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A new index 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 enables the evaluation of the load path dispersion within the structure by statistical means such as histograms and standard deviations. Presenter Tadashi Naito, Honda R&D Co., Ltd.

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.

With the objective of establishing the ultimate steering operation system for drivers, we developed, based on bioengineering considerations, the Twin Lever Steering (TLS) system which mimicks the bi-articular muscles, as shown in Fig. 1 . The bioengineering advantages are as follows: (1) force can be exerted more easily, (2) the steering can be accomplished quickly, (3) the positioning can be done accurately, and (4) the burden on the driver can be reduced (less fatigue). The advantages of the vehicle in terms of its motion are as follows: (1) the line-traceability is improved, (2) the drift control is improved, (3) the lane-change capability is improved, and (4) the lap time and stability are improved. We would like to report on these advantages of the TLS system from a bioengineering standpoint, and also describe the results of some verification test results obtained from vehicles equipped with this new steering system.

In this research, a simulation method was developed in which it was able to estimate, in the early stage of design, the strains that potentially lead to damages to motorcycle engine parts when tipped over from a stationary state. Splitting a series of phenomena from the start of tilting of motorcycle from the upright position up to the end of collision of engine parts after the contact on the ground to two groups by before and after the contact of engine parts on the ground, we applied the multi body dynamics analysis to the first group, and the elastro-plastic FEM analysis to the latter one. In the computer simulation of collision using the elastro-plastic FEM analysis, we minimized the FEM models from the entire motorcycle models and treated others as a solid model to shorten the computation period. It is also realized that the strains occurring in the engine parts can be simulated by considering only the mass of the parts which are rigidly mounted on the engine.

Designing a lightweight and durable engine is universally important from the standpoints of fuel economy, vehicle dynamics and cost. However, it is challenging to theoretically find an optimal solution which meets both requirements in products such as the cylinder head, to which various thermal loads and mechanical loads are simultaneously applied. In our research, we focused on “non-parametric optimization” and attempted to establish a new design approach derived from the weight reduction of a cylinder head. Our optimization process consists of topology optimization and shape optimization. In the topology optimization process, we explored an optimal structure with the theoretically-highest stiffness in the given design space. This is to provide an efficient structure for pursuing both lightweight and durable characteristics in the subsequent shape optimization process.

A new nitriding technology and material technology have been developed to increase the strength of microalloyed gears. The developed nitriding technology makes it possible to freely select the phase composition of the nitride compound layer by controlling the treatment atmosphere. The treatment environment is controlled to exclude sources of supply of [C], and H2 is applied as the carrier gas. This has made it possible to control the forward reaction that decomposes NH3, helping to enable the stable precipitation of γ′-phase, which offers excellent peeling resistance. A material optimized for the new nitriding technology was also developed. The new material is a low-carbon alloy steel that makes it possible to minimize the difference in hardness between the compound layer and the substrate directly below it, and is resistant to decline in internal hardness due to aging precipitation in the temperature range used in the nitriding treatment.

In this research, a new wire material made using surface-reforming heat treatment was developed in order to enhance the corrosion fatigue resistance of suspension springs. The aim of surface reforming is to improve hydrogen embrittlement characteristics through grain refinement and to improve crack propagation resistance by partial softening of hardness. The grain refinement method used an α'→γ reversed transformation by rapid short-term heating in repeated induction heating and quenching (R-IHQ) to refine the crystal grain size of SAE 9254 steel spring wire to 4 μm or less. In order to simultaneously improve the fatigue crack propagation characteristics, the possibility of reducing the hardness immediately below the spring surface layer was also examined. By applying contour hardening in the second IHQ cycle, a heat affected zone (HAZ) is obtained immediately below the surface.

In order to reduce automobile body weight and improve crashworthiness, the use of high-strength steels has increased greatly in recent years. An optimal combination of both crash safety performance and lightweight structure has been a major challenge in automobile body engineering. In this study, the Cockcroft-Latham fracture criterion was applied to predict the fracture of high-strength steels. Marciniak-type biaxial stretching tests for high-strength steels were performed to measure the material constant of the Cockcroft-Latham fracture criterion. Furthermore, in order to improve the simulation accuracy, local anisotropic parameters based on the plastic strain (strain dependent model of anisotropy) were measured using the digital image grid method and were incorporated into Hill's anisotropic yield condition by the authors. In order to confirm the validity of the Cockcroft-Latham fracture criterion, uniaxial tensile tests were performed.

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.

Cabin quietness is one of the important factors for product marketability. In particular, the importance of reducing road noise is increasing in recent years. Methods that reduce acoustic sensitivity as well as those that reduce the force transferred from the suspension to the body (the suspension transfer force) are used as means of reducing road noise. Reduction of the compliance of the body suspension mounting points has been widely used as a method of reducing acoustic sensitivity. However, there were cases where even though this method reduced acoustic sensitivity, road noise did not decrease. This mechanism remained unclear. This study focused on the suspension transfer force and analyzed this mechanism of change using the transfer function synthesis method. The results showed that the balance between the body's suspension mounting points, suspension bush, and suspension arm-tip compliance is an important factor influencing the change in suspension transfer force.

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.

