear set that was the subject of the relational expression. These stiffness values were calculated by numerical analysis using a 3D FEM, into which blueprint values and material property values were input.

A multi-objective optimization model using a piston behavior simulation for the prediction of NV, friction and scuffing was created. This model was used to optimize the piston skirt form, helping to enable well-balanced forms to be sought. Optimization calculations, involving extended analyses and numerous design variables, conventionally necessitate long calculation times in order to achieve adequate outcomes. Because of this, in the present project data was converted into functions in order to help enable the complex piston skirt form to be expressed using a small amount of coefficients. Using the limit values for manufacturability and the degree of contribution to the target functions, the scope of design variables was restricted, and the time necessary for the analysis was significantly reduced. This has helped to enable optimal solutions to be determined within a practical time frame.

When a vehicle drives over road seams or a bumpy surface, low-frequency noise called drumming is generated, causing driver discomfort. The generation of drumming noise is closely related to the vibration characteristics of the suspension, body frame, and body panels, as well as the acoustic characteristics of the vehicle interior. It is therefore difficult to take measures to get rid of drumming after the basic vehicle construction has been finalized. Aiming to ensure drumming performance in the drawing review phase, we applied the Finite Element Method (FEM) to obtain acoustical transfer functions of the body, and Multi Body Simulation to get suspension load characteristics. This paper presents the results of the study of drumming prediction technology using this hybrid approach.

An experimental study was carried out on visualization of liquid phase temperature distributions in high-pressure diesel sprays impinging on a heated wall. Naphthalene/TMPD-exciplex fluorescence method and pyrene-excimer fluorescence method were utilized for the thermometry. The sprays were injected into a high-pressure and high-temperature gaseous environment. The nozzle hole diameter was 0.100 mm or 0.139 mm. The results showed that cool pockets were formed at the tip and in the impinging part of the sprays. The spray for the nozzle with 0.100 mm hole was heated up faster near the nozzle than for the nozzle with 0.139 mm hole.