There have been a number of attempts to clarify the relationship between motorcycle specifications and shimmy phenomenon. Some of such efforts are based on equations of motion. The methods used in those efforts are suitable for analyzing motions in a fundamental structure. However, when the degree of freedom is large, it is extremely difficult to deliver an equation of motion. Therefore, a practical method cannot be found generally when applying the methods employing equations of motion. We also conducted the analysis of shimmy using multi-body dynamics simulation. The yielded results were useful only for clarifying the differences in shimmy levels among motorcycles. However, they were not helpful to understand the relationships between specifications and shimmy phenomenon.

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.

The suitability of FM radio receivers for automobiles has conventionally been rated by evaluating reception characteristics for broadcast waves in repeated driving tests in specific test environments. The evaluation of sound quality has relied on the auditory judgment due to difficulties to conduct quantitative evaluations by experiments. Thus the method had issues in terms of the reproducibility and objectivity of the evaluations. To address these issues, a two-stage method generating a virtual radio wave environment on a PC was developed. The research further defined the multipath distortion rate, MDr, as an index for the sound quality evaluation of FM receivers, and the findings concerning the suitability of the evaluation of FM terminals for automobiles were reported at the 2015 SAE World Congress.

The practical application of heat recovery using thermoelectrics requires the realization of reasonable cost effectiveness. Therefore, a thermoelectric generator (TEG) structure that can compatibly increase efficiency and reduce cost was investigated with the aim of enhancing cost effectiveness. To increase efficiency, a method of using a vacuum space structure to reduce the TEG size was investigated to enable installation just after the close-coupled catalyzer, which is subject to many space restrictions. It was found that by making it possible to use high temperature exhaust heat, power generation efficiency can be increased to approximately twice that of the typical under floor installation. In addition, coupled simulation of heat transfer and power generation using FEM, 1D cost effectiveness simulations, and bench tests were performed with the aim of reducing cost.

Vehicles are required durability in various environments all over the world. Especially water resistance on flooded roads is one of the important issues. To solve this kind of problem, a CFD technology was established in order to predict the water resistance performance of the vehicle at the early development stage. By comparison with vehicle tests on flooded roads, it is clarified the following key factors are required for accurate prediction; the vehicle velocity change, the vehicle height change and the air intake flow rate. Moreover, these three key factors should be appropriately determined from vehicle and engine specification to predict water intrusion for flooded roads at the early stage of development. In this paper, a methodology which determines appropriate analysis conditions mentioned above for flooding simulation from vehicle and engine specification is described. The methodology enables us to determine whether the vehicle provides sufficient waterproofness.

When a vehicle is cruising, unpleasant noise in the 4 to 5 KHz high-frequency band can be heard at the center of all seats in the vehicle cabin. In order to specify the source of this noise, the correlation between the noise and airborne noise from the outer surface of the transmission was determined, and transfer path analysis was conducted for the interior of the transmission. The results indicated that the source of the noise was the 0th-order breathing mode specific to the drive motor. To make it possible to predict this at the desk, a vibrational analysis method was proposed for drive motors made up of laminated electrical steel sheets and segment-type coils. Material properties data for the electrical steel sheets and coils was employed in the drive motor vibrational analysis model without change. The shapes of the laminated electrical steel sheets and coils were also accurately modeled.

When the belt contacts a pulley in a pushing belt-type CVT, vibration is generated by frictional force due to rubbing between the individual elements that are components of the belt, which is said to increase wear and noise. The authors speculated that the source of that vibration is misalignment of the secondary pulley and primary pulley V-surfaces. To verify that phenomenon, a newly developed micro data logger was attached to an element of a mass-produced metal pushing V-belt CVT and the acceleration was measured at rotations equal to those at drive (1000 to 2500 r/m). In addition, the results of calculations using a behavior analysis model showed that changes in pulley misalignment influence element vibration, and that the magnitude of the vibration is correlated to the change in the metal pushing V-belt alignment immediately before the element contacts the pulley.

Technology has been developed to increase the fatigue strength of powder-forged connecting rods. The fatigue strength of powder-forged materials was increased without adding special alloy components or lowering workability by adjusting the ratios of the conventional main mixed powders (iron, carbon, copper). In addition to solid solution strengthening of the ferrite using copper, reducing porosity, which is a material surface defect, is also an effective method of increasing fatigue strength. Reducing carbon content greatly reduced the occurrence of defects in the forging stage. The results of this research showed that the fatigue strength of high strength powder-forged connecting rods can be increased by 30% or more over that of conventional materials, allowing powder-forged connecting rods to be applied to even higher output and higher load engines than before.

Looking back on steering systems in more than a hundred years that have passed since the introduction of the automobile, it can be seen that original method of controlling cars pulled by animals such as horses was by reins, and early automobiles had a single push-pull bar (tiller steering). That became the steering wheel, and an indirect steering mechanism by rotating up and down caught on. While the steering wheel is the main type of steering system in use today, the team have developed the Twin Lever Steering (TLS) system controlled mainly by bi-articular muscles, making use of advancements in science and technology and bioengineering to develop based on bioengineering considerations as shown in Fig. 1. The objective of that is to establish the ultimate steering operation system for drivers. In the first report, the authors reported on results found by using race-car prototypes as shown in Fig. 2.